WO2011008169A1

WO2011008169A1 - Organic ambipolar light emitting materials

Info

Publication number: WO2011008169A1
Application number: PCT/SG2009/000251
Authority: WO
Inventors: Zhikuan Chen; Qinde Liu; Zhun Ma; Changgua Zhen
Original assignee: Agency For Science, Technology And Research
Priority date: 2009-07-14
Filing date: 2009-07-14
Publication date: 2011-01-20
Also published as: TW201111345A

Abstract

The present invention provides a blue light emitting compound comprising (1) a hole transporting core portion, which hole transporting core portion comprises a tertiary nitrogen portion; and (2) at least three electron transporting arm portions extending from the core portion, each electron transporting arm portion comprising an electron transporting portion and an emissive portion.

Description

ORGANIC AMBIPOLAR LIGHT EMITTING MATERIALS

FIELD OF THE INVENTION

The present invention relates generally to light emitting organic materials, particularly electroluminescent organic materials, and to light emitting devices containing such compounds. BACKGROUND

Certain organic materials are able to conduct charge due to inclusion of an extensive system of pi bonds in the molecule. That is, compounds with connected or conjugated pi systems, such as polyarylene compounds or polyarylenevinylene compounds (e.g.

poly(phenylenevinylene) and polyfluorene), have a set of pi molecular orbitals that overlap and extend along the molecule. These extended pi molecular orbitals, when unfilled or when only partially filled with electrons, provide "channels" for transport of additional electrons along the molecule when a voltage is applied to the molecule. Several such extended pi orbitals can form across a conductive organic material, each having different structure and energy levels. The molecular orbital having the lowest energy level is often an effective path for transport of electrons supplied from an electrode.

In order for these materials, and polymers in particular, to luminesce as an electron is being transported across the molecule, one or more electrons must move from a filled or partially filled higher energy orbital to an unfilled or partially filled lower energy orbital. If the energy released by the electron as it passes from a high energy state to a low energy state is in the visible spectrum, these molecules will emit light.

Briefly, when a hole is injected into a conductive organic molecule, the molecule becomes positively charged, and conversely when an electron is injected into such a molecule, it becomes negatively charged. A charged molecule can obtain an opposite charge from an adjacent molecule, resulting in charge transport in a composition containing the conductive organic molecule. An injected electron and hole can recombine within the emissive layer, forming a bound electron/hole pair, termed an exciton, which can emit energy when it relaxes from an excited state to a lower energy state. Depending on the wavelength of the emitted energy, the energy may be released as ultraviolet or visible light.

Electroluminescent organic materials can be conjugated polymers or organic small molecules. Examples of polymeric electroluminescent organic materials include poly(1 ,4- phenylenevinylene)s, polyfluorenes, and their derivatives. Electroluminescent polymers are attractive because of their solution processability, which is a relatively cost effective method for manufacturing electronic devices containing electroluminescent organic materials. However, high purity can be difficult to achieve for polymeric light emitting materials because polymeric materials may contain certain amount of structural defects in the polymer backbone, by-products produced during polymerization, and end groups remaining on the polymer chains. The existence of these impurities/defects in the polymers will dramatically affect device efficiency and lifetime. Non-polymeric organic small molecules represent another category of light emitting materials. Extremely high purity for small molecules could be achieved either through sublimation or recrystallization process, which is an advantage compared to light emitting polymers. Small molecules have been widely used in OLED devices either as emitters or as charge transporting materials. However, small molecules are normally processed through vacuum deposition, which is not cost effective. Such a process is not desirable for mass production. To overcome the drawbacks of poor purity of polymeric light emitting materials and high cost process for small molecules, there is a need to develop new light emitting materials, which could be processed through solution process. Both polymeric and non-polymeric materials have been used in organic light emitting devices, such as organic light emitting diodes (OLEDs).

However, many of the current organic light emitting materials typically have imbalanced charge transporting characteristics. Generally, light emitting materials are able to conduct only one charge carrier, either holes or electrons, but typically not both. For example, poly(1 ,4-phenylenevinylene)s or alkoxy-substituted poly(1 ,4-phenylenevinylene)s are good hole transporters, whereas tris-(8-hydroxyquinoline) aluminum (III) (Alq3) is an electron transporter. Imbalanced charge transporting in OLED devices results in low device efficiency. To address this issue, multilayer devices with one or more of a hole injection layer, hole transport layer, electron injection layer and electron transport layer have been explored. A typical construction includes a hole transport layer, an emissive layer and an electron transport layer, with possible inclusion of a hole injecting layer and/or electron injecting layer. This approach can improve device efficiency but results in increased complexity and cost.

Another approach to this problem is to tune the charge transporting property of the materials by incorporation of either hole transporting portions, or electron transporting portions or both into the material to try to improve the device performance.

Although some materials comprising one or both of hole transporting and electron transporting portions have been developed, and the performance may be better than materials containing only one component, to date the reported device performance based on such materials is still not satisfactory. In principle, when an ambipolar compound containing both hole transporting and electron transporting portions is used as the emissive layer, it can simplify OLED device structure and thus is cost effective. However, the present inventors have observed that ambipolar compounds generally possess large dipole moment, which will lead to strong intramolecular and/or intermolecular interaction. In particular, the coexistence of both electron donating and electron withdrawing moieties in the molecule will induce a dipole moment in the molecule. The present inventors have observed that the stronger the electron donating and electron withdrawing effect of the components, the larger dipole moment in the molecule. In addition, the closer the electron donating portion is to the electron withdrawing portion, the large the dipole moment.

The dipole moment in a molecule will generally cause strong molecular interaction, especially in the solid state. It is well known that intermolecular interaction will cause lower device efficiency because of the formation of excimer/exciplex in OLED devices. In addition, excimer/exciplex emission will shift the emissive spectra to longer wavelength side. This can result in low device efficiency and red-shift of emissive spectra.

As one of the key components for OLEDs, blue light emitting materials, which can be applied in full colour displays or solid state lighting, are the most challenging topic in OLED research because of their relative low device efficiency and short lifetime, compared to green or red light emitting materials. For example, the undesirable behaviour of the ambipolar compounds referred to above make it very challenging to develop high performance deep blue light emitting materials. In particular, the characteristic of red shift in such ambipolar compounds is particularly undesirable for blue light emission.

Thus, there exists a need for new materials that can be used in an organic light emitting layer in an electroluminescent device and in particular for new blue light emitting materials.

SUMMARY OF THE INVENTION The present invention provides luminescent compounds and materials, methods for their preparation, and their use in light emitting devices, including electroluminescent diodes.

The present invention is concerned with ambipolar compounds that have both electron donating moiety for hole-transport and multiple electron withdrawing moieties for electron- transport.

Embodiments of the present invention possess balanced charge transport property for both holes and electrons. Furthermore, embodiments of the light emitting materials described herein have a controlled molecular dipole moment, which can eliminate or reduce the intra- and/or inter-molecular interaction, leading to high efficiency and deep blue light emission. Embodiments also achieve better blue light colour purity.

At its most general, the present invention proposes that an ambipolar compound comprises a central hole transporting core and at least three arms connected to the core wherein each arm comprises an electron transporting portion and an emissive portion.

More particularly, the present invention relates to electroluminescent ambipolar materials, which comprise an electron donating tertiary nitrogen group in the core and three or more conjugated arms having an electron deficient group so as to provide an electron transporting function, methods for their manufacture, and electroluminescent devices incorporating the luminescent materials.

In one aspect, the present invention provides a compound comprising (1) a hole transporting core portion, which hole transporting core portion comprises a tertiary nitrogen portion; and (2) at least three electron transporting arm portions extending from the core, each electron transporting arm portion comprising an electron transporting portion and an emissive portion.

In a further aspect, the present invention provides a compound comprising the structure according to formula I

wherein: core portion

comprises at least one tertiary nitrogen-containing portion, which is optionally substituted; each of arm portions

independently comprises aryl, aryl vinylene or aryl ethynylene, and is optionally substituted;

and

each of n, p and q is independently 1 to 50

and wherein

at least three of the arm portions are electron transporting arm portions and independently comprise an emissive portion and an electron deficient aryl, aryl vinylene or aryl ethynylene, which is optionally substituted. In a further aspect, the present invention provides a compound comprising the structure according to formula II:

wherein:

each of Ar-i, Ar₂ and Ar₃ is independently arylene, arylene vinylene, arylene ethynylene or aminoarylene and is optionally substituted;

each of Bi, B₂ and B₃ is independently as defined above;

and

each of a, b and c is independently as 0 to 20; and

each of n, p and q is independently as defined above;

and wherein:

at least three B_x selected from (BO_n, (B₂)_p and (B₃)_q each independently comprise an emissive portion and an electron deficient aryl, aryl vinylene or aryl ethynylene which is optionally substituted.

In a further aspect, the present invention provides a compound comprising the structure according to formula III:

wherein Ar-i, Ar₂, and Ar₃ are as defined above; and

each of a, b, c, n, p and q are as defined above;

and wherein

each of Ar₄, Ar₅, Ar₆, Ar₇, Ar₈ and Ar₉ is independently arylene, arylene vinylene or arylene ethynylene and is optionally substituted;

each of d, f and h is independently 1 to 20; and

each of e, g and i is independently 1 to 20;

and wherein

at least three of Ar₅, Ar₇ and Ar₉ selected from [(Ar₄)_d(Ar₅)_e]_n , [(Ar₆)f(Ar₇)g]p and [(Ar₈)_h(Ar₉)i]_q each independently comprise an electron deficient aryl, aryl vinylene or aryl ethynylene.

In a further aspect, the present invention provides a compound according to formula (IV):

wherein

each of Ar_4a and Ar₄b is independently as defined for Ar₄ above;

each of Ar_5a and Ar₅b is independently as defined for Ar₅ above;

each of Ar_6a and Ar₆b is independently as defined for Ar₆ above;

each of Ar_7a and Ar_7b is independently as defined for Ar₇ above;

each of Ar_8a and Ar₈b is independently as defined for Ar₈ above; and each of Ar_9a and Ar_9b is independently as defined for Ar₉ above;

and wherein

each of di and d₂ is independently as defined for d above;

each of ei and e₂ is independently as defined for e above;

each of fi and f₂ is independently as defined for f above;

each Of Q₁ and g₂ is independently as defined for g above;

each of h-i and h₂ is independently as defined for h above; and

each of J₁ and i₂ is independently as defined for i above;

and wherein

at least three of Ar_5a , Ar_5b , Ar_7a , Ar_7b , Ar_9a and Ar_9b selected from (Ar_4a)_di(Ar_5a)_ei , (Ar_4b)_d2(Ar_5b)_e2 , (Ar_6a)_f1(Ar_7a)gi , (Ar_6b)_f2(Ar_7b)_g2 , (Ar_Sa)M(Ar₉₃)I₁ and (Ar_8b)_h2(Ar_9b)_i2 are each independently electron deficient aryl, aryl vinylene or aryl ethynylene and are optionally substituted. In a further aspect, the present invention provides a compound according to formula (V):

wherein

each of Ar₄, Ar₅, Ar₆, Ar₇, Ar₈ and Ar₉ is independently as defined above;

Ar₁₀ is independently as defined for Ar₄ above;

Ar₁₁ is is independently as defined for Ar₅ above;

each of d, e, f, g, h and i are independently as defined above; j is independently as defined for d above; and

k is independently as defined for e above;

and wherein

at least three Of Ar₅ , Ar₇ , Ar₉ and Ar₁₁ selected from (Ar₄)_d(Ar₅)_e , (Ar₆)f(Ar₇)g , (Ar₈)_h(Ar₉)i and (Ar-_I0)J(Ar₁ ^)_k are each independently electron deficient aryl, aryl vinylene or aryl ethynylene and are optionally substituted.

In a further aspect, the present invention provides an oligomer or polymer comprising two or more units derived from a compound as described herein.

In a further aspect, the present invention provides a dendrimer comprising two or more units derived from a compound as described herein.

In a further aspect, the present invention provides a light emitting device comprising a compound as described herein.

In another aspect, the present invention provides an organic electroluminescent device comprising a compound as described herein. In a related aspect, the present invention provides an organic light emitting diode (OLED) comprising a compound as described herein.

In another aspect, there is provided a thin film comprising a compound as described herein.

In a further aspect, there is provided a device comprising an anode, a cathode and a thin film as described herein, the thin film being disposed between the anode and the cathode.

In a further aspect, there is provided a device comprising: an anode; an emissive layer disposed on the anode, the emissive layer comprising a compound as described herein; and a cathode disposed on the emissive layer.

In another aspect, the present invention provides a device comprising an emissive layer, wherein the emissive layer comprises a compound or thin film as described herein. In another aspect, there is provided a device comprising: an anode; a hole transporting layer disposed on the anode; an emissive layer disposed on the hole transporting layer; an electron transporting layer disposed on the emissive layer; and a cathode disposed on the electron transporting layer; wherein at least one of the hole transporting layer, the emissive layer and the electron transporting layer comprises a compound or thin film as described herein.

In still another aspect, there is provided a device comprising: an anode; a hole injecting layer disposed on the anode; a hole transporting layer disposed on the hole injecting layer; an emissive layer disposed on the hole transporting layer; an electron transporting layer disposed on the emissive layer; and a hole blocking layer disposed on the electron transporting layer; an electron injecting layer disposed on the emissive layer; a cathode disposed on the electron injecting layer; wherein at least one of the hole transporting layer, the emissive layer or the electron transporting layer comprises a compound or thin film as described herein.

In a further aspect, the present invention provides a photovoltaic cell comprising an active layer wherein the active layer comprises a compound or thin film as described herein. In a further aspect, the present invention provides a chemical or bio sensor comprising a sensing layer wherein the sensing layer comprises a compound or thin film as described herein.

Suitably the devices referred to herein are display devices, for example a display panel.

Accordingly, a further aspect of the present invention provides a display device comprising a compound or thin film as described herein.

In a further aspect, the present invention provides a method of making a compound as described herein.

In a further aspect, the present invention provides a method of making a device (e.g. an OLED or a display device) as described herein. In a further aspect, the present invention provides a use of a compound as described herein in a device (e.g. an OLED or a display device) as described herein. Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of the invention including the examples, as read in conjunction with the accompanying figures.

Any one of the aspects may be combined with any one or more of the other aspects, optinal and preferred features associated with one aspect suitably apply to any one of the other aspects. In particular, features described with reference to a method or use suitably also apply to a product (compound, device, etc) and vice versa.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of compounds described herein are electroluminescent, meaning that these compounds emit light when an electrical current is passed through them. Thus, these compounds are adapted for use in a charge transport layer or a light emitting layer in an organic electronic device.

Conveniently, the compounds as described herein are composed of a hole transporting portion in the core of the compound and at least three arms extending from the core, each arm comprising an electron transporting portion. This combination of structural features not only provides the compounds with ambipolar transporting functionality but also achieves balanced charge transporting properties. Suitably this provides good device performance when the compounds are incorporated into light emitting devices. In particular, as described and illustrated herein, one or more of colour purity, emissive red shift, device efficiency, device lifetime and driving voltage can be favourably altered (e.g. increased, or reduced or eliminated as appropriate) by adopting the particular

arrangement of components described herein. As well, suitably these compounds are solution processable, and may be readily purified to a relatively high extent. Thus, embodiments address the problems described above and provide a compound that performs well in OLEDs for example.

Thus, in one aspect, the present invention provides a compound comprising (1) a hole transporting core portion, which hole transporting core portion comprises a tertiary nitrogen portion; and (2) at least three electron transporting arm portions extending from the core, each electron transporting arm portion comprising an electron transporting portion and an emissive portion. Suitably the compound comprises (3) at least one additional arm portion. In embodiments, at least one of said additional arm(s) comprises an emissive portion having a bandgap that is larger than the bandgap of said emissive portion of said electron transporting arm(s). This arrangement suitably ensures that emission occurs only from said emissive portion of the electron transporting arm (which as noted above is typically present on the same arm as an electron deficient portion), rather than from the emissive portion on the additional arm. The hole transporting portion, electron transporting arm portions, electron transporting portion and, if present, additional arm portion(s) are suitably selected as described herein.

