Cross-linkable organometallic light emitting ligands and complexes

Abstract

A 1, 4 bidentate ligand comprising first and second ligand centres, wherein the first ligand centre is an sp.sup.2-hybridised carbon or a nitrogen atom; wherein the second ligand centre is a nitrogen atom in a five- or six-membered aromatic or hetero-aromatic ring, said ring having a substantially linear substituent T.sup.1 meta or para to the nitrogen atom; wherein T.sup.1 has the formula 1:
—Ar.sup.1.sub.a—Y.sup.1.sub.b—Ar.sup.2—[Y.sup.2.sub.c—Ar.sup.2].sub.d—S—B  (1) and wherein T.sup.1 is attached to the ring by X.sup.1, wherein X.sup.1 is a bond, a methylene group, a substituted methylene group, an oxygen atom or a sulphur atom, wherein each Ar.sup.1 and Ar.sup.2 are independently selected from the group of C.sub.6 to C.sub.20 aromatic and C.sub.4 to C.sub.20 heteroaromatic groups, wherein Y.sup.1 and each Y.sup.2 is independently an optionally substituted C.sub.2 or acetonitrile trans double-bond linking moiety, wherein a is 0, 1, 2 or 3, wherein b is 0, 1 or 2, wherein each c is independently 0, 1 or 2, wherein d is 0, 1, 2, 3 or 4, S is a flexible spacer, and B represents a moiety having one or more cross-linkable functionalities. Network polymers, complexes, compositions, and devices based on this ligand. Method for forming devices based on this ligand.

Claims

1. A 1,4-bidentate ligand comprising first and second ligand centres, wherein the first ligand centre is an sp.sup.2-hybridised carbon or a nitrogen atom; wherein the second ligand centre is a nitrogen atom in a five- or six-membered aromatic or hetero-aromatic ring, said ring having a substantially linear substituent T.sup.1 meta or para to the nitrogen atom; wherein T.sup.1 has the formula 1:
—Ar.sup.1.sub.a—Y.sup.1.sub.b—Ar.sup.2—[Y.sup.2.sub.c—Ar.sup.2].sub.d—S—B   (1) and wherein T.sup.1 is attached to the ring by X.sup.1, wherein X.sup.1 is a bond, a methylene group, a substituted methylene group, an oxygen atom or a sulphur atom, wherein each Ar.sup.1 and Ar.sup.2 are independently selected from the group of C.sub.6 to C.sub.20 aromatic and C.sub.4 to C.sub.20 heteroaromatic groups, wherein Y.sup.1 and each Y.sup.2 is independently an optionally substituted C.sub.2 or acetonitrile trans double-bond linking moiety, wherein a is 0, 1, 2 or 3, wherein b is 0, 1 or 2, wherein each c is independently 0, 1 or 2, wherein d is 0, 1, 2, 3 or 4, S is a flexible spacer, and B represents a moiety having one or more cross-linkable functionalities; wherein the 1,4-bidentate ligand is coordinated to iridium (III), platinum (II), osmium (II) or ruthenium (II) in a complex.

2. The 1,4-bidentate ligand of claim 1, wherein b is 1 or 2.

3. The 1,4-bidentate ligand of claim 1, wherein each Ar.sup.1 and Ar.sup.2 are aromatic diradicals independently selected from the group consisting of 1,4-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, perylene-3,10-diyl, pyrene-2,7-diyl, fluorene-2,7-diyl, fluorene-3,6-diyl, 9,9-dialkylfluorene-2,7-diyl, 9,9-dialkylfluorene-3,6-diyl, 9-(1′-alkylidiene)fluorene-2,7-diyl, 2,5-dialkoxybenzene-1,4-diyl, m-xylene, p-xylene, durene, and/or heteroaromatic diradicals independently selected from the group consisting of benzo[1,2-b:4,5-b′]bis[1]benzothiophene-3,9-diyl, dibenzothiophene-3,7-diyl, [1]benzothieno[3,2-b][1]benzothiophene-2,7-diyl, 1,3,4-oxadiazole-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl, 2,1,3-benzothiadiazole-4,7-diyl, 2,2′-dithiophene-5,5′-diyl, 4,7-dithien-2-yl-2,1,3-benzothiazole-5′,5″-diyl, 4-alkyl-1,2,4-triazole-3,5-diyl, 4-thien-2-yl-2,1,3-benzothiazole-7,5′-diyl, 5,5-dioxodibenzothiophene-3,7-diyl, 5,11-dialkylindolo[3,2-b]carbazole-3,9-diyl, 5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl, 9-alkylcarbazole-2,7-diyl, 9-alkylcarbazole-3,6-diyl, benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl, benzo[1,2-b:5,4-b′]dithiophene-2,6-diyl, benzo[1,2-d:4,5-d′]bisoxazole-2,6-diyl, benzo[1,2-d:5,4-d′]bisoxazole-2,6-diyl, dithieno[3,2-b:2′,3′-d]thiophene-2,6-diyl, imidazo[4,5-d]imidazole-2,5-diyl, oxazole-2,5-diyl, oxazolo[4,5-d]oxazole-2,5-diyl, oxazolo[5,4-d]oxazole-2,5-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 5,5-dialkyl-5H-dibenzo[b,d]silole, pyridine-2,5-diyl, pyrimidine-2,5-diyl, thiazolo[4,5-d]oxazole-2,5-diyl, thiazolo[4,5-d]thiazole-2,5-diyl, thiazolo[5,4-d]oxazole-2,5-diyl, thiazolo[5,4-d]thiazole-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl, thiophene-2,5-diyl, furan-2,5-diyl and 1,2,4,5-tetrazine-3,6-diyl.

