GB2564134A - Asymmetric mesogens and a method of manufacture - Google Patents

Abstract

Asymmetric mesogens for use in an OLED device, wherein the asymmetric mesogen has the structure (I): E1-(B1)n-A-B2-E2 (I) wherein: (B1)n-A-B2 is a chromophore that comprises a conjugated pi-system, A, B1 and B2 each independently comprise an optionally substituted aromatic ring system; E1 and E2 are end groups which terminate the conjugated pi-system of the chromophore; n is 0 or 1; and wherein the asymmetric mesogen does not possess a C2 symmetry axis. Also shown is an OLED device comprising the asymmetric mesogen and a method of manufacturing an OLED.

Description

The present disclosure relates to asymmetric mesogens, particularly, but not exclusively, asymmetric mesogens for use in an organic light emitting diode (OLED) device. This disclosure also concerns methods for the preparation of the asymmetric mesogens and devices comprising the asymmetric mesogens.

BACKGROUND

An organic light emitting diode (OLED) display is an electroluminescent (EL) display comprising a film of organic compound that emits light in response to an applied electric current. OLED displays have various advantages over other types of flat panel displays, such as LCD and plasma displays, due to their simple manufacturing processes, lower cost, relatively high brightness, low power consumption, wide angle of view and improved response times.

Numerous organic materials are capable of producing electroluminescence. The organic electroluminescent material utilised in OLED displays are categorised into two main families: those based on small molecules and those employing polymers. Both families rely on the use of extended pi-bonding networks or conjugated systems to provide a chromophore with the desired emission characteristics, for example, switch on voltage, colour, efficiency and brightness. The properties of the chromophore may be tuned by adjusting the chromophore conjugation.

In solution or at the solid-liquid interface, small molecule organic EL materials can associate by virtue of the strong van der Waal’s-like attractive force between the extended pi-bonding networks. The interaction of the pi-binding networks in this way can have an effect on the spectral pattern of the material as a whole and are often referred to by change in wavelength of emission, for example, H-aggregation (hypsochromically shifted, i.e. shifted to a shorter wavelength), or J-aggregation (bathochromically shifted, i.e. shifted to a longer wavelength). J-aggregates in dyes have been found to exhibit exceptionally high photoluminescence quantum yields (Chan, Julian M. W.; Tischler, Jonathan R.; Kooi, Steve E.; Bulovic, Vladimir; Swager, Timothy M. (2009). Synthesis of J-Aggregating Dibenz[a,j]anthracene-Based Macrocycles. J. Am. Chem. Soc. 131: 5659-5666); whereas H-aggregates were observed to have low or no fluorescence.

The prior art symmetric small molecule organic EL materials have a tendency to form H-aggregates (Liedtke, A. O’Neill, M. Kelly, S.M. Kitney, S.P. Van Averbeke, B. Boudard, P. Beljonne, D. Cornil, J. (2010). “Optical properties of light-emitting nematic liquid crystals: A joint experimental and theoretical study J. Phys. Chem. B. 114: 11975 - 11982); Therefore previously most small molecule EL materials that are solution processed into thin films have a limit to their emission performance, in particular in terms of their efficiency and brightness. Low brightness and low efficiency therefore remain significant problems to be addressed in the prior art small molecule EL materials used, for example, in OLED displays.

The present invention has been devised to mitigate or overcome at least some of the above-mentioned problems.

SUMMARY OF THE INVENTION

In a first aspect of the present invention is provided an asymmetric mesogen for use in an OLED device, wherein the asymmetric mesogen has the structure (I):

E₁-(B₁)_n-A-B₂-E₂ (I) wherein:

(B₁)_n-A-B₂ is a chromophore that comprises a conjugated pi-system, wherein A, Bt and B₂ each independently comprise an optionally substituted aromatic ring system;

Et and E₂ are end groups which terminate the conjugated pi-system of the chromophore;

n is 0 or 1; and wherein the asymmetric mesogen does not possess a C₂ symmetry axis.

The groups Βτ (when present), A and B₂ within the chromophore (Β^π-Α-Βς may be directly linked or they may be linked by any group suitable for providing a continuous pi-bonding network across the groups and the chromophore as a whole. The link between the groups may be at least one atom or moiety containing suitable bonding p-orbitals, for example heteroatoms such as O or N, optionally substituted carbon-carbon double or triple bonds, and optionally-substituted aromatic or heteroaromatic systems or groups. Typically, the groups Bt (when present), A and B₂ within the chromophore (Β^π-Α-Βς are directly linked

Suitably, the group labelled A is any group that can link the chromophore portions Bt (when present) and B₂ (or Et and B₂ when Bt is not present) to form a contiguous or continuously conjugated pi-bonding system extending from Et to E₂.

Suitably, group A may be an optionally substituted aromatic or heteroaromatic group. Typically, group A may comprise fluorene, vinylethylphenylene, anthracene, perylene, thiophene, phenyl, thieno[3,2-b]thiophene, benzo[1,2-b:4,5-b']dithiophene and derivatives thereof. Useful chromophores are described, for example, in A. Kraft, A. C. Grimsdale and A. B. Holmes, Angew. Chem. Int. Ed. Eng. (1998), 37, 402.

In an embodiment, group A comprises mono- fluorene. Group A may alternatively comprise di- or tri- fluorene. The fluorenes may be linked through any suitable position that maintains pi-conjugation. Typically, the fluorenes are substituted or connected through the 2- and/or 7-positions. Suitably, Group A may be a mono-, dior tri-fluorene optionally substituted or connected through the 2- and/or 7- position.

In embodiments, the fluorene is substituted at the 9-position on the central 5membered ring. Substitution at the 9 position may be partial (mono substitution) or complete (di-substitution), i.e.:

wherein Ri and R₂ may be independently selected from alkyl, aryl, heteroaryl, alkoxy, esters, and amides. Ri and R₂ may be the same or different. The groups may be optionally substituted and, as appropriate, the groups may be branched or straight chained. Suitably, and R₂ are alkyl chains having from 1 to 12 carbon atoms. Typically, Rt and R₂ are the same and have from 6 to 8 carbon atoms. In an embodiment, Rt and R₂ are the same and are hexyl or octyl groups. When group A comprises more than one fluorene group, the Rt and R₂ on each fluorene may be the same or different.

In an embodiment of the present invention the mesogens may have the structure (II):

wherein m is 1, 2, or 3;

Alternatively, in an embodiment A may comprise 2,1,3-benzothiadiazole. In this embodiment, 2,1,3-benzothiadiazole may be substituted at any suitable position on the phenyl ring. Typically, when A comprises 2,1,3-benzothiadiazole, substitution is via the 4- and/or the 7-position. Suitably, A may be a 2,1,3-benzothiadiazole substituted at the 4- and 7-position.

In an embodiment of the present invention the mesogens may have the structure (III):

(HI)

In embodiments, Bt and B₂ are portions of a chromophore each separately comprising a conjugated pi-bonding system that is covalently bonded to A to form a contiguous or continuously conjugated pi-bonding system across BrA-B₂ when Bt is present, and A-B₂ when Bt is not present.

Typically, Βτ and B₂ may each be an optionally substituted aromatic or heteroaromatic group.

Suitably, Bt and B₂ may be independently selected from the group comprising:

In embodiments, Et and E₂ are end groups which terminate the generally linear chromophore BrA-B₂ (when Bt is present) or A-B₂ (when Bt is not present) at each 10 end. Et and E₂ can be any suitable group that provides a point of attachment to at least one end of the chromophore BrA-B₂ (or A-B₂ where Bt is absent) and is (1) a group that terminates the conjugated pi-system of the chromophore; or (2) a group that has either no other substitution or is substituted only by one or more groups that terminate the conjugated pi-system of the chromophore. Et and E₂ may form part of 15 the conjugated pi-system of the chromophore. Suitably, Et and E₂ may comprise groups that interact with the conjugated pi-system of the chromophore, for example groups that may donate or withdraw electron density from the conjugated pi-system of the chromophore. The interaction of the substituent of the end group Et or E₂ may be used to moderate the properties of the chromophore, for example, alter the emission frequency (colour) of the chromophore. Suitably, Et or E₂ may be para-alkoxy phenyl groups:

wherein R₃ is selected from a group consisting of alkyl, alkoxy, ester, and amide. In a specific embodiment, R₃ is a lower alkyl group, suitably methyl, ethyl, propyl, isopropyl, butyl, iso-butyl or tert-butyl. Optionally, R₃ is methyl.

Et and E₂ may provide reactive functionality that enables the asymmetric 10 chromophore to be linked to another molecule or itself via crosslinking or polymerisation process. Suitably, the crosslinking or a polymerisation process may be via radical based polymerisation with the reaction being initiated by, for example, light (for example UV radiation), heat or chemicals such as acid or alkali. Suitable end groups include acrylates, methacrylates and non-conjugated 1,4, 1,5 and 1,6 dienes.

An example of such an end group R₃ is (CH₂)7CO₂CH(CH=CH₂)₂.

Specific embodiments of the asymmetric mesogen according to the present invention are provided below:

Table 1: Structural representations of exemplified asymmetric mesogens according to the present invention.

Compound no.	Structure
13	CeH-isx^CgHis
	[5-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)- 5'-(4-methoxyphenyl)-2,2'-bithiophene]

46	^θΗ-Ιβ^/ΟθΗ-Ιβ y==\ ^6^13^χζ^6^13 rYQ<)-OA_rtA-0_0-<\s H3ccr\^ ΟβΗ17<ΧβΗ17 5-(4-methoxyphenyl)-5'-(9,9,9,9-tetrahexyl-7-(5-(4methoxyphenyl)thiophen-2-yl)-9',9'-dioctyl-[2,2':7',2-terfluoren]-7yl)-2,2'-bithiophene
19
	5-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)- 5-(4-methoxyphenyl)-2,2':5',2-terthiophene
16	C6Hi3><C6Hl3 q
penta-1,4-dien-3-yl-8-(4-(5-(9,9-dihexyl-7-(5'-(4-((8-oxo-8-(penta- 1,4-dien-3-yloxy)octyl)oxy)phenyl)-[2,2'-bithiophen]-5-yl)-fluoren-2yl)thiophen-2-yl)phenoxy)octanoate
39	C6Hi3^zC6Hi3 h3co-/A ΓΛ '==j^y2z~n^s^ys>^C/OCH3
	5-(9,9-άίΗθχγί-7-(4-ΠΊθ1ΗοχγρήθηγΙ)-ΑυοΓθη-2-γΟ-5'-(4- methoxyphenyl)-2,2'-bithiophene
	C6Hi3xX^6Hi3
38	VsA-OCHj
	2-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)-5-(4- methoxyphenyl)thiophene
25	CeHn^XeH-is ¢. /“’N—OCH3
	2-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)- 5-(4-methoxyphenyl)thieno[3,2-b]thiophene

27	θθΗ-ιβχθθΗ-ο s~- 2-(9,9-dihexyl-7-(5'-(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)fluoren-2-yl)-5-(4-methoxyphenyl)thieno[3,2-b]thiophene
33	H3CO^xA
	2-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)- 6-(4-methoxyphenyl)benzo[1,2-b:4,5-b']dithiophene
	HsCO-^ZU /S.. C6Hi3^C6His _
40	2-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)-5-(4- methoxyphenyl)thieno[3,2-b]thiophene
36
	2-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thieno[3,2-b]thiophen-2-yl)- fluoren-2-yl)-6-(4-methoxyphenyl)benzo[1,2-b:4,5-b']dithiophene
57	H;C CeHirO-ve /1 ΡϋΟ'-ΠΤα /'’'.-Ο'-π C,H” LWAJ μΛΧΪΛ7 4-(5'-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2yl)-[2,2'-bithiophen]-5-yl)-7-(5-(9,9-dihexyl-7-(5-(4methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)thiophen-2yl)benzo[c][1,2,5]thiadiazole

47	2-(4-methoxyphenyl)-5-(9,9,9',9'-tetrahexyl-7'-(4-methoxyphenyl)- [2,2'-bifluoren]-7-yl)thiophene
50	lj ι C6H13x<C6H13 __ H'jCO—ZZ FF^ocH3
	5-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)-5-(4- methoxyphenyl)-2,2':5',2-terthiophene
60	f=N-0CH3 h3co^ °θΗΐ3Λ6Η13 CgHi3 CgH-|3
	4-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)- 7-(5-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2yl)thiophen-2-yl)benzo[c][1,2,5] thiadiazole

In an embodiment, specific embodiments of the asymmetric mesogen according to the present invention are identified as compound numbers 13, 46, 19, 39, 38, 25 and 60 above.

