WO2013045402A1 - Light emitting material - Google Patents

Abstract

This invention pertains to novel phosphorescent light emitting materials and more particularly to blue-emitting materials involving metallic complexes wherein at least one ligand comprises a 9,9'-spirobifluorenyl and/or a 9,9-diphenyl-9H-fluorenyl moiety.

Description

Description

LIGHT-EMITTING MATERIAL

Technical field

[0001] This invention relates to novel light-emitting materials, to the use of said material and to light-emitting devices capable of converting electric energy to light.

Background art

[0002] Today, various light-emitting devices are under active study and

development, in particular those based on electroluminescence (EL) from organic materials.

[0003] In the contrast to photoluminescence, i.e. the light emission from an active material as a consequence of optical absorption and relaxation by radiative decay of an excited state, electroluminescence (EL) is a nonthermal generation of light resulting from the application of an electric field to a substrate. In this latter case, excitation is accomplished by

recombination of charge carriers of contrary signs (electrons and holes) injected into an organic semiconductor in the presence of an external circuit.

[0004] A simple prototype of an organic light-emitting diode (OLED), i.e. a single layer OLED, is typically composed of a thin film of an active organic material which is sandwiched between two electrodes, one of which needs to have a degree of transparency sufficient in order to observe light emission from the organic layer.

[0005] If an external voltage is applied to the two electrodes, charge carriers, i.e. holes, at the anode and electrons at the cathode are injected to the organic layer beyond a specific threshold voltage depending on the organic material applied. In the presence of an electric field, charge carriers move through the active layer and are non-radiatively discharged when they reach the oppositely charged electrode. However, if a hole and an electron encounter one another while drifting through the organic layer, excited singlet (anti-symmetric) and triplet (symmetric) states, so-called excitons, are formed. Light is thus generated in the organic material from the decay of molecular excited states (or excitons). For every three triplet excitons that are formed by electrical excitation in an OLED, only one antisymmetric state (singlet) exciton is created.

[0006] Many organic materials exhibit fluorescence (i.e. luminescence from a symmetry-allowed process) from singlet excitons: since this process occurs between states of like symmetry it may be very efficient. On the contrary, if the symmetry of an exciton is different from that of the ground state, then the radiative relaxation of the exciton is disallowed and luminescence will be slow and inefficient. Because the ground state is usually anti-symmetric, decay from a triplet breaks symmetry: the process is thus disallowed and efficiency of EL is very low. Thus the energy contained in the triplet states is mostly wasted.

[0007] Phosphorescence emission is a phenomenon of light emission in the

relaxation process from a triplet excited state, but because the relaxation process is normally conducted by thermal deactivation, it is in many cases not possible to observe phosphorescence emission at room temperature. Characteristically, phosphorescence may persist for up to several seconds after excitation due to the low probability of the transition, in contrast to fluorescence which originates in the rapid decay.

[0008] The theoretical maximum internal quantum efficiency of light-emitting

devices comprising light-emitting materials based on an emission phenomenon in the relaxation process from a singlet excited state, (i.e. fluorescence emission), is at maximum 25 %, because in organic EL devices the ratio of the singlet to the triplet state in the excited state of light-emitting materials is always 25:75. By using phosphorescence emission (emission from triplet states) this efficiency could be raised to the theoretical limit of 100 %, thereby significantly increasing the efficiency of the EL device.

[0009] Thus, successful utilization of phosphorescent materials holds enormous promises for organic electroluminescent devices.

[0010] In display applications, it is advantageous that the light emitting material provides electroluminescence emission in a relatively narrow band centered near selected spectral regions, which correspond to one of the three primary colors, red, green and blue, so that they may be used as a colored layer in an OLED. In other applications like e.g. lighting or the like, broader ennission bands might be advantageous.

[001 1] As mentioned above, it is difficult to get phosphorescence emission from an organic compound because of prohibited intersystem crossing and concurrent thermal deactivation in the triplet relaxation process. However, it has been found that certain "organic" compounds containing a

complexed heavy metal show phosphorescence emission because of the spin-orbit interaction resulting from the heavy metal atom effect.

Accordingly, a number of phosphorescent materials having iridium or platinum as a heavy metal have been developed.

[0012] For example, there has been reported a green light-emitting device

utilizing the emission from an ortho-metalated iridium referred to as lr(PPy)3 , a tris-ortho-metalated complex of iridium (III) with 2- phenylpyridine. Appl. phys. lett. 1999, vol.75, p.4.

[0013] WO2006/12181 1 discloses phosphorescent neutral metal complexes of a mono- or multidentate ligand, said ligand comprising at least one first aryl or heteroaryl ring directly bonded to the metal, said first ring being substituted by a second aryl or heteroaryl ring not directly bonded to the metal, said second ring substituted at both ortho positions by substituents other than H or halide. According to said document, the lifetime of blue OLEDs devices involving 2-phenylimidazole derived complexes can be significantly increased by substituting the imidazole ring of the

phenylimidazole unit by a second phenyl ring substituted at its both ortho positions compared to complexes comprising alkyl N-substituted imidazole rings. So, lifetime device when using 1 -(2,6-dimethylphenyl)-2-phenyl-1 H- imidazole complex (formula (1)) is reported to be significantly higher than when using 1-methyl-2-phenyl-1 H-imidazole complex (formula (2))

[0014]

[0015] Blue to deep-blue emitting complexes of Ir with 1 -phenyl-1 H-pyrazole type ligands have been described inter alia in EP 2062908 and in Inorg. Chem. 2005, 44, 7992-8003 but the unsubstituted complex [lr(ppz)₃] hereafter doesn't emit at all at room temperature.

[0016] Despite great progress made these last years in development of

phosphorescent OLEDs, there are still some issues which need to be addressed before successfully commercialization for display and lighting applications.

[0017] One of the main issues is triplet-triplet (T1 -T1) annihilation which leads to roll-off in efficiency at high current densities. T1 -T1 annihilation is due to the relatively long phosphorescence lifetimes, which cause saturation of emission sites and emission quenching.

[0018] Another issue is luminescence self quenching (concentration quenching) due to intermolecular interaction between phosphors at high doping levels in the emitting layer. Small molecular phosphors aggregation and/or crystallisation may also lead to formation of excimers and exciplexes which decrease device efficiency. To address this issue, amorphous small molecules are well suited.

[0019] Most of the OLEDs devices for both display and lighting applications

based on organometallic complexes are prepared through vacuum deposition which is inherently limited in terms of cost, substrate size and volume. To fully realize their potential as mass market application, OLEDs need to be fabricated by low cost, large area manufacturing processes such as roll-to-roll printing processes, requiring the development of soluble materials that can be printed. In this context new phosphorescent emitters with enhanced solubility and dispersion properties need to be developed as the majority of phosphorescent emitters are not soluble enough in organic solvent. For example, the blue-emitting complex of formula (1 ) here above which leads to rather high devices lifetimes shows a too low room temperature toluene solubility to be successfully processed via solution, being comprised following our measurements between 0.23 and 0.38 wt %.

[0020] Phosphorescent organometallic dendrimers have been proposed to

circumvent these problems. Dendritic structures may facilitate solution processability and prevent concentration dependent self-quenching of the complexes as well as T-T annihilation. For example, WO2002/066552 discloses dendrimers having metal ions as part of the core. Metal chromophore at the core of the dendrimer will be relatively isolated from core chromophores of adjacent molecules, which is proposed to minimize concentration quenching and/or T-T annihilation. Other non-dendritic bulky ligands could have the same effects on devices performances.

[0021] In Semicond. Sci. Technol 2009, 24, 105019 heteroleptic Ir complexes comprising two ligands with pyridyl ring substituted in 2-position with a spirobifluorene unit (= SBF) and an ancillary acetylacetonate ligand are described. The spirobifluorenyl substituent is bonded through its 2 - position to the pyridyl ring. Respective homoleptic complexes with three spirobifluorene containing substituted pyridyl ligands are known from J. Phys. Chem. Letters, 2010, 1 272-276. The spirobifluorene conta ligands have the following formula

[0022] According to the data given in the last reference, metal complexes

comprising ligands with the spirobifluorene unit show better properties than respective complexes with fluorene units.

[0023] WO 2006/093466 discloses phosphorescent organometallic complexes with 2-phenylpyridine ligands wherein the 2-phenylpyridine ligands are substituted inter alia by at least a SBF.

[0024] In all the above disclosed emitters with SBF moieties, the spirobifluorenyl substituent is bonded through its 2 - position to the rest of the ligand. This leads to increased effective conjugation length within the resulting ligand as compared with the homolog complex with unsubstituted 2- phenylpyridine ligand wherein only one phenyl is conjugated with the pyridine group instead of two in the case of the spirobifluorenyl substituent bonded through its 2 - position. This increased conjugation length leads to some red shifted emission, so that all the disclosed emitters show emission limited to the yellow or red region.

[0025] Problems to be solved

[0026] The known metal complexes referred to above still are not fully satisfactory in their properties and especially there is still a need for long lived and efficient, preferably solution processible phosphorescent emitters capable of emitting light with emission bands centered near the primary colours, especially in the blue region and further preferably showing reduced T-T annihilation at high current densities (low roll-off in efficiency) and/or reduced concentration quenching at high doping levels.

[0027] For example, the blue emitting complex of formula (1) leads to rather long lifetime devices but show a too limited solubility in most organic solvents to be successfully used in solution-processed devices.

[0028] Moreover, albeit efficient OLEDs have been prepared using dendritic

ligands (Chem. Rev. 2007, vol. 107, p. 1097), this approach suffers from tedious synthesis and also from troublesome purifications which could be very problematic in term of devices lifetime, given that very high purity materials are needed to achieve high lifetime devices.

[0029] Furthermore, all the disclosed emitters with SBF moieties show emission in the yellow or red region.

[0030] Object of the present invention

[0031] It was thus an object of the present invention to help to solve the above- mentioned problems and to provide improved high efficiency and long lived, preferably solution processible phosphorescent light-emitting materials, especially in the blue region, which further preferably show reduced roll-off in efficiency at high current densities and/or reduced concentration quenching at high doping levels.

[0032] This object has been achieved with the phosphorescent compounds in accordance with claim 1.

[0033] Preferred compounds in accordance with the present invention are

described in the dependent claims and the detailed description hereinafter.

[0034] Further objects of the invention are the use of the compounds in

accordance with the present invention in EL devices and EL devices comprising the compounds in accordance with the instant invention.

[0035] Figure description

[0036] Figure 1 shows the principal setup of an organic light emitting diode

comprising a light emitting material in accordance with the present invention.