4. The 1,4-bidentate ligand of claim 1, wherein S has the formula (2):
—K—S.sup.1—K—  (2) wherein S.sup.1 is a straight chain or branched C.sub.4-C.sub.14 alkyl group, wherein from 1 to 10 CH.sub.2 groups are optionally each replaced by an oxygen, provided that no acetal, ketal, peroxide or vinyl ether is present in the S group, and wherein each K is independently selected from a bond, or an ether, ester or carbonate linkage.

5. The 1,4-bidentate ligand of claim 4, wherein S.sup.1 is a linear C7 alkyl chain and/or wherein B is methacrylate.

6. The 1,4-bidentate ligand of claim 1, wherein B is of the formula (3) or the formula (4):
—B.sup.1   (3)
—Z(—S—B.sup.1).sub.2   (4) wherein B.sup.1 is a cross-linkable functionality selected from the group consisting of ethylenic, diene, thiol and oxetane cross-linkable groups, wherein Z is a straight-chain C.sub.1-C.sub.12 alkyl, C.sub.1-C.sub.12 haloalkyl, C.sub.3-C.sub.8 cycloalkyl, C.sub.6-C.sub.16 aryl or C.sub.4-C.sub.15 heteroaryl group, and wherein S has the formula 2.

7. The 1,4-bidentate ligand of claim 1, wherein the first ligand centre is in a six-membered aromatic- or hetero-aromatic ring, and wherein said ring comprises a substantially linear substituent T.sup.2 meta to the first ligand centre, wherein T.sup.2 has the formula (1) and may be the same or different from T.sup.1, and wherein T.sup.2 is attached to the ring by X.sup.2, wherein X.sup.2 is a bond, a methylene group, a substituted methylene group, an oxygen atom or a sulphur atom, and wherein T.sup.2 is meta to the first ligand centre.

8. The 1,4-bidentate ligand of claim 1, wherein the first ligand centre is a sp.sup.2 hybridised carbon and forms part of a 6-membered aromatic ring; and/or wherein the second ligand centre forms part of a 6-membered aromatic ring.

9. The 1,4-bidentate ligand of claim 1, wherein the complex has an octahedral bis-heteroleptic or tris-heteroleptic structure, or a square planar bis-homoleptic or bis-heteroleptic structure.

10. The ligand of claim 1 comprising a complex, wherein the complex has two 1,4-bidentate ligands each comprising the same T.sup.1 and, where present, T.sup.2 substituents.

11. The 1,4-bidentate ligand of claim 1 wherein the 1,4-bidentate ligand is coordinated to iridium (III), platinum (II), osmium (II) or ruthenium (II) in a complex, in a composition with a nematic liquid crystalline material; wherein the nematic liquid crystalline material is cross-linkable.

12. The 1,4-bidentate ligand of claim 11 wherein the complex constitutes from 1 to 50 wt % of the composition.

13. A device comprising one or more charge transport layers and/or emissive layers comprising a network polymer formed by exposure of the 1,4-bidentate ligand of claim 1 to radiation.

14. The device according to claim 13, wherein the device is an OLED device, a photovoltaic device or a thin film transistor (TFT) device.

15. The device according to claim 13, wherein the network polymer is provided in a hole transporting layer or an electron transporting layer provided directly adjacent an electron transporting layer or a hole transporting layer respectively.

16. A device according to claim 13 which is an OLED device having a light emitting emissive layer and wherein the network polymer forms a uniformly aligned liquid crystalline structure within the emissive layer whereby the light emitting emissive layer emits linearly polarised light.

17. A method for forming a device comprising one or more charge transport layers and/or emissive layers comprising a network polymer, the method comprising: providing a layer comprising the 1,4-bidentate ligand of claim 1; selectively irradiating the layer with irradiation to form a network polymer; and washing away any non-irradiated and unpolymerized ligand.