Preferably, the total number of arm portions (electron transporting and additional) is 4 or more, 5 or more, 6 or more, or 10 or more. Typically a maximum number of arm portions is 100, preferably 50, and most preferably 20. The arm portions can be attached directly or indirectly to the hole transporting core portion. In embodiments, some or all of the arm portions are part of a branched structure. That is, the peripheral (non-core) part of the compound can be branched and suitably some or all of the branches comprise an arm portion.

Compounds according to this design suitably permit a reduction in the intramolecular dipole moment. Furthermore, compounds with a bulky structure arising from the presence of three or more arms can prevent molecules from approaching each other, thus effectively reducing the intermolecular interactions. The reduced intramolecular dipole moment and intermolecular interaction suitably results in high efficiency of OLED device and may avoid the side effect of red-shift of the emission spectrum.

In particular, embodiments of the present invention address the drawbacks discussed above by providing an ambipolar compound with three or more arms, wherein the hole transport function is provided in the core and the electron transport function is distributed in the three or more peripheral arms.

Thus, by providing a compound as described herein in an emissive layer for example, both holes and electrons can be injected into an emissive layer and transported in the emissive layer. In particular, by providing three or more peripheral arms, the present inventors have achieved a significant improvement in the problem of balancing charge transport properties. Specifically, the present inventors have found that placement of an electron deficient group in these arms, in combination with the tertiary nitrogen-containing (e.g. triarylamine) portion in the core, can significantly reduce the dipole moment of the compound.

This approach is particularly effective when the arms are arranged substantially symmetrically and/or substantially evenly spaced around the core. In this connection, references herein to such symmetrical arrangements and/or even spacing around the core will be understood by the skilled reader and suitably pertain to the arrangement of the arms around the core such that, assuming each arm to be equal in size and shape, one or more lines of symmetry extending through an arm of group of arms can be identified when the compound is drawn in the normal way and/or the distribution of arms around the core occurs at regular intervals, preferably with substantially the same angle between neighbouring arms or groups of arms.

Furthermore, the present inventors have found that by providing three or more arms around the hole transporting core, it is possible to tailor or "fine tune" the electron transporting character of the compound more effectively. For example, this might be achieved by adjusting the electron transporting portion in only one of the arms and/or to provide different electron transporting portions in different arms.

Another advantage is that the provision of three or more arms permits a more balanced distribution of groups that may contribute to the dipole moment of the compound. In this way, the dipole moment may be adjusted more easily, for example by changing the components or substituents of only one or some of the arms. Preferably the compound has dipole moment in the range 0 to 5 debyes, preferably 0 to 4 debyes, preferably 0 to 3.5 debyes and most preferably 0 to 3.25 debyes.

In embodiments, the structures of one or more, for example all, of the arms are bulky enough to assist in reducing or preventing intermolecular interaction. Accordingly, the design of the compounds described herein suitably enhances the colour stability of light emitting materials, particularly for blue light emission applications and especially for fluorene-based light emitting materials. The luminescent compounds as described herein can be used in the emissive layer of a light emitting device, or as dopant in a suitable layer in such a device. A further use is as a host material for electroluminescent light emitting diodes. The compounds defined herein can be fabricated into LED devices, for example through a solution process.

Suitably the compounds emit blue, green, red or white light.

Preferably the compound is a blue-light-emitting compound. Suitably the compound emits light at a wavelength in the range 400nm to 495nm, preferably 400nm to 480nm. Suitably the emission maxima is less than 450nm, preferably less than 440nm, preferably less than 430nm and most preferably less than 420nm. A particularly preferred range is 400nm to 420nm, preferably 405nm to 415nm.

In other embodiments, the compound is a green-light-emitting compound.

In other embodiments, the compound is a red-light-emitting compound.

In other embodiments, the compound is a white-light-emitting compound. The emissive portions of the arm portions can be adjusted to produce the desired colour out put. An advantage of providing three or more arms is that there is more flexibility in the provision of emissive portions. In embodiments wherein the emissive portio is adjacent the electron deficient portion in some or all of the electron transport arm portions, adjustment of the output can be controlled particualrly effectively because the proximity of the emission portion to the electron deficient portion can improve emission efficiency.

Suitably the compound has the structure according to formula I:

wherein: core por ttiioonn

and

each of n, p and q is independently 1 to 50

and wherein

at least three of the arm portions are electron transporting arm portions and independently comprise an. emissive portion and an electron deficient aryl, aryl vinylene or aryl ethynylene, which is optionally substituted.

In accordance with formula I, the compound has at least three arms (n+p+q >3). Suitably the arm portions are arranged substantially symmetrically around the core portion.

Any combination of one or more of B₁, one or more of B₂ and one or more of B₃ selected from any occurrence of B₁, B₂ and B₃ can provide the required electron deficient group. Suitably at least one B-i, at least one B₂ and at least one B₃ provide therequired electron deficient groups.

Suitable emissive portions are known to the skilled reader and examples are discussed herein.

Suitably, at least one of the arm portions (e.g. at least one occurrence of B₂) comprises a supplementary emissive portion with a bandgap that is larger than the band gap of the said emissive portion of the electron transporting arm portion.

Typically, the tertiary nitrogen portion is selected from nitrogen, triarylamine and poly(arylamino). Suitably the core portion comprises one, two, three or more tertiary nitrogens.

In embodiments, the tertiary nitrogen portion suitably has the formula N(Ar)₃ or (Ar)₂-N- (Ar)-N-(Ar)₂, wherein each Ar is selected independently as described herein.

Nevertheless, greater numbers of tertiary nitrogens are possible, for example 3 or more, 4 or more, 5 or more, or 10 or more tertiary nitrogens. Typically, each tertiary nitrogen is substituted with three aryl or arylene groups (one or more of which may in turn be bonded to a further nitrogen).

By providing a core portion with one or more tertiary nitrogens (e.g. triarylamine or poly(arylamino)), suitably the HOMO energy level of the compound can be increased, which may facilitate hole injection and transporting, particularly at lower operational voltages of an OLED device comprising the compound.

In the case of the tertiary nitrogen-containing core

being nitrogen, the nitrogen is suitably attached directly to the arm portions, for example as follows:

Suitably, each B₁ independently comprises C_5-iooaryl, C_5-1Ooaryl vinylene or C_5-1Ooaryl ethynylene, preferably C₅.₈oaryl, C_5-80aryl vinylene or C_5-80aryl ethynylene, and more preferably C_5-5oaryl, C_5-50aryl vinylene or C₅.₅oaryl ethynylene and is optionally substituted.

Suitably, each B₂ independently comprises C_5-i₀oaryl, C_5-1Ooaryl vinylene or C_5-1Ooaryl ethynylene, preferably C_5-8oaryl, C_5-80aryl vinylene or C_5-80aryl ethynylene, and more preferably C_5-5oaryl, C₅.₅₀aryl vinylene or C_5-50aryl ethynylene and is optionally substituted.

Suitably, each B₃ independently comprises C_5-iooaryl, C_5-1Ooaryl vinylene or C_5-io_Oaryl ethynylene, preferably C₅.₈oaryl, C_5-80aryl vinylene or C₅.₈₀aryl ethynylene, and more preferably C_5-50aryl, C_5-50aryl vinylene or C_5-50aryl ethynylene and is optionally substituted.

Suitably each B₁ is independently (Ar₄)_d(Ar₅)_e as described below.

Suitably each B₂ is independently (Ar₆)_f(Ar₇)_g as described below.

Suitably each B₃ is independently (Ar₈)_h(Ar₉)i as described below.

Preferably each of n, p and q is independently 1 to 20, more preferably 1 to 10, more preferably 1 to 5, more preferably 1 to 3 and most preferably 1 or 2.

Suitably n + p + q <100, preferably <50, and more preferably <10. Suitably the compound contains 4 or more, 5 or more, or 6 or more arm portions. Thus, in embodiments, one or more of n, p and q is 2 or more. Values for each of n, p and q of >1 can be achieved by, for example, providing two or more arms on an aryl attached to a tertiary nitrogen in the core. An example is a triarylamine core with at least one of the aryls attached to the nitrogen being substituted by two or more arms.

Alternatively or additionally, one or more of the aryls attached to the tertiary nitrogen- containing core (e.g. triarylamine) may be attached to a further tertiary nitrogen-containing group such as a triarylamine or poly(arylamine) group. In this way, branching of the arm structure can be achieved, as discussed above.

Examples of suitable aryls and branching are described herein.

In embodiments, the core portion

comprises a single tertiary amine unit or multiple tertiary nitrogen units, for example as shown in formula Ia:

wherein

each of Ar-i, Ar₂ and Ar₃ is independently arylene, arylene vinylene, arylene ethynylene or aminoarylene, and is optionally substituted;

each of a, b and c is independently 0 to 20; and

I is independently 1 to 20.

Thus, in some embodiments, where l>1 and b=0, adjacent tertiary nitrogens may share a common aryl, e.g. Ar₁. Suitably, each of Ar-i, Ar₂ and Ar₃ is independently C_5-iooarylene, C_5-1Ooarylene vinylene, C_5- iooarylene ethynylene or amino C_5-1Ooarylene, preferably C_5-50arylene, C_5-5oarylene vinylene, C_5-50arylene ethynylene or amino C_5-50arylene, more preferably C_5-30arylene, C_5- ₃oarylene vinylene, C_5-3oarylene ethynylene or amino C_5-30arylene, more preferably C_5- i₅arylene, C_5-15arylene vinylene, C_5-i₅arylene ethynylene or amino C_5-15arylene, and is optionally substituted.

Suitably, the arylene of each Of Ar₁, Ar₂ and Ar₃ is independently carboarylene or heteroarylene. Preferably the arylene of each Of Ar₁, Ar₂ and Ar₃ is carboarylene.

Suitably any two of An, Ar₂ and Ar₃ are connected. That is, any one or more of Ar₁ and Ar₂, or Ar₁ and Ar₃, or Ar₂ and Ar₃ are preferably connected to each other, suitably by a single bond or O, S, Si or an optionally substituted alkylene (preferably C_1-3 alkylene). Preferably each Of Ar₁, Ar₂ and Ar₃ is independently phenylene, fluorenylene,

carbazolylene, diarylamino, spirobifluorenylene, spirosilabifluorenylene,

indenocarbazolylene, indenofluorenylene or aminoarylene and is optionally substituted.

Preferably each Of Ar₁, Ar₂ and Ar₃ is independently phenylene or fluorenylene and is optionally substituted.

In embodiments, each of Ar₁, Ar₂ and Ar₃ is independently carbazoyl-substituted phenylene and is optionally further substituted, suitably as follows:

In embodiments, the carbazoyl group is bonded at one or both of the 3- and 6-positions, suitably as follows:

In embodiments, each of Ar₁, Ar₂ and Ar₃ is independently fluorenylene and is optionally substituted, suitably as follows:

Typically each Of Ar₁, Ar₂ and Ar₃ is independently substituted fluorenylene, preferably substituted at the 9-position, suitably as follows:

Preferably each Of Ar₁, Ar₂ and Ar₃ is independently substituted fluorenylene, preferably di-substituted at the 9-position, suitably as follows:

A particularly preferred substituent is alkyl, preferably C_2-15alkyl, more preferably C_2-10alkyl, more preferably C_3-8alkyl, more preferably C_5-7alkyl and most preferably C₆alkyl, and the alkyl substituent is optionally substituted.

In particularly preferred embodiments, each of Ar₁, Ar₂ and Ar₃ is independently

Suitably, An, Ar₂ and Ar₃ are the same. However, in other embodiments Ar₁, Ar₂ and Ar₃ are different.

Preferably each of a, b, and c is independently 1 to 20, more preferably 1 to 10, more preferably 1 to 5, more preferably 1 to 3 and most preferably 1 or 2.

In embodiments, a, b and c are the same. In other embodiments, not all of a, b and c are the same. In some embodiments, all of a, b and c are different.

Suitably core por ttiioonn

iiss ttrrii∑arylamine according to formula Ib:

wherein

each of Ar₁, Ar₂ and Ar₃ is independently as defined above; and

each of a, b and c is independently as defined above.

Suitably each of Ar₁, Ar₂ and Ar₃ is bonded directly or indirectly to an arm portion as described herein.

In embodiments, one or more Of Ar₁, Ar₂ and Ar₃ is independently aminoaryl and preferably the aminoaryl has the structure -(Ar_r)-N(Ar₂0 (Ar₃O wherein each of Ar_1' Ar_2' and Ar_3' is independently as defined for Ar₁, Ar₂ and Ar₃ respectively above. Suitably one or two of Arr Ar_2' and Ar_3', preferably one or both of Ar₂' and Ar_3', is independently bonded to an arm portion as described herein.

Thus, in one embodiment, core portion

is a poly(arylamine) comprising two tertiary nitrogens according to formula Ic:

wherein

Ar₃ is independently as defined above;

each of Ar₃- and Ar_3" is independently as defined for Ar₃ above;

each of a, b and c are independently as defined above; and

each of c' and c" is independently as defined for c above.

In such an arrangement, suitably Ar₃, Ar_3' and Ar₃- are independently not an aminoaryl.

In this way, any three or more of Ar₁, Ar₂, Ar_3' and Ar_3" can be bonded directly or indirectly to an arm portion.

Preferably the compound comprises the structure according to formula II:

wherein:

each Of Ar₁, Ar₂ and Ar₃ is independently as defined above;

each of Bi₁ B₂ and B₃ is independently as defined above;

each of a, b and c is independently as defined above; and

each of n, p and q is independently as defined above;

and wherein:

at least three B_x selected from (B₁ )_n, (B₂)_p and (B₃)_q each independently comprise an emissive portion and an electron deficient aryl, aryl vinylene or aryl ethynylene which is optionally substituted.

Thus, the at least three electron deficient (i.e. electron transporting) portions can be provided by any occurence of B₁, B₂ or B₃. In other words, any one of the at least three B_x can be any one of B-i, B₂ and B₃. Preferably at least one of the said at least three B_x comprises an emissive portion.

Suitably at least one further B₁, B₂ or B₃ comprises a supplementary emissive portion having a bandgap that is larger than the bandgap of the said emissive portion. Thus, in such compounds, the hole transporting function is provided by the portion:

which, as discussed above, can comprise multiple nitrogen centres (e.g. poly(arylamine)), for example in accordance with formula Ia or Ic. The electron transporting function is provided by the at least three B_x that comprise an electron deficient portion. Suitable electron deficient portions are known to the skilled reader and examples are set out herein. The electron deficiency may be achieved by using an aryl, aryl vinylene or aryl ethynylene that is inherently electron deficient/electron withdrawing and/or by attaching an electron withdrawing group to the aryl, aryl vinylene or aryl ethynylene group. Suitably each Bi is independently (Ar₄)_d(Ar₅)_e wherein each Ar₄ and each Ar₅ is independently arylene, arylene vinylene or arylene ethynylene and is optionally substituted; and each of d and e is independently 1 to 20.

Preferably each of d and e is independently 1 to 10, more preferably 1 to 5, more preferably 1 to 3 and most preferably 1 or 2. In embodiments, d is 1 to 3 and e is 1.

Suitably each B₂ is independently (Ar₆)_f(Ar₇)_g wherein each Ar₆ and each Ar₇ is independently arylene, arylene vinylene or arylene ethynylene and is optionally substituted; and each of f and g is independently 1 to 20.