[0037] Figures 2 to 8 show the emission spectra of various complexes prepared in the working examples. [0038] Figure 2 shows the emission spectra of the complexes of examples 12 and

21 in 2-methyl tetrahydrofurane at 77K.

[0039] Figure 3 shows the emission spectra of the complexes of working

examples 10 to 12 in 2-methyl tetrahydrofurane at room temperature.

[0040] Figure 4 shows the emission spectra of the complexes of examples 13, 15 and 19 in 2-methyl tetrahydrofurane at 77K.

[0041] Figure 5 shows the emission spectra of the complexes of examples 15 and 21 in 2-methyl tetrahydrofurane at 77K.

[0042] Figure 6 shows the emission spectra of the complex of example 21 in 2- methyl tetrahydrofurane at 77K and at room temperature.

[0043] Figure 7 shows the emission spectra of the complexes of example 22 and the comparative example in 2-methyl tetrahydrofurane at room

temperature.

[0044] Figure 8 shows the emission spectra of the complexes of example 27 and the comparative example in 2-methyl tetrahydrofurane at room

temperature.

[0045] Detailed description of the invention

[0046] The present invention relates to light emitting materials comprising a

complex of a transition metal M of atomic number at least 40 comprising at least one ligand L1 of general formulae E1 -SBF, E1 -Ar1 -SBF, E1-Open SBF and/or E1 -Ar1 -Open SBF wherein

1 °) E1 is a 5 -membered heteroaryl ring containing at least one donor nitrogen atom. Said ring may be un-substituted or substituted by

substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl group and/or may form an annealed ring system with other rings selected from

cycloalkyl, aryl and heteroaryl rings. Heteroaryl substituents may be preferably un-substituted or substituted carbazolyl or un-substituted or substituted dibenzofuranyl. Said ring E1 is bound to the metal atom by covalent or dative bonds.

More particularly E1 is a heteroaryl ring derived from the heteroarenes group consisting of 2H-pyrrole, 3H-pyrrole, 1 H-imidazole, 2H-imidazole, 4H-imidazole,1 H-1 ,2,3-triazole, 2H-1 ,2,3-triazole, 1 H-1 ,2,4-triazole, 1 H- pyrazole, 1 H-1 ,2,3,4-tetrazole, imidazol-2-ylidene, oxazole, isoxazole, thiazole, isothiazole, 1 ,2,3-oxadiazole, 1 ,2,5-oxadiazole, 1 ,2,3- thiadiazole and 1 ,2,5-thiadazole rings.

[0047] 2°) Ar1 is selected from the group consisting of substituted or un- substituted C6-C30 arylene and substituted or un-substituted C2-C30 heteroarylene groups. Said Ar1 group may be un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl group. Said Ar1 group may be bound to the metal atom by covalent or dative bonds.

[0048] 3°) SBF represents 9,9'-spirobifluorenyl and

Open SBF represents 9,9-diphenyl-9H-fluorenyl.

Both SBF and Open SBF units may be un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl group

[0049] Thus, in the light emitting materials of the present invention, a nitrogen containing ring system E1 is bonded to the metal atom which nitrogen- containing ring system E1 is substituted, directly or indirectly through an arylene or heteroarylene ring system Ar1 , with at least one 9,9'- spirobifluorene unit or at least one 9,9-diphenyl-9H-fluorene unit as shown below. The 9,9'-spirobifluorene unit will be referred to as SBF hereinafter whereas the 9.9-diphenyl-9H-fluorene unit, despite not being a real spiro structure, due to the similarity of its structure with the SBF unit, will be referred to as Open SBF unit.

[0050]

wherein the SBF and Open SBF unit may be substituted as indicated above or may be unsubstituted.

[0051] The attachment of the SBF or open SBF unit to the remainder of the

molecule can be preferably in 2,3 or 4 position of the SBF or Open SBF unit, the attachment in position 2 or 3 being most preferred.

[0052] Accordingly, a first preferred group of ligands of the light emitting materials in accordance with the present invention can be characterized by the following general structures I to IV:

[0057] wherein E1 and Ar1 are as defined above.

[0058] The respective nitrogen containing heteroaryl ring systems E1 are

preferabl derived from the heteroarenes shown as such below

2H-pyrrole 3H-pyrrole 1 -substituted 2H-imidazole 4H-imidazole

1 /-/-imidazole

1 -substituted-1 H-1 ,2,3-triazole

2-substituted-2H-1 ,2,3-triazole

1 -substituted-"! H-1 , 2,4-triazole 1 -substituted-1 H-pyrazole

1 -substituted 1 H-1 ,2,3,4-tetrazole

1 ,3-disubstituted imidazol-2-ylidene

[0059]

[0060] wherein R, Ri and R2 may be selected from a broad variety of

substituents, which include SBF and Open SBF unit, Ar1 ring as well as the group consisting of hydrogen, alkyl, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl groups.

[0061] A further preferred group of ring systems E1 is derived from the following heteroarenes

1 ,2,3-oxadiazole 1 ,2,5-oxadiazole 1 ,2, 3-th iadiazole 1 ,2,5-thiadiazole

[0062]

[0063] wherein the rings can be unsubstituted or substituted with one or more substituents described above for R, R¹ and R² .

[0064] The nitrogen containing ring system E1 may be bonded to the metal atom via nitrogen or a carbon atom and the bond to the SBF or open SBF unit through the 2, 3 or 4 position of the SBF or open SBF unit may be in any position of the ring system E1. In case Ar1 is present, same can again be bonded to any atom of the nitrogen containing ring system E1. The SBF or Open SBF substituent may be bonded to any atom of Ar1 through the 2, 3 or 4 position of the SBF or open SBF substituent.

[0065] Ar1 is selected from the group consisting of substituted or un-substituted C6-C30 arylene groups and substituted or un-substituted C2-C30

heteroarylene groups. Said Ar1 group may be un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl group. Preferred substituted or un-substituted arylene groups comprise 6 to 14 carbon atoms which may correspond to ligand formulae shown as such below.

Preferred substituted or un-substituted heteroarylene groups comprise 2 to 14 carbon atoms which may particularly preferably correspond to the li and formulae shown as such below.

SBF

wherein R³ may be selected from the group consisting of hydrogen, alkyl, alkoxy, aryl and heteroaryl group. SBF in the above formulae includes SBF as well as Open SBF.

The Ar1 group may be bound to the metal atom by covalent or

coordinating bonds.

[0070] The metal M in the compounds in accordance with the present invention represents a transition metal of atomic number of at least 40, preferably of groups 8 to 12, more preferably Ir, Pt, Os, Rh, Cu, Ag, Au or Ru, preferably Ir or Pt and most preferably Ir.

[0071] Amongst the nitrogen containing ring systems E1 bound to the metal atom, a first preferred group comprises 1 H-imidazole and 1 H-pyrazole rings. Preferably the SBF or Open SBF unit is attached to the 2-position of the 1 H-imidazole ring and to the 1 -position of the 1 H-pyrazole ring. Such compounds can generally be characterized by the following structures V to VIII

Open SBF

[0072] (VIII)

(VII)

[0073] wherein the SBF or Open SBF unit is linked through its 2, 3 or 4 positions, the 2 and 3 positions being particularly preferred and wherein R⁴, R⁵ or R⁶ independently from one another, can be an organic substituent. R⁴ and R⁵ are preferably selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl group. Preferred R⁶ substituents are cycloalkyl groups, an aryl or heteroaryl groups both being substituted at both ortho positions by groups other than H and halide, preferably by alkyl group and more preferably by alkyl group having two or more carbon atoms.

[0074] The respective ligands where E1 is bonded to an aryl ring are

characterized by the following structures if Ar1 is a phenyl ring:

[0075] (^|χ) (X)

[0076] wherein R⁷ to R¹³, independently of one another, represent a hydrogen atom or an organic radical at least one of substituents R⁷ to R¹³ is a SBF or an Open SBF unit, preferably linked through its 2, 3 or 4 position, the 2 and 3 positions being particularly preferred.

[0077] Apart from this requirement R⁷ to R¹³ may be selected from a broad variety of substituents, no specific limitation being present. They may be selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl groups. Particularly preferred R¹¹ is a cycloalkyl group, an aryl or a heteroaryl group both being substituted at both ortho positions by groups other than H and halide, preferably by alkyl group and more preferably by alkyl group having two or more carbon atoms.

[0078] Amongst the nitrogen containing ring systems E1 bound to the metal atom, a second preferred group comprises imidazol-2-ylidene rings which involves N-heterocyclic carbene ligands of the general structures represented by the formulae: SBF Open SBF R

[0080] wherein R⁴ to R¹³ can have the meaning described above and at least one of R⁷ to R¹³ is a SBF or an Open SBF unit.

[0081] As for innidazoles and pyrazoles, the SBF or Open SBF unit can be linked at the 2, 3 or 4 positions thereof, the 2 and 3 positions being particularly preferred.

[0082] The preferred light emitting materials in accordance with the present

invention as depicted above contain at least one ligand L1 complexing the metal atom. Metal complexes comprising only one type of ligand are generally designated as homoleptic complexes, whereas complexes with different ligands are designated as heteroleptic complexes.

[0083] The light emitting materials in accordance with the present invention may be homoleptic or heteroleptic.

[0084] A particularly preferred group of homoleptic complexes in accordance with the instant invention based on imidazole ring systems E1 is given below (for convenience the metal is indicated as Ir, but Ir may be substituted by any other metal as defined in claim 1 ):

wherein a preferred R¹⁴ substituent is an aryl or heteroaryl group substituted at both its ortho positions with group others than H and halide particularly preferred aryl group substituent being 2,6-dimethylphenyl, 2,6 diisopropylphenyl and mesityl which leads in the mesityl case to the following particular formula:

Another particularly preferred group of homoleptic complexes in accordance with the instant invention based on pyrazole ring systems E1 is given below (for convenience the metal is indicated as Ir, but Ir may be substituted by any other metal as defined in claim 1 :

wherein preferred R¹⁵ substituents are selected from the group consisting of H, alkyl, aryl and heteroaryl groups. Preferred aryl and heteroaryl groups are substituted at both ortho positions with group others than H and halide, particularly preferred aryl group substituent being 2,6- dimethylphenyl, 2,6-diisopropylphenyl and mesityl, which leads to the particular following formulae when R is an H or a mesityl group.