18. The method according to claim 17, further comprising providing a further layer comprising a 1,4-bidentate ligand comprising first and second ligand centres, wherein the first ligand centre is an sp.sup.2-hybridised carbon or a nitrogen atom; wherein the second ligand centre is a nitrogen atom in a five- or six-membered aromatic or hetero-aromatic ring, said ring having a substantially linear substituent T.sup.1 meta or para to the nitrogen atom; wherein T.sup.1 has the formula (1):
—Ar.sup.1.sub.a—Y.sup.1.sub.b—Ar.sup.2—[Y.sup.2.sub.c—Ar.sup.2].sub.d—S—B   (1) and wherein T.sup.1 is attached to the ring by X.sup.1, wherein X.sup.1 is a bond, a methylene group, a substituted methylene group, an oxygen atom or a sulphur atom, wherein each Ar.sup.1 and Ar.sup.2 are independently selected from the group of C.sub.6 to C.sub.20 aromatic and C.sub.4 to C.sub.20 heteroaromatic groups, wherein Y.sup.1 and each Y.sup.2 is independently an optionally substituted C.sub.2 or acetonitrile trans double-bond linking moiety, wherein a is 0, 1, 2 or 3, wherein b is 0, 1 or 2, wherein each c is independently 0, 1 or 2, wherein d is 0, 1 ,2, 3 or 4, S is a flexible spacer, and B represents a moiety having one or more cross-linkable functionalities; selectively irradiating the further layer with irradiation to form a network polymer; and washing away any non-irradiated and unpolymerized ligand from the further layer.

19. The method of claim 17 wherein providing the layer comprises providing a layer of a complex or composition comprising the ligand.

20. The 1,4-bidentate ligand of claim 8, wherein the 6-membered aromatic ring is pyridine.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is the normalised absorption and emission spectra of an iridium complex Ir(4-p-2-ppy).sub.2(acac) described herein in dilute toluene solution.

(2) FIG. 2 is the normalised absorption and emission spectra of an iridium complex Ir(4-bp-2-ppy).sub.2(acac) described herein in dilute toluene solution.

PREFERRED EMBODIMENTS

(3) In the following the structure of the 1,4-bidentate ligand described above will be referred to as L. The ligand L can form complexes with a transition metal M through the first and second ligand centres, which are referred to as P and Q respectively in the text which follows.

(4) In the case of La, which is an embodiment of L, there is a linear arm of structure (I)
—Ar.sup.1.sub.a—Y.sup.1.sub.b—Ar.sup.2—[Y.sup.2.sub.c—Ar.sup.2].sub.d—S—B  structure (I)

(5) attached to the five membered ring (Q.sup.5) or six membered ring (Q.sup.6) containing the second ligand centre as appropriate via a bond, an optionally substituted bridging methylene group, an oxygen atom or a sulfur atom that is meta to the centre of Q.sup.5 or para to the ligand centre of Q.sup.6. a is 0, 1, 2 or 3. b is 0, 1 or 2. Each c is independently 0, 1 or 2. d is 0, 1,2, 3 or 4. Ar.sup.1 and Ar.sup.2 are in each instance independently selected from the group of C.sub.6 to C.sub.20 aromatic and C.sub.4 to C.sub.20 heteroaromatic groups. S is a flexible spacer which in each occurrence is independently selected from the group of straight chain or branched achiral C.sub.4-C.sub.14 alkyl and ether groups linked to adjacent components of the arm through a bond or an ether, ester or carbonate linkage

(6) In the case of Lb, first and second linear arms of the structure (I) as defined above are attached meta to the ligand centres P and Q each of which form part of separate 6-membered aromatic rings, P.sup.6 and Q.sup.6.

(7) In one embodiment there is provided a ligand Lc of the general structure L in which P is a sp.sup.2 hybridised carbon and wherein Q and the components of the arm(s) of structure (I) are as defined above for La and Lb.

(8) In one embodiment there is provided a ligand Ld of the general structure L in which P is a nitrogen atom and wherein Q and the components of the arm(s) of structure (I) are as defined above for La and Lb.

(9) In one embodiment there is provided a ligand Le of the general structure L in which Q is a nitrogen and wherein P is a sp.sup.2 hybridised carbon and forms part of a 6-membered aromatic ring and the components of the arm(s) of structure (I) are as defined above for La, Lb, Lc and Ld.

(10) In one embodiment there is provided a ligand Lf of the general structure L in which Q is a nitrogen and forms part of a six membered aromatic ring and wherein P and the components of the arm(s) of structure (I) are as defined above for La, Lb, Lc and Ld.

(11) In one embodiment there is provided a ligand Lg of the general structure La in which P is located within a five membered aromatic ring P.sup.5 and wherein P and the components of the arm of structure (I) are as defined above for Lc, Ld, Le and Lf.

(12) In one embodiment there is provided a ligand Lh of the general structure L in which P is located within a six membered aromatic ring P.sup.6 and wherein P and the components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le and Lf.