In a second aspect of the invention, there is provided an OLED device comprising the asymmetric mesogen of the first aspect of the invention.

In a third aspect of the invention, there is provided a method of manufacturing an OLED device comprising the steps of:

providing a substrate;

depositing a first electrode onto the substrate; and, depositing a light-emitting layer onto the first electrode; wherein the lightemitting layer comprises an asymmetric mesogen of any one of claims 1 to 10;

depositing a second electrode onto the light-emitting layer.

In an embodiment of the third aspect of the invention, the first electrode is a cathode and the second electrode is an anode. In an alternative embodiment, the first electrode is an anode and the second electrode is a cathode.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, reference will now be made, by way of example only, to the accompanying drawings, in which:

Figure 1 is a reaction scheme illustrating the synthesis of a first asymmetric mesogen.

Figure 2 is a reaction scheme illustrating the synthesis of a second asymmetric mesogen.

Figure 3 is a reaction scheme illustrating the synthesis of a third asymmetric mesogen.

Figure 4 is a reaction scheme illustrating the synthesis of a fourth asymmetric mesogen.

Figure 5 is a reaction scheme illustrating the synthesis of a fifth asymmetric mesogen.

Figure 6 is a reaction scheme illustrating the synthesis of a sixth asymmetric mesogen.

Figure 7 is a reaction scheme illustrating the synthesis of a seventh asymmetric mesogen.

Figure 8 is a reaction scheme illustrating the synthesis of an eighth asymmetric mesogen.

Figure 9 is a reaction scheme illustrating the synthesis of a ninth asymmetric mesogen.

Figure 10 is a reaction scheme illustrating the synthesis of a tenth asymmetric mesogen.

Figure 11 is a reaction scheme illustrating the synthesis of an eleventh asymmetric mesogen.

Figure 12 is a reaction scheme illustrating the synthesis of a twelfth asymmetric mesogen.

Figure 13 is a reaction scheme illustrating the synthesis of a thirteenth asymmetric mesogen.

Figure 14 is a reaction scheme illustrating the synthesis of a fourteenth asymmetric mesogen.

DETAILED DESCRIPTION

All references cited herein are incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

The invention relates, in a specific embodiment, to asymmetric mesogens for use in an OLED device. The invention further extends to the preparation of the asymmetric mesogens and to use of the symmetric mesogens in an OLED display

Prior to further setting forth the invention, a number of definitions are provided that will assist in the understanding of the invention.

As used herein, the term comprising means any of the recited elements are necessarily included and other elements may optionally be included in addition. Consisting essentially of” means any recited elements are necessarily included, elements that would materially affect the basic and novel characteristics of the listed elements are excluded, and other elements may optionally be included. Consisting of” means that all elements other than those listed are excluded. Embodiments defined by each of these terms are within the scope of this invention.

The term “mesogen” as used herein is a compound that displays liquid crystal properties. Liquid crystals are a state of matter having properties between those of conventional liquids and solids having the ability to flow like a liquid but having some degree of ordering in the arrangement of its molecules.

The term “asymmetric” in the context of the present invention is to be understood to mean that the structures lack rotational symmetry, i.e. they lack a rotational symmetry axis.

The term “rotational symmetry axis” as used herein refers to an axis around which a rotation by 360°/n (where n is an integer) may result in a molecule being superimposed on, and indistinguishable from, the molecule prior to rotation. This is also called an n-fold rotational axis and can be abbreviated to “C_n” (where n is an integer). The symmetry of the molecule is defined by the structural framework of the molecule as defined by covalent bonding. A molecule does not possess, or lacks, a rotational symmetry axis when there is no rotational symmetry axis present in the molecule, including in any potential rotational variants and/or canonical forms that do not otherwise affect the framework of the molecule.

The terms “C₂ rotational symmetric axis”, “C₂ symmetric axis”, “C₂ rotational symmetry axis”, “C2 symmetry axis” or “C₂ axis” as used herein each refer to a 2-fold symmetry axis, where rotation of 180° around an axis results in a molecule being superimposed on, and indistinguishable from, the molecule prior to rotation.

The term “pi-bonding system” or “π-bonding system”, often referred to as a “conjugated system” as used herein refers to a continuous or contiguous system of connected p-orbitals in which are present delocalised electrons (“pi electrons”).

Pi-bonding and/or conjugated systems generally reduce the energy required to excite an electron from its ground state to an excited state, from which the electron can relax back to the ground state with concomitant emission of light. The energy required for excitation may be provided by any form of energy including light, heat, or electrical potential (voltage). Typically, the energy requirement to excite the electron varies with the length of the conjugated system, with longer conjugated systems generally requiring less energy, leading to emitted light having a lower frequency. A suitable conjugated system can result in emission of light in the visible (coloured) range (approximately wavelengths of approximately 390nm to 700nm). A conjugated system responsible for the emission of light is defined herein as a “chromophore”.

The term “H-aggregation” as used herein refers to an association of one or more mesogens leading to a hypsochromic shift in its emission profile, i.e. a shift to a shorter wavelength. The term “J-aggregation” as used herein refers to an association of one or more mesogens leading to a bathochromic shift in its emission profile, i.e. shifted to a longer wavelength.

The term “substitution” as used herein refers to the replacement of a hydrogen atom in a molecular structure with an atom or group that is not hydrogen.

Referring to the accompanying figures 1 to 14, there are illustrated reaction schemes for the synthesis of reactive mesogens numbered 13, 46, 19, 16, 39, 38, 25, 27, 33, 40, 36, 57, 47, 50 and 60 above.

In Figure 1, there is shown the synthesis of an asymmetric mesogens according to the present invention is prepared by reacting 2-bromo-7-iodo-9,9dihexylfluorene (3) with 2-[(4-methoxyphenyl)-5-tributylstannyl]thiophene (7) to give 2(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) which is subsequently reacted with tributyl(5'-(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12) to provide 5-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)-5'-(4methoxyphenyl)-2,2'-bithiophene (13). Following demethylation the resultant bisphenol compound 4-(5-(9,9-dihexyl-7-(5'-(4-hydroxyphenyl)-[2,2'-bithiophen]-5-yl)fluoren-2-yl)thiophen-2-yl)phenol (14) is alkylated with penta-1,4-dien-3-yl 6bromootanoate (15) to provide the asymmetric mesogen penta-1,4-dien-3-yl-8-(4-(5(9,9-dihexyl-7-(5'-(4-((8-oxo-8-(penta-1,4-dien-3-yloxy)octyl)oxy)phenyl)-[2,2'bithiophen]-5-yl)-fluoren-2-yl)thiophen-2-yl)phenoxy)octanoate (16).

Turning to Figure 2, a further asymmetric mesogen (19) according to the present invention is prepared from the reaction of 2-bromo-5-(9,9-dihexyl-7-(5-(4methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)thiophene (18) with tributyl(5'-(4methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12).

In Figure 3 it is shown that the reactive mesogen (25) is formed from the reaction of 2-(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) and tributyl(5-(4-methoxyphenyl)thieno[3,2-b]thiophen-2-yl)stannane (24). The stannane 24 being previously prepared from 2-(4-methoxyphenyl)thieno[3,2-b]thiophene (23), which is in turn prepared from the reaction of 2-bromothieno[3,2-b]thiophene (21) and 4methoxyphenyl-boronic acid (22).

Figure 4 shows the synthesis a further asymmetric mesogen (27) according to the present invention from the reaction of 2-(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4methoxyphenyl)thieno[3,2-b]thiophene (26) and tributyl(5'-(4-methoxyphenyl)-[2,2'bithiophen]-5-yl)stannane (12). The bromoflourene (26) being formed from reaction of 2-Bromo-7-iodo-9,9-dihexylfluorene (3) and tributyl(5-(4-methoxyphenyl)thieno[3,2b]thiophen-2-yl)stannane (24).

In Figure 5, the synthetic route to another asymmetric mesogen (33) according to the present invention is shown. Benzo[1,2-b:4,5-b']dithiophen-2-yl tributylstannane (29) is formed by stannylation of benzo[1,2-b:4,5-b']dithiophene (28), before it is reacted with 2-(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) to provide 2-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)benzo[1,2b:4,5-b']dithiophene (30). Asymmetric mesogen (33) is then formed from dithiophene 30 via (6-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)benzo[1,2b:4,5-b']dithiophen-2-yl)boronic acid (31).

Figure 6 shows a further synthetic route to an asymmetric mesogen (36) of the present invention. Specifically, 2-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thieno[3,2b]thiophen-2-yl)-fluoren-2-yl)benzo[1,2-b:4,5-b']dithiophene (34) is provided via reaction of benzo[1,2-b:4,5-b']dithiophen-2-yl tributylstannane (29) and 2-(7-bromo-9,9dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thieno[3,2-b]thiophene (26). Asymmetric mesogen 36 is then formed from dithiophene (34) via (6-(9,9-dihexyl-7-(5-(4methoxyphenyl)thieno[3,2-b]thiophen-2-yl)-fluoren-2-yl)benzo[1,2-b:4,5-b']dithiophen2-yl)boronic acid (35).

The synthetic route to an asymmetric mesogen 38 according to the present invention is shown in Figure 7. 2-Bromo-7-iodo-9,9-dihexylfluorene (3) is reacted with 4-methoxyphenyl-boronic acid (22) to provide 2-bromo-9,9-dihexyl-7-(4methoxyphenyl)-fluorene (37), which is subsequently reacted with 2-[(4methoxyphenyl)-5-tributylstannyl]thiophene (7) to provide asymmetric mesogen (38).

Figure 8 shows the synthetic route to asymmetric mesogen 39. 2-Bromo-7iodo-9,9-dihexylfluorene (3) is reacted with 4-methoxyphenyl-boronic acid (22) to provide 2-bromo-9,9-dihexyl-7-(4-methoxyphenyl)-fluorene (37) which is subsequently reacted with tributyl(5'-(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12) to provide 5-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)-5'-(4-methoxyphenyl)-2,2'bithiophene (39).

The route to asymmetric mesogen 40 according to the present invention is shown in Figure 9 via reaction of 2-(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4methoxyphenyl)thieno[3,2-b]thiophene (26) and 4-methoxyphenyl-boronic acid (22).

Figure 10 shows the reaction of 2-(7'-bromo-9,9-dihexyl-9',9'-dioctyl-[2,2'bifluoren]-7-yl)-5-(4-methoxyphenyl) thiophene (43) with 9,9-dihexyl-7-(5'-(4methoxyphenyl)-[2,2'-bithiophen]-5-yl)-fluoren-2-yl)boronic acid (45) to provide 5-(4methoxyphenyl)-5'-(9,9,9,9-tetrahexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-9',9'dioctyl-[2,2':7',2-terfluoren]-7-yl)-2,2'-bithiophene (46). Thiophene 43 is prepared from the reaction of 9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)boronic acid (41) and 2-Bromo-7-iodo-9,9-dioctylfluorene (42), which are prepared from 2-(7bromo-9,9-dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) and 2-Bromo-7iodofluorene (2) respectively. Boronic acid 45 is prepared from the reaction of 2bromo-7-iodo-9,9-dihexylfluorene (3) and tributyl(5'-(4-methoxyphenyl)-[2,2'bithiophen]-5-yl)stannane (12) via 5-(7-bromo-9,9-dihexylfluoren-2-yl)-5'-(4methoxyphenyl)-2,2'-bithiophene (44).

The route to asymmetric mesogen 47 according to the present invention is shown in Figure 11 via reaction of 9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)fluoren-2-yl)boronic acid (41) and 2-bromo-9,9-dihexyl-7-(4-methoxyphenyl)-fluorene (37).