In all the homoleptic complexes listed hereabove one of the carbon atom of the SBF or Open SBF unit is directly linked to the metal ion but as pointed out previously the SBF or Open SBF unit could also play the role of a "simple" substituent which is not directly involved in the coordination to the metal as for e.g. in the following two complexes

3

In case of heteroleptic complexes there is at least one ligand L2 present which differs from ligand L1. Ligand L2 is not subject to specific limitations and can thus be chosen from a wide variety of structures known to the skilled person and described in the literature for use in heteroleptic complexes like e.g. acetylacetonate (acac), picolinate (pic) or

tetrakispyrazolylborate. The skilled person will choose the suitable ligand L2 based on his expertise based on the remaining structure of the material. Thus, detailed explanations concerning the ligand L2 are not necessary here. [0094] A preferred group of ligands L2 comprises bidentate cyclometalating C^AN ligands which could both covalently link to the metal via one of their carbon atom and coordinate to the metal via one of their nitrogen donor atom. The cyclometalating C^AN ligand L2 may contain ring systems E1 or Ar1 -E1 as defined above but without bearing SBF or Open SBF groups. Most preferred cyclometalating C^AN ligands L2 are those for which tris homoleptic complexes [lr(L2)3] show a room temperature emission spectrum in solution in 2-MeTHF or in CH2CI2 and/or in neat films characterized by a first emission peak located at a wavelength inferior or equal to 500 nm, more preferably inferior or equal to 480 nm in order to keep the emission of the heteroleptic complexes in the green to blue region.

[0095] A particularly preferred group of ligands L2 is reproduced below:

(L2-2)

[0096] (^{L2_ 1} )

[0097]

[0098] wherein R¹⁶ and R¹⁷ may be the same or different and are groups other than H and halide, like alkyl, aryl and heteroaryl group and wherein R¹⁸ to R²⁰ may be the same or different and may be selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl groups. In case R¹⁸ to R²⁰ are different from hydrogen, the rings may bear one, two or three respective substituents. Preferably both R¹⁶ and R¹⁷ substituents are alkyl groups and more preferably alkyl groups having two or more carbon atoms. Preferred R¹⁸ substituents are selected from the group consisting of H, alkyl, heteroaryl and aryl group; when R¹⁸ is an aryl or heteroaryl group, it is preferably attached in para position to the C-N bond with the innidazole moiety. Most preferred L2 ligands are the following:

-3) (L2-4) (L2-5)

(L2-6) (L2-7)

(L2-8) (L2-9) (L2-10)

(L2-1 1 ) (L2-12) wherein R²¹ and R²² are selected from the group consisting of H, alkyl, heteroaryl and aryl groups, preferably from the group consisting of H and alkyl groups containing from 1 to 4 carbon atoms. Based on these preferred ligands L2 a particularly preferred further group of light emitting materials in accordance with the present invention are the metal heteroleptic complexes [lr(L1 >2(L2)] and [lr(L1 )(L2)2] , in particular those which combine anyone of the preferred ligands L1 described hereinbefore (in particular as in complexes C-1 to C-1 1 or comprising preferred ring systems E1 as described hereinbefore) with anyone of the preferred ligands L2 (L2-1 to L2-12) described hereinbefore, like in the following examples (C-12) to (C-26), in which again Ir may be replaced by any other metal as defined in claim 1 :

(C-14) 







[00101] The light ennitting materials in accordance with the present invention may be prepared using known methods described in the literature for respective compounds, so that detailed explanations are not necessary here.

[00102] Octahedral tris homoleptic iridium complexes involving a bidentate

cyclometalated C^AN ligand which is both covalently linked to the metal via one of its carbon atom and datively bonded to the metal via one of its nitrogen donor atom could exist under two isomeric forms, namely, facial(fac) and meridional(mer), following the position of the three coordinating nitrogen atoms. When three identical donor atoms (nitrogen or carbon) occupy a triangular face in the (pseudo)octahedral coordination polyhedron, the isomer is said to be facial or fac. If these three identical donor atoms and the metal ion are in one plane, then the isomer is said to be meridional or mer. If "Identical donor atoms" in the hereabove definitions are taken to mean those which consist of the same elements (e.g carbon or nitrogen) irrespective of the ligand structure in which they are involved, the hereabove definition could be enlarged to heteroleptic complexes which involve at least two different types of bidentate ligands so long as the three bidentate ligands around the metal are linked to the metal by at least one identical donor atom (e.g. carbon or nitrogen). While it is well known that fac-isomers of tris homoleptic complexes are generally more desirable in OLED applications since they show higher quantum yields, it is much less clear for heteroleptic complexes which involve three bidentate cyclometalated C^AN ligands, given the limited number of disclosed heteroleptic complexes and a fortiori of published structural characterizations.

[00103] The preparation of fac-isomers or a mixture of fac- and mer-isomers of tris homoleptic complexes involving bidentate cyclometalated C^AN ligands by using solvents such as ethoxyethanol, diol, acetylacetone and the like in the presence of certain additives (e.g. chloride scavengers) is well known in the field of organic electronics. [00104] Tamayo et al. (Journal American Chemical Society, 2003, 125, 7377- 7387) describes different synthesis routes of a tris homoleptic complex (fac- and mer-isomer), which are performed in glycerol from lr(acac)3, from dichloro bridged dimer or from heteroleptic complex with acac.

[00105] US 2007/0080342, tris homoleptic complexes were prepared from

lrCl3.3H2O and ligands in the presence of a halide scavenger (e.g., Ag trifluoroacetate) at a temperature from 140°C to 230°C in glycerol. Even if not obviously mentioned, the reaction proceeds probably via the dichloro- bridged dimer which reacts in a second step with the silver salt.

[00106] WO 2005/056567 discloses a similar method which involves use of a diol solvent and silver trifluoroacetate as as a chloride scavenger in a temperature range between 140 and 220°C.

[00107] In the same way, WO 2005/124889 relates to method of preparing fac- isomers of tris homoleptic involving 2-phenylpyridine type ligand by using a mixture of 80 vol.% of ethoxyethanol and 20 vol.% of water, and silver trifluoroacetate as a salt

[00108] WO 2006/12181 1 discloses a one-step facial isomer synthesis of a series of tris homoleptic complexes involving 2-phenylimidazole type ligand starting from lr(acac)3 and ligand at high temperature (e.g. from 240 to 260°C) in fused ligand without any added solvent.

[00109] JP2008/303150 describes a three-step synthesis of tris homoleptic

complexes involving 2-phenylimidazole type ligands which starts from IrC and passes successively by the chloro-bridged dimer and the heteroleptic acac complex to finally obtain the tris homoleptic complexes. Following the used ligand, this synthesis mode leads either to a facial isomer or to a mixture of fac and mer isomers.

[001 10] US 2008/0200686 discloses a process of converting a mer-isomer of a metal complex to a facial tris-cyclometallated metal complex by using organic solvents such as dioxane, water or combination thereof in the presence of a Bronsted acid.

[001 1 1] Photoisomerization of a mer-isomer of a tris homoleptic iridium complex to a facial isomer is a well known phenomenon (Journal American Chemical Society, 2003, 125, 7377-7387) which could be used at a preparative scale

[001 12] U.S. Patent Application Publication No. 2008/0312396 relates to a method of preparing facial and meridional tris-cyclometalated homoleptic and heteroleptic metal complexes involving mainly 2-phenylpyridine and 2- phenylisoquinoline type ligands in the presence of a salt, which contains at least two oxygen atoms, and in a solvent mixture comprising at least one organic solvent and at least 2% by volume of water.

[001 13] All the processes described in the aforementioned references are

principally suitable for manufacture of the light emitting materials in accordance with the present invention and their content is hereby incorporated by reference in its entirety.

[001 14] A preferred process for the manufacture of the light emitting materials in accordance with the present invention uses a water-rich mixture to prepare a tris heteroleptic metal complex or a fac-isomer for a tris homoleptic metal complex which involve both cyclometalating C^AN ligands.

[001 15] This process can be conducted at a relatively low temperature such as 80°C to 130°C (compared to other fac-isomer synthesis routes generally performed at temperatures >200°C). Low temperature can generally lead to high yields due to the decrease of secondary reaction and by-products. Further, the excess ligand and un-reacted starting materials can be recovered and reused.

[001 16] The preferred process allows the preparation of a large variety of emitters (blue, green, orange and red) at a relatively low temperature (e.g., from 80°C to 130°C) by using water-rich solvent mixtures (e.g. dioxane/water).

[001 17] The preferred process is carried out using a mixture comprising less than 75 vol.% of an organic solvent and more than 25 vol.% of water, preferably not more than 70 vol.% of an organic solvent and at least 30 vol.% of water, and more preferably not more than 66 vol.% of an organic solvent and at least 34 vol.% of water, optionally in the presence of a salt, and when this salt contains at least two oxygen atoms, it is used in an amount of less than 1 : 1 molar ratio of sal metal, where metal denotes the amount of metal in the starting metal material used for the synthesis (e.g., dihalo- briged dimer or metal halide complex) In the preferred embodiments, the preparation of the metal complex is conducted in the absence of an added chloride ion, specifically in the absence of an added halide ion, more specifically in the absence of any added salt. Halide ions, in particular chloride ions, decrease the fac-isomer yield, which is not desired. Without being bound to any theory, it is believed that the fac-isomer formation from halide-bridged dimer should involve cleavage of the halide bridge and release of halide ions into the reaction mixture; and if this reaction or one step of this reaction is an equilibrium reaction, adding halide ions would have a wrong effect shifting the equilibrium back towards the dimer. In addition to the halide ions, proton ions, hbO^"1", produced during the reaction also have an inhibitor effect. Thus, a neutralization step is preferably carried out during the reaction in order to obtain higher fac-isomer yield.

[001 18] The above salt containing at least two oxygen atoms can be either organic salt or inorganic salt. Specifically, Zwitterionic compounds (so-called internal salts) can be used in the preferred process, and at least one of the oxygen atoms may be negatively charged. The oxygen atoms may be further bonded in the salts in a 1 ,3-, 1 ,4- or 1 ,5-arrangement. Examples of inorganic salts are alkali metal, alkaline earth metal, ammonium, tetraalkylammonium, tetraalkylphosphonium and/or tetraarylphosphonium salts of carbonate, hydrogencarbonate, sulfate, hydrogensulfate, sulfite, hydrogensulfite, nitrate, nitrite, phosphate, hydrogenphosphate, dihydrogenphosphate, borate, particularly the alkali metal, ammonium and tetraalkylammonium salts. Examples of organic salts are alkali metal, alkaline earth metal, ammonium, tetraalkylammonium,

tetraalkylphosphonium and/or tetraarylphosphonium salts of organic carboxylic acids, particularly formate, acetate, fluoroacetate,

trifluoroacetate, trichloroacetate, propionate, butyrate, oxalate, benzoate, pyridinecarboxylate, salts of organic sulfonic acids, in particular MeSO3^~, EtSOs^", PrSOs^", F3CSO3-, C F₉SO₃-, C F₉SO₃-, phenyl-SOs^", ortho-, meta- or para-tolyl-SO3^", salts of a -ketobutyric acid, and salts of pyrocatechol and salicylic acid. The molar ratio of metal in the starting metal material used for the synthesis (e.g. dihalo-briged dimer or metal halide complex) to the added salt can be greater than 1 : 1 , preferably greater than 2: 1 , more preferably greater than 10: 1. Most preferably, salt is not added into the mixture, which leads to a more simple process.