Preferably each of f and g is independently 1 to 10, more preferably 1 to 5, more preferably 1 to 3 and most preferably 1 or 2. In embodiments, f is 1 to 3 and g is 1.

Suitably each B₃ is independently (Ar₈)_h(Arg)i wherein each Ar₈ and each Ar₉ is independently arylene, arylene vinylene or arylene ethynylene and is optionally substituted; and each of h and i is independently 1 to 20.

Preferably each of h and i is independently 1 to 10, more preferably 1 to 5, more preferably 1 to 3 and most preferably 1 or 2. In embodiments, h is 1 to 3 and i is 1.

Preferably the compound has the structure according to formula Il

(III) wherein

Ar-i, Ar₂, and Ar₃ are as defined above; and

each of a, b, c, n, p and q are as defined above;

and wherein

each of d, f and h is independently as defined above; and

each of e, g and i is independently as defined above;

and wherein

at least three of Ar₅, Ar₇ and Ar_g selected from [(Ar₄)_d(Ar₅)_e]_n , [(Ar₆)_f(Ar₇)g]p and [(Ar₈)_h(Ar₉)i]_q each independently comprise an electron deficient aryl, aryl vinylene or aryl ethynylene. Thus, the at least three electron deficient (i.e. electron transporting) portions can be provided by any occurence of Ar₅, Ar₇ or Ar_g.

Suitably, each of Ar₄, Ar₆ and Ar₈ is independently C_5-1Ooarylene, C_5-1Ooarylene vinylene or C_5-1Ooarylene ethynylene, preferably C_5-5oarylene, C_5-50arylene vinylene or C_5-50arylene ethynylene, more preferably C_5-3oarylene, C_5-3oarylene vinylene or C_5-30arylene ethynylene, and most preferably C_5-15arylene, C_5-i₅arylene vinylene or C_5-15arylene ethynylene, and is optionally substituted.

Suitably, the arylene of each of Ar₄, Ar₆ and Ar₈ is independently carboarylene or heteroarylene.

In the case of the arylene of any one or more Of Ar₄, Ar₆ and Ar₈ being heteroarylene, the heteroarylene may contain one or more heteroatoms selected from O, S, N, Si and P, preferably one or more selected from O, S and N, more preferably one or more selected from O and N, and most preferably N.

Suitably, if the arylene of any one or more Of Ar₄, Ar₆ and Ar₈ is heteroarylene, the heteroarylene contains one, two, three or four heteroatoms. Where a plurality of heteroatoms are present, they may be the same or different. Preferably the arylene of each of Ar₄, Ar₆ and Ar₈ is carboarylene.

Suitably any one or more of the pairs of Ar groups Ar₄ and Ar₅, Ar₆ and Ar₇, and Ar₈ and Ar₉ are connected to each other by a single bond or O, S, Si or an optionally substituted alkylene (preferably C_1-3 alkylene).

Preferably each Of Ar₄, Ar₆ and Ar₈ is independently phenylene, fluorenylene,

carbazolylene, diarylamino, spirobifluorenylene, spirosilabifluorenylene,

indenocarbazolylene, indenofluorenylene or aminoaryl and is optionally substituted.

Preferably each of Ar₄, Ar₆ and Ar₈ is independently fluorenylene and is optionally substituted, suitably as follows:

Typically each of Ar₄, Ar₆ and Ar₈ is independently substituted fluorenylene, preferably substituted at the 9-position, suitably as follows:

Preferably each of Ar₄, Ar₆ and Ar₈ is independently substituted fluorenylene, preferably di-substituted at the 9-position, suitably as follows:

A particularly preferred substituent is alkyl, preferably C_2-15alkyl, more preferably C_2-i₀alkyl, more preferably C_3-8alkyl, more preferably C_5-7alkyl and most preferably C₆alkyl, and the alkyl substituent is optionally substituted.

In particularly preferred embodiments, each Of Ar₄, Ar₆ and Ar₈ is independently

Suitably, Ar₄, Ar₆ and Ar₈ are the same. However, in other embodiments Ar₄, Ar₆ and Ar₈ are different.

Suitably, each Of Ar₅, Ar₇ and Ar₉ is independently C_5-i_Ooarylene, C_5-1Ooarylene vinylene or C_5-1o_Oarylene ethynylene, preferably C₅.₃oarylene, C₅.₃oarylene vinylene or C_5-30arylene ethynylene, and most preferably C_5-i₅arylene, C_5-i₅arylene vinylene or C_5-i₅arylene ethynylene, and is optionally substituted.

As appropriate, and in accordance with formula III for example, each of Ar₅, Ar₇ and Ar₉ is independently electron deficient. For example, each of Ar₅, Ar₇ and Ar₉ is independently electron deficient C_5-io_Oarylene, C_5-1Ooarylene vinylene or C₅_i_Ooarylene ethynylene.

Suitably the electron deficiency is achieved by providing the arylene with an electron withdrawing group. Accordingly, the arylene, arylene vinylene or arylene ethynylene is typically substituted with at least one electron withdrawing group. Suitable electron withdrawing groups are known to the skilled reader. Examples are given herein.

Preferably each electron withdrawing group is selected independently from: halo, cyano, nitro, carbonyl, thionyl, sulphonyl and perfluoroalkyl. Cyano is particularly preferred. Suitably, the arylene of each of Ar₅, Ar₇ and Ar₉ is independently carboarylene or heteroarylene.

In the case of the arylene of any one or more of Ar₅, Ar₇ and Ar₉ being heteroarylene, the heteroarylene may contain one or more heteroatoms selected from O, S, N, Si and P, preferably one or more selected from O, S and N, more preferably one or more selected from O and N, and most preferably N. Suitably, if the arylene of any one or more Of Ar₅, Ar₇ and Ar₉ is heteroarylene, the heteroarylene contains one, two, three or four heteroatoms. Where a plurality of heteroatoms are present, they may be the same or different. Preferably each of Ar₅, Ar₇ and Ar_g is independently selected from the following groups:

wherein

each of R, R¹, R" and R"' is independently halo (especially -F or -Cl), -CN, -NO₂,

CO, thionyl, sulphonyl, C_1-2Oalkyl, C_1-20perfluoroalkyl, C_1-20alkoxy, C_5-5oaryl, C_5-50arylene vinylene, or C_5-50arylene ethynylene, and q is an integer from 0 to 6.

It will be appreciated that although certain of the aryl groups above are depicted as either monovalent or bivalent, any of those groups may be either monovalent or bivalent, depending on the context in which the aryl group occurs in the compound as described herein. As well, certain of the compounds are depicted with the bond that attaches the group to the remaining portion of the compound as entering into the centre of the aryl group ring, either at an atom or across a bond. It will be appreciated that such depiction is intended to represent that the particular aryl group may be attached to the remaining portion of the compound by a bond at any available position on the ring.

Preferably the arylene of each of Ar₅, Ar₇ and Ar_g is carboarylene. Preferably each of Ar₅, Ar₇ and Ar₉ is independently phenylene and is optionally substituted. Preferably each Of Ar₅, Ar₇ and Ar₉ is independently cyano substituted phenylene.

Preferably the compound has the structure according to formula (IV):

wherein

each of Ar_4a and Ar_4b is independently as defined for Ar₄ above;

each of Ar_5a and Ar_5b is independently as defined for Ar₅ above; each of Ar_6a and Ar_6b is independently as defined for Ar₆ above;

each of Ar_7a and Ar_7b is independently as defined for Ar₇ above;

each of Ar_8a and Ar_8b is independently as defined for Ar₈ above; and

each of Ar_9a and Ar_9b is independently as defined for Ar_g above;

and wherein

each of di and d₂ is independently as defined for d above;

each of ei and e₂ is independently as defined for e above;

each of f-i and f₂ is independently as defined for f above;

each of Q₁ and g₂ is independently as defined for g above;

each of hi and h₂ is independently as defined for h above; and

each of i-i and i₂ is independently as defined for i above;

and wherein

at least three of Ar_5a , Ar_5b , Ar_7a , Ar_7b , Ar_9a and Ar_9b selected from (Ar_4a)_d1(Ar_5a)_ei , (Ar_4b)_d2(Ar_5b)_e2 , (Ar_6a)_f1(Ar_7a)_g1 , (Ar_6b)_f2(Ar_7b)_g2 , (Ar₈₃)_Hi(Ar₉₈)_H and (Ar_8b)_h2(Ar_9b)_i2 are each independently electron deficient aryl, aryl vinylene or aryl ethynylene and are optionally substituted.

Thus, each of the at least three electron deficient (i.e. electron transporting) portions can be provided by any occurence of Ar_5a , Ar_5b , Ar_7a , Ar_7b , Ar_9a and Ar_9b.

Preferably the compound has the structure according to formula (V):

(V) wherein

Ar₁₀ is independently as defined for Ar₄ above;

Ar₁-_I is is independently as defined for Ar₅ above;

each of d, e, f, g, h and i are independently as defined above;

j is independently as defined for d above; and

k is independently as defined for e above;

and wherein

at least three Of Ar₅ , Ar₇ , Ar₉ and Ar₁₁ selected from (Ar₄)_d(Ar₅)_e , (Ar₆)_f(Ar₇)g , (Ar₈)_h(Ar₉)i and (Ar₁₀)J(Ar₁₁)_K are each independently electron deficient aryl, aryl vinylene or aryl ethynylene and are optionally substituted. Thus, each of the at leat three electron deficient (i.e. electron transporting) portions can be provided by any occurence Of Ar₅ , Ar₇ , Ar₉ and Ar₁₁.

As shown schematically in Figure 1 , a compound 10 as described herein, can be a discrete compound or repeating unit in an oligomer or polymer, for example a dendritic polymer. The compound 10 includes a core tertiary nitrogen-containing portion 12 that provides a hole transporting function. In some embodiments this is a triarylamine, in others there are two, three or more nitrogen centres.

Compound 10 has three arms 14, 16 and 18. More than three arms are possible, for example 4, 5 or 6 or more.

Each of the arms has an electron transporting portion, illustrated as 20 on arm 14. In the case of arm 14, the electron transporting (i.e. electron deficient portion) group is (Ar₅)_e wherein Ar₅ is electron deficient and is optionally substituted by one or more electron withdrawing groups (which electron withdrawing groups can provide the required electron deficiency). Arm 14 also includes an emissive portion 22 comprising, in this example, the group -(Ar₄)_d. The proximity of electron deficient portion 20 to the emissive portion suitably assists the device efficiency.

Arms 16 and 18 also include respective electron transporting an emissive portions, iluustrated as features 24 and 26 respectively.

In embodiments, each of arms 14, 16 and 18 may be branched, for example when any of n, p and q are greater than 1.

Suitably any one or more of An, Ar_1a, Ar_1b, Ar₂, Ar_2a, Ar_2b, Ar₃, Ar_3a, Ar₃₁₃, Ar₃', Ar₃", Ar₄, Ar_4a, Ar_4b, Ar₅, Ar_5a, Ar_5b, Ar₆, Ar_6a, Ar_6b, Ar₇, Ar_7a, Ar_7b, Ar₈, Ar_8a, Ar_8b, Ar₉, Ar_9a, Ar_9b, Ar₁₀ and Ar-n is independently substituted. Suitable substituents include one or more of branched or unbranched alkyl, branched or unbranched heteroalkyl, branched or unbranched alkenyl, branched or unbranched heteroalkenyl, branched or unbranched alkynyl, branched or unbranched heteroalkynyl, branched or unbranched alkoxy, aryl and heteroaryl. Suitably, where such Ar groups are substituted, each of An, Ar_1a, Ar_1b, Ar₂, Ar_2a, Ar_2b, Ar₃, Ar_3a, Ar_3b, Ar₃., Ar₃-, Ar₄, Ar_4a, Ar_4b, Ar₅, Ar_5a, Ar_5b, Ar₆, Ar_6a, Ar_6b, Ar₇, Ar_7a, Ar_7b, Ar₈, Ar_8a, Ar_8b, Ar₉, Ar_9a, Ar_9b, Ar₁₀ and Ar₁₁ is independently substituted by one or more of C_1-2oalkyl, C_1-2oalkoxy and C_5-5oaryl, which substituents are optionally further substituted.

If any one of a, b, c, d, Cl₁, d₂, e, B₁, e₂, f, f-i, f₂, g, g_{1 f} g₂, h, h_{1 ?} h₂, i, i-i, i₂, j, k, I, n, p or q is greater than one, then the relevant Ar group (for example Ar-i for a) is chosen

independently for each occurrence of that Ar group. For example, where a is 3, each of the 3 Ar₁ groups is chosen independently from the remaining 2 Ar₁ groups.

Similarly, for example, if n is greater than one, then the relevant groups within the bracketed portion, i.e. [(Ar₄)_d(Ar₅)_e)] is chosen independently for each occurrence of n. Thus, for example, different electron transporting portions are possible for each occurrence of e and/or n. Suitably the compound as described herein is an oligomer or polymer. Preferably the compound is a dendritic polymer or dendrimer.

Preferably the compound (which can be, e.g., a dendrimer) has a molecular weight Mw in the range 500 to 1 ,000,000 Da, more preferably 500 to 300,000 Da.

Embodiments of compounds of the present invention are luminescent, suitably

electroluminescent, and as such are useful in light emitting devices, for example organic electroluminescent devices.

Suitably the organic electroluminescent device is or comprises an organic light emitting diode (OLED). That is, the compounds described herein are for use in organic light emitting diodes (OLEDs). Thus, in another aspect, the present invention provides an organic electroluminescent device comprising a compound as described herein.

In a related aspect, the present invention provides an organic light emitting diode (OLED) comprising a compound as described herein.

Suitably the compounds as described herein are used as an emissive layer for organic electroluminescent devices.

Thus, in another aspect, the present invention provides an organic electroluminescent device comprising an emissive layer, wherein the emissive layer comprises a compound as described herein. Typically the compound of the present invention is present in an organic layer in such organic electroluminescent devices. Such embodiments may be used to form one or more of the emissive layer, a charge injection layer, a charge transport layer or a hole blocking layer. Typically the layer has the form of a thin film.

Thus, in another aspect, there is provided a thin film comprising a compound as described herein.

The thin film (e.g. a thin film forming the emissive layer) is typically a thin layer containing a compound as described herein, which layer may be formed to be in the order of from about 0.1 to about 1000 nm thick, preferably from about 1 to about 500 nm thick, more preferably from about 5 to about 250 nm thick, and most preferably from about 5 to about 100 nm thick.

The thin film may contain other components. For example, the thin film may comprise a host material such as a conductive organic chemical and a compound as described herein. The host material may be for example poly(9-vinylcarbazole) (PVK), 4,4'-N₁NT- dicarbazole-biphenyl (CBP), 4,4',4"-tri(N-carbazole)triphenylamine (TCTA), N,N'-diphenyl- N,N'-bis(3-methylphenyl)(1 ,1'-biphenyl)-4,4'-diamine (TPD), N,N'-bis(1-naphthyl)-N,N'- diphenyl-1,1"-biphenyl-4,4'-diamine (NPB), 4,4',4"-tris(N,N-diphenyl-amino)

triphenylamine (TDATA), 1 ,3,5-tris(diphenylamino)benzene (TDAB), 1 ,3,5-tris(4-(di-2- pyridylamino)phenyl)benzene (TDAPB), TTBND, PPD, PTDATA, BFA-1T, p-dmDPS, p- DPA-TDAB, MTBDAB, spiro-mTTB, DBC, poly(1 ,4-phenylenevinylene), polyfluorene, poly(styrenesulfonic acid), poly(3,4-ethylenedioxythiophene), polyacetylene, polypyrrole, polyaniline, 3-phenyl-4(1 'napthyl)-5-phenyl-1 ,2,4-triazole (TAZ), 2-(4-biphenyl)-5(4- tertbutyl-phenyl)-1 ,3,4,oxadiazole (PBD), 1 ,3,4-oxadiazole,2,2'-(1 ,3-phenylene)bis[5-[4- (1 ,1-dimethylethyl)phenyl]] (OXD-7) or poly[2-(6-cyano-6-methyl)heptyloxy-1 ,4- phenylene(CNPP), AIOq, AIq(CIq)₂, Al(Saph-q), AI(ODZ)₃, Ph₂Bq, Zn(BIZ)₂, Bepp₂, Bebq₂, Zn(ODZ)₂, spiro-PBD and BMB-3T.