Figure 12 shows the preparation of 2-bromo-5-(9,9-dihexyl-7-(4methoxyphenyl)-fluoren-2-yl)thiophene (49) from the precursors 2-(9,9-dihexyl-7-(4methoxyphenyl)-fluoren-2-yl)thiophene (48) 2-bromo-9,9-dihexyl-7-(4-methoxyphenyl)fluorene (37), thiophene 49 is reacted with tributyl(5'-(4-methoxyphenyl)-[2,2'bithiophen]-5-yl)stannane (12) to provide asymmetric mesogen 50.

Figure 13 shows the synthetic route to asymmetric mesogen 57 via reaction of 4-(5'-bromo-[2,2'-bithiophen]-5-yl)-7-(5-bromothiophen-2-yl)benzo[c][1,2,5]thiadiazole (56) 9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)boronic acid (41). Thiadiazole 56 is prepared sequentially from 4,7-dibromobenzo-2,1,3-thiadiazole (52) via 4,7-dibromobenzo-2,1,3-thiadiazole (52), 4,7-di(thiophen-2-yl)benzo-2,1,3thiadiazole (53), 4-(5-bromothiophen-2-yl)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (54) and 4-([2,2'-bithiophen]-5-yl)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (55).

Figure 14 shows the synthetic route to asymmetric mesogen 60 via reaction of 4-bromo-7-(5-bromothiophen-2-yl)benzo[c][1,2,5]thiadiazole (59) and 9,9-dihexyl-7-(5(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)boronic acid (41). Thiadiazole 59 is prepared from 4,7-dibromobenzo-2,1,3-thiadiazole (52) via 4-bromo-7-(thiophen-2yl)benzo[c][1,2,5]thiadiazole (58).

EXAMPLES

Example 1: Initial device testing of asymmetric mesogens

The asymmetric mesogens 13, 46, 19, 16, 39, 38, 25, 27, 33, 40, 36, 57, 47, 50 and 60 according to the present invention were subjected to initial device testing. The results are shown in Table 2. A comparison to a prior art symmetric mesogen, indicated as “comparative example”, is also provided in Table 2.

The same device configuration has been used for each emissive material and the results are un-optimised.

The method of preparing the emissive materials for test was as follows:

A layer of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS ex-Sigma-Aldrich), was deposited as a hole-injection layer (30 nm) from aqueous solution on a glass substrate with a 100 nm pre-coated transparent indium tin oxide (ITO) anode by spin coating (2000 rpm for 30s) using Laurell WS-400-6NPP-Lite Spin Processer. The film thickness was measured using Dektak.

N4,N4’-bis(4-{6-[(3-Ethyloxetan-3-yl)methoxy]hexyl}phenyl)-N4,N4’diphenylbiphenyl-4,4’-diamine (OTPD), used as a hole-transporting layer after photochemical crosslinking, was deposited from a 0.5 wt% in toluene solution by spincoating (2000 rpm for 30s) to form a hole-transporting layer (15 nm) on top of the PEDOT/PSS hole-injection layer. 0.5 wt% (4-octyloxyphenyl) phenyliodonium hexafluoroantimonate (OPPI) was added as a photoinitiator and the OTPD was photochemically crosslinked using UV irradiation with a fluence of 100 mJ cm'².

The sample was annealed at 110 °C for 5 min. A layer (60 nm) of one of the asymmetric compounds was deposited as the emissive layer by spincoating at 2000 rpm for 30s from solution (1 wt% in toluene).

A layer (20 nm) of 2,7-bis(diphenylphosphoryl)-9,9’-spirobifluorene (SPPO13) used as electron-transporting layer was deposited by thermal evaporation at a pressure of 8 x 10'⁶ mbar. A layer (1 nm) of lithium fluoride, used as the electroninjection layer was then evaporated, followed by an aluminium (100 nm) cathode.

All materials are stable in solution. This is shown as the energy levels of each material were measured using cyclic voltammetry. All materials remain electrochemically stable during repeat CV (Cyclic Voltammetry) cycles.

OLED device performance was measured using Labview software monitoring the current / voltage curve while measuring the OLED brightness with a Konica Minolta luminance meter.

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The data in Table 2 relates to three important criteria for OLED devices, namely the OLED switch on voltage, the efficiency and the brightness at maximum efficiency.

When compared with the prior art symmetric mesogen, improvements are seen for each of the mesogens according to the present invention for at least one of the measured criteria. Particularly relevant examples are:

• asymmetric mesogen 13 which shows a reduction in switch on voltage from 5.7V (comparative) to 3.3V; an increase in efficiency from 1.55cd/A (comparative) to 6.3cd/A; and an increase in brightness at maximum efficiency from 1116cd/m² (comparative) to 3949cd/m²;

• asymmetric mesogen 19 which shows a reduction in switch on voltage from 5.7V (comparative) to 3.5V; an increase in efficiency from 1.55cd/A (comparative) to 2.5cd/A; and an increase in brightness at maximum efficiency from 1116cd/m² (comparative) to2025cd/m²; and • asymmetric mesogen 39 which shows a reduction in switch on voltage from 5.7V (comparative) to 3.5V; an increase in efficiency from 1.55cd/A (comparative) to 6.1cd/A; and an increase in brightness at maximum efficiency from 1116cd/m² (comparative) to 1900cd/m².

Without wishing to be bound by theory, it is believed that the increase in the efficiency and brightness is caused by a shift from H-aggregation to J-aggregation of the asymmetric mesogen compared to the symmetric comparative example leading to a reduction in quenching of emission.

From the data provided it is clear that the asymmetric mesogens according to the present invention provide an improved mesogen (emissive material) for use in OLED devices.

Although particular embodiments of the invention have been disclosed herein in detail, these have been provided by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the invention. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention.

Example 2: Synthesis of asymmetric mesogens according to the invention

2.1. Synthesis of 2-Bromo-7-iodofluorene (2)

A 500 ml_ 3 neck round bottom flask was charged with 2-bromo-9/7-fluorene (1) (15.00 g, 0.061 mol), iodine (6.60 g, 0.026 mol) and potassium iodate (3.20 g, 0.015 mol), flushed with nitrogen, and then acetic acid (260 ml_), concentrated sulphuric acid (6 ml_) and water (12 ml_) were added. The reaction mixture was heated at 90 °C for 2 h under nitrogen. After cooling to room temperature, the purple suspension was filtered off, washed with acetic acid (150 ml_), Na₂SO₃ (150 ml_, 15%), water (300 ml_), and air dried. The crude light yellow solid was recrystallized from toluene (100 ml_) to afford a white solid (15.85 g, 70%).

Melting Point/°C: 181-182.

¹H NMR (400 MHz, 400 MHz, CDCI₃) δ_Η: 7.88 (1H, d, J= 1.2 Hz), 7.71 (1H, dd, J = 7.2 & 1.0 Hz), 7.67 (1H, d, J = 1.2 Hz), 7.61 (1H, d, J = 8.0 Hz), 7.51 (2H, dd, J = 8.0 & 2.0 Hz), 3.86 (2H, s).

2.2. Synthesis of 2-bromo-7-iodo-9,9-dihexylfluorene (3)

Powered potassium hydroxide (9.15 g, 0.163 mol) was added in a small portion into a mixture of 2-bromo-7-iodofluorene (2) (12.15 g, 0.032 mol), 1-bromohexane (11.10 g, 0.067 mol), potassium iodide (0.50 g, 0.002 mol) and DMSO at room temperature. The resultant mixture was stirred for 4 h, washed with water (100 ml_), and extracted with DCM (3 x 100 cm3). The combined organic layers were washed with water (2 χ 100 ml_), dried over magnesium sulphate (MgSO₄), filtered and then concentrated down under reduced pressure. The residue was purified by flash column chromatography using Hexane to provide pale-yellow needles (16.53 g, 91%).

Melting Point/°C: 57-58.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.66 (2H, dd, J = 8.0 & 1.6 Hz), 7.53 (1H, d, J = 8.4 Hz), 7.46 (1H, d, J = 1.6 Hz), 7.43 (1H, d, J = 2.0 Hz), 7.40 (1H, d, J = 8.0 Hz), 1.91 (4H, m), 1.02-1.13 (12H, m), 0.79 (6H, t, J = 7.2 Hz), 0.53-0.60 (4H, m).

2.3. Synthesis of 2-(4-methoxyphenyl)thiophene (6)

Pd(PPh₃)₄ (1.11 g, 9.6 x10'⁴ mol), sodium carbonate (9.00 g, 0.084 mol) and water (36 ml_) were added to a mixture of the 4-bromoanisole (4) (15.00 g, 0.048 mol) and thiophene-2-boronic acid (5) (9.18 g, 0.024 mol) in DME (40 ml_) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (300 cm³) and the crude product extracted into DCM (2 x 200 ml_). The combined organic extracts were washed with brine (2 x 200 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, DCM: hexane, 1 : 5] to yield the desired product as a light yellow solid (11.10 g, 80%).

Melting point/ °C: 69-71.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.52 (2H, d, J = 9.0 Hz), 7.18-7.21 (2H, m), 7.04 (1H, dd, J = 1.4, 3.6 Hz), 6.89 (2H, d, J = 9.0 Hz), 3.99 (2H, t, J = 6.5 Hz), 1.80 (2H, quint, J = 6.7 Hz), 1.42-1.49 (2H, m), 1.27-1.36 (8H, m), 0.88 (3H, t).

2.4. Synthesis of 2-[(4-methoxyphenvl)-5-tributvlstannvl1thiophene (7}

A solution of 2.5 M n-BuLi (in hexanes) (15 mL) was added slowly to a solution of 2-(4methoxyphenyl)thiophene (6) (8.40 g, 0.003 mol) in THF (dry, 300 mL) at -78 °C. After stirring for 1 h at -78 °C, tri n-butyltin chloride (8.60 mL) was added slowly and the temperature of the reaction mixture was allowed to reach RT after completion of the addition. The reaction mixture was stirred overnight. Water (100 mL) was added and the product extracted into diethyl ether (2 x 200 mL). The combined ethereal extracts were dried (MgSO₄), filtered and concentrated under reduced pressure to yield the desired product as a pale brown oil, which was not purified further (15.00 g, 88%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.53 (2H, d, J = 9.0 Hz), 7.31 (1H, d, J = 3.4 Hz), 7.10 (1H, d, J = 3.4 Hz), 6.89 (2H, d, J = 9.0 Hz), 3.96 (2H, t, J = 6.7 Hz), 1.58-1.60 (6H, m), 1.27-1.43 (16H, m), 1.11 (6H, m), 0.86-0.94 (12H, m).

2.5. Synthesis of 2-(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8)

Pd(PPh₃)₄ (0.50 g, 4.3 x10'⁴ mol) was added to a heated solution of 2-bromo-7-iodo9,9-dihexylfluorene (3) (13.00 g, 0.024 mol), 2-[(4-Methoxyphenyl)-5-tributylstannyl] thiophene (7) (11.50 g, 0.023 mol) and DMF. The mixture was heated at 90 °C 22 overnight, allowed to cool and the crude product extracted into DCM (2 χ 300 mL). The combined organic layers were washed with brine (2 χ 100 mL), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 2 : 1] and recrystallization from DCM/EtOH to yield a pale yellow solid (10.10 g, 69%).

Melting Point/ °C: 98-99.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.64 (1H, d, J = 7.2 Hz), 7.61 (1H, d, J= 1.6 Hz), 7.59 (2H, dd, J = 7.2 &2.0 Hz), 7.53 (2H, d, J = 1.0 Hz), 7.46 (2H, m), 7.34 (1H, d, J = 1.0 Hz), 7.21 (1H, d, J = 4.0 Hz), 6.95 (2H, d, J = 8.8 Hz), 3.85 (3H, s), 1.97 (4H, m), 1.041.11 (12H, m), 0.78 (6H, t, J = 6.8 Hz), 0.62-0.68 (4H, m).