[001 19] According to the preferred process, the reaction is carried out in a solvent mixture comprising an organic solvent and water, preferably in a homogeneous solution. The term "homogeneous solution" used herein relates to the solvent mixture. The term "water rich" used herein denotes a mixture containing more than 25 vol.% of water. The volume percent of organic solvent to overall solution mixture can be less than 75%, preferably not more than 70%, and more preferably not more than 66% and the volume percent of water to overall solution mixture can be more than 25%, preferably at least 30%, and more preferably at least 34%.

[00120] The above organic solvent may be any solvent, which can form

homogeneous solution with water. Preferably, the organic solvent may be at least one selected from a group consisting of C1-C20 alcohol, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol or tert-butanol, oxane, for example, dioxane or trioxane, C1-C20 alkoxyalkyl ether, for example, bis(2-methoxyethyl) ether, C1-C20 dialkyl ether, for example, dimethyl ether, C1-C20 alkoxy alcohol, for example, methoxyethanol or ethoxyethanol, diol or polyalcohol, for example, ethylene glycol, propylene glycol, triethylene glycol or glycerol,

polyethylene glycol, DMSO, NMP, DMF, and combinations thereof. More preferably, the organic solvent may be at least one selected from a group consisting of dioxane, trioxane, bis(2-methoxyethyl) ether, 2-ethoxyethanol and combinations thereof. Most preferably, the organic solvent is dioxane or bis(2-methoxyethyl) ether.

[00121 ] As starting materials dihalo-bridged dimers, preferably dichloro- or

dibromo-bridged dimers may be preferably used. The non-limiting examples of dihalo-bridged dimer include those containing a bridged halogen, such as a chloride bridged dimer Ι_2Μ(μ-ΟΙ)2ΜΙ_2, with L being a bidentate cyclometalated C^AN ligand and M being a metal.

[00122] In another embodiment, the desired product is prepared from a metal

halide complex, preferably a metal chloride complex or a metal bromide complex. The synthetic procedure from a dihalo-bridged dimer or from a metal halide complex is described in U.S. Patent Application Publication No.2008/0312396, which is incorporated herein as reference in its entirety.

[00123] Although in principle any metal halide may be used, the non-limiting

examples of metal halide complex include Ir halide complex and hydrates thereof.

[00124] According to another embodiment or the preferred process, at least one ligand compound is added to the reaction mixture to prepare the desired product. A stoichiometric excess amount of the ligand compound is generally preferably used. In a more specific embodiment, the ligand compound is used in an amount of 10 to 3000 mol percent excess, preferably 50 to 1000 mol percent excess, most preferably 100 to 500 mol percent excess.

[00125] The process can be carried out at a temperature from 50 to 260 C,

preferably from 80 to 130 C. The temperature may depend on which solvent mixture and/or ligand are used. In some further specific

embodiments, the preferred process is carried out at a pressure of from 1 x 10³ to 1 x 10⁸ Pa, preferably 1 χ 10⁴ to 1 χ 10⁷ Pa, and most preferably 1 x 10⁵ to 1 x 10⁶ Pa.

[00126] The light emitting materials in accordance with the present invention

generally have a number of advantageous properties. The increased bulkyness of the ligands often leads to a reduced T-T annihilation at high current densities as well as to a reduced aggregate-induced concentration quenching at high doping levels, which in turn leads to an increased device efficiency.

[00127] Furthermore, thin films comprising the light-emitting materials in

accordance with the present invention often show excellent amorphous properties combined with an enhanced morphological stability. An important characteristic which should be optimized in the development of low molecular weight organic materials is the ability to form

morphologically stable amorphous films. The thermal stress undergone during device operation can lead to phase transitions of the metastable amorphous film into thermodynamically stable polycrystalline state. The crystallisation induces a fast degradation of the device, as grain boundaries between crystallites act as traps for charges. Moreover, the contact between the electrodes and the organic film is diminished. An important measure of the amorphous state stability of a low molecular- weight compound or of a polymer is the glass transition temperature (T_g). If an amorphous film is heated above T_g, the molecular motion increases rapidly, which favours transition into the crystalline state. Therefore, it is advantageous to design the molecular structure of low-molecular weight compounds in such a way that a high glass transition temperature is achieved.

[00128] The light-emitting materials in accordance with the present invention in preferred embodiments show improved solubility in organic solvents as compared to homologous emitters without any SBF unit in the same solvent, thereby favoring processability from solution which is

advantageous for low cost OLED production.

[00129] The light-emitting materials in accordance with the present invention are particularly well suited, given their similarity, to newly developed and promising spirobifluorene based hosts, favoring better stability of the emitters/hosts dispersion in the emitting layer, which is an important point in devices lifetime.

[00130] The light-emitting materials in accordance with the present invention in most cases emit in the blue region, i.e. are blue-emitters. As mentioned before, especially blue-emitters need improvement in terms of lifetime and stability and the light-emitting materials provide significant advantages over the prior art in this regard as they show a high efficiency while still providing a long lifetime. [00131] Another object of the invention is the use of the light ennitting materials as above described in the emitting layer of an organic light emitting device.

[00132] In particular, the present invention is directed to the use of the light

emitting material as above described as dopant in a host layer, functioning as an emissive layer in an organic light emitting device.

[00133] Should the light emitting material used as dopant in a host layer, it is

generally used in an amount of at least 1 % wt, preferably of at least 3 % wt, more preferably of least 5 % wt with respect to the total weight of the host and the dopant and generally of at most 35 % wt, preferably at most 25 % wt, more preferably at most 15 % wt.

[00134] The present invention is also directed to an organic light emitting device (OLED) comprising an emissive layer (EML), said emissive layer comprising the light emitting material or mixture of these materials as above described, optionally with a host material (wherein the light emitting material as above described is preferably present as a dopant), said host material being notably suitable in an EML in an OLED.

[00135] The OLED generally comprises :

a substrate, for example (but not limited to) glass, plastic, metal;

an anode, generally transparent anode, such as an indium-tin oxide (ITO) anode;

a hole injection layer (HIL) for example (but not limited to) PEDOT/PSS; a hole transporting layer (HTL);

an emissive layer (EML);

an electron transporting layer (ETL);

an electron injection layer (EIL) such as LiF, CS2CO3

a cathode, generally a metallic cathode, such as an Al layer.

[00136] For a hole conducting emissive layer, one may have a hole blocking layer (HBL) that can also act as an exciton blocking layer between the emissive layer and the electron transporting layer. For an electron conducting emissive layer, one may have an electron blocking layer (EBL) that can also act as an exciton blocking layer between the emissive layer and the hole transporting layer. The emissive layer may be equal to the hole transporting layer (in which case the exciton blocking layer is near or at the anode) or to the electron transporting layer (in which case the exciton blocking layer is near or at the cathode).

[00137] The ennissive layer may be formed with a host material in which the light emitting material or mixture of these materials as above described resides as a guest or the emissive layer may consist essentially of the light emitting material or mixture of these materials as above described itself. In the former case, the host material may be a hole-transporting material selected from the group of substituted tri-aryl amines. Preferably, the emissive layer is formed with a host material in which the light emitting material resides as a guest. The host material may be an electron- transporting material selected from the group of oxadiazoles, triazoles and ketones (e.g. Spirobifluoreneketones SBFK) or a hole transporting material. Examples of host materials are 4,4'-N,N'-dicarbazole-biphenyl [" CBP"] or 3,3'-N,N'-dicarbazole-biphenyl ["mCBP"] which have the formula :

[00138]

mCPB

[00139] Optionally, the emissive layer may also contain a polarization molecule, present as a dopant in said host material and having a dipole moment, that generally affects the wavelength of light emitted when said light emitting material as above described, used as dopant, luminesces.

[00140] A layer formed of an electron transporting material is advantageously used to transport electrons into the emissive layer comprising the light emitting material and the (optional) host material. The electron transporting material may be an electron-transporting matrix selected from the group of metal quinoxolates (e.g. Alq3, Liq), oxadiazoles triazoles and ketones (e.g. Spirobifluorene ketones SBFK). Examples of electron transporting materials are tris-(8-hydroxyquinoline)aluminum of formula ["Alq3"] and spirobifluoreneketone SBFK:

SBFK

[00141] A layer formed of a hole transporting material is advantageously used to transport holes into the emissive layer comprising the light emitting material as above described and the (optional) host material. An example of a hole transporting material is 4,4'-bis[N-(1 -naphthyl)-N- phenylamino]biphenyl ["a-NPD"].

[00142] The use of an exciton blocking layer ("barrier layer") to confine excitons within the luminescent layer ("luminescent zone") is greatly preferred. For a hole-transporting host, the blocking layer may be placed between the emissive layer and the electron transport layer. An example of a material for such a barrier layer is 2,9-dimethyl-4,7-diphenyl-1 ,10-phenanthroline (also called bathocuproine or "BCP"), which has the formula

[00143] The OLED has preferably a multilayer structure, as depicted in Figure 1 , wherein 1 is a glass substrate, 2 is an ITO layer, 3 is a HIL layer comprising PEDOT/PSS, 4 is a HTL layer comprising a-NPD, 5 is an EML comprising mCBP as host material and the light emitting material or mixture of these materials as above defined as dopant in an amount of about 15 % wt with respect to the total weight of host plus dopant; 6 is a HBL comprising BCP; 7 is an ETL comprising Alq3; 8 is an EIL comprising LiF and 9 is an Al layer cathode.

[00144] Some examples of the present invention are reported hereinafter, whose purpose is merely illustrative but not limitative of the scope of the invention itself.