The ratio of the host material to the compound as described herein may be from about 100:0.01 to about 100:30.

Alternatively, the thin film may comprise a compound as described herein as a host material and may further comprise an organic dye or phosphorescent emitter, for example, dyes such as 10-(2-benzothiazolyl)-1 ,1 ,7,7-tetramethyl-2,3,6,7-tetrahydro- 1H,5H,11H-[l]benzo-pyrano[6,7,8-ij]quinolizin-11-one, 3-(2-benzothiazolyl)-7- (diethylamino)-2H-1-benzopyran-2-one, 4-(dicyanomethylene)-2-t-butyl-6-(1 ,1 ,7,7- tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), rubrene, 4-(dicyanomethylene)-2-t-butyl-6- (p-diphenylaminostyryl)-4H-pyran (DCTP), 3-(dicyanomethylene)-5,5-dimethyl-1 -[(4- dimethylamino)styryl]cyclohexene (DCDDC), 6-methyl-3-[3-(1 ,1 ,6,6-tetramethyl-10-oxo- 2,3,5,6-tetrahydro-1 H,4H,10H-11-oxa-3a-azabenzo[de]- anthracen-9-yl)acryloyl]pyran-2,4-dione (AAAP), 6,13-diphenylpentacene (DPP) and 3-(N-phenyl-N-p-tolylamino)-9-(N-p-styrylphenyl-N-p-tolylamino)perylene [(PPA)(PSA)Pe- 1], 1 ,1'-dicyano-substituted bis-styrylnaphthalene derivative (BSN), or phosphorescent emitters such as PtOEP, lr(ppy)₃ or their derivatives.

The ratio of the compound as described herein to the dye or the phosphorescent emitter is from about 100:0.01 to about 1 :1.

The thin film may be formed on a suitable substrate, which may be any solid substrate, including quartz, glass, mica, a plastic substrate such as polyethylene terephthalate or polycarbonate, paper, metal, or silicon. The thin film may also be layered onto another layer when forming a multilayered device, or onto an electrode.

To form the thin film, the compound as described herein and any additional film

components may be dissolved in a suitable organic solvent. Suitable solvents include chloroform, toluene, xylene, ethyl benzoate, 1 ,1 ,2,2-tetrachloroethane, THF,

dichlorobenzene, mesitylene and mixtures of the aforesaid solvents.

The thin film may be formed on a suitable surface using standard deposition or coating methods including solution coating. Solution coating includes spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, flexo printing, offset printing and inkjet printing. The compounds as described herein and thin films containing such compounds may be used to construct electroluminescent devices, including single layer and multilayer devices. The compounds as described herein and thin films containing such compounds may form the emissive layer in an organic light emitting diode, the active layer in an organic thin film transistor or the active layer in an organic photovoltaic cell. Such devices and layers, as well as their construction, are known in the art.

In a further aspect, there is provided a device comprising an anode, a cathode and a thin film as described herein, the thin film being disposed between the anode and the cathode. In a further aspect, there is provided a device comprising: an anode; an emissive layer disposed on the anode, the emissive layer comprising a compound or thin film as described herein; and a cathode disposed on the emissive layer.

In another aspect, there is provided a device comprising: an anode; a hole transporting layer disposed on the anode; an emissive layer disposed on the hole transporting layer; an electron transporting layer disposed on the emissive layer; and a cathode disposed on the electron transporting layer; wherein at least one of the hole transporting layer, the emissive layer and the electron transporting layer comprises a compound or thin film as described herein.

In embodiments, the compounds described herein are used as active layers for photovoltaic cells. In a further aspect, the present invention provides a photovoltaic cell comprising an active layer wherein the active layer comprises a compound or thin film as described herein.

In embodiments, the compounds described herein are used as a sensing layer for a chemical sensor or biosensor.

In a further aspect, the present invention provides a chemical or bio sensor comprising a sensing layer wherein the sensing layer comprises a compound or thin film as described herein. Suitably the devices referred to herein are display devices, for example a display panel. Accordingly, a further aspect of the present invention provides a display device comprising a compound or thin film as described herein.

In a further aspect, the present invention provides a method of making a device (e.g. an OLED or a display device) as described herein. In a further aspect, the present invention provides a use of a compound as described herein in a device (e.g. an OLED or a display device) as described herein.

Definitions The term "triarylamine" as used herein pertains to a tertiary amine group NR₃ wherein each R is independently an aryl or arylene, or aryl or arylene conjugatedly linked to the N. For example each R can be independently aryl, arylalkenylene or arylalkynylene.

Preferred examples of the congujating linker group are vinylene and alkynylene: such that R is aryl/arylene vinylene or aryl/arylene ethynylene. In the context of the triarylamine being located in the core portion of a compound as described herein, at least one of the amine substituents R is bidentate (e.g. arylene) to permit connection to the arm portions. The discussion of aryl above therefore applies to the corresponding arylene.

The term "aryl" as used herein pertains to a monovalent aromatic radical derived from an aromatic compound by removal of one hydrogen atom. An aromatic compound is a cyclic compound having 4n+2 pi electrons where n is an integer equal to or greater than 0. In embodiments, the aryl group may have from 5 to 100 ring atoms, preferably 5 to 80, more preferably 5 to 50, more preferably 5 to 30 and most preferably 5 to 20 ring atoms.

Examples of aryls in the context of substituents are set out below.

The term "arylene" as used herein pertains to a bivalent aromatic radical derived from an aromatic compound by removal of two hydrogen atoms. An aromatic compound is a cyclic compound having 4n+2 pi electrons where n is an integer equal to or greater than 0. In embodiments, the arylene group may have from 5 to 100 ring atoms, preferably 5 to 80, more preferably 5 to 50, more preferably 5 to 30 and most preferably 5 to 20 ring atoms. Examples of arylenes in the context of substituents are set out below. The term "heteroaryl" group as used herein pertains to an aryl group in which one or more of the backbone carbon atoms has been replaced with a hetero atom, for example one or more of N, O, S, Si or P.

The term "heteroarylene" as used herein pertains to an arylene group in which one or more of the backbone carbon atoms has been replaced with a hetero atom, for example one or more of N, O, S, Si or P. The symbol "Ar" as used herein pertains generally to an aryl group, an arylene group, a heteroaryl group, a heteroarylene group, an aryl group and an adjacent vinylene group ("aryl vinylene"), an arylene group and an adjacent vinylene group ("arylene vinylene"), a heteroaryl group and an adjacent vinylene group ("heteroaryl vinylene"), a heteroarylene group and an adjacent vinylene group ("heteroarylene vinylene"), an aryl group and an adjacent ethynylene group ("aryl ethynylene"), an arylene group and an adjacent ethynylene group ("arylene ethynylene"), a heteroaryl group and an adjacent ethynylene group ("heteroaryl ethynylene"), or a heteroarylene group and an adjacent ethynylene group ("heteroarylene ethynylene"), or an aryl or arylene group and an adjacent nitrogen or amine group ("aminoaryl" or "aminoarylene"). As noted above, the term "aryl" includes heteroaryl, but heteroaryl is recited in the above list for completeness. The same applies to the corresponding heterarylene, heteroarylene vinylene and heteroarylene ethynylene.

It will be appreciated that where a particular Ar group is described as including an arylene or heterarylene group, but where such an arylene or heteroarylene occurs at an end of the molecule and is monovalent, that the particular group will be aryl or heteroaryl. Similarly, it will be appreciated that where a particular Ar group is described as including an aryl or heteraryl group, but where such an aryl or heteraryl occurs within the molecule and is bivalent, that the particular group will be arylene or heteroarylene. The term "vinylene" as used herein pertains to the bivalent radical represented by the formula -CH=CH-.

The term "ethynylene" as used herein pertains to the bivalent radical represented by the formula -C≡C-. The terms "aminoaryl" and "aminoarylene" as used herein pertain generally to an amine group attached to an aryl or arylene. For example, -Ar-N(R)₂ Or -Ar-N(R)-Ar-, wherein R is an amine substituent. The term "poly(arylamine)" as used herein pertains to at least two adjacent arylamine groups. Suitably one or more of the aryl groups is shared between two amine nitrogens. For example, -Ar-(Ar)N-Ar-N(Ar)-Ar-. As is appropriate in the context in which the poly(arylamine) occurs, it will suitably be monodentate or bidentate. The term "alkyl" as used herein pertains to a branched or unbranched monovalent hydrocarbon group, having 1 to 20 carbon atoms. Similarly, an "alkylene" group as used herein refers to a branched or unbranched bivalent hydrocarbon group, having 1 to 20 carbon atoms. It will be understood that alkenyl and alkenylene are the respective terms for a monovalent and bivalent hydrocarbon radical that contains one or more double bonds and that alkynyl and alkynylene are the respective terms for a monovalent and bivalent hydrocarbon radical that contains one or more triple bonds.

The term "carbo," "carbyl," "hydrocarbo," and "hydrocarbyl," as used herein, pertain to compounds and/or groups which have only carbon and hydrogen atoms (but see

"carbocyclic" below).

The term "hetero," as used herein, pertains to compounds and/or groups which have at least one heteroatom, for example, multivalent heteroatoms (which are also suitable as ring heteroatoms) such as boron, silicon, nitrogen, phosphorus, oxygen, sulfur, and selenium (more commonly nitrogen, oxygen, and sulfur) and monovalent heteroatoms, such as fluorine, chlorine, bromine, and iodine.

The term "saturated," as used herein, pertains to compounds and/or groups which do not have any carbon-carbon double bonds or carbon-carbon triple bonds.

The term "unsaturated," as used herein, pertains to compounds and/or groups which have at least one carbon-carbon double bond or carbon-carbon triple bond. Compounds and/or groups may be partially unsaturated or fully unsaturated. The term "monodentate substituents," as used herein, pertains to substituents which have one point of covalent attachment. The term "monovalent monodentate substituents," as used herein, pertains to substituents which have one point of covalent attachment, via a single bond. Examples of such substituents include halo, hydroxy, and alkyl.

The term "bidentate substituents," as used herein, pertains to substituents which have two points of covalent attachment, and which act as a linking group between two other moieties. Examples of such substituents include alkylene and arylene. The term "electron deficient" as used herein pertains to a pi system that has a deficiency of valence electrons such that the pi system (e.g. aryl group) suitably exhibits an electron withdrawing effect on the group to which it is attached. That is, it has a tendency to pull electrons away from the group to which it is attached. Examples of electron deficient aryls include pyridyl, thiazolyl, oxadiazolyl and triazolyl, and their corresponding arylene structures.

The ability of an electron withdrawing aryl group to withdraw electrons from a

neighbouring aryl group tends to make an electron-withdrawing aryl group more electron- dense than a neighbouring aryl group that is not electron-withdrawing, similar to n-type materials used in a Si semiconductor, and thus more able to transport electrons.

Generally, electron-withdrawing groups are groups that create a positive or delta-positive region adjacent to the backbone so as to pull electrons from the backbone toward the substituent.

Preferably the electron deficient pi system has one or more electron withdrawing substituents attached to it. Indeed, the electron deficiency of the group may be caused by the presence of the electron withdrawing substituent(s). Thus, in the case Of Ar₆, the aryl or arylene pi system is electron deficient, for example as a result of attached electron withdrawing groups.

Examples of electron withdrawing groups include -CN, -COOH, halo (especially -F and - Cl), -NO₂, -CO, perfluoroalkyl, ammonio, thionyl, sulfonyl, amido linked via the oxygen, pyridinium, phosphonium, pyridyl, thiazolyl, oxadiazolyl and triazolyl. Functional groups may conveniently be classified as "electron withdrawing" (-δ) or "electron donating" (+δ) groups, relative to hydrogen. Examples of electron donating groups include, but are not limited to, in approximate order of decreasing strength, -O^" , -COO^", -CR₃, -CHR₂, -CH₂R, -CH₃, and -D. Examples of electron withdrawing groups include, but are not limited to, in approximate order of decreasing

strength, -NR₃ ⁺, -SR₂ ⁺, -NH₃ ⁺, -NO₂, -SO₂R, -CN, -SO₂Ar, -COOH, -F, -Cl, -Br, -I₁ -OAr, -C 0OR, -OR, -COR, -SH, -SR, -OH, -Ar, and -CH=CR₂ (wherein Ar denotes an aryl group). See, for example, Ceppi et al., 1973, Tetrahedron Letters, p. 3627. Substituents

The phrase "optionally substituted," as used herein, pertains to a parent group which may be unsubstituted or which may be substituted. Unless otherwise specified, the term "substituted," as used herein, pertains to a parent group which bears one or more substitutents. The term "substituent" is used herein in the conventional sense and refers to a chemical moiety which is covalently attached to, or if appropriate, fused to, a parent group. A wide variety of substituents are well known, and methods for their formation and introduction into a variety of parent groups are also well known.

Examples of substituents are described in more detail below.

Alkyl: As noted above, the term "alkyl," as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 20 carbon atoms (unless otherwise specified), which may be aliphatic or alicyclic, and which may be saturated or unsaturated (e.g., partially unsaturated, fully unsaturated). Thus, the term "alkyl" includes the sub-classes alkenyl, alkynyl, cycloalkyl, cycloalkyenyl, cylcoalkynyl, etc., discussed below.

In the context of alkyl groups, the prefixes (e.g., C_1-4, Ci_-7, Ci_-20, C_2-7, C_3-7, etc.) denote the number of carbon atoms, or range of number of carbon atoms. For example, the term "Ci_-4alkyl," as used herein, pertains to an alkyl group having from 1 to 4 carbon atoms. Examples of groups of alkyl groups include C_1-4alkyl ("lower alkyl"), Ci_-7alkyl, and

Ci_-2Oalkyl. Note that the first prefix may vary according to other limitations; for example, for unsaturated alkyl groups, the first prefix must be at least 2; for cyclic and branched alkyl groups, the first prefix must be at least 3; etc.

Examples of (unsubstituted) saturated alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), propyl (C₃), butyl (C₄), pentyl (C₅), hexyl (C₆), heptyl (C₇), octyl (C₈), nonyl (C₉), decyl (Ci₀), undecyl (Cn), dodecyl (Ci₂), tridecyl (Ci₃), tetradecyl (Cu), pentadecyl (Ci₅), hexadecyl (Ci₆), octadecyl (Ci₈), and eicodecyl (C₂o).

Examples of (unsubstituted) saturated linear alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), n-propyl (C₃), n-butyl (C₄), n-pentyl (amyl) (C₅), n-hexyl (C₆), and n- heptyl (C₇), n-octyl (C8), n-decyl (Ci₀), n-dodecyl (Ci₂), n-tetradecyl (C₁₄), n-hexadecyl (Ci₆), n-octadecyl (Ci₈), and n-eicodecyl (C₂₀).

Examples of (unsubstituted) saturated branched alkyl groups include iso-propyl (C₃), iso-butyl (C₄), sec-butyl (C₄), tert-butyl (C₄), 3-pentyl, iso-pentyl (C₅), 3-methylbutyl, and neo-pentyl (C₅), 3,3-dimethylbutyl, 2-ethylbutyl, 4-methylpentyl, 2-hexyl, 2-heptyl, 2-octyl, 2-ethylhexyl, 3,7-dimethyloctyl, 2-butyloctyl, 2-hexyldecyl, 2-octyldodecyl.