2.6. Synthesis of 2,2’-(5-tributvlstannanyl)bithiophene (10)

A solution of 2.5 M n-BuLi (in hexanes) (16.0 mL) was added drop-wise to a dry THF (150 mL) solution of 2,2-bithiophene (9) (6.00 g, 0.037 mol) at -78 °C, and the resultant mixture was stirred for 1 h at -78 °C. After stirring for 1 h at -78 °C, tri nbutyltin chloride (11.0 mL) was added slowly and the temperature of the reaction mixture was allowed to reach RT after completion of the addition. The reaction mixture was stirred overnight. THF was evaporated from the reaction mixture and dried under vacuum to afford the product as a dark liquid (16.20 g, 96%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.31 (1H, d, J = 3.6 Hz), 7.19 (2H, dd, J = 4.0 & 1.2 Hz), 7.07 (1H, d, J = 3.2 Hz), 7.01 (1H, dd, J = 4.0 & 1.0 Hz), 1.59 (6H, t, J = 7.6 Hz), 1.37 (6H, m), 1.13 (6H, m), 0.90 (9H, t, J = 7.6 Hz).

2.7. Synthesis of 5-(4-methoxyphenvl)-2,2'-bithiophene (11)

Pd(PPh₃)₄ (0.25 g, 2.4 x10'⁴ mol) was added to a heated solution of 2,2’-(5tributylstannanyl)bithiophene (10) (10.00 g, 0.021 mol), 4-bromoanisole (4) (3.92 g, 0.021 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into ethyl acetate (2 χ 300 mL). The combined organic layers were washed with brine (2 χ 100 mL), dried (MgSO4), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, ethyl acetate/hexane 2 : 1] to yield a yellow solid (4.50 g, 78%).

Melting Point/°C: 140-142.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.53 (d, 2H,y= 8.36 Hz), 7.21 (dd, 1H, 1.02 & 4.69 Hz), 7.18 (dd, 1H, 1.02 & 4.69 Hz), 7.11 (dd, 2H,y= 3.67 & 2.86 Hz), 7.02 (dd, 1H, y = 3.47, 8.57 Hz), 6.91 (d, 2H,y = 8.36 Hz), 3.84 (s, 3H).

2.8. Synthesis of tributyl(5'-(4-methoxvphenyl)-r2,2'-bithiophen1-5-yl)stannane (12)

A solution of 2.5 M n-BuLi (in hexanes) (8.0 mL) was added drop-wise to a dry THF (80 mL) solution of 5-(4-methoxyphenyl)-2,2'-bithiophene (11) (5.00 g, 0.018 mol) at 78 °C, and the resultant mixture was stirred for 1 h at -78 °C. After stirring for 1 h at -78 °C, tri n-butyltin chloride (5.0 mL) was added slowly and the temperature of the reaction mixture was allowed to reach RT after completion of the addition. The reaction mixture was stirred overnight. THF was evaporated from the reaction mixture and dried under vacuum to afford the product as a dark liquid (8.20 g, 80%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.53 (d, 2H,y = 7.75 Hz), 7.29 (d, 1H, y = 3.47 Hz), 7.10 (dd, 2H, j = 3.46 & 2.04 Hz), 7.00 (d, 1H,y = 3.26 Hz), 6.91 (d, 2H,y = 7.75 Hz), 3.84 (s, 3H), 1.45 (6H, t, J = 7.6 Hz), 1.36 (6H, m), 1.12 (6H, m), 0.90 (9H, t, J = 7.6 Hz).

2.9. Synthesis of 5-(9,9-dihexyl-7-(5-(4-methoxvphenvl)thiophen-2-vl)-fluoren-2-yl)5'-(4-methoxyphenvl)-2,2'-bithiophene (13)

Pd(PPh₃)₄ (0.25 g, 2.1 x10'⁴ mol) was added to a heated solution of 2-(7-bromo-9,9dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) (3.00 g, 0.005 mol), tributyl(5'(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12) (4.20 g, 0.007 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 200 mL). The combined organic layers were washed with brine (2 χ 200 mL), dried (MgSO4), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1 : 2] to yield a yellow solid (2.90 g, 73%).

Transition Temperature/ °C: Cr 157 N 233 I ¹H NMR (400 MHz, CDCI₃) δ_Η: 7.68 (2H, d, J = 7.96 Hz), 7.61-7.51 (8H, m), 7.34 (1H, d, J =3.67 Hz), 7.30 (1H, d, J = 3.67 Hz), 7.21 (1H, d, J = 3.67 Hz), 7.17 (1H, d, J =

3.88 Hz), 7.16 (1H, d, J = 3.88 Hz), 7.13 (1H, d, J = 3.67 Hz), 6.95-6.91 (4H, dd, J =

5.10. 8.98 Hz), 3.84 (6H, d), 2.09 (4H, m), 1.15-0.99 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.10. Synthesis of 4-(5-(9₁9-dihexvl-7-(5'-(4-hvdroxyphenvl)-[2₁2'-bithiophen]-5-vl)fluoren-2-yl)thiophen-2-yl)phenol (14)

A 1.0M boron tribromide solution (0.4 mL) was added dropwise to a cooled (0°C) solution of 5-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)-5'-(4methoxyphenyl)-2,2'-bithiophene (13) (1.00 g, 0.001 mol) in DCM (50 cm³). The reaction mixture was allowed to warm to room temperature and stirred for 4 h. The solution was poured into iced water (100 mL) with vigorous stirring. The resultant mixture was stirred for 30 min then further DCM (100 mL) was added. The aqueous layer was separated off and washed with DCM (2 x 50 mL). The combined organic layers were washed with brine (100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification was carried out via column chromatography [silica gel, ethyl acetate in hexane 1 : 1] to yield a yellow crystalline solid (0.70 g, 73%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.71 (2H, d, J = 7.96 Hz), 7.61-7.51 (8H, m), 7.32 (1H, d, J =3.67 Hz), 7.31 (1H, d, J = 3.67 Hz), 7.22 (1H, d, J = 3.67 Hz), 7.18 (1H, d, J =

3.88 Hz), 7.18 (1H, d, J = 3.88 Hz), 7.11 (1H, d, J = 3.67 Hz), 6.95-6.91 (4H, dd, J =

5.10. 8.98 Hz), 2.09 (4H, m), 1.15-1.00 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.11. Synthesis of penta-1,4-dien-3-yl-8-(4-(5-(9,9-dihexyl-7-(5'-(4-((8-oxo-8-(penta1.4-dien-3-vloxv)octvl)oxv)phenvl)42.2'-bithiophen1-5-vl)-fluoren-2-vl)thiophen-2yl)phenoxy)octanoate (16)

A mixture of 4-(5-(9,9-dihexyl-7-(5'-(4-hydroxyphenyl)-[2,2'-bithiophen]-5-yl)-fluoren-2yl)thiophen-2-yl)phenol (14) (0.70 g, 0.0009 mol), potassium carbonate (0.5 g, 0.003 mol), penta-1,4-dien-3-yl 6-bromootanoate (15) (0.65 g, 0.002 mol) and DMF (20 mL) was heated (80 °C) overnight. The mixture was allowed to cool to room temperature then poured into methanol (200 mL) and filtered. Purification was carried out via column chromatography [silica gel, ethyl acetate : DCM] to yield a yellow solid (0.87 g, 87%).

Transition Temperature/°C: Cr83 N 114 1.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.69 (2H, d, J = 7.96 Hz), 7.61-7.51 (8H, m), 7.34 (1H, d, J =3.67 Hz), 7.31 (1H, d, J = 3.88 Hz), 7.21 (1H, d, J = 3.67 Hz), 7.19 (2H, d, J =

3.88 Hz), 7.13 (1H, d, J = 3.88 Hz), 6.91 (4H, dd, J = 3.67 Hz), 5.88-5.80 (4H, m), 5.79-5.70 (2H, t. J = 6.12 Hz), 5.30 (4H, d, J = 8.77 Hz), 5.22 (4H, d, J = 8.77 Hz),

4.00-3.96 (4H, m), 2.36 (4H, t. J = 7.34 Hz), 2.02 (4H, m), 1.83-1.76 (4H, m), 1.70-1.65 (4H, m), 1.48-1.26 (10H, m), 1.14-1.03 (12H, m), 0.73 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.12. Synthesis of 2-(9,9-dihexyl-7-(thiophen-2-yl)-fluoren-2-yl)-5-(4-methoxyphenyl) thiophene (17)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ mol), sodium carbonate (9.00 g, 0.084 mol) and water (36 mL) were added to a mixture of the of 2-(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4methoxyphenyl)thiophene (8) (0.80 g, 0.001 mol) and thiophene-2-boronic acid (5) (0.35 g, 0.002 mol) in THF (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (300 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (2 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 2 : 5] to yield the desired product as a pale yellow liquid (0.54 g, 68%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.68 (2H, d, J = 7.75 Hz), 7.60 (3H, d, J = 7.75 Hz), 7.57 (3H, d, J = 6.73 Hz), 7.38 (1H, d, J = 3.67 Hz), 7.34 (1H, d, J = 3.67 Hz), 7.30 (1H, d, J = 3.88 Hz), 7.21 (1H, d, J = 3.88 Hz), 7.11 (1H, dd, J = 3.67 & 8.16 Hz), 6.95 (2H, d, J = 8.98 Hz), 3.85 (3H, s), 2.02 (4H, m), 1.13-1.01 (12H, m), 0.73 (6H, t, J = 6.8 Hz), 0.62-0.68 (4H, m).

2.13. Synthesis of 2-bromo-5-(9,9-dihexvl-7-(5-(4-methoxyphenvl)thiophen-2-vl)fluoren-2-yl)thiophene (18) /V-bromosuccinimide (0.20 g, 0.001 mol) was added slowly (over a period of 15 min) to a mixture of 2-(9,9-dihexyl-7-(thiophen-2-yl)fluoren-2-yl)-5-(4-methoxyphenyl) thiophene (17) (0.54 g, 0.0008 mol) in dichloromethane (50 mL) and silica gel (0.3 g) was added to the resultant solution. Once the addition was complete, the reaction mixture was stirred at room temperature for 4 h. The precipitate formed was filtered through a pad of silica. The filtrate was washed with sodium metabisulphite solution (2 x 20 mL) and water (50 cm³), dried (MgSO₄), filtered and concentrated under reduced pressure. The crude product was used without further purification (0.50 g, 92%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.69-7.66 (2H, m), 7.62-7.55 (4H, m), 7.50 (1H, dd, J = 1.63 & 8.36 Hz), 7.45 (1H, d, J = 2.45 Hz), 7.34 (1H, d, J = 3.67 Hz), 7.21 (1H, d, J = 26

3.88 Hz), 7.12 (1H, d, J = 3.67 Hz), 7.05 (1H, d, J = 3.88 Hz), 6.95 (2H, d, J = 8.98

Hz), 3.85 (3H, s), 2.02 (4H, m), 1.13-1.01 (12H, m), 0.73 (6H, t, J = 6.8 Hz), 0.62-0.68 (4H, m).

2.14. Synthesis of 5-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-vl)-fluoren-2-yl)5-(4-methoxyphenyl)-2,2':5'₁2-terthiophene (19)

Pd(PPh₃)₄ (0.25 g, 2.1 x10'⁴ mol) was added to a heated solution of 2-bromo-5-(9,9dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)thiophene (18) (0.50 g,

0.0007 mol), tributyl(5'-(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12) (0.78 g, 0.001 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 200 mL). The combined organic layers were washed with brine (2 χ 200 mL), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 2 : 1] to yield an orange solid (0.56 g, 73%).

Transition Temperature/ °C: Cr 156 N 277 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.66-7.63 (2H, m), 7.59-7.50 (8H, m), 7.33 (1H, d, J =3.67 Hz), 7.28 (1H, d, J = 3.88 Hz), 7.20 (1H, d, J = 3.67 Hz), 7.16 (1H, d, J = 3.88 Hz), 7.13-7.09 (3H, m), 7.07 (1H, d, J = 3.67 Hz), 6.95-6.89 (4H, m), 3.84 (6H, d), 2.09 (4H, m), 1.15-0.99 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.15. Synthesis of 2-bromothieno[3,2-b1thiophene (21) /V-bromosuccinimide (0.12 g, 0.0006 mol) was added slowly (over a period of 20 min) to a mixture of thieno[3,2-b]thiophene (20) (1.00 g, 0.007 mol) in dichloromethane (20 mL) and silica gel (0.2 g) was added to the resultant solution. Once the addition was complete, the reaction mixture was stirred at room temperature for 3 h. The precipitate formed was filtered off and washed with dichloromethane (100 cm³). The filtrate was washed with sodium metabisulphite solution (2 x 50 cm³) and water (100 cm³), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1 : 2] to yield a colourless solid (1.00g, 65%).