[00145] Examples

Ligands synthesis

[00146] 1 -(2,4,6-trimethylphenyl)-imidazole intermediate was synthesized

according to a published procedure by J. Liu et al.(J.liu, J. Chen, J. Zhao, Y. Zhao, L. Li and H. Zhang, Synthesis 2003, 17, 2661-2666), 9-(4- bromophenyl)-9-phenyl-9H-fluorene intermediate was synthesized following a procedure by Shih et al. (Ping-I Shih, Chen-Han Chien, Chu- Ying Chuang, Ching-Fong Shu, Cheng-Han Yang, Jian-Hong Chen and Yun Chi J. Mater. Chem., 2007, 17, 1692-1698), 2-bromo-9,9'- spirobifluorene intermediate was synthesized following a procedure by Winter et al. (Winter, Werner, B.; Diederich, F.; Gramlich, V. Helv. Chim. Acta 1996, 79, 1338-1360).

[00147] 3-bromo-9,9'-spirobifluorene intermediate was prepared as follows: [00148] 3-Bromo-fluorenone

[00150] In a three ways flask 60 ml of water were added to 8.9 ml of HCI (37 % w/w, 2.1 equivalents) and the medium was cooled to 0°C. NaNO2 (1.5 equivalents), dissolved in 50 ml of water, was added dropwise at 0°C. At the end of the addition, 4-amino-2-bromobenzophenone (one equivalent, 15.0 g, 51.6 mmol) solubilized in a mixture of acetone/water (400/230 ml), was added carefully. After 30 minutes at room temperature, the mixture was warmed at 60 °C for 3 hours.

[00151] After extraction with methylene chloride and evaporation of the organic phase, a brown solid was recovered (17.4 g) and a flash chromatography was realized. The pure compound was recovered after crystallization with hexane (4.2 g, 32 % yield).

[00152] 3-bromo-spirobifluorene (3-SBF)

[00154] This compound was made in two steps from 3-bromofluorenone. First, 2- bromobiphenyl (1.05 equivalents, 4.0 g, 16.5 mmol) was solubilized in 102 ml of anhydrous diethyl ether (Et.20). This solution was cooled to -60°C and BuLi (1.16 eq.) was added dropwise. After 10 min at this temperature, a white precipitate appeared which was redissolved when the medium was warmed to room temperature. 3-bromofluorenone was then added and the reaction mixture was let at 45 °C for one night.

[00155] After addition of NH₄CI (5% aq., 260 ml) and extraction with diethyl ether 7.0 g of the alcohol was obtained. This solid was solubilized in 141 ml of acetic acid (AcOH) and hydrolized by the addition of 78 ml of HCI/dioxane (20 eq.). After evaporation of the solvents, the solid was chromatographied to afford 5.86 g of the target compound (94 % yield).

[00156] [00157] Example 1: 1-mesityl-2-(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-imidazole

[00158]

[00159] In a 250 ml round bottom flask flushed with argon was dissolved 1 -(2,4,6- trimethylphenyl)-1 /-/-imidazole (7 g, 37.6 mmol) in dry THF (100 ml_). The reaction mixture was cooled to -78 °C and nBuLi 1.6 M in hexane (27 ml, 43.2 mmol) was added dropwise. After 1 h of stirring at this temperature, ZnC 1.9 M in Me-THF was added dropwise to the resulting solution. The reaction mixture was stirred at -78 °C for 30 min and was allowed to warm to room temperature. 9-(4-bromophenyl)-9-phenyl-9H-fluorene (16.9 g, 42.5 mmol) and Pd(PPh3)4 (3.5 g, 3.03 mmol) were concomitantly added and the resulting solution was refluxed for 1 h. Extra ZnCh 1.9M in Me-THF (45.6 ml, 86.6 mmol) was added to the solution that was refluxed overnight. The reaction was quenched with a solution of EDTA (100 g, 342 mmol) and K2CO3 (50 g, 362 mmol) in 250 ml of water and extracted with chloroform. The organic phase was dried over MgSO₄ and concentrated under vacuum. The crude solid was purified by silica gel column chromatography using a gradient of hexane/THF (v/v) from 1 :9 to 4:6. The product was finally washed with 150 ml of ethanol, yielding 12.1 g (65 % yield) of the desired product as a white solid.

[00160] Example 2: 2-(9,9'-spirobifluoren-2-yl)-1-mesityl-imidazole ligand (formula L1 -1)

[00162] This ligand was obtained as described for example 1 from 1 -(2,4,6- trimethylphenyl)-1 /-/-imidazole and 2-bromo-9,9'-spirobifluorene with 55 % yield.

[00163] Example 3: 2-(2'-methyl-9,9^,-spirobifluoren-2-yl)-1-mesityl-imidazole ligand

[00164]

[00165] This ligand was obtained as described for example 1 from 1 -(2,4,6- trimethylphenyl)-1 /-/-imidazole and 2-bromo-2'-methyl-9,9'-spirobifluorene with 60 % yield.

[00166] Example 4: 2-(9,9'-spirobifluoren-3-yl)-1-mesityl-imidazole ligand (L1 -2)

[00168] This ligand was obtained from 1 -(2,4, 6-trimethylphenyl)-1 /-/-imidazole and 3-bromo-9,9'-spirobifluorene following the same procedure as for example 1 with 52 % yield.

-(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-pyrazole ligand (L1 -8)

[00171] In a 500 mL round bottom flask flushed with argon was dissolved 9-(4- bromophenyl)-9-phenyl-9H-fluorene (33 g, 83.0 mmol) in dry DMF (200 ml). Pyrazole (8.52 g, 125 mmol), Cs₂CO₃ (55 g, 166 mmol), Cu₂O (6 g, 4.15 mmol) and salicylaldoxime (2.29 g, 16.6 mmol) were added to the resulting solution and the mixture was heated at 120°C for 60h. The solution was then diluted with 250 ml of a mixture of hexane/THF (v/v) 8:2. The solution was flushed over a plug of silica which was first eluted with a solution of hexane/THF 9: 1 and finally eluted with a solution of hexane/THF (v/v) 65:35. The organic phase was concentrated in vacuo and the crude product was further purified by crystallization in ethanol 96% to yield 28 g of the product as a white solid (87% yield). [00172] Example 6: 1-(9,9'-spirobifluoren-2-yl)-pyrazole ligand (L1-4)

[00174] This ligand was obtained following the same procedure as described in example 5 from pyrazole and 2-bromo-9,9'-spirobifluorene with 82 % yield.

[00175] '-spirobifluoren-3-yl)-pyrazole ligand (L1-5)

[00176]

[00177] This ligand was obtained following the same procedure as described in example 5 from pyrazole and 3-bromo-9,9'-spirobifluorene with 74 % yield.

[00178] Example 8: 5-mesityl-1-(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-pyrazole

ligand (L1-9)

[00180] In a 11 round bottonn flask was dissolved 1 -(4-(9-phenyl-9H-fluoren-9- yl)phenyl)-pyrazole (28 g, 71.3 mmol) in dry THF (400ml) and the mixture was cooled to -40°C. n-BuLi 1.6M in hexane (62.5 ml_, 100 mmol) was added dropwise and the solution left to stir at this temperature for 2 h. The solution was further cooled to -60°C and a solution of CBr₄ (37.5 g, 1 13 mmol) in dry THF (150 ml) was added dropwise. The resulting solution was allowed to stir for 1 h at this temperature. The solution was quenched with a saturated solution of NH₄CI (200 ml_) and extracted two times with MTBE (300 ml). The organic phase was dried over MgSO₄ and

concentrated under vacuum. The crude solid was purified by flash column chromatography using hexane/ethyl acetate 7:3 (v/v) as the eluent. The product was further purified by crystallization using ethanol/toluene (v/v) 98.5: 1.5 yielding the product as a whitish solid (74% yield).

[00181] The previously prepared compound (4.55 g, 9.66 mmol) and 2,4,6

trimethylphenyl boronic acid (2.5 g, 15.2 mmol) were dissolved in a mixture of dioxane/water 91 :9 and the resulting solution subsequently degassed. K₃PO (6.6 g, 31.1 mmol) followed by Pd₂(dba)₃ (0.435 g, 0.475 mmol) and 2-Dicyclohexylphosphino-2',6'-dimethoxybiphenyl (SPhos, 0.780 g, 1.90 mmol) in solution in 50 ml_ degassed dioxane were added to the solution. After 8h of stirring at reflux temperature the reaction was quenched with water (200 ml_) and extracted with Methyl-tert-butyl ether (MTBE, 200 ml). The organic phase was washed with saturated sodium chloride solution (200 ml), dried over MgSO₄ and concentrated under vacuum. The crude solid was purified with silica gel column chromatography using hexane/ethyl acetate (v/v) 85: 15 as the eluent. The product was then washed twice with hot hexane (20 ml) to yield the pure product as a white solid (50% yield).

yl)-5-mesityl-pyrazole ligand (L1-6)

[00184] This ligand was obtained following the same procedure as for Example 8 from 1-(9,9'-spirobifluoren-2-yl)-pyrazole and mesityl boronic acid. The first step yielded the brominated compound with 50% yield and the second step yielded the final product with 52 % yield. The compound was obtained with an overall yield of 26 %.

[00185]

[00186] Homoleptic complexes synthesis

[00187] All the reactions were performed in the dark and under inert atmosphere.

[00188]

[00189] Example 10. Preparation of a fac-isomer of the homoleptic complex of formula (C-2) (= [lr(L1-2)₃])

[00190] 2-(9,9'-spirobifluoren-3-yl)-1 -mesityl-imidazole L1 -2 ligand (0.806 g, 1.61 mmol) and lr(acac)3 (0.154 g, 0.306 mmol) were introduced in a 5 ml vial which was subsequently evacuated and backfilled with argon. The vial was then heated up to 265°C for 48h. After cooling, the resulting solid was purified by silica gel column chromatography using

dichloromethane/hexane 8:2 (v/v) as the eluent. NMR spectrum of the yellow recovered product was consistent with a C3 symmetric facial isomer (yield: 2 %).

[00191]

[00192] Example 11. Preparation of the homoleptic complex [lr(L1 -12)3]

[00193] The complex was synthesized (T = 240 °C) and purified following the

same procedure as described in example 10. The compound was obtained from 2-(2'-methyl-9,9'-spirobifluoren-2-yl)-1-mesityl-imidazole L1 - 12 ligand (1.05 g, 2.04 mmol) and lr(acac)₃ (0.197 g, 0.39 mmol) with 6% yield. NMR spectrum is indicative of an asymmetric facial isomer or a meridional isomer.