Alkenyl: As noted above, the term "alkenyl," as used herein, pertains to an alkyl group having one or more carbon-carbon double bonds. Examples of groups of alkenyl groups include C_2-4alkenyl, C_2-7alkenyl, C_2-20alkenyl.

Examples of (unsubstituted) unsaturated alkenyl groups include, but are not limited to, ethenyl (vinyl, -CH=CH₂), 1-propenyl (-CH=CH-CH₃), 2-propenyl (allyl, -CH-CH=CH₂), isopropenyl (1-methylvinyl, -C(CH₃)=CH₂), butenyl (C₄), pentenyl (C₅), and hexenyl (C₆).

Alkynyl: As noted above, the term "alkynyl," as used herein, pertains to an alkyl group having one or more carbon-carbon triple bonds. Examples of groups of alkynyl groups include C_2-4alkynyl, C_2-7alkynyl, C_2-20alkynyl.

Examples of (unsubstituted) unsaturated alkynyl groups include, but are not limited to, ethynyl (ethinyl, -C≡CH) and 2-propynyl (propargyl, -CH₂-CsCH).

Cycloalkyl: The term "cycloalkyl," as used herein, pertains to an alkyl group which is also a cyclyl group; that is, a monovalent moiety obtained by removing a hydrogen atom from an alicyclic ring atom of a carbocyclic ring of a carbocyclic compound, which carbocyclic ring may be saturated or unsaturated (e.g., partially unsaturated, fully unsaturated), which moiety has from 3 to 20 carbon atoms (unless otherwise specified), including from 3 to 20 ring atoms. Thus, the term "cycloalkyl" includes the sub-classes cycloalkyenyl and cycloalkynyl. Preferably, each ring has from 3 to 7 ring atoms. Examples of groups of cycloalkyl groups include C_3-2ocycloalkyl, C₃.i₅cycloalkyl, C_3-iocycloalkyl, C_3-7cycloalkyl.

Examples of cycloalkyl groups include, but are not limited to, those derived from:

saturated monocyclic hydrocarbon compounds:

cyclopropane (C₃), cyclobutane (C₄), cyclopentane (C₅), cyclohexane (C₆), cycloheptane (C₇), methylcyclopropane (C₄), dimethylcyclopropane (C₅), methylcyclobutane (C₅), dimethylcyclobutane (C₆), methylcyclopentane (C₆), dimethylcyclopentane (C₇), methylcyclohexane (C₇), dimethylcyclohexane (C₈), menthane (Ci₀);

unsaturated monocyclic hydrocarbon compounds:

cyclopropene (C₃), cyclobutene (C₄), cyclopentene (C₅), cyclohexene (C₆),

methylcyclopropene (C₄), dimethylcyclopropene (C₅), methylcyclobutene (C₅),

dimethylcyclobutene (C₆), methylcyclopentene (C₆), dimethylcyclopentene (C₇), methylcyclohexene (C₇), dimethylcyclohexene (C₈);

saturated polycyclic hydrocarbon compounds:

thujane (C₁₀), carane (C₁₀), pinane (C₁₀), bornane (Ci₀), norcarane (C₇), norpinane (C₇), norbornane (C₇), adamantane (C₁₀), decalin (decahydronaphthalene) (Ci₀);

unsaturated polycyclic hydrocarbon compounds:

camphene (C₁₀), limonene (C₁₀), pinene (C₁₀);

polycyclic hydrocarbon compounds having an aromatic ring:

indene (C_g), indane (e.g., 2,3-dihydro-1 H-indene) (C₉), tetraline

(1 ,2,3,4-tetrahydronaphthalene) (C₁₀), acenaphthene (C₁₂), fluorene (C₁₃), phenalene (C₁₃), acephenanthrene (C₁₅), aceanthrene (C₁₆), cholanthrene (C₂₀).

Alkylidene: The term "alkylidene," as used herein, pertains to a divalent monodentate moiety obtained by removing two hydrogen atoms from an aliphatic or alicyclic carbon atom of a hydrocarbon compound having from 1 to 20 carbon atoms (unless otherwise specified). Examples of groups of alkylidene groups include Ci_-20alkylidene,

C_1-7alkylidene, Ci_-4alkylidene.

Examples of alkylidene groups include, but are not limited to, imethylidene (=CH₂), ethylidene (=CH-CH₃), vinylidene (=C=CH₂), isopropylidene (=C(CH₃)₂), cyclopentylidene, and benzylidene (=CH-Ph). Alkylidyne: The term "alkylidyne," as used herein, pertains to a trivalent monodentate moiety obtained by removing three hydrogen atoms from an aliphatic or alicyclic carbon atom of a hydrocarbon compound having from 1 to 20 carbon atoms (unless otherwise specified). Examples of groups of alkylidyne groups include Ci_-2oalkylidyne,

C_1-7alkylidyne, Ci_-4alkylidyne.

Examples of alkylidyne groups include, but are not limited to, methylidyne ( MDH), ethylidyne ( s€-CH₃), and benzylidyne (≡C-Ph).

Carbocyclyl: The term "carbocyclyl," as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a carbocyclic compound, which moiety has from 3 to 20 ring atoms (unless otherwise specified). Preferably, each ring has from 3 to 7 ring atoms.

In this context, the prefixes (e.g., C_3-2O, C_3-7, C_5-6, etc.) denote the number of ring atoms, or range of number of ring atoms. For example, the term "C_5-6carbocyclyl," as used herein, pertains to a carbocyclyl group having 5 or 6 ring atoms. Examples of groups of carbocyclyl groups include C_3-2ocarbocyclyl, C_3-10carbocyclyl, Cs-iocarbocyclyl,

Cs-_T-carbocyclyl, and C_5-7carbocyclyl.

Examples of carbocyclic groups include, but are not limited to, those described above as cycloalkyl groups; and those described below as carboaryl groups. Heterocyclyl: The term "heterocyclyl," as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound, which moiety has from 3 to 20 ring atoms (unless otherwise specified), of which from 1 to 10 are ring heteroatoms. Preferably, each ring has from 3 to 7 ring atoms, of which from 1 to 4 are ring heteroatoms.

In this context, the prefixes (e.g., C_3-20, C_3-7, C_5-6, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term "C_5-6heterocyclyl," as used herein, pertains to a heterocyclyl group having 5 or 6 ring atoms. Examples of groups of heterocyclyl groups include C_3-20heterocyclyl,

C_5-20heterocyclyl, C_3-15heterocyclyl, C_5-i₅heterocyclyl, C_3-i₂heterocyclyl, C_5-i₂heterocyclyl, C_3-10heterocyclyl, C_5-10heterocyclyl, C_3-7heterocyclyl, C_5-7heterocyclyl, and Cs-eheterocyclyl. Examples of heterocyclyl groups which are also heteroaryl groups are described below with aryl groups. Aryl: As noted above, the term "aryl," as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety may have from 5 to 100 ring atoms (unless otherwise specified). Preferably, each ring has from 5 to 7 ring atoms. In this context, the prefixes (e.g., C_5-2O, C_5-7, C_5-6, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term "C₅.₆aryl," as used herein, pertains to an aryl group having 5 or 6 ring atoms.

Examples of groups of aryl groups include C_5-2oaryl, C_5-15aryl, C_5-i₂aryl, C_5-i₀aryl, C_5-7aryl, C_5-6aryl, C₅aryl, and C₆aryl.

The ring atoms may be all carbon atoms, as in "carboaryl groups." Examples of carboaryl groups include C_5-100carboaryl, C_5-20carboaryl, C_5-15carboaryl, C_5-12carboaryl,

C_5-iocarboaryl, C_5-7carboaryl, C_5-6carboaryl, C₅carboaryl, and C₆carboaryl. Examples of carboaryl groups include, but are not limited to, those derived from benzene (i.e., phenyl) (C₆), naphthalene (Ci₀), azulene (C₁₀), anthracene (C₁₄), phenanthrene (C₁₄), naphthacene (Ci₈), and pyrene (C₁₆).

Examples of aryl groups which comprise fused rings, at least one of which is an aromatic ring, include, but are not limited to, groups derived from indane (e.g., 2,3-dihydro-1 H- indene) (C₉), indene (C₉), isoindene (C₉), tetraline (1 ,2,3,4-tetrahydronaphthalene (C₁₀), acenaphthene (C₁₂), fluorene (Ci₃), phenalene (Ci₃), acephenanthrene (Ci₅), and aceanthrene (Ci₆). Alternatively, the ring atoms may include one or more heteroatoms, as in "heteroaryl groups." Examples of heteroaryl groups include C_5-i₀₀heteroaryl, C_5-20heteroaryl,

C_5-i₅heteroaryl, C_5-i₂heteroaryl, C_5-i₀heteroaryl, C_5-7heteroaryl, C_5-6heteroaryl,

C₅heteroaryl, and C₆heteroaryl. Examples of monocyclic heteroaryl groups include, but are not limited to, those derived from: N₁: pyrrole (azole) (C₅), pyridine (azine) (C₆);

O₁: furan (oxole) (C₅);

Si : thiophene (thiole) (C₅);

N₁O₁: oxazole (C₅), isoxazole (C₅), isoxazine (C₆);

N₂O₁: oxadiazole (furazan) (C₅);

N₃O₁: oxatriazole (C₅);

N₁S₁: thiazole (C₅), isothiazole (C₅);

N₂: imidazole (1 ,3-diazole) (C₅), pyrazole (1 ,2-diazole) (C₅), pyridazine (1 ,2-diazine) (C₆), pyrimidine (1 ,3-diazine) (C₆) (e.g., cytosine, thymine, uracil), pyrazine (1 ,4-diazine) (C₆); N₃: triazole (C₅), triazine (C₆); and,

N₄: tetrazole (C₅).

Examples of heterocyclic groups (some of which are also heteroaryl groups) which comprise fused rings, include, but are not limited to:

Cgheterocyclic groups (with 2 fused rings) derived from benzofuran (O₁), isobenzofuran (O₁), indole (N₁), isoindole (N₁), indolizine (N₁), indoline (N₁), isoindoline (N-i), purine (N₄) (e.g., adenine, guanine), benzimidazole (N₂), indazole (N₂), benzoxazole (N₁Oi), benzisoxazole (N₁Oi), benzodioxole (O₂), benzofurazan (N₂O₁), benzotriazole (N₃), benzothiofuran (S₁), benzothiazole (N₁S₁), benzothiadiazole (N₂S);

C₁₀heterocyclic groups (with 2 fused rings) derived from chromene (O₁), isochromene (O₁), chroman (O-i), isochroman (Oi), benzodioxan (O₂), quinoline (Ni), isoquinoline (Ni), quinolizine (Ni), benzoxazine (N₁O₁), benzodiazine (N₂), pyridopyridine (N₂), quinoxaline (N₂), quinazoline (N₂), cinnoline (N₂), phthalazine (N₂), naphthyridine (N₂), pteridine (N₄); Cnheterocylic groups (with 2 fused rings) derived from benzodiazepine (N₂);

Ci₃heterocyclic groups (with 3 fused rings) derived from carbazole (Ni), dibenzofuran (Oi), dibenzothiophene (Si), carboline (N₂), perimidine (N₂), pyridoindole (N₂); and,

Ci₄heterocyclic groups (with 3 fused rings) derived from acridine (Ni), xanthene (Oi), thioxanthene (Si), oxanthrene (O₂), phenoxathiin (O₁S₁), phenazine (N₂), phenoxazine (Niθi), phenothiazine (N₁Si), thianthrene (S₂), phenanthridine (Ni), phenanthroline (N₂), phenazine (N₂).

Heterocyclic groups (including heteroaryl groups) which have a nitrogen ring atom in the form of an -NH- group may be N-substituted, that is, as -NR-. For example, pyrrole may be N-methyl substituted, to give N-methylpyrrole. Examples of N-substitutents include, but are not limited to C_1-7alkyl, C_3-20heterocyclyl, C_5-2oaryl, and acyl groups. Heterocyclic groups (including heteroaryl groups) which have a nitrogen ring atom in the form of an -N= group may be substituted in the form of an N-oxide, that is, as -N(→O)= (also denoted -N⁺(→-O^")=). For example, quinoline may be substituted to give quinoline N- oxide; pyridine to give pyridine N-oxide; benzofurazan to give benzofurazan N-oxide (also known as benzofuroxan).

The above groups, whether alone or part of another substituent, may themselves optionally be substituted with one or more groups selected from themselves and the additional substituents listed below.

Hydrogen: -H. Note that if the substituent at a particular position is hydrogen, it may be convenient to refer to the compound or group as being "unsubstituted" at that position.

Halo: -F, -Cl, -Br, and -I.

Hydroxy: -OH.

Ether: -OR, wherein R is an ether substituent, for example, a Ci_-7alkyl group (also referred to as a C-ι_-7alkoxy group, discussed below), a C_3-2oheterocyclyl group (also referred to as a C_3-20heterocyclyloxy group), or a C_5-20aryl group (also referred to as a C_5-2oaryloxy group), preferably a Ci_-7alkyl group.

Alkoxy: -OR, wherein R is an alkyl group, for example, a Ci_-7alkyl group. Examples of Ci_-7alkoxy groups include, but are not limited to, -OMe (methoxy), -OEt (ethoxy), -O(nPr) (n-propoxy), -O(iPr) (isopropoxy), -O(nBu) (n-butoxy), -O(sBu) (sec-butoxy), -O(iBu) (isobutoxy), and -O(tBu) (tert-butoxy).

Acetal: -CH(OR¹ )(OR²), wherein R¹ and R² are independently acetal substituents, for example, a C-ι_-7alkyl group, a C_3-2oheterocyclyl group, or a C_5-2oaryl group, preferably a C_1-7alkyl group, or, in the case of a "cyclic" acetal group, R¹ and R², taken together with the two oxygen atoms to which they are attached, and the carbon atoms to which they are attached, form a heterocyclic ring having from 4 to 8 ring atoms. Examples of acetal groups include, but are not limited to, -CH(OMe)₂, -CH(OEt)₂, and -CH(OMe)(OEt). Oxo (keto, -one): =0. Thione (thioketone): =S. lmino (imine): =NR, wherein R is an imino substituent, for example, hydrogen, C_1-7alkyl group, a C_3-2oheterocyclyl group, or a C_5-2oaryl group, preferably hydrogen or a Ci_-7alkyl group. Examples of ester groups include, but are not limited to, =NH, =NMe, =NEt, and =NPh.

Formyl (carbaldehyde, carboxaldehyde): -C(=O)H. Acyl (keto): -C(=O)R, wherein R is an acyl substituent, for example, a C-|.₇alkyl group (also referred to as Ci_-7alkylacyl or C_1-7alkanoyl), a C_3-20heterocyclyl group (also referred to as C_3-2oheterocyclylacyl), or a C_5-2oaryl group (also referred to as C_5-2oarylacyl), preferably a C_1-7alkyl group. Examples of acyl groups include, but are not limited to, -C(=O)CH₃ (acetyl), -C(=O)CH₂CH₃ (propionyl), -C(=O)C(CH₃)₃ (t-butyryl), and -C(=O)Ph (benzoyl, phenone).

Carboxy (carboxylic acid): -C(=O)OH.

Thiocarboxy (thiocarboxylic acid): -C(=S)SH.

Thiolocarboxy (thiolocarboxylic acid): -C(=O)SH.