2.16. Synthesis of 4-methoxyphenyl-boronic acid (22)

A solution of 2.5 mol/L n-BuLi in hexanes (64.2 mL) was added to a solution of 1bromo-4-methoxybenzene (4) (20.00 g, 0.107 mol) in THF (200 mL) at -78 °C. The 27 resultant mixture was maintained for 1 h at -78 °C, then 2-triisopropyl borate (52 ml_) was added dropwise. The reaction mixture was stirred for 1 h at -78 °C, then allowed to warm to room temperature and stirred overnight. Hydrochloric acid (180 ml_) was added to the reaction mixture and stirred for 1 h. The reaction mixture was quenched with water (200 ml_) and extracted with diethyl ether (3 χ 150 ml_). The combined organic extracts were washed with water (2 χ 150 ml_), dried over anhydrous magnesium sulphate (MgSO₄), filtered and concentrated down under reduced pressure. The white solid was obtained (14.60 g, 90%).

Melting Point/°C: 197-201.

¹H NMR (CDCI₃) δ_Η: 8.17 (2H, d, J = 8.4 Hz), 7.68 (1H, d, J = 8.8 Hz), 7.02 (2H, d, J = 8.0 Hz), 6.92 (1H, d, J = 6.8 Hz), 3.88 (3H, s).

2.17. Synthesis of 2-(4-methoxvphenvl)thienot3,2-b1thiophene (23)

Pd(PPh₃)₄ (0.05 g, 4.3 x10'⁵ mol), sodium carbonate (1.00 g, 0.009 mol) and water (20 ml_) were added to a mixture of the of 2-bromothieno[3,2-b]thiophene (21) (1.00 g, 0.004 mol) and 4-methoxyphenyl-boronic acid (22) (1.00 g, 0.006 mol) in DME (20 ml_) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 ml_) and the crude product extracted into dichloromethane (2 x 100 ml_). The combined organic extracts were washed with brine (2 x 100 ml_), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 4 : 1] to yield the desired product as a light yellow solid (0.80 g, 81%).

¹H NMR (CDCI₃) δ_Η: 7.56 (2H, d, J = 7.96 Hz), 7.37 (1H, s), 7.31 (1H, d, J = 5.30 Hz), 7.29 (1H, d, J = 5.71 Hz), 6.94 (2H, d, J = 7.96 Hz), 3.84 (3H, s).

2.18. Synthesis of tributvl(5-(4-methoxvphenvl)thieno[3,2-b1thiophen-2-vl)stannane (24)

A solution of 2.5 M n-BuLi (in hexanes) (2.0 ml_) was added drop-wise to a dry THF (20 ml_) solution of 2-(4-methoxyphenyl)thieno[3,2-b]thiophene (23) (0.80 g, 0.003 mol) at -78 °C, and the resultant mixture was stirred for 1 h at -78 °C. After stirring for 1 h at -78 °C, tri n-butyltin chloride (0.96 ml_) was added slowly and the temperature of the reaction mixture was allowed to reach RT after completion of the addition. The reaction mixture was stirred overnight. THF was evaporated from the reaction mixture and dried under vacuum to afford the product as a dark viscous liquid (1.30 g, 75%).

¹H NMR (CDCI₃) δ_Η: 7.56 (2H, d, J = 8.57 Hz), 7.35 (1H, s), 7.23 (1H, s), 6.94 (2H, d, J = 8.57 Hz), 3.84 (3H, s).

2.19. Synthesis of 2-(9₁9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)5-(4-methoxyphenyl)thieno[3₁2-b1thiophene (25)

Pd(PPh₃)₄ (0.05 g, 4.5 x10'⁵ mol) was added to a heated solution of 2-(7-bromo-9,9dihexyl-fluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) (0.50 g, 0.0008 mol), tributyl(5(4-methoxyphenyl)thieno[3,2-b]thiophen-2-yl)stannane (24) (0.80 g, 0.001 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 100 ml_). The combined organic layers were washed with brine (2 χ 100 ml_), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1 : 2] to yield a yellow solid (0.40 g, 61%).

Transition Temperature/ °C: Cr 186 N 269 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.69 (2H, d, J = 7.75 Hz), 7.62-7.57 (8H, m), 7.55 (1H, s), 7.37 (1H, s), 7.35 (1H, d, J =3.67 Hz), 7.21 (1H, d, J = 3.67 Hz), 6.93 (4H, dd, J = 1.84, 6.32 Hz), 3.85 (6H, d), 2.09 (4H, m), 1.14-1.04 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.20. Synthesis of 2-(7-bromo-9,9-dihexvlfluoren-2-vl)-5-(4-methoxyphenvl)thieno (3,2-blthiophene (26)

Pd(PPh₃)₄ (0.06 g, 5.2 x10'⁵ mol) was added to a heated solution of 2-bromo-7-iodo9,9-dihexylfluorene (3) (3.00 g, 0.005 mol), tributyl(5-(4-methoxyphenyl)thieno[3,2b]thiophen-2-yl)stannane (24) (2.90 g, 0.005 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 300 ml_). The combined organic layers were washed with brine (2 χ 100 ml_), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 2:1] and recrystallization from DCM/EtOH to yield a yellow solid (2.71 g, 84%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.66 (1H, d, J = 7.55 Hz), 7.61-7.53 (6H, m), 7.47-7.44 (2H, m), 7.37 (1H, s), 6.95 (2H, d, J = 7.14 Hz), 3.85 (3H, s), 2.02 (4H, m), 1.13-1.01 (12H, m), 0.73 (6H, t, J = 6.8 Hz), 0.64-0.68 (4H, m).

2.21. Synthesis of 2-(9₁9-dihexyl-7-(5'-(4-methoxyphenyl)-[2,2'-bithiophen1-5-yl)fluoren-2-yl)-5-(4-methoxyphenyl)thieno[3,2-b1thiophene (27)

Pd(PPh₃)₄ (0.06 g, 5.1 x10'⁵ mol) was added to a heated solution of 2-(7-bromo-9,9dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thieno[3,2-b]thiophene (26) (0.15 g, 0.0002 mol), tributyl(5'-(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12) (0.20 g, 0.0003 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 100 mL). The combined organic layers were washed with brine (2 χ 100 mL), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 2 : 1] to yield an orange solid (0.11 g, 62%).

Transition Temperature/ °C: Cr 186 N 327 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.69 (2H, dd, J = 1.43 & 7.55 Hz), 7.62-7.53 (9H, m), 7.37 (1H, s), 7.31 (1H, d, J =3.67 Hz), 7.17 (2H, dd, J = 3.67 & 3.88 Hz), 7.14 (1H, d, J =3.88 Hz), 6.93 (4H, dd, J= 1.84, 6.31 Hz), 3.85 (6H, d), 2.09 (4H, m), 1.14-1.02 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.22. Synthesis of benzo[1,2-b:4,5-b'1dithiophen-2-yl tributylstannane (29)

A solution of 2.5 M n-BuLi (in hexanes) (2.1 mL) was added drop-wise to a dry THF (20 mL) solution of benzo[1,2-b:4,5-b']dithiophene (28) (1.00 g, 0.005 mol) at -78 °C, and the resultant mixture was stirred for 1 h at -78 °C. After stirring for 1 h at -78 °C, tri n-butyltin chloride (1.42 mL) was added slowly and the temperature of the reaction mixture was allowed to reach RT after completion of the addition. The reaction mixture was stirred overnight. THF was evaporated from the reaction mixture and dried under vacuum to afford colourless liquid (2.40 g, 96%).

2.23. Synthesis of 2-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2yl)benzo[1 ^-bA.S-b'Idithiophene (30)

Pd(PPh₃)₄ (0.01 g, 8. 6 x10'⁶ mol) was added to a heated solution of 2-(7-bromo-9,9dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) (0.70 g, 0.001 mol), benzo[1,2b:4,5-b']dithiophen-2-yl tributylstannane (29) (0.55 g, 0.001 mol) and DMF. The mixture 30 was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 x 100 mL). The combined organic layers were washed with brine (2 χ 100 ml_), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1 : 1] to yield a yellow solid (0.40 g, 61%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 8.26 (2H, s), 7.75-7.68 (4H, m), 7.65 (1H, s), 7.62-7.54 (5H, m), 7.47 (1H, d, J = 5.514 Hz), 7.35 (2H, d, J =6.12 Hz), 6.93 (2H, d, J = 6.73 Hz), 3.85 (3H, s), 2.06 (4H, m), 1.11-1.03 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.24. Synthesis of (6-(9₁9-dihexyl-7-(5-(4-methoxvphenvl)thiophen-2-yl)-fluoren-2vl)benzo[1,2-b:4,5-b'1dithiophen-2-yl)boronic acid (31).

A solution of 2.5 mol/L n-BuLi in hexanes (0.3 mL) was added to a solution of 2-(9,9dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)benzo[1,2-b:4,5b']dithiophene (30) (0.40 g, 0.0005 mol) in THF (30 mL) at -78 °C. The resultant mixture was maintained for 1 h at -78 °C, then 2-triisopropyl borate (0.26 mL) was added dropwise. The reaction mixture was stirred for 1 h at -78 °C, then allowed to warm to room temperature and stirred overnight. Hydrochloric acid (50 mL) was added to the reaction mixture and stirred for 1 h. The reaction mixture was quenched with water (100 mL) and extracted with diethyl ether (2 χ 100 mL). The combined organic extracts were washed with water (2 χ 100 mL), dried over anhydrous magnesium sulphate (MgSO₄), filtered and concentrated down under reduced pressure to afford yellow solid (0.40 g, 95%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 8.00 (2H, m), 7.68 (1H, s), 7.47-7.41 (5H, m), 7.34-7.30 (5H, m), 7.12 (1H, s), 6.65 (2H, d, J = 8.77 Hz), 5.50 (2H, s), 3.85 (3H, s), 2.06 (4H, m), 1.11-1.03 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.25. Synthesis of 2-(9₁9-dihexyl-7-(5-(4-methoxvphenvl)thiophen-2-vl)-fluoren-2-yl)6-(4-methoxyphenyl)benzo[1 .Z-bAS-b'Idithiophene (33)

Pd(PPh₃)₄ (0.05 g, 4.3 x10'⁵ mol), sodium carbonate (0.10 g, 0.0009 mol) and water (20 mL) were added to a mixture of the of (6-(9,9-dihexyl-7-(5-(4methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)benzo[1,2-b:4,5-b']dithiophen-2-yl)boronic acid (31) (0.40 g, 0.0005 mol) and 1-iodo-4-methoxybenzene (32) (0.25 g, 0.001 mol) in DME (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (2 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 1] to yield the desired product as an orange solid (0.22 g, 51%).

Transition Temperature/°C: Cr241 N 352 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 8.08 (2H, s), 7.63 (1H, s), 7.62-7.55 (10H, m), 7.41 (1H, s), 7.35 (1H, d, J = 3.88 Hz), 7.22 (1H, d, J = 3.88 Hz), 6.95 (4H, d, J = 8.36 Hz), 3.85 (6H, d), 2.09 (4H, m), 1.14-1.02 (12H, m), 0.78 (6H, t, J = 6.12 Hz), 0.62-0.68 (4H, m).

2.26. Synthesis of 2-(9,9-dihexvl-7-(5-(4-methoxvphenvl)thieno[3,2-b1thiophen-2-vl)fluoren-2-vl)benzo[1,2-b:4,5-b'1dithiophene (34)

Pd(PPh₃)₄ (0.03 g, 2.6 x10'⁵ mol) was added to a heated solution of 2-(7-bromo-9,9dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thieno[3,2-b]thiophene (26) (0.80 g, 0.001 mol), benzo[1,2-b:4,5-b']dithiophen-2-yltributylstannane (29) (0.70 g, 0.001 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 100 mL). The combined organic layers were washed with brine (2 χ 100 mL), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1 : 3] to yield a yellow solid (0.83 g, 90%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 8.26 (2H, s), 7.73-7.70 (4H, m), 7.62 (1H, s), 7.60 (1H, s), 7.59 (2H, d, J = 8.16 Hz), 7.54 (2H, d, J = 7.55 Hz), 7.46 (1H, d, J = 6.53 Hz), 7.36 (2H, d, J = 4.90 Hz), 6.93 (2H, d, J = 7.96 Hz), 3.85 (3H, s), 2.06 (4H, m), 1.13-1.02 (12H, m), 0.78 (6H, t, J = 6.73 Hz), 0.62-0.68 (4H, m).