[00194]

[00195] Example 12. Preparation of a fac-isomer of the homoleptic complex of formula (C-3) (= [lr(L1-3)₃])

[00196] The complex was synthesized and purified following the same procedure as described in example 10. The compound was obtained from 1 -mesityl- 2-(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-imidazole L1 -3 ligand (0.837 g, 1.67 mmol) and lr(acac)3 (0.158 g, 0.315 mmol) with 28% yield. NMR spectrum of the pure product was consistent with a C3 symmetric facial isomer.

[00197]

[00198] Example 13. Preparation of a fac-isomer of the homoleptic complex of formula (C-4) (= [lr(L1-4)3]) starting from lr(acac)3

[00199] The complex was synthesized (T = 240 °C) and purified following the

same procedure as described in example 10. The compound was obtained from 1 -(9,9'-spirobifluoren-2-yl)-pyrazole L1 -4 ligand (0.604 g, 1.58 mmol) and lr(acac)₃ (0.151 g, 0.30 mmol) with 4% yield. NMR spectrum of the pure product was consistent with a C4 symmetric facial isomer.

[00200]

[00201] Example 14. Preparation of a fac-isomer of the homoleptic complex of formula (C-4) (= [lr(L1-4)3]) via chloro-bridged dimer

[00202] a) Preparation of a chloro-bridged dimer from \rCh 3H2O (following the synthesis route of Nonoyama, Bull. Chem. Soc. Jpn., 1974, 47, 767). [00203] In a 100 ml round bottom flask flushed with argon was introduced lrCI₃ xH₂O (0.352 g, 0.96 mmol) and 1 -(9,9'-spirobifluoren2-yl)-pyrazole L1 -4 ligand (1.10 g, 2.88 mmol) followed by addition of a mixture of ethoxy-ethanol/water 3: 1 (v/v) (20 ml). The resulting mixture was degassed and heated at 1 10°C for 21 h. The precipitate was collected by filtration and washed twice with MeOH (10 ml) and ether (20 ml) to yield the product as a pale yellow powder (74 % yield).

[00204] b) Preparation of a fac-isomer of the metal complex of formula C-4

In a 50 ml vial were introduced the chloro-bridged dimer (0.218 g, 0.1 1 mmol) and 1-(9,9'-spirobifluoren-2-yl)-pyrazole L1 -4 ligand (0.337 g, 0.88 mmol) followed by addition of a mixture of diethylene glycol dimethyl ether/water 1 :1 (v/v) (22 ml). The solution was degassed and the mixture heated at 130°C for 144h. The resulting precipitate was filtered off and washed with 3 x 25 ml of hexane. NMR spectrum of the "crude" recovered solid was consistent with a C3 symmetric facial isomer (estimated yield: 14 %).

[00205]

[00206] Example 15. Preparation of a fac-isomer of the homoleptic complex of formula (C-8) (= [lr(L1-8)₃])

[00207] The complex was synthesized as described in example 14 starting from 1- (4-(9-phenyl-9H-fluoren-9-yl)phenyl)-pyrazole L1 -8 ligand (3.195 g, 8.31 mmol) and IrC 3H₂O (1.019 g, 2.77 mmol) to yield the chloro-bridged dimer with a yield of 87%. The fac-complex was prepared from the dimer (0.177 g, 0.089 mmol) and 1 -(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-pyrazole L1 -8 ligand (0.274 g, 0.71 mmol) and purified by silica gel column chromatography using dichloromethane/hexane 8:2 (v/v) as the eluent. NMR spectrum of the recovered product was consistent with a C8 symmetric facial isomer (estimated yield: 9%).

[00208]

[00209] Example 16. Preparation of a mer-isomer of the homoleptic complex of formula (C-6) (= [lr(L1-6)₃])

[00210] a) Preparation of a chloro-bridged dimer from lrCh 3H20 [0021 1] In a round bottonn flask flushed with argon were introduced IrCb Sh O

(0.135 g, 0.365 mmol) and 1 -(9,9'-spirobifluoren-2-yl)-5-mesityl-pyrazole L1 -6 ligand (0.550 g, 1.10 mmol) followed by addition of a mixture of 2- ethoxy-ethanol/water 3:1 (v/v) (7 ml). The resulting mixture was degassed and heated at 1 10°C for 21 h. The precipitate was collected by filtration and washed with MeOH (10 ml) and ether (10 ml) to yield the product as a pale yellow powder (65 % yield).

[00212] b) Preparation of a mer-isomer of the metal complex of formula (C-6) [00213] In a round bottom flask flushed under argon were introduced the chloro- bridged dimer (0.245 g, 0.10 mmol), 1 -(9,9'-spirobifluoren-2-yl)-5-mesityl- pyrazole L1 -6 ligand (0.396 g, 0.79 mmol) and Na₂CO₃ (0.154 g, 1.45 mmol) which was subsequently evacuated and backfilled with argon. Diethylene glycol diethyl ether (4 ml) was then added and the resulting mixture was degassed and heated at 195°C for 21 h. After cooling, the precipitate was filtered off, washed with water and hexane while the solid stuck on the wall was recovered using CH2CI2 which was then evaporated to dryness. The two solids were gathered and purified by silica gel column chromatography using dichloromethane/hexane 8:2 (v/v) as the eluent yielding the pure product with 43% yield. NMR spectrum was consistent with a meridional isomer.

[00214]

[00215] Example 17. Preparation of a mer-isomer of the homoleptic complex of formula (C-3) (= [lr(L1-3)₃])

[00216] a) The chloro-bridged dimer was synthesized as described in example 16 starting from 1-mesityl-2-(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-imidazole L1 -3 ligand and lrCI₃3H₂O (74% yield).

b) In a 25 ml vial flushed under argon were introduced the chloro-bridged dimer (0.234 g, 0.095 mmol), 1-mesityl-2-(4-(9-phenyl-9H-fluoren-9- yl)phenyl)-imidazole L1 -3 ligand (0.441 g, 0.88 mmol) and Na₂CO₃ (0.151 g, 1.42 mmol). 2-ethoxyethanol (3.7 ml) was then added and the resulting mixture was degassed and heated at reflux for 20h. The precipitate was filtered off, washed with water and hexane. NMR spectrum of the "crude" solid was consistent with a meridional isomer and led to an estimated yield equal to 88 %. Purification by silica gel column chromatography using dichloromethane/hexane 8:2 (v/v) led to some decomposition. A pure sample of the mer-isomer could however be recovered allowing for photophysical characterization.

[00217]

[00218] Example 18. Preparation of a mer-isomer of the homoleptic complex of formula (C-5) (= [lr(L1-5)₃])

[00219] The compound was synthesized as described in example16 starting from 1 -(9,9'-spirobi[fluorene]-3-yl)-1 H-pyrazole L1 -5 ligand and lrCI₃.3H₂O to yield the chloro-bridged dimer (88% yield). The dimer was then reacted with 1 -(9,9'-spirobi[fluorene]-3-yl)-1 H-pyrazole L1 -5 ligand and Na2CO3 leading, as shown by NMR spectrum of the "crude" solid, to the meridional isomer (78 wt %) in admixture with some facial isomer (5.3 wt %) and L1-5 ligand (1 1 wt %) (C5 global yield: 64 %).

Purification by silica gel column chromatography using

dichloromethane/hexane 8:2 (v/v) led to some decomposition as in the case of mer-isomer of complex C-5.

[00220]

[00221] Example 19. Preparation of a fac-isomer of the homoleptic complex of formula (C-5) (= [lr(L1-5)₃])

[00222] The fac-isomer could be obtained by mer-isomer photoisomerization at room temperature in deaerated DMSO as confirmed by NMR analysis.

[00223]

[00224] Example 20. Preparation of a mer-isomer of the homoleptic complex of formula (C-9) (= [lr(L1-9)₃])

[00225] The compound was synthesized as described in example 16 starting from 5-mesityl-1 -(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-pyrazole L1 -9 ligand and lrCl3.3H2O to yield the chloro-bridged dimer (76% yield). The dimer was reacted with 5-mesityl-1 -(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-pyrazole L1- 9 ligand and Na2CO3 yielding, after purification by silica gel column chromatography using dichloromethane/hexane 8:2 (v/v) as the eluent, the pure mer-complex with 59% yield as shown by NMR analysis.

[00226] [00227] Example 21. Preparation of a fac-isomer of the homoleptic complex of formula (C-9) (= [lr(L1-9)₃])

[00228] The fac-isomer was obtained by photoisomerization at room temperature of the mer-isomer in deaerated DMSO as confirmed by NMR analysis.

[00229]

[00230] Heteroleptic complexes synthesis

[00231] All the reactions were performed in the dark and under inert atmosphere.

[00232]

[00233] Example 22. Synthesis of heteroleptic∞mplex of formula C-13 (= [lr(L1-

8) ₂(L2-3)])

[00234] The dichloro-bridged dimer [(L2-3)2l r^-CI)₂lr(L2-3)2] was reacted in a sealed vial flushed beforehand with argon with ligand compound L1 -8 (7 mol/mol dimer) in a 1 : 1 v/v mixture of diglyme and water. The chloro- bridged dimer concentration in the solvent reaction mixture was equal to 0.005 mol/l and the reaction temperature was 130°C for 144 h.

[00235] After cooling, the precipitate was filtered off with suction and washed with water and hexane. The recovered solid was purified by silica gel column chromatography using Ch C /hexane 8:2 (v/v) as the eluent, yielding the C13 heteroleptic complex with a purity determined by NMR using octamethylcyclotetrasiloxane as internal standard equal to 98 wt % and a yield equal to 71 %.

[00236]

[00237] Example 23. Synthesis of heteroleptic complex of formula C-12 (= [lr(L1- 3)₂(L2-3)])

[00238] C-12 heteroleptic complex was obtained using the same conditions as for C-13 in example 22 and replacing ligand compound L1-8 by ligand compound L1 -3 (8 mol/mol dimer). Isolated yield after purification by silica gel column chromatography using Ch C /hexane 8:2 (v/v) as the eluent was equal to 49 % (NMR purity using octamethylcyclotetrasiloxane as internal standard was equal to 95 wt %).

[00239]

[00240] Example 24. Synthesis of heteroleptic complex of formula C-14 ([lr(L1-

9) 2(12-3)] [00241] [lr(L1-9)₂(L2-3)] heteroleptic complex was obtained similarly to [lr(L1 -

8) 2(L2-3)] in example 22 replacing L1-8 ligand compound by L1-9 ligand compound. Yield estimated from NMR spectrum of the product recovered after purification by silica gel column chromatography using

Ch C /hexane 8:2 (v/v) as the eluent was equal to 15 %.