Thionocarboxy (thionocarboxylic acid): -C(=S)OH. Ester (carboxylate, carboxylic acid ester, oxycarbonyl): -C(=O)OR, wherein R is an ester substituent, for example, a Ci_-7alkyl group, a C_3-2oheterocyclyl group, or a C_5-2oaryl group, preferably a C_1-7alkyl group. Examples of ester groups include, but are not limited to, -C(=O)OCH₃, -C(=O)OCH₂CH₃, -C(=O)OC(CH₃)₃, and -C(O)OPh. Acyloxy (reverse ester): -OC(=O)R, wherein R is an acyloxy substituent, for example, a C-ι_-7alkyl group, a C_3-2oheterocyclyl group, or a C_5-20aryl group, preferably a C-i_-7alkyl group. Examples of acyloxy groups include, but are not limited to, -OC(=O)CH₃

(acetoxy), -OC(=O)CH₂CH₃, -OC(=O)C(CH₃)₃, -OC(=O)Ph, and -OC(=O)CH₂Ph. Oxycarboyloxy: -0C(=0)0R, wherein R is an ester substituent, for example, a Ci_-7alkyl group, a C_3-20heterocyclyl group, or a C_5-20aryl group, preferably a Ci_-7alkyl group. Examples of ester groups include, but are not limited

to, -OC(=O)OCH₃, -OC(=O)OCH₂CH₃, -OC(=O)OC(CH₃)₃, and -OC(=O)OPh.

Amino: -NR¹R², wherein R¹ and R² are independently amino substituents, for example, hydrogen, a C_1-7alkyl group (also referred to as C_1-7alkylamino or di-C_1-7alkylamino), a C_3-2oheterocyclyl group, or a C_5-2oaryl group, preferably H or a Ci_-7alkyl group, or, in the case of a "cyclic" amino group, R¹ and R², taken together with the nitrogen atom to which they are attached, form a heterocyclic ring having from 4 to 8 ring atoms. Amino groups may be primary (-NH₂), secondary (-NHR¹), or tertiary (-NHR¹R²), and in cationic form, may be quaternary (-⁺NR¹R²R³). Examples of amino groups include, but are not limited to, -NH₂, -NHCH₃, -NHC(CH₃)₂, -N(CH₃J₂, -N(CH₂CH₃)₂, and -NHPh. Examples of cyclic amino groups include, but are not limited to, aziridino, azetidino, pyrrolidino, piperidino, piperazino, morpholino, and thiomorpholino. Amido (carbamoyl, carbamyl, aminocarbonyl, carboxamide): -C(=O)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of amido groups include, but are not limited

to, -C(=O)NH₂, -C(=O)NHCH₃, -C(=O)N(CH₃)₂, -C(=O)NHCH₂CH₃,

and -C(=O)N(CH₂CH₃)₂, as well as amido groups in which R¹ and R², together with the nitrogen atom to which they are attached, form a heterocyclic structure as in, for example, piperidinocarbonyl, morpholinocarbonyl, thiomorpholinocarbonyl, and piperazinocarbonyl.

Thioamido (thiocarbamyl): -C(=S)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of amido groups include, but are not limited to, -C(=S)NH₂, -C(=S)NHCH₃, -C(=S)N(CH₃)₂, and -C(=S)NHCH₂CH₃.

Acylamido (acylamino): -NR¹C(=O)R², wherein R¹ is an amide substituent, for example, hydrogen, a Ci_-7alkyl group, a C_3-20heterocyclyl group, or a C_5-20aryl group, preferably hydrogen or a C_1-7alkyl group, and R² is an acyl substituent, for example, a C_1-7alkyl group, a C_3-20heterocyclyl group, or a C_5-20aryl group, preferably hydrogen or a C_1-7alkyl group. Examples of acylamide groups include, but are not limited to, -NHC(=O)CH₃ , -NHC(=O)CH₂CH₃, and -NHC(=O)Ph. R¹ and R² may together form a cyclic structure, as in, for example, succinimidyl, maleimidyl, and phthalimidyl:

Aminocarbonyloxy: -OC(=O)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of aminocarbonyloxy groups include, but are not limited to, -OC(=O)NH₂, -OC(=O)NHMe, -OC(=O)NMe₂, and -OC(=O)NEt₂.

Ureido: -N(R¹)CONR²R³ wherein R² and R³ are independently amino substituents, as defined for amino groups, and R1 is a ureido substituent, for example, hydrogen, a Ci_-7alkyl group, a C_3-2oheterocyclyl group, or a C_5-20aryl group, preferably hydrogen or a C_1-7alkyl group. Examples of ureido groups include, but are not limited to, -NHCONH₂, - NHCONHMe, -NHCONHEt, -NHCONMe₂, -NHCONEt₂, -NMeCONH₂, - NMeCONHMe, -NMeCONHEt, -NMeCONMe₂, and -NMeCONEt₂.

Tetrazolyl: a five membered aromatic ring having four nitrogen atoms and one carbon atom,

Imino: =NR, wherein R is an imino substituent, for example, for example, hydrogen, a C_1-7alkyl group, a C_3-2oheterocyclyl group, or a C_5-20aryl group, preferably H or a Ci_-7alkyl group. Examples of imino groups include, but are not limited to, =NH, =NMe, and =NEt.

Amidine (amidino): -C(=NR)NR₂, wherein each R is an amidine substituent, for example, hydrogen, a C_1-7alkyl group, a C_3-2oheterocyclyl group, or a C_5-20aryl group, preferably H or a Ci_-7alkyl group. Examples of amidine groups include, but are not limited

to, -C(=NH)NH₂, -C(=NH)NMe₂, and -C(=NMe)NMe₂.

Nitro: -NO₂.

Nitroso: -NO. Cyano (nitrile, carbonitrile): -CN. Isocyano: -NC. Cyanato: -OCN. Isocyanato: -NCO.

Thiocyano (thiocyanato): -SCN. lsothiocyano (isothiocyanato): -NCS.

In many cases, substituents are themselves substituted. For example, a C_1-7alkyl group may be substituted with, for example:

hydroxy (also referred to as a hydroxy-C_1-7alkyl group);

halo (also referred to as a halo-Ci_-7alkyl group);

amino (also referred to as a amino-Ci_-7alkyl group);

carboxy (also referred to as a carboxy-Ci_-7alkyl group);

Ci_-7alkoxy (also referred to as a Ci_-7alkoxy-Ci_-7alkyl group);

C_5-2oaryl (also referred to as a C_5-2oaryl-Ci_-7alkyl group).

Similarly, a C_5-2oaryl group may be substituted with, for example:

hydroxy (also referred to as a hydroxy-C_5-2oaryl group);

halo (also referred to as a halo-C_5-20aryl group);

amino (also referred to as an amino-C_5-2oaryl group, e.g., as in aniline);

carboxy (also referred to as an carboxy-C_5-20aryl group, e.g., as in benzoic acid);

Ci_-7alkyl (also referred to as a C_1-7alkyl-C_5-20aryl group, e.g., as in toluene);

C_1-7alkoxy (also referred to as a Ci_-7alkoxy-C_5-2oaryl group, e.g., as in anisole);

C_5-20aryl (also referred to as a C_5-2oaryl-C_5-2oaryl, e.g., as in biphenyl).

These and other specific examples of such substituted-substituents are described below. Hydroxy-C-i_-7alkyl: The term " hyd TOXy-C_{1 -7}a Iky I," as used herein, pertains to a C-ι_-7alkyl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been replaced with a hydroxy group. Examples of such groups include, but are not limited

to, -CH₂OH, -CH₂CH₂OH, and -CH(OH)CH₂OH.

Halo-Ci_-7alkyl group: The term " halo-C_1-7alkyl," as used herein, pertains to a C_1-7alkyl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been replaced with a halogen atom (e.g., F, Cl, Br, I). If more than one hydrogen atom has been replaced with a halogen atom, the halogen atoms may independently be the same or different. Every hydrogen atom may be replaced with a halogen atom, in which case the group may conveniently be referred to as a C-i_-7perhaloalkyl group." Examples of such groups include, but are not limited to, -CF₃, -CHF₂, -CH₂F, -CCI₃, -CBr₃, -CH₂CH₂F, -CH₂CHF₂, and -CH₂CF₃.

Amino-C_1-7alkyl: The term " amino-C_1-7alkyl," as used herein, pertains to a C_halky! group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been replaced with an amino group. Examples of such groups include, but are not limited to, -CH₂NH₂, -CH₂CH₂NH₂, and -CH₂CH₂N(CHs)₂.

Carboxy-C-ι_-7alkyl: The term "carboxy-Ci_-7alkyl," as used herein, pertains to a C_1-7alkyl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been replaced with a carboxy group. Examples of such groups include, but are not limited to, -CH₂COOH and -CH₂CH₂COOH.

C_1-7alkoxy-Ci_-7alkyl: The term "Ci_-7alkoxy-Ci_-7alkyl," as used herein, pertains to a C_1-7alkyl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been replaced with a

Ci_-7alkoxy group. Examples of such groups include, but are not limited

to, -CH₂OCH₃, -CH₂CH₂OCH₃, and ,-CH₂CH₂OCH₂CH₃

C_5-20aryl-Ci_-7alkyl: The term "C_5-20aryl-C_1-7alkyl," as used herein, pertains to a Ci_-7alkyl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been replaced with a C_5- ₂oaryl group. Examples of such groups include, but are not limited to, benzyl

(phenylmethyl, PhCH₂-), benzhydryl (Ph₂CH-), trityl (triphenylmethyl, Ph₃C-), phenethyl (phenylethyl, Ph-CH₂CH₂-), styryl (Ph-CH=CH-), cinnamyl (Ph-CH=CH-CH₂-).

Hydroxy-C_5-20aryl: The term " hydroxy-C_5-20aryl," as used herein, pertains to a C_5-20aryl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been substituted with an hydroxy group. Examples of such groups include, but are not limited to, those derived from: phenol, naphthol, pyrocatechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol.

Halo-C_5-2oaryl: The term "halo-C_5-2oaryl," as used herein, pertains to a C_5-2oaryl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been substituted with a halo (e.g., F, Cl, Br, I) group. Examples of such groups include, but are not limited to, halophenyl (e.g., fluorophenyl, chlorophenyl, bromophenyl, or iodophenyl, whether ortho-, meta-, or para- substituted), dihalophenyl, trihalophenyl, tetrahalophenyl, and pentahalophenyl. C_1-7alkyl-C_5-2oaryl: The term "C_1-7alkyl-C_5-2oaryl," as used herein, pertains to a C_5-2oaryl group in which at least one hydrogen atom (e.g., 1 , 2, 3) has been substituted with a Ci_-7alkyl group. Examples of such groups include, but are not limited to, tolyl (from toluene), xylyl (from xylene), mesityl (from mesitylene), and cumenyl (or cumyl, from cumene), and duryl (from durene).

Hydroxy-Ci_-7alkoxy: -OR, wherein R is a hydroxy-C-ι_-7alkyl group. Examples of

hydroxy-Ci_-7alkoxy groups include, but are not limited to, -OCH₂OH, -OCH₂CH₂OH, and -OCH₂CH₂CH₂OH. Halo-C_1-7alkoxy: -OR, wherein R is a halo-Ci_-7alkyl group. Examples of halo-C-i_-7alkoxy groups include, but are not limited

to, -OCF₃, -OCHF₂, -OCH₂F, -OCCI₃, -OCBr₃, -OCH₂CH₂F, -OCH₂CHF₂, and -OCH₂CF₃.

Carboxy-C-ι_-7alkoxy: -OR, wherein R is a carboxy-Ci_-7alkyl group. Examples of carboxy- C_1-7alkoxy groups include, but are not limited to, -OCH₂COOH, -OCH₂CH₂COOH, and -OCH₂CH₂CH₂COOH.

Ci_-7alkoxy-C-ι_-7alkoxy: -OR, wherein R is a Ci_-7alkoxy-C_1-7alkyl group. Examples of C_1-7alkoxy-C_1-7alkoxy groups include, but are not limited to, -OCH₂OCH₃, -OCH₂CH₂OCH₃, and -OCH₂CH₂OCH₂CH₃.

C_5-20aryl-Ci_-7alkoxy: -OR, wherein R is a C_5-2oaryl-C_1-7alkyl group. Examples of such groups include, but are not limited to, benzyloxy, benzhydryloxy, trityloxy, phenethoxy, styryloxy, and cimmamyloxy. Ci_-7alkyl-C₅-₂oaryloxy: -OR, wherein R is a C_1-7alkyl-C_5-2oaryl group. Examples of such groups include, but are not limited to, tolyloxy, xylyloxy, mesityloxy, cumenyloxy, and duryloxy. Amino-C_1-7alkyl-amino: The term "amino-C_1-7alkyl-amino," as used herein, pertains to an amino group, -NR¹R², in which one of the substituents, R¹ or R², is itself a amino-C_1-7alkyl group (-Ci_-7alkyl-NR³R⁴). The amino-Ci_-7alkylamino group may be represented, for example, by the formula -NR¹-Ci_-7alkyl-NR³R⁴. Examples of such groups include, but are not limited to, groups of the formula -NR¹(CH₂)_nNR¹R², where n is 1 to 6 (for

example, -NHCH₂NH₂, -NH(CH₂)₂NH₂, -NH(CH₂)₃NH₂, -NH(CH₂)₄NH_2> -NH(CH₂)₅NH₂, -NH (CH₂)₆NH₂), -NHCH₂NH(Me), -NH(CH₂)₂NH(Me), -NH(CH₂)₃NH(Me), -NH(CH₂)₄NH(Me), - NH(CH₂)₅NH(Me), -NH(CH₂)₆NH(Me), -NHCH₂NH(Et), -NH(CH₂)₂NH(Et), -NH(CH₂)₃NH(Et ), -NH(CH₂)₄NH(Et), -NH(CH₂)₅NH(Et), and -NH(CH₂)₆NH(Et). Certain Preferred Substituents

In one preferred embodiment, the substituent(s), often referred to herein as R, are independently selected from: halo; hydroxy; ether (e.g., C-i_-7alkoxy); formyl; acyl (e.g., C_1-7alkylacyl , C_5-20arylacyl); acylhalide; carboxy; ester; acyloxy; amido; acylamido;

thioamido; tetrazolyl; amino; nitro; nitroso; azido; cyano; isocyano; cyanato; isocyanato; thiocyano; isothiocyano; sulfhydryl; thioether (e.g., Ci_-7alkylthio); sulfonic acid; sulfonate; sulfone; sulfonyloxy; sulfinyloxy; sulfamino; sulfonamino; sulfinamino; sulfamyl;

sulfonamido; Ci_-7alkyl (including, e.g., unsubstituted Ci_-7alkyl, Ci_-7haloalkyl,

C_1-7hydroxyalkyl, C-i_-7carboxyalkyl, Ci_-7aminoalkyl, C_5-20aryl-C_1-7alkyl); C_3-20heterocyclyl; or C_5-20aryl (including, e.g., C_5-20carboaryl, C_5-20heteroaryl, C_1-7alkyl-C_5-20aryl and

C_5-20haloaryl)).

In one preferred embodiment, the substituent(s), often referred to herein as R, are independently selected from: -F, -Cl, -Br, -I, -OH, -OMe, -OEt, -SH, - SMe, -SEt, -C(=O)Me, -C(=O)OH, -C(=O)OMe, -CONH₂, -CONHMe, -NH₂, -NMe₂, - NEt₂, -N(nPr)₂, -N(IPr)₂, -CN, - NO₂, -Me, -Et, -CF₃, -OCF₃, -CH₂OH, -CH₂CH₂OH, -CH₂NH₂, -CH₂CH₂NH₂, and -Ph.