2.27. Synthesis of (6-(9₁9-dihexyl-7-(5-(4-methoxyphenyl)thieno[3₁2-b1thiophen-2-yl)fluoren-2-yl)benzo[1 ^-b^.S-b'Idithiophen^-vDboronic acid (35)

A solution of 2.5 mol/L n-BuLi in hexanes (0.4 mL) was added to a solution of 2-(9,9dihexyl-7-(5-(4-methoxyphenyl)thieno[3,2-b]thiophen-2-yl)-fluoren-2-yl)benzo[1,2b:4,5-b']dithiophene (34) (0.67 g, 0.0008 mol) in THF (30 mL) at -78 °C. The resultant mixture was maintained for 1 h at -78 °C, then 2-triisopropyl borate (0.25 mL) was added dropwise. The reaction mixture was stirred for 1 h at -78 oC, then allowed to warm to room temperature and stirred overnight. Hydrochloric acid (50 mL) was added to the reaction mixture and stirred for 1 h. The reaction mixture was quenched with water (100 mL) and extracted with diethyl ether (2 χ 100 mL). The combined organic extracts were washed with water (2 χ 100 mL), dried over anhydrous magnesium sulphate (MgSO₄), filtered and concentrated down under reduced pressure to afford green solid (0.64 g, 100%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 8.01 (2H, m), 7.68 (1H, s), 7.47-7.41 (5H, m), 7.34-7.30 (5H, m), 7.12 (1H, s), 6.68 (2H, d, J = 8.77 Hz), 5.52 (2H, s), 3.57 (3H, s), 2.06 (4H, m), 1.13-1.02 (12H, m), 0.78 (6H, t, J = 6.73 Hz), 0.62-0.68 (4H, m).

2.28. Synthesis of 2-(9₁9-dihexyl-7-(5-(4-methoxyphenyl)thieno[3,2-b1thiophen-2-yl)fluoren-2-vl)-6-(4-methoxvphenvl)benzoH,2-b:4,5-b'1dithiophene (36)

Pd(PPh₃)₄ (0.02 g, 1.7 x10'⁵ mol), sodium carbonate (0.20 g, 0.001 mol) and water (10 mL) were added to a mixture of the of (6-(9,9-dihexyl-7-(5-(4methoxyphenyl)thieno[3,2-b]thiophen-2-yl)-fluoren-2-yl)benzo[1,2-b:4,5-b']dithiophen2-yl)boronic acid (35) (0.70 g, 0.0008 mol) and 1-iodo-4-methoxybenzene (32) (0.3 g, 0.002 mol) in DME (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (100 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (2 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 1] to yield the desired product as an orange solid (0.60 g, 80%).

Transition Temperature/ °C: Cr276 N 416 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 8.13 (2H, s), 7.69-7.54 (12H, m), 7.44 (1H, s), 7.36 (1H, s), 6.94 (4H, dd, J = 6.94 Hz), 3.85 (6H, d), 2.06 (4H, m), 1.13-1.01 (12H, m), 0.78 (10H, t, J = 6.73 Hz).

2.29. Synthesis of 2-bromo-9,9-dihexyl-7-(4-methoxyphenyl)-fluorene (37)

Pd(PPh₃)₄ (0.08 g, 7 x10'⁵ mol), sodium carbonate (1.56 g, 0.014 mol) and water (10 mL) were added to a mixture of the of 2-bromo-7-iodo-9,9-dihexylfluorene (3) (4.00 g, 0.007 mol), 4-methoxyphenyl-boronic acid (22) (1.12 g, 0.007 mol) in DME (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 ml_) and the crude product extracted into dichloromethane (2 x 100 ml_). The combined organic extracts were washed with brine (2 x 100 ml_), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 4] to yield the desired product as half white solid (2.90 g, 79%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.69 (1H, d, J = 7.34 Hz), 7.99 (2H, d, J = 8.77 Hz), 7.56-7.44 (5H, m), 7.00 (2H, d, J = 9.18 Hz), 3.85 (3H, s), 1.97 (4H, m), 1.17-1.03 (12H, m), 0.76 (6H, t, J = 7.34 Hz), 0.62-0.66 (4H, m).

2.30. Synthesis of 2-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)-5-(4-methoxy phenvDthiophene (38)

Pd(PPh₃)₄ (0.02 g, 1.7 x10'⁵ mol) was added to a heated solution of 2-bromo-9,9dihexyl-7-(4-methoxyphenyl)-fluorene (37) (1.00 g, 0.002 mol), 2-[(4-Methoxyphenyl)5-tributylstannyl]thiophene (7) (1.50 g, 0.003 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 200 ml_). The combined organic layers were washed with brine (2 χ 200 ml_), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1:1] and recrystallization from DCM/EtOH to yield a pale yellow solid (1.00 g, 83%).

Transition Temperature/ °C: Cr 120 N 71 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.69 (2H, dd, J = 7.75 & 9.59 Hz), 7.61-7.57 (6H, m), 7.53-7.50 (2H, m), 7.33 (1H, d, J = 3.67 Hz), 7.20 (1H, d, J = 3.88 Hz), 7.00 (2H, d, J = 8.16 Hz), 6.93 (2H, d, J = 7.96 Hz), 3.88 (6H, d), 2.04 (4H, m), 1.15-1.04 (12H, m), 0.78 (10H, t, J = 6.73 Hz).

2.31. Synthesis of 5-(9₁9-dihexvl-7-(4-methoxyphenvl)-fluoren-2-vl)-5'-(4-methoxv phenyl)-2,2'-bithiophene (39)

Pd(PPh₃)₄ (0.02 g, 1.7 x10'⁵ mol) was added to a heated solution of 2-bromo-9,9dihexyl-7-(4-methoxyphenyl)-fluorene (37) (0.80 g, 0.001 mol), tributyl(5'-(4methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12) (1.20 g, 0.002 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ150 ml_). The combined organic layers were washed with brine (2 χ 150 mL), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1 : 1] to yield a yellow solid (0.60 g, 60%).

Transition Temperature/ °C: Cr 152 N 170 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.70 (2H, dd, J = 7.75 & 9.59 Hz), 7.62-7.52 (8H, m), 7.30 (1H, d, J = 3.67 Hz), 7.13 (1H, d, J = 3.88 Hz), 7.17 (2H, dd, J = 8.16 Hz), 7.02 (2H, d, J = 8.16 Hz), 6.93 (2H, d, J = 7.96 Hz), 3.88 (6H, d), 2.04 (4H, m), 1.15-1.04 (12H, m), 0.78 (10H, t, J = 6.73 Hz).

2.32. Synthesis of 2-(9₁9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)-5-(4-methoxy phenvDthieno 13,2-blthiophene (40)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ moi), sodium carbonate (0.15 g, 0.001 mol) and water (20 mL) were added to a mixture of the of 2-(7-bromo-9,9-dihexylfluoren-2-yl)-5-(4methoxyphenyl)thieno[3,2-b]thiophene (26) (0.40 g, 0.0006 mol), 4-methoxyphenylboronic acid (22) (0.20 g, 0.0013 moi) (0.25 g, 0.001 moi) in DMF (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (2 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 1] to yield the desired product as yellow solid (0.31 g, 73%).

Transition Temperature/ °C: Cr 170 N 191 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.70 (2H, dd, J = 8.16 Hz), 7.62-7.50 (9H, m), 7.36 (1H, s), 7.01 (2H, d, J = 8.16 Hz), 6.93 (2H, d, J = 7.14 Hz), 3.87 (6H, d), 2.04 (4H, m), 1.15-1.01 (12H, m), 0.78 (10H, t, J = 6.73 Hz).

2.33. Synthesis of 9₁9-dihexvl-7-(5-(4-methoxvphenyl)thiophen-2-vl)-fluoren-2-vl) boronic acid (41)

A solution of 2.5 mol/L n-BuLi in hexanes (16.00 mL) was added to a solution of 2-(7bromo-9,9-dihexylfluoren-2-yl)-5-(4-methoxyphenyl)thiophene (8) (11.50 g, 0.019 mol) in THF (150 mL) at -78 °C. The resultant mixture was maintained for 1 h at -78 °C, then 2-triisopropyl borate (9.00 mL) was added dropwise. The reaction mixture was stirred 35 for 1 h at -78 °C, then allowed to warm to room temperature and stirred overnight. Hydrochloric acid (100 ml_) was added to the reaction mixture and stirred for 1 h. The reaction mixture was quenched with water (200 ml_) and extracted with diethyl ether (3 χ 150 ml_). The combined organic extracts were washed with water (2 χ 150 mL), dried over anhydrous magnesium sulphate (MgSO₄), filtered and concentrated down under reduced pressure. The white solid was obtained (8.00 g, 74%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.86 (2H, d, J = 6.94 Hz), 7.70 (2H, t, J = 7.75 Hz), 7.61-7.56 (4H, m), 7.34 (1H, d, J = 3.88 Hz), 7.21 (1H, d, J = 3.88 Hz), 6.95 (2H, d, J = 8.57 Hz), 6.56 (2H, s), 3.86 (3H, s), 2.02 (4H, m), 1.07-0.90 (12H, m), 0.74 (6H, t, J = 6.94 Hz), 0.66-0.59 (4H, m).

2.34. Synthesis of 2-Bromo-7-iodo-9,9-dioctylfluorene (42)

Powered potassium hydroxide (8.00 g, 0.142 mol) was added in a small portion into a mixture of 2-bromo-7-iodofluorene (2) (10.00 g, 0.026 mol), 1-bromooctane (10.54 g, 0.054 mol), potassium iodide (0.50 g, 0.0027 mol) and DMSO at room temperature. The resultant mixture was stirred for 4 h, washed with water (200 mL), and extracted with DCM (3 χ 150 mL). The combined organic layers were washed with water (2 χ 200 mL), dried over magnesium sulphate (MgSO₄), filtered and then concentrated down under reduced pressure. The residue was purified by flash column chromatography using Hexane to provide pale-yellow needles (12.30 g, 79%).

Melting point/ °C: 51-53.

¹H NMR (CDCI₃) δ_Η: 0.55 - 0.61 (4H, m), 0.83 (6H, t), 1.05 - 1.26 (20H, m), 1.89 (4H, quint), 7.39 - 7.46 (3H, m), 7.51 (1H, dd, J= 7.9, 0.8 Hz), 7.65 (2H, d).

2.35. Synthesis of 2-(7'-bromo-9₁9-dihexvl-9'₁9'-dioctvl-(2₁2'-bifluoren1-7-vl)-5-(4methoxyphenyl) thiophene (43)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ mol), sodium carbonate (0.33 g, 0.003 mol) and water (10 mL) were added to a mixure of the of (9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2yl)-fluoren-2-yl)boronic acid (41) (0.90 g, 0.001 mol), 2-bromo-7-iodo-9,9dioctylfluorene (42) (0.90 g, 0.001 mol) in THF (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (2 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 3] to yield the desired product as light yellow liquid (0.70 g, 70%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.77-7.71 (3H, m), 7.65-7.58 (9H, m), 7.48 (2H, s), 7.35 (1H, d, J = 3.67 Hz), 7.22 (1H, d, J = 3.67 Hz), 6.94 (2H, d, J = 8.43 Hz), 3.86 (3H, s), 2.02 (8H, m), 1.28-1.03 (32H, m), 0.90-0.74 (20H, m).