[00242] Example 24': Synthesis of heteroleptic complex of formula C-14 ([lr(L1-

9) 2(L2-3)] using Ag⁺ variant

[00243] To 0.261 g of [(L2-3)2lr^-CI)₂lr(L2-3)2] dimer were successively added 10 ml of CH2CI2 and 0.098 g of silver triflate dissolved in 10 ml of methanol. After being stirred for 2 hours at room temperature, the resulting mixture was filtered off and evaporated to dryness. 36 ml of a 1 : 1 v/v mixture of dioxane and water was poured onto the residue. The resulting mixture was transferred into a 100 ml Buchi Miniclave glass autoclave flushed with argon. After having added 0.735 g of the ligand compound L1 -9, the reaction mixture was heated at 130 °C for 144 h. After cooling, the precipitate was filtered off with suction and washed with water and hexane. Yield estimated from NMR spectrum of the product recovered after purification by silica gel column chromatography using Ch C /hexane 8:2 (v/v) as the eluent was equal to 47 %.

[00244]

[00245] Example 25. Synthesis of heteroleptic complex of formula C-15 (= [lr(L1- 5)₂(L2-3)])

[00246] C-15 heteroleptic complex was obtained using the same conditions as for C-13 in example 22 replacing ligand compound L1 -8 by ligand compound L1 -5 (8 mol/mol dimer). Isolated yield after purification by silica gel column chromatography using Ch C /hexane 8:2 (v/v) as the eluent was equal to 18 % (NMR purity using octamethylcyclotetrasiloxane as internal standard was equal to 100 wt %).

[00247]

[00248] Example 26. Synthesis of heteroleptic complex of formula C-16 (= [lr(L1- 8)2(12-4)])

[00249] C-16 heteroleptic complex was obtained using the same conditions as C- 13 in example 22 replacing [(L2-3)2lr^-CI)₂lr(L2-3)2] dimer involving L2-3 ligand by [(Ι_2-4)2ΐ ΐ"(μ-ΟΙ)2ΐ ΐ"(Ι_2-4)2] dimer which involves L2-4 ligand. Yield estimated from NMR spectrum of the product recovered after purification by silica gel column chromatography using Ch C /hexane 8:2 (v/v) as the eluent was equal to 40 %.

[00250]

[00251] Example 27. Synthesis of heteroleptic complex of formula C-17 (= [lr(L1- 9)₂ (L2-4)])

[00252] To 0.297 g of [(Ι_2-4)₂ΐ Γ(μ-α)₂ΐ Γ(Ι_2-4)₂] dimer (0.178 mmol) were

successively added 10 ml of CH2CI2 and 0.097 g of silver triflate (0.38 mmol) dissolved in 10 ml of methanol. After being stirred for 2 hours at room temperature, the resulting mixture was filtered and evaporated to dryness. 36 ml of a 1 : 1 v/v dioxane/water mixture was poured onto the residue and the resulting mixture was transferred into a 100 ml Buchi Miniclave glass autoclave flushed with argon. After having added 0.452 g of the ligand compound L1 -9 (0.90 mol/mol), the reaction mixture was heated at 130 °C for 144 h. After cooling, the precipitate was filtered off with suction and washed with water and hexane. C-17 yield estimated from NMR spectrum of the product recovered after purification by silica gel column chromatography using CH₂CI₂/hexane 8:2 (v/v) as the eluent was equal to 27 %, the tris homoleptic complex [lr(L1 -9)3] appearing as the main impurity (yield: 26 %).

[00253]

[00254] Example 28. Synthesis of isomer 1 of heteroleptic complex of formula C- 27 (= [lr(L1-8)(L2-3)₂])

[00255] To a 100 ml round-bottom flask flushed under argon were successively introduced 1.36 g of [(L2-3)₂lr^-CI)₂lr(L2-3)₂] dimer (0.94 mmol), 1.80 g of the ligand compound L1-8 (4.69 mmol), 1.467 g of Na₂CO₃ (13.8 mmol) and 38 ml of 2-ethoxyethanol. The resulting mixture was heated at reflux for 24 h. After cooling, the precipitate was filtered off with suction and washed successively with water, hexane and acetone, leading after drying to 1.54 g of the C27 complex as a yellow solid (NMR purity using octamethylcyclotetrasiloxane as internal standard: 96 wt %; yield: 77 %). [00256] Example 29. Synthesis of isomer 2 of heteroleptic complex of formula C- 27 (= [lr(L1-8)(L2-3)₂])

[00257] A 2^nd isomer (isomer 2) could be obtained by isomer 1 photoisomerisation at room temperature in deaerated DMSO as confirmed by NMR analysis. Thermal isomerisation to isomer 2 was also observed, besides some decomposition, during sublimation of isomer 1 at 320 °C /10^"6 bar; indeed the recovered sublimate consisted mainly of isomer 2 (97 wt% from NMR).

[00258]

[00259] Example 30 Synthesis of isomer 1 of heteroleptic complex of formula C-18 (= [lr(L1-9)(L2-4)₂])

[00260] To 0.272 g of [(L2-4)₂lr(M-CI)₂lr(L2-4)¾] dimer (0.163 mmol) were

successively added 10 ml of CH2CI2 and 0.088 g of silver triflate (0.344 mmol) dissolved in 10 ml of methanol. After being stirred for 2 hours at room temperature, the resulting mixture was filtered and evaporated to dryness. 6.5 ml of 2-ethoxyethanol was poured onto the residue and the resulting mixture was transferred into a 25 ml round-bottom flask flushed with argon. After having added 0.330 g of the ligand compound L1 -9 (0.656 mmol) and 0.254 g of Na₂CO₃ (2.39 mmol), the reaction mixture was heated at 80 °C for 21 h. After cooling, a slight greyish white precipitate, which consisted mainly of ligand compound L1 -9, was removed by fitration and water was added to the filtrate to precipitate the C-18 complex. The so formed yellow solid was filtered off with suction and washed with hexane. Yield estimated from NMR spectrum of the recovered "crude" solid was equal to 82 %, the main impurity being the L1 - 9 ligand compound (15-20 wt %).

[00261] Example 31. Synthesis of isomer 2 of heteroleptic complex of formula C- 18 (= [lr(L1-9)(L2-4)₂])

[00262] A 2^nd isomer (isomer 2) of the heteroleptic complex of formula C-18 (=

[lr(L1-9)(L2-4)2]) could be obtained by using the same conditions as for C- 17 complex (= [lr(L1 -9>2(L2-4)]) in example 27 but the 2^nd step temperature which was reduced to 80 °C. As shown by its NMR spectrum, the product so obtained after purification by silica gel column chromatography using Ch C /hexane 8:2 (v/v) as the eluent was a mixture of C-17 complex (22 wt %) and of a heteroleptic complex of formula C-18 (= [lr(L1 -9)(L2-4)₂]; 64 wt %) which was different from isomer 1 from example 30.

[00263] This 2^nd isomer could also be obtained by isomer 1 photoisomerisation at room temperature in deareated DMSO as confirmed by NMR analysis.

[00264]

[00265] Comparative example: Preparation of a fac-isomer of the homoleptic

complex [lr(L2-3)]3 (formula 1 on p. 4)

[00266] a) Preparation of a chloro-bridged dimer from

[00267] In a 250 ml round bottom flask flushed with argon were introduced 3 g of lrCI₃3H₂O (8.2 mmol) and 6.1 g of of 1 -(2,6-dimethylphenyl)-2-phenyl-1 H- imidazole L2-3 ligand (24.6 mmol) followed by addition of 168 ml of a 3: 1 (v/v) mixture of 2-ethoxyethanol and water. The resulting mixture was outgassed and maintained under stirring at reflux for 21 h. After cooling, the precipitate was filtered off with suction, washed with methanol and diethylether and dried under vacuum. The reaction yield was 90 %.

[00268] b) Preparation of a fac-isomer of the homoleptic complex [lr(L2-3)]3 in a

[00269] 1/1 v/v mixture of dioxane and water

[00270] To a 50 ml vial flushed with argon were introduced 0.265 g of the chloro- bridged dimer synthesized hereabove, 0.358 g of 1 -(2,6-dimethylphenyl)- 2-phenyl-1 H-imidazole L2-3 ligand and 34 ml of a 1 : 1 v/v mixture of dioxane and water. After sealing, the vial was heated under stirring at 80°C for 144 hours. After cooling, the precipitate was filtered off with suction and washed with water and hexane. NMR analysis indicated that the recovered solid contained 87 wt % of the fac-isomer and 9.3 wt % of un-reacted dimer, which corresponds to a fac-isomer yield equal to 75 %. Pure fac-isomer could be isolated from un-reacted dimer using classical flash chromatography.

[00271]

Photoluminescence measurements

[00272] The photoluminescence measurements were performed on highly diluted emitter solutions (¾ 10^~5 mol/l) in spectroscopic grade 2-methyl-THF using a HORIBA JOBIN WON Fluoromax -4 P spectrofluorimeter (excitation wavelength: 350 nm). Measurements at 77K were carried out using 5 mm diameter quartz tubes which were placed in the FL-2013 Dewar liquid nitrogen assembly from HORIBA JOBIN YVON. The wavelengths, X_ma*, corresponding to the maximum of the two highest energy emission peaks observed at room temperature and at 77K have been collected in table 1 .]