In one preferred embodiment, the substituent(s), often referred to herein as R, are independently selected from: hydroxy; ether (e.g., Ci_-7alkoxy); ester; amido; amino; and, C_1-7alkyl (including, e.g., unsubstituted Ci_-7alkyl, Ci_-7haloalkyl, Ci_-7hydroxyalkyl,

C_1-7carboxyalkyl, C_1-7aminoa!kyl, C₅.₂₀aryl-Ci_-7alkyl). BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will now be described with reference to the accompanying figures, in which:

Figure 1 shows a schematic illustration of the compounds described herein;

Figure 2 shows the UV spectra for compounds 1 to 4;

Figure 3 shows the photoluminescence (PL) spectra for compounds 1 to 4 in toluene;

Figure 4 shows the UV spectra of compound 1, compound 2 and comparative compounds A and B, in toluene;

Figure 5 shows the PL spectra of compound 1 , compound 2 and comparative compounds A and B, in toluene;

Figure 6 shows the I-V-L characteristics of OLED devices using 4% of compound 1 in CBP and pure compound 1 as the emissive layers; and

Figure 7 shows the current efficiency vs voltage of OLED devices using 4% of compound 1 in CBP and pure compound 1 as the emissive layers.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention is further described with reference to the following examples, being embodiments of the present invention.

Whilst a number of features are referred to in the examples in the context of specific combinations of features and, where appropriate, with those features having particular values, it is to be understood that any one of those features can be present in other embodiments of the invention with or without other features. Similarly, any particular values associated with a feature may be adjusted in accordance with the general disclosures given herein.

Instruments and characterisation methods Nuclear magnetic resonance (NMR) spectra were collected on a Bruker DPX 400 MHz spectrometer using chloroform-d or dichloromethane-d₂ as the solvent and

tetramethylsilane (TMS) as an internal standard. Matrix-Assisted Laser Desorption/lonization Time-Of-Flight (MALDI-TOF) mass spectra were obtained on a Bruker Autoflex TOF/TOF instrument.

Differential scanning calorimetry (DSC) was carried out under nitrogen on a TA Instrument DSC 2920 module (scanning rate of 20 °C/min).

Thermal gravimetric analysis (TGA) was carried out using a TA Instrument TGA 2050 module (heating rate of 20 °C/min).

Cyclic voltammetry (CV) experiments were performed on an Autolab potentiostat (model PGSTAT30). All CV measurements were recorded in dichloromethane with 0.1 M tetrabutylammonium hexafluorophosphate as supporting electrolyte (scan rate of 50 mV/s) using a conventional three electrode configuration consisting of a platinum wire working electrode, a gold counter electrode, and a Ag/AgCI in 3 M KCI reference electrode. The measured potentials were converted to SCE (saturated calomel electrode) and the corresponding ionization potential (IP) and electron affinity (EA) values were derived from the onset redox potentials, based on -4.4 eV as the SCE energy level relative to vacuum (EA = E_red._onset + 4.4 eV, IP = E_ox-onset + 4.4 eV).

The absorption spectra were recorded on a Shimadzu UV-3101 PC UV-vis-NIR spectrophotometer using dichloromethane solution, except where stated otherwise, with concentration ranging from 1.8 * 10^"6 to 3.1 x 10^~6 M.

Synthesis

The following schemes show the methodology used to produce the ambipolar compounds of the present invention.

Part I— synthesis of intermediates Example 1 - Synthesis of compound A 1

To a mixture of 4-cyanophenylboronic acid (3.15 g, 21.4 mmol), 9,9-dihexyl-2,7- dibromofluorene (21.14g, 43.0 mmol), and tetrakis(triphenylphosphine)palladium (0.495 g, 0.428 mmol, 2% per C-Br bond), was added degassed K₂CO₃ aqueous solution (100 ml_) and degassed toluene (150 ml_). The solution was refluxed under N₂ protection for 24 h. The resulting brown solution was extracted with CH₂CI₂ (100 ml_ * 4). The combined organic layers were dried over MgSO₄ and evaporated under reduced pressure to remove the solvent. The residue was then purified with a silicon gel column using CH₂CI₂/hexane (1 :2) as the eluent to obtain the desired product as a light yellow solid (7.40 g, 67% yield). ¹H NMR (400 MHz, CDCI₃): δ (ppm) 7.75 - 7.77 (m, 5H), 7.56 -7.60 (m, 2H), 7.47 - 7.52 (m, 3H), 1.95 - 2.04 (m, 4H), 1.06 - 1.15 (m, 12H), 0.77 (t, 6H, J = 7.6 Hz), 0.62 - 0.66 (m, 4H).

Example 2 - Synthesis of compound A3

In the same mannar as discribed for compound A1 , the reaction between 4- cynaphenylboronic acid (0.7 g, 4.76 mmol) and dibromo-ter(9,9-dihexyl)fluorene (11.0 g, 9.52 mmol) afforded compound A3 as light yellow solid (4.28 g, 76% yield). ¹H NMR (400 MHz, CDCI₃): δ (ppm) 7.58 - 7.83 (m, 20H), 7.47 -7.49 (m, 2H), 1.98 - 2.13 (m, 12H), 1.09 - 1.15 (m, 36 H), 0.77 - 0.80 (m, 30H).

Example 3 - Synthesis of compound C In the same mannar as discribed for compound A1 , the reaction between 3- cynaphenylboronic acid (0.8 g, 4.76 mmol) and dibromo-ter(9,9-dihexyl)fluorene (11.0 g, 9.52 mmol) afforded compound C as light yellow solid (4.28 g, 56% yield). ¹H NMR (400 MHz, CDCI₃): δ (ppm) 7.96 (s, 1 H), 7.91 (d, 1 H, J = 8.0 Hz), 7.74 -7.84 (m, 6H), 7.54 - 7.70 (m, 12H), 7.47 - 7.49 (m, 1 H), 7.31 - 7.38 (m, 1 H), 1.97 - 2.11 (m, 12H), 1.09 - 1.12 (m, 36 H), 0.77 - 0.80 (m, 30H). Example 4 - Synthesis of compound B1.

To a mixture of compound A1 (5.0 g, 9.73 mmol), bis(pinacolato)diboron (3.70 g, 14.57 mmol), dichloro[1 ,1 '-bis(diphenylphosphino)ferrocene]palladium (240 mg, 0.29 mmol, 3% per C-Br bond), and potassium acetate (1.72 g, 17.53 mmol), was added degassed 1 ,4- dioxane (100 mL). The solution was heated at 80 ⁰C for 3h. The solution was then extracted with CH₂CI₂ (50 mL * 4). The combined organic layers were dried over MgSO₄ and evaporated under reduced pressure to remove the solvent. The residue was then purified with a silicon gel column using CH₂CI₂/hexane (1 :2) as the eluent to obtain the desired product as a light yellow solid (5.16g, 95% yield). ¹H NMR (400 MHz, CDCI₃): δ (ppm) 7.79 - 7.84 (m, 2H), 7.72 - 7.77 (m, 6H), 7.57 (d, 1 H, J = 8.0 Hz), 7.53 (s, 1 H), 1.99 - 2.08 (m, 4H), 1.39 (s, 12H), 1.02 - 1.11 (m, 12H), 0.74 (t, 6H, J = 7.6 Hz), 0.59 - 0.66 (m, 4H).

Example 5 - Synthesis of compound B3

In the same mannar as discribed for compound B1 , the reaction between compound A3 (1.02 g, 0.865 mmol) and bis(pinacolato)diboron (0.263 g, 1.04 mmol) afforded compound B3 as light yellow solid (0.639 g, 60% yield). ¹H NMR (400 MHz, CDCI₃): δ (ppm) 7.57 - 7.85 (m, 22H), 2.05 - 2.14 (m, 12H), 1.39 (s, 12H), 1.05 - 1.12 (m, 36H), 0.72 - 0.83 (m, 30H).

Example 6 - Synthesis of compound D

In the same mannar as discribed for compound B1 , the reaction between compound C (0.6 g, 0.51 mmol) and bis(pinacolato)diboron (0.155 g, 0.61 mmol) afforded compound D as light yellow solid (0.39 g, 62% yield). ¹H NMR (400 MHz, CDCI₃): δ (ppm) 7.96 (s, 1H), 7.91 (d, 1 H₁ J = 7.6 Hz), 7.78 - 7.84 (m, 7H), 7.74 (d, 1 H, J = 7.6 Hz), 7.54 - 7.70 (m, 12 H), 2.04 - 2.11 (m, 12H), 1.40 (s, 12H), 1.07 - 1.12 (m, 36H), 0.70 - 0.82 (m, 30 H).

Part Il - Synthesis of ambipolar compounds

Example 7 - Synthesis of compound 1 To a mixture of compound B1 (4.00 g, 7.13 mmol), 4,4',4"-tris(3,6-dibromocarbazol-0-yl)- triphenylamine (1.15 g, 0.95 mmol), and tetrakis(triphenylphosphine)palladium (0.197 g, 0.17 mmol, 3% per C-Br bond), was added degassed K₂CO₃ aqueous solution (100 ml_) and degassed toluene (150 ml_). The solution was refluxed under N₂ protection for 24 h. The resulting brown solution was extracted with CH₂CI₂ (100 ml_ x 4). The combined organic layers were dried over MgSO₄ and evaporated under reduced pressure to remove the solvent. The residue was then purified with a silicon gel column using CH₂CI₂/hexane (8:1) as the eluent to obtain the desired product as a light yellow solid (1.91 g; 62% yield). ¹H NMR (400 MHz, CD₂CI₂): δ (ppm) 8.62 (s, 6H), 7.66 -7.92 (m, 84H), 2.10 - 2.21 (m, 24H), 1.06 - 1.16 (m, 72H), 0.75 - 0.80 (m, 60H)₁ MS (MALDI): m/z = 3341.99 (calcd. for C₂₄₆H₂₄₆N₁₀: 3342.65). HOMO: - 5.17 eV, LUMO: - 2.02 eV. Quantum efficiency in toluene solution: 0.74.

Example 8 - Synthesis of compound 2

In the same mannar as described for compound 1 , the reaction between compound B3 (0.632 g, 0.515 mmol) and 4,4',4"-tris(3,6-dibromocarbazol-0-yl)-triphenylamine (0.083 g, 0.069 mmol) afforded compound 2 as white solid. (0.305 g, 58% yield). ¹H NMR (400 MHz, CD₂CI₂): δ (ppm) 8.66 (s, 6H), 7.72 - 7.94 (m, 144H), 7.66 (d, 12H, J = 7.6 Hz), 2.13 - 2.20 (m, 72H), 1.11 - 1.20 (m, 216H), 0.76 - 0.83 (m, 180H), MS (MALDI): m/z = 7733.63 (calcd. for C₅₄₆H₆₃₀N₁₀: 7732.91). HOMO: - 5.17 eV, LUMO: - 2.13 eV. Quantum efficiency in toluene solution: 0.72.

Example 9 - Synthesis of compound 3

In the same manner as described for compound 1 , the reaction between compound D (0.318 g, 0.259 mmol) and 4,4',4"-tris(3,6-dibromocarbazol-0.-yl)-triphenylamine (0.035 g, 0.029 mmol) afforded compound 3 as white solid (0.152 g, 72% yield). ¹H NMR (400 MHz, CD₂CI₂): δ (ppm) 8.66 (s, 6H), 8.02 (s, 6H), 7.86 -7.97 (m, 60H), 7.60 - 7.81 (m, 90H), 2.13 - 2.20 (m, 72H), 1.11 - 1.19 (m, 216H), 0.76 - 0.83 (m, 180H), MS (MALDI): m/z = 7333.65 (calcd. for C₅₄₆H₆₃₀N₁₀: 7332.91). HOMO: - 5.16 eV, LUMO: -2.09 eV. Quantum efficiency in toluene solution: 0.65. Example 10 - Synthesis of compound 4

To a mixture of compound A3 (0.537 g, 0.455 mmol), benzidine (17 mg, 0.092 mmol), palladium acetate (6 mg, 0.027 mmol, 5% per C-Br bond), and 1 ,1'- bis(diphenylphosphino)ferrocene (27 mg, 0.048 mmol), was added 25 ml. of degassed dry toluene. The solution was heated at 95 ⁰C for 2 days. Then the solution was extracted with CH₂CI₂ (30 ml_ * 4).. The combined organic layers were dried over MgSO₄ and evaporated under reduced pressure to remove the solvent. The residue was then purified with a silicon gel column using CH₂CI₂/hexane (1.5:1), then ethyl acetate/hexane (1 :4) as the eluents to obtain the desired product as a light yellow solid (0.153 g, 36 % yield). ¹H NMR (400 MHz, CD₂CI₂): δ (ppm) 7.57 - 7.83 (m, 80 H), 7.58 (d, 4H, J = 8.4 Hz), 7.33 (s, 4H), 7.28 (d, 4H, J = 8.4 Hz), 7.16 (d, 4H, J = 8.4 Hz), 1.99 - 2.14 (m, 48H), 1.11 - 1.24 (m, 144H), 0.80 - 0.86 (m, 120H), MS (MALDI): m/z = 4578.92 (calcd. for C₃₄₀H₄₀₈N₆: 4579.08). HOMO: - 4.97 eV, LUMO: -2.15 eV. Quantum efficiency in toluene solution: 0.41.

Example 11 - Synthesis of 2-bromo-9,9-dihexylfluorene

9.8 g of 2-bromofluorene, 39.6 g 1-bromohexane, 2.58 g tetrabutylammonium bromide and 75 ml 50% NaOH were added into a 250 ml round bottom flask. The mixture was stirred and heated to 80 ⁰C over night. The organic layer was separated and the aqueous phase was extracted with ether. The organic layers were washed with brine, and dried with anhydrous MgSO4. The solvent was evaporated and the residue went through a short silica-gel column, yielding 15.45 g of product (93.8%).

Example 12 - Synthesis of 2-bromo-7-nitro-9,9-dihexylfluorene

A mixture of 7.0 g of 2-bromo-9,9-dihexylfluorene, 56.6 ml acetic acid and 3.39 ml 100% HNO3 was stirred for 2 hours, then poured into large amount ice water, basified with Na2CO3 powder until ph>7, extracted by ethyl estate. The organic layers were washed with brine, and dried with anhydrous MgSO4. The solvent was evaporated and the residue went through silica-gel column, yielding 4.91 g of 2-bromo-7-nitro-9,9-dihexylfluorene (63.2%). Example 13 - Synthesis of 2-amino-7-bromo-9,9-dihexylfluorene

2.6 g of Zn powder was carefully gradually added into a mixture of 10 ml of 2-bromo-7- nitro-9,9-dihexylfluorene, 20 ml concentrated HCI and 50 ml ethanol under stirred.

Refluxed the mixture for half hour. After cooled down, the mixture was extracted by ether. The organic layers were washed with brine, and dried with anhydrous MgSO₄. The solvent was evaporated and the residue went through silica-gel column, yielding 3.42 g of 2-amino-7-bromo-9,9-dihexylfluorene (80.1 %).

Example 14 - Synthesis of N,N,N-tris(7-bromo-9,9-dihexylfluoren-7-yl)amine

A mixture of 2.14 g of 2-amino-7-bromo-9,9-dihexylfluorene, 0.72 g of copper (I) oxide, and 10.78 g of 2-bromo-9,9-dihexyl-7-iodo-9H-fluorene in 1-phenoxybenzene was heated to 220 ^°C in an oil bath for 24 hours under N₂ atmosphere. The reaction mixture was cooled to room temperature and then filtered to remove excess copper complex. The filtrate was evaporated to dryness and went through silica gel column to give product, yielding 3.13 g of product (50%).