2.36. Synthesis of 5-(7-bromo-9₁9-dihexylfluoren-2-yl)-5'-(4-methoxyphenyl)-2,2'bithiophene (44)

Pd(PPh₃)₄ (0.06 g, 5.6 x10'⁵ mol) was added to a heated solution of 2-bromo-7-iodo9,9-dihexylfluorene (3) (1.00 g, 0.001 mol), tributyl(5'-(4-methoxyphenyl)-[2,2'bithiophen]-5-yl)stannane (12) (0.56 g, 0.001 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 200 mL). The combined organic layers were washed with brine (2 χ 100 mL), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 1 : 2] and recrystallization from DCM/EtOH to yield a yellow solid (0.51 g, 73%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.66 (1H, d, J = 7.96 Hz), 7.59-7.51 (5H, m), 7.46-7.44 (2H, m), 7.30 (1H, d, J = 3.88 Hz), 7.17 (2H, t, J = 3.88 Hz), 7.13 (1H, d, J = 3.88 Hz), 6.93 (2H, d, J = 8.98 Hz), 3.85 (3H, s), 1.98 (4H, m), 1.14-1.01 (12H, m), 0.76 (6H, t, J = 6.94 Hz), 0.67-0.59 (4H, m).

2.37. Synthesis of 9,9-dihexvl-7-(5'-(4-methoxyphenvl)-[2,2'-bithiophen1-5-vl)-fluoren2-vl)boronic acid (45)

A solution of 2.5 mol/L n-BuLi in hexanes (0.60 mL) was added to a solution of 5-(7bromo-9,9-dihexylfluoren-2-yl)-5'-(4-methoxyphenyl)-2,2'-bithiophene (44) (0.50 g, 0.0007 mol) in THF (100 mL) at -78 °C. The resultant mixture was maintained for 1 h at -78 °C, then 2-triisopropyl borate (0.30 mL) was added dropwise. The reaction mixture was stirred for 1 h at -78 °C, then allowed to warm to room temperature and stirred overnight. Hydrochloric acid (80 mL) was added to the reaction mixture and stirred for 1 h. The reaction mixture was quenched with water (100 mL) and extracted with diethyl ether (2 χ 100 mL). The combined organic extracts were washed with water (2 χ 150 mL), dried over anhydrous magnesium sulphate (MgSO₄), filtered and concentrated down under reduced pressure to provide yellow solid (0.45 g, 95%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.71 (1H, d, J = 7.86 Hz), 7.58-7.51 (5H, m), 7.46-7.42 (2H, m), 7.30 (1H, d, J = 3.88 Hz), 7.27 (2H, t, J = 3.68 Hz), 7.13 (1H, d, J = 3.88 Hz), 6.93 (2H, d, J = 8.98 Hz), 3.85 (3H, s), 1.98 (4H, m), 1.14-1.01 (12H, m), 0.76 (6H, t, J = 6.94 Hz), 0.67-0.59 (4H, m).

2.38. Synthesis of 5-(4-methoxyphenyl)-5'-(9,9₁9₁9-tetrahexyl-7-(5-(4-methoxy phenvl)thiophen-2-vl)-9',9'-dioctyl-[2,2':7',2-terfluoren1-7-vl)-2,2'-bithiophene (46)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ mol), sodium carbonate (0.12 g, 0.001 mol) and water (10 mL) were added to a mixture of the of 2-(7'-bromo-9,9-dihexyl-9',9'-dioctyl-[2,2'bifluoren]-7-yl)-5-(4-methoxyphenyl) thiophene (43) (0.40 g, 0.0004 mol), (9,9-dihexyl7-(5'-(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)-fluoren-2-yl)boronic acid (45) (0.39 g, 0.0006 mol) in THF (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (2 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 3] to yield the desired product as light yellow liquid (0.46 g, 76%).

Transition Temperature/ °C: Cr 158 N 224 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.82 (2H, d, J = 7.96 Hz), 7.78 (2H, d, J = 7.75 Hz), 7.73 (2H, d, J = 7.96 Hz), 7.68-7.55 (14H, m), 7.56 (2H, d, J = 6.94 Hz), 7.35 (1H, d, J = 3.67 Hz), 7.32 (1H, d, J = 3.67 Hz), 7.22 (1H, d, J = 3.88 Hz), 7.19 (2H, t, J = 3.68 Hz), 7.14 (1H, d, J = 3.67 Hz), 6.95 (2H, d, J = 4.28 Hz), 6.93 (2H, d, J = 4.68 Hz), 3.85 (6H, d), 2.08 (12H, m), 1.21-1.10 (44H, m), 0.81-0.75 (30H, m).

2.39. Synthesis of 2-(4-methoxyphenyl)-5-(9₁9₁9',9'-tetrahexyl-7'-(4-methoxyphenyl)[2,2'-bifluoren1-7-yl)thiophene (47)

Pd(PPh₃)₄ (0.02 g, 1.7 x10'⁵ mol), sodium carbonate (0.33 g, 0.003 mol) and water (10 mL) were added to a mixture of the of (9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2yl)-fluoren-2-yl)boronic acid (41) (0.60 g, 0.001 mol), 2-bromo-9,9-dihexyl-7-(4methoxyphenyl)-fluorene (37) (0.40 g, 0.0007 mol) in THF (20 mL) and the resultant reaction mixture heated under reflux at 80 °C for 2 h. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (2 χ 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 3] to yield the desired product as light yellow solid (0.54 g, 73%).

Transition Temperature/°C: Cr50 N 111 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.79-7.71 (4H, m), 7.66-7.53 (12H, m), 7.35 (1H, d, J = 3.67 Hz), 7.22 (1H, d, J = 3.67 Hz), 7.03 (2H, d, J = 7.96 Hz), 6.93 (2H, d, J = 7.75 Hz), 3.87 (6H, d), 2.05 (8H, m), 1.17-1.08 (24H, m), 0.77-0.74 (20H, m).

2.40. Synthesis of 2-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)thiophene (48)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ mol), sodium carbonate (0.25 g, 0.002 mol) and water (10 mL) were added to a mixture of the of 2-bromo-9,9-dihexyl-7-(4-methoxyphenyl)fluorene (37) (0.60 g, 0.001 mol) and thiophene-2-boronic acid (5) (0.35 g, 0.002 mol) in DIME (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (1 x 100 mL). The combined organic extracts were washed with brine (1 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, DCM: hexane, 2 : 5] to yield the desired product as a colourless viscous liquid (0.57 g, 98%).

¹H NMR (400 MHz, CDCI3) δ_Η: 7.70 (2H, dd, J = 7.79 Hz), 7.65-7.49 (6H, m), 7.37 (1H, dd, J = 3.67 Hz), 7.28 (1H, d, J = 5.04 Hz), 7.10 (1H, d, J = 5.04 Hz), 7.01 (2H, d, J = 8.71 Hz), 3.89 (3H, s), 2.01 (4H, m), 1.15-1.01 (12H, m), 0.77-0.74 (10H, m).

2.41. Synthesis of 2-bromo-5-(9,9-dihexvl-7-(4-methoxvphenvl)-fluoren-2-vl) thiophene (49) /V-bromosuccinimide (0.20 g, 0.001 mol) was added slowly (over a period of 15 min) to a mixture of 2-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)thiophene (48) (0.56 g, 0.001 mol) in dichloromethane (20 mL) and silica gel (0.1 g) was added to the resultant solution. Once the addition was complete, the reaction mixture was stirred at room temperature for 2 h. The precipitate formed was filtered through a pad of silica. The filtrate was washed with sodium metabisulphite solution (2 x 20 mL) and water (50 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. The light brown liquid was used without further purification (0.58 g, 87%).

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.70 (1H, d, J = 7.79 Hz), 7.67 (1H, d, J = 7.79 Hz), 7.59 (2H, d, J = 8.71 Hz), 7.53-7.47 (3H, m), 7.45 (1H, s), 7.10 (1H, d, J = 3.67 Hz), 7.05 (1H, d, J = 3.67 Hz), 7.00 (2H, d, J = 8.71 Hz), 3.88 (3H, s), 2.00 (4H, m), 1.121.01 (12H, m), 0.77-0.74 (10H, m).

2.42. Synthesis of 5-(9,9-dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)-5-(4-methoxy phenvl)-2,2':5'₁2-terthiophene (50)

Pd(PPh₃)₄ (0.25 g, 2.1 x10'⁴ mol) was added to a heated solution of 2-bromo-5-(9,9dihexyl-7-(4-methoxyphenyl)-fluoren-2-yl)thiophene (49) (0.58 g, 0.001 mol), tributyl(5'(4-methoxyphenyl)-[2,2'-bithiophen]-5-yl)stannane (12) (1.20 g, 0.002 mol) and DMF. The mixture was heated at 90 °C overnight, allowed to cool and the crude product extracted into DCM (2 χ 100 mL). The combined organic layers were washed with brine (2 χ 100 mL), dried (MgSO₄), filtered and then concentrated under reduced pressure. Purification was carried out via column chromatography [silica, DCM/hexane 2 : 1] to yield a yellow solid (0.55 g, 72%).

Transition Temperature/ °C: Cr 183 N 235 I.

¹H NMR (400 MHz, CDCI₃) δ_Η: 7.70 (2H, dd, J = 7.75 & 9.59 Hz), 7.62-7.52 (8H, m), 7.30 (1H, d, J = 3.67 Hz), 7.13 (1H, d, J = 3.88 Hz), 7.20-7.05 (5H, m), 7.01 (2H, d, J = 8.16 Hz), 6.93 (2H, d, J = 7.96 Hz), 3.88 (6H, d), 2.01 (4H, m), 1.12-1.01 (12H, m), 0.78 (10H, t, J = 6.73 Hz).

2.43. Synthesis of 4,7-dibromobenzo-2,1,3-thiadiazole (52)

A solution containing bromine (11.3 mL) in 48% w/w hydrogen bromide solution (100 mL) was added dropwise very slowly to a mixture of 2,1,3-benzothiadiazole (51) (10.00 g, 0.073 mol) and 48% w/w hydrogen bromide solution (150 mL). After the addition had been completed, the reaction solution was heated at reflux for 6 h. A precipitation of a dark orange solid was noted. The mixture was then cooled to room temperature and a sufficient amount of a saturated aqueous solution of sodium bisulphite (NaHSO₃) was added to completely consume any excess of bromine. The mixture was filtered under vacuum, washed exhaustively with portions of water and then washed with cold diethyl ether (200 mL). The solid was reiterated with ethanol for 6 h and then dried under vacuum overnight to afford the desired product as a white product. (13.40 g, 62%).

Melting Point/°C: 189-190.

¹H NMR (CDCI₃) δ_Η: 7.74 (2H, s).

2.44. Synthesis of 4_l7-di(thiophen-2-yl)benzo-2_l1,3-thiadiazole (53)

Pd(PPh₃)₄ (0.06 g, 5.1 x10'⁵ mol), sodium carbonate (2.54 g, 0.031 mol) and water (20 mL) were added to a mixture of the of 4,7-dibromobenzo-2,1,3-thiadiazole (52) (2.00 g, 0.006 mol) and thiophene-2-boronic acid (5) (2.60 g, 0.02 mol) in DME (50 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 200 mL). The combined organic extracts were washed with brine (1 x 200 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 3] to yield the desired product as an orange solid (1.40 g, 77%).

¹H NMR (CDCI₃) δ_Η: 8.12 (2H, dd, J = 3.6, 1.2 Hz), 7.89 (2H, s), 7.48 (2H, dd, J = 5.1 & 1.2 Hz), 7.20 (2H, dd, J = 5.1 & 3.6 Hz).

2.45. Synthesis of 4-(5-bromothiophen-2-yl)-7-(thiophen-2-yl)benzo[c1[1,2,51 thiadiazole (54)

To a solution of 4,7-di(thiophen-2-yl)benzo-2,1,3-thiadiazole (53) (0.95 g, 0.003 mol) in DMF (250 mL), NBS (0.56, 0.003 mol) was added. The reaction mixture was sonicated for 1 h at room temperature. The solvent was removed and the product was purified by column chromatography (hexane: ether, 5 : 1). An orange solid was obtained (0.62 g, 55%) ¹H NMR (CDCI₃) δ_Η: 8.12 (1H, dd, J = 4.02, 1.02 Hz), 7.86 (1H, d, J = 7.55 Hz), 7.797.76 (2H, m), 7.46 (1H, dd, J = 4.69, 1.22 Hz), 7.21 (1H, d, J = 3.88 & 8.26 Hz), 7.51 (1H, d, J = 4.08 Hz).