[00274] Table 1 : Photoluminescence data

m_ax emission (nm)

Complexes

Room T° 77K

[Ir(Ll-12)]₃)

530 / 574 528 / 574

Example 11

fac C-2 (= [Ir(Ll-2)]₃)

491 / 525 484 / 523

Example 10

fac C-3 (= [Ir(Ll-3)]₃)

478 / 512 472 / 508

Example 12

mer C-3 (= [Ir(Ll-3)]₃)

480 / 510 469 / 504

Example 17

fac C-4 (= [Ir(Ll-4)]₃)

480 / 514 478 / 513

Homoleptic Example 13

complexes mer C-6 (= [Ir(Ll-6)₃])

487 / 519 482 / 520

Example 16

fac C-5 (= [Ir(Ll-5)₃])

476 / 495 467 / 498

Example 19

fac C-8 (= [Ir(Ll-8)₃])

No emission 431 / 462

Example 15

fac C-9 (= [Ir(Ll-9)₃]) 469

431 / 462

Example 21 (broad peak)

mer C-9 (= [Ir(Ll-9)₃])

No emission 444 / 465

Example 20

C-12 (= [Ir(Ll-3)₂(L2-3)])

477 / 509 469 / 503

Example 23

C-15 (= [Ir(Ll-5)₂(L2-3)])

473 / 487 463 / 495

Example 25

C-27 (= [Ir(Ll-8)(L2-3)₂])

467 / 495 459 / 492

Isomer 1 Example 28

C-27 (= [Ir(Ll-8)(L2-3)₂])

465 / 493 456 / 490

Heteroleptic Isomer 2 Example 29

complexes C-18 (= [Ir(Ll-9)(L2-4)₂D 464 / 495 459 / 493

Isomer 2 Example 31

C-13 (= [Ir(Ll-8)₂(L2-3)])

459 / 489 455 / 487

Example 22

C-14 (= [Ir(Ll-9)₂(L2-3)])

460 / 490 454 / 487

Example 24

C-17 (= [Ir(Ll-9)₂(L2-4)])

458 / 488 449 / 483

Example 27

fac [Ir(L2-3)₃]

472 / 502 464 / 498

Comparative example (formula 1 on p. 4)

[00275] As shown by the data gathered in table 1 , homoleptic and heteroleptic complexes which comprise ligands combining heteroaryl 5-membered E1 rings with SBF and Open SBF units in accordance with the present invention lead to a large variety of new light-emitting materials most of which interestingly emit in the bluish-green to blue region.

[00276] Furthermore, when looking at the homoleptic complexes series in table 1 , it appears that the emission spectra of the light-emitting materials in accordance to the present invention could be tuned following the nature of the 5-membered ring E1 , imidazole or pyrazole, the nature of the

"spirobifluorene" unit, SBF or Open SBF, and the position through which these units are bonded to the rest of the ligand, 2- or 3-.

So, when comparing in table 1 examples 1 1 , 10 and 12, which are based on E1 imidazole ring, with respectively examples 16, 19 and 21 which correspond to their pyrazole analogs, it appears clearly that, the rest being unchanged, E1 pyrazole rings lead to blue shifted emission as compared to their imidazole counterparts, as shown in figure 2 for examples 12 and 21.

When comparing example 1 1 with 10 (E1 = imidazole ring, figure 3) or example 13 with 19 (E1 = pyrazole ring, figure 4), it appears that the emission are blue-shifted when passing from SBF units bonded through their 2-position to SBF units bonded through their 3-position. Similarly, changing from a SBF to an Open SBF unit bonded on the same way leads to a blue shifted emission, as shown in figure 3 for examples 10 and 12 (E1 = imidazole ring) and in figure 4 for examples 19 and 15 (E1 = pyrazole ring). Without wishing to be bound by theory, the inventors believe that these blue-shifted emissions could be correlated with a decreased conjugation length of the "spirobifluorene" unit with the rest of the ligand.

As expected from these observed trends, the deeper blue emitting homoleptic complex at room temperature correspond to a facial one (= fac C-9) which involve ligand combining one pyrazole E1 ring with one Open SBF unit bonded through its 3-position.

[00277] It must also be noted that while their emission spectra at 77 K appear

rather similar (figure 5), the homoleptic complexes from examples 15 and 21 (resp. fac C-8 and C-9), which involve ligands differing only by the presence of a mesityl substituent on the 5-position of their E1 pyrazole ring (resp.), show quite different emissive behaviour at room temperature, C-8 being not emissive while C-9 shows a very broad emission spectrum peaking at about 469 nm (figure 6).

[00278] Heteroleptic complexes comprising "spirobifluorene" units according to the present invention could also lead to blue light-emitting materials by properly selecting the two ligands involved in the complexes. More interestingly and particularly well suited for lighting and display

applications, a selection could be made which leads to complexes emitting at lower wavelengths than the well known comparative example [lr(L2-3)3] which corresponds to formula 1 on p. 4 (compare examples 28, 29, 31 , 22, 24 and 27 with [lr(L2-3)3] comparative example in table 1 ). The deeper blue-emitting heteroleptic complexes are those comprising two ligands combining one pyrazole E1 ring with one Open SBF unit bonded through its 3-position (examples 22, 24 and 27, see figures 7 and 8). It appears in fact from table 1 that the emission is blue shifted as the number of L1 -8 or L1 -9 ligand increases in the following series [lr(L2-3)₃], [lr(L1 -8)(L2-3)₂], [lr(L1 -8)₂(L2-3)], [lr(L1 -8)₃] and [lr(L1 -9)(L2-4)₂], [lr(L1 -9)₂(L2-4)], [lr(L1 -9)₃]. It must be noted that the three heteroleptic complexes comprising one or two 1 -(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-pyrazole L1 -8 ligand (examples 28, 29 and 22) behave as bright emitters at room temperature while the homoleptic complex fac-[lr(L1 -8)3] (example15) is not emissive at room temperature like its well known analog homoleptic complex [lr(ppz)3] based on 1 -phenyl-1 H-pyrazole ligand mentioned on p. 4.

[00279]

[00280] Solubility measurements

[00281 ] Light-emitting materials according to our invention are particularly well suited for solution-process given their increased solubility as compared to the well-known comparative example [lr(L2-3)3] . For example, the heteroleptic complex C-13 from example 22 shows a room temperature toluene solubility comprised between 0.50 and 0.66 wt % which is about twice larger than that of comparative example [lr(L2-3)3] which is comprised between 0.23 and 0.38 wt %. The deeper blue emitting heteroleptic complex C-17 from example 27 shows a still higher solubility, being superior to 1.0 wt %.

Claims

Claims

1. A light emitting material comprising a complex of a transition metal M of atomic number at least 40 comprising at least one ligand L1 of general formulae E1 - SBF, E1 -Ar1 -SBF, E1 -Open SBF and/or E1 -Ar1 -Open SBF wherein

E1 is a 5 -membered heteroaryl ring, bound to the metal atom by covalent or dative bonds and containing at least one donor nitrogen atom, wherein said heteroaryl ring may be un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyi, aryl and heteroaryl group and/or may form an annealed ring system with other rings selected from cycloalkyl, aryl and heteroaryl rings;

Ar1 when present is bound to the metal atom by covalent or dative bonds and is selected from the group consisting of substituted or un-substituted C6-C30 arylene and substituted or un-substituted C2-C30 heteroarylene group, which Ar1 group may be un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyi, aryl and heteroaryl groups;

SBF represents 9,9'-spirobifluorenyl, Open SBF represents 9,9-diphenyl-9H- fluorenyl, in both cases un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyi, aryl and heteroaryl groups.

2. Light emitting material in accordance with claim 1 wherein the ligand L1

corresponds to one of formulae I to IV

(I)

wherein SBF and/or Open SBF are un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl groups.

Light emitting material in accordance with 2 wherein E1 respectively Ar1 are bound to the atom bearing number 2 or 3 of the SBF or Open SBF unit.

Light emitting material in accordance with at least one of claims 1 to 3 wherein E1 is an heteroaryl ring derived from the heteroarenes group consisting of

2H-pyrrole 3H-pyrrole 1 -substituted 2H-imidazole 4H-imidazole

1 /-/-imidazole

1-substituted-1H-1,2,3-triazole

2-substituted-2H-1 ,2,3-triazole

1 -substituted-"! H-1,2,4-triazole 1-substituted-1H-pyrazole

1 -substituted 1H-1,2,3,4-tetrazole 1,3-disubstituted imidazol-2-ylidene

wherein R, R¹ and R² are selected from the group consisting of SBF and Open SBF unit, Ar1 ring, hydrogen, alkyl, alkenyl, alkynyl, arylalkyi, aryl and heteroaryl groups

orfronn the group of heteroarenes consisting of

oxazole isoxazole thiazole isothiazole

,2,3-oxadiazole 1,2,5-oxadiazole 1,2, 3-th iadiazole 1,2,5-thiadiazole wherein the rings can be unsubstituted or substituted with one or more

substituents described above for R, R¹ and R².

Light emitting material in accordance with at least one of claims 1 to 4, wherein Ar1 is selected from the group consisting of substituted or un-substituted arylene groups comprising 6 to 14 carbon atoms and of substituted or un-substituted heteroarylene group comprising 2 to 14 carbon atoms, the substituents being selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl groups.

Light emitting material in accordance with claim 5 wherein Ar1 is selected from the group of formulae

wherein R³ is selected from the group consisting of hydrogen, alkyl, alkoxy, aryl and heteroaryl groups, and wherein said Ar1 may be un-substituted or substituted by substituents selected from the group consisting of halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl groups.

7. Light emitting material in accordance with at least one of claims 1 to 6 wherein E1 is selected from imidazolyl or pyrazolyl rings.

8. Light emitting material in accordance with claim 7 wherein the ligand L1 has one of the following formulae

Open SBF

(IX) (X) wherein R⁴, R⁵, R⁶ independently from one another and R⁷, R⁸, R⁹, R¹⁰, R^{1 1}, R¹² and R¹³ independently of one another represent a hydrogen atom or an organic radical with the proviso that at least one of R⁷ to R¹³ is SBF or Open SBF.

9. Light emitting material in accordance with at least one of claims 1 to 6 wherein ligand L1 has one of the following structures

wherein R⁴ to R¹³ independently of one another represent a hydrogen atom or an organic radical and at least one of R⁷ to R¹³ is SBF or Open SBF.

10. Light emitting material in accordance with at least one of claims 1 to 9 comprising at least one second ligand L2

1 1. Light emitting material in accordance with claim 10 where the ligand L2 is

represented by one of the following formulae:

(L2-1 ) (L2-2) wherein R¹⁶ and R¹⁷ may be the same or different and are groups other than H and halide and wherein R¹⁸ to R²⁰ may be the same or different and are selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, amino, cyano, alkenyl, alkynyl, arylalkyl, aryl and heteroaryl groups.

12. Light emitting material in accordance with claim 1 1 wherein the ligand L2 is

represented by one of the following formulae:

-3) (L -4) (L2-5)

(L2-6) (L2-7)

(L2-8) (L2-9) (L2-10)

(L2-1 1 ) (L2-12) wherein R²¹ and R²² are selected from the group consisting of H, alkyl, heteroaryl and aryl groups.

13. Use of the light ennitting material or mixture of these materials according to

anyone of claims 1 to 12 in the emitting layer of an organic light emitting device.

14. Use of the light emitting material or mixture of these materials according to

anyone of claims 1 to 13 as dopant in a host layer, functioning as an emissive layer in an organic light emitting device.

15. An organic light ennitting device (OLED) connprising an emissive layer (EML), said emissive layer comprising the light emitting material or mixture of these materials according to anyone of claims 1 to 12, optionally with a host material.