Example 15 - Synthesis of Compound 5

A mixture of 0.126 g of N,N,N-tris(7-bromo-9,9-dihexylfluoren-7-yl)amine, 0.088 g of 4- cyanophenylboronic acid, and 3.4 mg tetrakis(triphenylphosphine) palladium were added to an air-free two-phase mixture of toluene (15 ml_) and an aqueous 2M Na₂CO₃ solution (12 ml_). The resulting mixture was intensively stirred under argon atmosphere at 110 ⁰C for 24 hours. The organic layer was separated and the aqueous phase was extracted with ether. The organic layers were washed with brine (2 x 50 mL), and dried with anhydrous MgSO₄. The solvent was evaporated and the residue went through silica-gel column. Pure Compound 5 were obtained by recrystallization in heptane, yielding 0.096 g of Compound 5 (71%). ¹H NMR (400 MHz, CDCI3): δ (ppm) 7.756- 7.525 (m, 24H), 7.40- 7.20 (overlapped with CHCI₃, 3H), (s, 3H), 2.013-1.865 (m, 12H), 1.227-1.135 (m, 36H), 0.815-0.697 (m, 30H). MS (MALDI-TOF): m/z = 1318.01 (calcd. for C96H108N4: 1317.86). Anal. Found: C, 87.52; H, 8.25, N, 4.29 (calcd.: C, 87.49; H₁ 8.26; N₁ 4.25). HPLC:

99.87%.

Part III - Device fabrication and measurement

Example 16 - Fabrication of OLED device with configuration of

ITO/PEDOT.PSS/Compound 1/TPBI/LiF/AI

30 mg compound 1 was dissolved in 4 ml of chloroform and filtered through a 0.2 mm PTFE filter for device fabrication. The light-emitting devices were prepared on patterned indium tin oxide (ITO) coated glass substrates. The substrates were cleaned and treated with oxygen plasma and spin-coated with 45 nm of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonic acid) (PSS)₁ followed by drying at 120 °C in air for 15 min. The polymer solutions were spin-coated to form the emitting layer with a thickness of about 40 nm and transferred into a chamber under vacuum of 1 ^χ10^'5 Pa. A 25 nm 1 ,3,5-tris(phenyl-2-benzimidazolyl)benzene (TPBI) was deposited onto the surface of the emitting layer for electron injection and hole blocking. The cathode was composed with 0.5 nm LiF, and 150 nm Al₁ which were thermal deposited sequentially. All the measurements were carried out in air at room temperature. The current-voltage, current- luminance characteristics of the devices were recorded using a Keithley 2420 source meter and a calibrated photodiode. EL spectra were recorded with an Ocean Optics USB2000 miniature fiber optic spectrometer. The photometric data were calculated using current-voltage-luminance data and EL spectra of the devices. The turn on voltage for the device is 3.5 V. Maximum brightness is 4627cd/m². The maximum current efficiency is 1.44 cd/A at 3700 cd/m² (9.5 V) with CIE coordinates of (0.16, 0.14). The I-V-L characteristics and plot for current efficiency vs voltage are illustrated in Figure 6 and Figure 7.

Example 17 - Fabrication OLED device with a configuration of

ITO/PEDOT:PSS/Compound 1 (4%)+CBP/TPBI/LiF/AI

1.2 mg of compound 1 and 28.8 mg of CBP were dissolved in 4 ml of chloroform and filtered through a 0.45 μm PTFE filter for device fabrication. The light-emitting devices were prepared on patterned indium tin oxide (ITO) coated glass substrates. The substrates were cleaned and treated with oxygen plasma and spin-coated with 45 nm of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonic acid) (PSS), followed by drying at 120 °C in air for 15 min. The light emitting molecular solutions were spin-coated to form the emitting layer with a thickness of about 40 nm and transferred into a chamber under vacuum of 1 ^χ10^"5 Pa. A 25 nm 1 ,3,5-tris(phenyl-2- benzimidazolyl)benzene (TPBI) was deposited onto the surface of the emitting layer for electron injection and hole blocking. The cathode was composed with 0.5 nm LiF, and 150 nm Al, which were thermal deposited sequentially. The turn on voltage for the device is 5.5 V. Maximum brightness is 5630 cd/m². The maximum current efficiency is 2.83 cd/A at 534 cd/m² (8.5 V) with CIE coordinates of (0.15, 0.08). The I-V-L characteristics and plot for current efficiency vs voltage are illustrated in Figure 6 and Figure 7.

Results and analysis

Table 1 shows a comparison of values obtained from the UV and PL spectra of compound 1 , compound 2 and comparative compounds A and B disclosed in

WO2008/069756A1 , in toluene.

The examples comprising a hole transporting core and 3 or more peripheral arm substituents have a smaller dipole moment, compared to other ambipolar compounds having fewer arms (for comparison, compounds A and B of WO2008/069756A1 are reported in table 1). Table 1 showed the comparison of the calculated dipole moment between the disclosed compounds (Compound 1 and 2) in this invention and the ambipolar compounds of WO2008/069756A1. UV and PL measurement of the four compounds in toluene solutions showed significant blue shift of both absorption spectra and emissive spectra when the change the chemical structure from asymmetric two arms to symmetric six arms.

The UV and photoluminescence (PL) spectra of compounds 1 to 4 are set out in Figures 2 and 3. The UV spectra of compound 1 and compound 2 are compared with the spectra of comparative compounds A and B in Figure 4. The PL spectra of compound 1 and compound 2 are compared with the spectra of comparative compounds A and B in Figure 5. There is a significant shift to lower wavelengths as a result of providing a compound having the multi-arm structure of compounds 1 and 2. Indeed, the branched multi-arm structure permits considerable flexibility in the emission wavelength: by appropriate adjustment of the emissive portions distributed in the multiple arms, "tuning" of the wavelength can be achieved.

The I-V-L characteristics of OLED devices using 4% of compound 1 in CBP and pure compound 1 as the emissive layers are shown in Figure 6.

The current efficiency vs voltage plot obtained from OLED devices using 4% of compound 1 in CBP and pure compound 1 as the emissive layers are shown in Figure 7. The maximum current efficiency of 2.83 is particularly good, especially in combination with the deep blue emission (corresponding to colour coordinates of 0.15, 0.08).

Claims

1. A compound comprising (1 ) a hole transporting core portion, which hole transporting core portion comprises a tertiary nitrogen portion; and (2) at least three electron transporting arm portions extending from the core portion, each electron transporting arm portion comprising an electron transporting portion and an emissive portion.

2. A compound according to claim 1 , wherein the electron transporting arms are arranged substantially symmetrically around the core portion.

3. A compound according to claim 1 or claim 2, wherein the compound comprises (3) at least one additional arm portion, wherein said additional arm(s) comprises an emissive portion having a bandgap that is larger than the bandgap of said emissive portion of said electron transporting arm(s).

4. A compound according to any one of claims 1 to 3, wherein the total number of arm portions is 4 or more, preferably 6 or more.

5. A compound according to any one of the preceding claims, wherein the compound has the structure according to formula I:

wherein: core portion

and

each of n, p and q is independently 1 to 50

and wherein

at least three of the arm portions are emissive electron transporting arm portions and independently comprise an emissive portion and an electron deficient aryl, aryl vinylene or aryl ethynylene, which is optionally substituted.

6. A compound according to claim 5, wherein the compound has a dipole moment of 0 to 4 debye.

7. A compound according to claim 5 or claim 6, wherein at least one of the arm portions comprises a supplementary emissive portion with a bandgap that is larger than the band gap of the said emissive electron transporting arm portion.

8. A compound according to any one of claims 5 to 7, wherein the tertiary nitrogen portion is selected from nitrogen, triarylamine and poly(arylamine).

9. A compound according to any one of claims 5 to 8, wherein the core portion comprises one, two, three or more tertiary nitrogens.

10. A compound according to any one of claims 5 to 9, wherein each of n, p and q is independently 1 to 20, preferably 1 to 3.

11. A compound according to any one of claims 5 to 10, wherein the core portion

has a structure according to formula Ia:

wherein

each of Ar₁, Ar₂ and Ar₃ is independently arylene, arylene vinylene, arylene ethynylene or aminoarylene, and is optionally substituted;

each of a, b and c is independently 0 to 20; and

I is independently 1 to 20.

12. A compound according to claim 11, wherein, each of Ar-i, Ar₂ and Ar₃ is

independently C_5-i_Ooarylene, C_5-1Ooarylene vinylene, C_5-10oarylene ethynylene or amino C_5- iooarylene, preferably C_5-30arylene, C_5-30arylene vinylene, C_5-30arylene ethynylene or amino C_5-3oarylene, and is optionally substituted.

13. A compound according to any one of claims 5 to 12, wherein any two of An, Ar₂ and Ar₃ are connected to each other by a single bond, O, S, Si or an optionally substituted alkylene.

14. A compound according to any one of claims 5 to 13, wherein each Of Ar₁, Ar₂ and Ar₃ is independently phenylene, fluorenylene, carbazolylene, diarylamino,

spirobifluorenylene, spirosilabifluorenylene, indenocarbazolylene, indenofluorenylene or aminoaryl and is optionally substituted.

15. A compound according to any one of claims 5 to 14, wherein each Of Ar₁, Ar₂ and Ar₃ is independently phenylene or fluorenylene and is optionally substituted.

16. A compound according to any one of the preceding claims, wherein the compound comprises the structure according to formula II:

wherein:

each Of Ar₁, Ar₂ and Ar₃ is independently as defined in claim 11 or claim 12;

each of B₁, B₂ and B₃ is independently as defined in claim 5;

and

each of a, b and c is independently as defined in claim 11 ; and

each of n, p and q is independently as defined in claim 5 or claim 10;

and wherein:

17. A compound according to claim 16, wherein at least one further B₁, B₂ or B₃ comprises a supplementary emissive portion having a bandgap that is larger than the bandgap of the said emissive portion.

18. A compound according to any one of claims 15 to 17, wherein each B₁ is independently (Ar₄)_d(Ar₅)_e , and wherein each Ar₄ and each Ar₅ is independently arylene, arylene vinylene or arylene ethynylene and is optionally substituted; and wherein each of d and e is independently 1 to 20.

19. A compound according to claim 18, wherein each of d and e is independently 1 to 10, preferably 1 to 3.

20. A compound according to any one of claims 17 to 19, wherein each B₂ is independently (Ar₆)_f(Ar₇)_g , and wherein each Ar₆ and each Ar₇ is independently arylene, arylene vinylene or arylene ethynylene and is optionally substituted; and each of f and g is independently 1 to 20.

21. A compound according to claim 20, wherein each of f and g is independently 1 to 10, preferably 1 to 3.

22. A compound according to any one of claims 15 to 21 , wherein each B₃ is independently (Ar₈)_h(Ar_g)i , and wherein each Ar₈ and each Ar₉ is independently arylene, arylene vinylene or arylene ethynylene and is optionally substituted; and each of h and i is independently 1 to 20.

23. A compound according to claim 22, wherein each of h and i is independently 1 to 10, preferably 1 to 3. 24. A compound according to any one of the preceding claims, wherein the compound has the structure according to formula III:

wherein

Ar₁, Ar₂, and Ar₃ are as defined in claim 16; and

each of a, b, c, n, p and q are as defined in claim 16 ;

and wherein

each Of Ar₄, Ar₅, Ar₆, Ar₇, Ar₈ and Ar₉ is independently as defined in claims 18 to

24;

each of d, f and h is independently as defined in claims 18 to 23; and

each of e, g and i is independently as defined in claims 18 to 23;

and wherein

at least three of Ar₅, Ar₇ and Ar₉ selected from [(Ar₄)_d(Ar₅)_e]_π , [(Ar₆)_f(Ar₇)_g]_p and

[(Ar₈)_h(Ar₉)i]_q each independently comprise an electron deficient aryl, aryl vinylene or aryl ethynylene.

25. A compound according to claim 24, wherein each Of Ar₄, Ar₆ and Ar₈ is

independently C_5-i_Ooarylene, C_5-i_OOarylene vinylene or C_5-1Ooarylene ethynylene, preferably C_5-3oarylene, C_5-30arylene vinylene or C_5-30arylene ethynylene, and is optionally

substituted.

26. A compound according to claim 24 or claim 25, wherein any one or more of the pairs of Ar groups Ar₄ and Ar₅, Ar₆ and Ar₇, and Ar₈ and Ar₉ are connected to each other by a single bond, O, S, Si or an optionally substituted alkylene.

27. A compound according to any one of claims 24 to 26, wherein each Of Ar₄, Ar₆ and Ar₈ is independently fluorenylene and is optionally substituted.

28. A compound according to claim 27, wherein each of Ar₄, Ar₆ and Ar₈ is

independently

29. A compound according to any one of claims 24 to 28, wherein each of Ar₅, Ar₇ and Ar₉ is independently C_5-1Ooarylene, C_5-iooarylene vinylene or C_5-i_Ooarylene ethynylene, preferably C_5-3oarylene, C_5-30arylene vinylene or C_5-30arylene ethynylene, and is optionally substituted.

30. A compound according to any one of claims 24 to 29, wherein each of Ar₅, Ar₇ and Ar₉ is independently electron deficient.

31. A compound according to any one of claims 24 to 30, wherein each of Ar₅, Ar₇ and Ar₉ is independently arylene, arylene vinylene or arylene ethynylene substituted with at least one electron withdrawing group.

32. A compound according to claim 31 , wherein each electron withdrawing group is selected independently from: halo, cyano, nitro, carbonyl, thionyl, sulphonyl and perfluoroalkyl.

33. A compound according to any one of claims 24 to 32, wherein each of Ar₅, Ar₇ and Ar₉ is independently phenylene and is optionally substituted.

34. A compound according to claim 33, wherein each of Ar₅, Ar₇ and Arg is

independently cyano substituted phenylene.

35. A compound according to any one of the preceding claims, wherein the compound has the structure according to formula (IV):

wherein

each of Ar_4a and Ar_4b is independently as defined for Ar₄ in claim 24;

each of Ar_5a and Ar_5b is independently as defined for Ar₅ in claim 24;

each of Ar_6a and Ar_6b is independently as defined for Ar₆ in claim 24;

each of Ar_7a and Ar_7b is independently as defined for Ar₇ in claim 24;

each of Ar_8a and Ar_8b is independently as defined for Ar₈ in claim 24; and each of Ar_ga and Ar_gb is independently as defined for Ar₉ in claim 24;

and wherein

each of d-i and d₂ is independently as defined for d in claim 24;

each of ei and e₂ is independently as defined for e in claim 24;

each of f-i and f₂ is independently as defined for f in claim 24;

each of gi and g₂ is independently as defined for g in claim 24;

each of h-i and h₂ is independently as defined for h in claim 24; and each of i-i and i_∑ is independently as defined for i in claim 24;

and wherein

at least three of Ar_5a , Ar_5b , Ar_7a , Ar_7b , Ar_9a and Ar_9b selected from (Ar_4a)di(Ar_5a)ei , (Ar_4b)_d2(Ar_5b)_e2 , (Ar_6a)_fi(Ar_7a)_g1 , (Ar_6b)_f2(Ar_7b)_g2 , (Ar₈₃)I₁₁(Ar₉₃)I₁ and (Ar_8b)_h2(Ar_9b)i₂ are each independently electron deficient aryl, aryl vinylene or aryl ethynylene and are optionally substituted.

36. A compound according to any one of claims 1 to 34, wherein the compound has the structure according to formula (V):

wherein

each of Ar₄, Ar₅, Ar₆, Ar₇, Ar₈ and Ar₉ is independently as defined in claim 24;

Ar₁₀ is independently as defined for Ar₄ in claim 24;

Ar-_{I 1} is is independently as defined for Ar₅ in claim 24;

each of d, e, f, g, h and i are independently as defined in claim 24;

j is independently as defined for d in claim 24; and

k is independently as defined for e in claim 24;

and wherein

at least three Of Ar₅ , Ar₇ , Ar₉ and Ar₁₁ selected from (Ar₄)_d(Ar₅)_e , (Ar₆)_f(Ar₇)_g , (Ar₈)_h(Ar₉)i and (Ar-i O)J(Ar₁ -,)_k are each independently electron deficient aryl, aryl vinylene or aryl ethynylene and are optionally substituted.

37. A thin film comprising a compound according to any one of claims 1 to 36.

38. A light emitting device comprising a compound according to any one of claims 1 to 36 or a thin film according to claim 37.