2.46. Synthesis of 4-([2₁2'-bithiophen]-5-vl)-7-(thiophen-2-yl)benzo[c][1_l2₁5] thiadiazole (55)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ moi), sodium carbonate (0.34 g, 0.003 mol) and water (10 mL) were added to a mixture of the of 4-(5-bromothiophen-2-yl)-7-(thiophen-2yl)benzo[c][1,2,5]thiadiazole (54) (0.62 g, 0.0001 moi) and thiophene-2-boronic acid (5) (0.41 g, 0.003 moi) in DME (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (1 x 200 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 2] to yield the desired product as a red solid (0.35 g, 57%).

¹H NMR (CDCIs) δ_Η: 8.12 (1H, dd, J = 1.22, 3.88 Hz), 8.04 (1H, d, J = 3.88 Hz), 7.86 (2H, d, J = 3.88 Hz), 7.45 (1H, dd, J = 4.69, 1.22 Hz), 7.30-7.26 (3H, m), 7.23 (1H, dd, J = 4.90 Hz) 7.06 (1H, dd, J = 3.67 Hz).

2.47. Synthesis of 4-(5'-bromo-12,2'-bithiophen1-5-vl)-7-(5-bromothiophen-2vDbenzolcin ,2,51thiadiazole (56)

To a solution of 4-([2,2'-bithiophen]-5-yl)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (55) (0.33 g, 0.0008 mol) in DMF (50 mL), NBS (0.33, 0.001 mol) was added. The reaction mixture was stirred overnight at room temperature. The solvent was removed and the product was purified by column chromatography (hexane: DCM, 1 : 3). A maroon solid was obtained (0.40 g, 87%) as a product.

¹H NMR (CDCIs) δ_Η: 8.22 (1H, d, J = 3.88 Hz), 7.85-7.79 (3H, d, J = 3.88 Hz), 7.20 (1H, d, J = 3.88 Hz) 7.16 (1H, dd, J = 3.88 Hz), 7.36 (2H, d, J = 3.88 Hz).

2.48. Synthesis of 4-(5'-(9,9-dihexvl-7-(5-(4-methoxyphenvl)thiophen-2-vl)-fluoren-2vl)-[2₁2'-bithiophen1-5-vl)-7-(5-(9₁9-dihexvl-7-(5-(4-methoxyphenvl)thiophen-2-vl)fluoren-2-vl)thiophen-2-yl)benzo[c1[1,2,51thiadiazole (57)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ moi), sodium carbonate (0.25 g, 0.002 mol) and water (10 mL) were added to a mixure of the of 4-(5'-bromo-[2,2'-bithiophen]-5-yl)-7-(5bromothiophen-2-yl)benzo[c][1,2,5]thiadiazole (56) (0.10 g, 0.0001 moi) and (9,9dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)boronic acid (41) (0.40 g,

0.0007 mol) in THF (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (1 x 100 mL). The combined organic extracts were washed with brine (1 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 2 : 1] to yield the desired product as a black solid (0.10 g, 40%).

Transition Temperature/ °C: Cr-N 234 I.

¹H NMR (CDCIs) δ_Η: 8.14 (1H, d, J = 3.88 Hz), 8.06 (1H, d, J = 3.88 Hz), 7.89 (2H, dd, J = 7.34 Hz) 7.69-7.52 (16H, m), 7.49 (1H, d, J = 3.67 Hz), 7.38-7.30 (5H, m), 7.22 (2H, d, J = 3.67 Hz), 6.95 (4H, d, J = 8.59 Hz), 3.87 (6H, s), 2.06 (8H, m), 1.13-1.08 (24H, m), 0.78-0.73 (20H, m).

2.49. Synthesis of 4-bromo-7-(thiophen-2-vl)benzo(c1(1,2,51thiadiazole (58)

Pd(PPh₃)₄ (0.1 g, 8.6 x10'⁵ mol), potassium carbonate (1.42 g, 0.01 mol) and water (20 mL) were added to a mixure of the of 4,7-dibromobenzo-2,1,3-thiadiazole (52) (2.00 g, 0.006 mol) and thiophene-2-boronic acid (5) (1.24 g, 0.009 mol) in THF (30 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 200 mL). The combined organic extracts were washed with brine (1 x 200 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 2] to yield the desired product as yellow solid (0.97 g, 50%).

¹H NMR (CDCh) δ_Η: 8.09 (1H, dd, J = 5.04 Hz), 7.89 (1H, d, J = 7.79 Hz), 7.70 (1H, d, J = 7.34 Hz), 7.45 (1H, dd, J = 6.42 Hz), 7.19 (1H, dd, J = 5.1 & 3.90 Hz).

2.50. Synthesis of 4-bromo-7-(5-bromothiophen-2-yl)benzo[c1[1_l2_l51thiadiazole (59)

To a solution of 4-bromo-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (58) (0.72 g, 0.0024 mol) in DMF (20 mL), NBS (1.20, 0.006 mol) was added. The reaction mixture was stirred for 24 h at room temperature. The precipitate formed was filtered through a pad of silica and washed with DCM. The filtrate was washed with sodium metabisulphite solution (2 x 20 mL) and water (50 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. The orange solid obtained was used without further purification (0.70 g, 78%).

¹H NMR (CDCI₃) δ_Η: 7.84 (1H, d, J = 7.79 Hz), 7.77 (1H, d, J = 3.64 Hz), 7.64 (1H, d, J = 7.79 Hz), 7.13 (1H, d, J = 3.64 Hz).

2.51. Synthesis of 4-(9,9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-vl)-fluoren-2-yl)7-(5-(9₁9-dihexyl-7-(5-(4-methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)thiophen-2νΙ^θηζο[ο1[1,2,51 thiadiazole (60)

Pd(PPh₃)₄ (0.01 g, 8.6 x10'⁶ mol), sodium carbonate (0.30 g, 0.002 mol) and water (10 mL) were added to a mixture of the of 4-bromo-7-(5-bromothiophen-2yl)benzo[c][1,2,5]thiadiazole (59) (0.50 g, 0.001 mol) and (9,9-dihexyl-7-(5-(4methoxyphenyl)thiophen-2-yl)-fluoren-2-yl)boronic acid (41) (1.72 g, 0.003 mol) in THF (20 mL) and the resultant reaction mixture heated under reflux at 80 °C overnight. The reaction mixture allowed to cool to RT, poured into water (200 mL) and the crude product extracted into dichloromethane (2 x 100 mL). The combined organic extracts were washed with brine (1 x 100 mL), dried (MgSO₄), filtered and concentrated under reduced pressure. Purification of the crude product was carried out via column chromatography [silica gel, dichloromethane: hexane, 1 : 1] to yield the desired product as bright red solid (0.82 g, 50%).

Transition Temperature/ °C: Cr-N 208 I.

¹H NMR (CDCI₃) δ_Η: 8.16 (1H, dd, J = 3.67 Hz), 8.03 (2H, d, J = 7.79 Hz), 7.99 (1H, s), 7.84 (2H, t, J = 6.88 Hz), 7.79-7.58 (13H, m), 7.51 (1H, d, J = 3.67 Hz), 7.35 (2H, t, J = 3.90 Hz), 7.21 (2H, dd, J = 3.67 Hz), 6.94 (4H, d, J = 8.71 Hz), 3.85 (6H, s), 2.10 (8H, m), 1.20-1.01 (24H, m), 0.85-0.68 (20H, m).

Although particular embodiments of the invention have been disclosed herein in detail, this is by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the invention. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention.

Claims (18)

1. An asymmetric mesogen for use in an OLED device, wherein the asymmetric mesogen has the structure (I):

E1-(B1)n-A-B2-E2 (I) wherein:

(Β^π-Α-Βς is a chromophore that comprises a conjugated pi-system, wherein A, Bt and B2 each independently comprise an optionally substituted aromatic ring system;

Et and E2 are end groups which terminate the conjugated pi-system of the chromophore;

n is 0 or 1; and wherein the asymmetric mesogen does not possess a C2 symmetry axis.

2. An asymmetric mesogen of claim 1, wherein A is selected from the group consisting of: fluorene; difluorene; trifluorene; and 2,1,3-benzothiadiazole.

3. An asymmetric mesogen of claim 2, wherein the asymmetric mesogen has the structure (II):

wherein m is 1, 2, or 3.

4. An asymmetric mesogen of claim 3, wherein and R2are independently selected from n-hexyl or n-octyl.

5. An asymmetric mesogen of claim 2, wherein the asymmetric mesogen has the structure (III):

6. An asymmetric mesogen of claim 5, wherein:

i) substitution of E1-(B1)n- is at the 4-position of the 2,1,3-benzothiadiazole and substitution of -B2-E2 is at the 7-position of the 2,1,3-benzothiadiazole; or ii) substitution of E1-(B1)n- is at the 7-position of the 2,1,3-benzothiadiazole and substitution of -B2-E2 is at the 4-position of the 2,1,3-benzothiadiazole.

7. An asymmetric mesogen of any one of claims 1 to 6, wherein Bt and B2 may be independently selected from the group comprising:

wherein q is 0 or 1.

8. An asymmetric mesogen of any one of claims 1 to 7, wherein Et or E2 are para-alkoxy phenyl groups: wherein R3 is selected from a group consisting of alkyl, alkoxy, ester, and amide.

9. An asymmetric mesogen of claim 8, wherein R3 is an alkyl group comprising 1 to 4 carbons.

10. An asymmetric mesogen of claim 9, wherein R3 is methyl.

11. An asymmetric mesogen of claim 8, wherein R3 is selected from a group consisting of acrylates, methacrylates and non-conjugated 1,4, 1,5 and 1,6 dienes.

12. An asymmetric mesogen of claim 11, wherein R3 is

-(CH2)7CO2CH(CH=CH2)2.

13. An asymmetric mesogen of claim 1, wherein the asymmetric mesogen has a structure selected from the group comprising:

ch3J

C6H13^ to6H13 „ Γ V-OCH3 Tv-CQ^ h3co^\ Όύύ © \ /

c6H13

H3C0 och3

14. An asymmetric mesogen of claim 1, wherein the asymmetric mesogen has a structure selected from the group comprising:

λ C6H13^ /¾¾. C6H13X x6h13 £z Όλ yxi ^S. Γ \ /A Ύοοη3 h3co-%A ~ C8Hi7 U8Hl7 Ϊ__y

rxXyW ί5 <C6Hi3 75ΎΎΑ7 V-s -och3 η3οο\^ ~~

15. An OLED device comprising the asymmetric mesogen of any one of claim 1 to 14.

16. A method of manufacturing an OLED device comprising the steps of:

providing a substrate;

depositing a first electrode onto the substrate; and, depositing a light-emitting layer onto the first electrode, wherein the light-emitting layer comprises an asymmetric mesogen of any one of claims 1 to 10;

depositing a second electrode onto the light-emitting layer.

17. The method of claim 16, wherein the first electrode is a cathode and the second electrode is an anode.

18. The method of claim 16, wherein the first electrode is an anode and the second electrode is a cathode.

Intellectual Property Office

Application No: GB1710754.1 Examiner: Dr Jonathan Corden

Claims searched: XXXXXXXXX Date of search: 22 December 2017

Patents Act 1977: Search Report under Section 17

Documents considered to be relevant:

Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-4, 7, 8, H,12, 15-18 W02006/058182 A2 (KELLY et al) see paragraphs [0033], [0037] and compounds 41 and 45 especially X 1 2 7-9 15-18 WO2016/177449 Al (MERCK PATENT) see pages 91-92 and compounds TDC-13 to TDC15 especially

Categories:

X Document indicating lack of novelty or inventive step A Document indicating technological background and/or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of before the filing date of this invention. same category. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.

Field of Search:

Search of GB, EP, WO & US patent documents classified in the following areas of the UKCX :

Worldwide search of patent documents classified in the following areas of the IPC

C09K; H01L

The following online and other databases have been used in the preparation of this search report

WPI, EPODOC, CAS ONLINE, Patent Fulltext International Classification: Subclass Subgroup Valid From C09K 0019/38 01/01/2006 C09K 0011/06 01/01/2006 C09K 0019/32 01/01/2006 C09K 0019/34 01/01/2006 H01L 0051/00 01/01/2006 H01L 0051/50 01/01/2006

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