(13) In one embodiment there is provided a ligand Lm of the general structure L in which Ar.sup.1 and Ar.sup.2 where present are in each instance independently selected from phenyl, naphthyl, fluorene, 9-9-dialkyl fluorene, 9-(1′-alkylidiene)fluorene, thiophene, furan and N-alkylcarbazole, oxadiazole, thiadiazole, pyridine, pyrimidine and tetrazine each of which are optionally substituted with one to four halogen and/or C.sub.1-C.sub.6-alkyl and/or C.sub.1-C.sub.6-alkoxy groups and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, and Lh.

(14) In one embodiment there is provided a ligand Ln of the general structure L in which Ar.sup.1 and Ar.sup.2 where present are phenyl groups optionally substituted with one to four halogen and/or C.sub.1-C.sub.8-alkyl and/or C.sub.1-C.sub.6-alkoxy groups and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, and Lh.

(15) In one embodiment there is provided a ligand Lo of the general structure L in which Ar.sup.1 and Ar.sup.2 where present are phenyl groups and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm and Ln.

(16) In one embodiment there is provided a ligand Lp of the general structure L in which S is a flexible spacer which in each occurrence is independently selected from the group of straight chain or branched achiral C.sub.5-C.sub.14 alkyl groups and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln and Lo.

(17) In one embodiment there is provided a ligand Lq of the general structure L in which S is a flexible spacer which in each occurrence is independently selected from the group of straight chain C.sub.5-C.sub.12 alkyl groups and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln and Lo.

(18) In one embodiment there is provided a ligand Lr of the general structure L in which each B is independently selected from the group of alkene, diene, thiol and oxetane cross-linkable groups wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp and Lq.

(19) In one embodiment there is provided a ligand Ls of the general structure L in which each B is independently selected from the group of alkene cross-linkable groups wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp and Lq.

(20) In one embodiment there is provided a ligand Lt of the general structure L in which each B is independently selected from the group of cross-linkable groups that undergo cross-link on exposure to radiation, for example UV light wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp and Lq.

(21) In one embodiment there is provided a ligand Lu of the general structure L in which each B is independently selected from straight chain and cyclic □□□-unsaturated esters, □□□-unsaturated amides, vinyl ethers and non-conjugated diene cross-link groups wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp and Lq.

(22) In one embodiment there is provided a ligand Lv of the general structure L in which each B is independently selected from methacrylate, ethacrylate, ethylmaleato, ethylfumarato, N-maleimido, vinyloxy, alkylvinyloxy, vinylmaleato, vinylfumarato, N-(2-vinyloxymaleimido), 1,4-pentadien-3-yl and 1,4-cyclohexadienyl and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp and Lq.

(23) In one embodiment there is provided a ligand Lw of the general structure L in which each B is independently selected from electron-rich alkene cross-linkable groups, for example an ethylene group substituted with one or more electron donating groups selected from O, N or S and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp and Lq.

(24) In one embodiment there is provided a ligand Lx of the general structure L in which each B is independently selected from electron-rich alkene cross-linkable groups, for example a cyclic or acyclic vinyl ether group and wherein P, Q and the other components of the arm(s) of structure (I) are as defined above for La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp and Lq.

(25) In a further aspect the invention provides a complex C comprising a ligand of structure L (e.g. La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp, Lq, Lr, Ls, Lt, Lu, Lv, Lw and Lx) as described above coordinated to iridium (III), osmium (II), ruthenium (II) and platinum (II).

(26) In one embodiment there is provided an octahedral bis-heteroleptic or tris-heteroleptic complex Ca comprising one or two ligands of structure La (e.g. Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp, Lq, Lr, Ls, Lt, Lu, Lv, Lw and Lx) as described above coordinated to iridium (III), osmium (II) or ruthenium (II).

(27) In one embodiment there is provided a octahedral bis-heteroleptic or tris-heteroleptic organometallic complex Cb comprising one or two ligands of structure La (e.g. Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp, Lq, Lr, Ls, Lt, Lu, Lv, Lw and Lx) as described above coordinated to iridium (III).

(28) In one embodiment there is provided a octahedral bis-heteroleptic or tris-heteroleptic complex Cc of structure (Ia)
L.sup.1L.sup.2MA  (Ia)

(29) wherein L.sup.1 and L.sup.2 are 1,4-bidentate ligands that each coordinate to M through a) a first ligand centre that is an sp.sup.2-hybridised carbon or nitrogen and b) a second ligand centre that is a nitrogen atom or an sp.sup.2-hybridised carbon that is part of a 5- or 6-membered aromatic ring. The second ligand centres of L.sup.1 and L.sup.2 in the complex are trans to each other and at least one of L.sup.1 and L.sup.2 is of structure La (e.g. Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp, Lq, Lr, Ls, Lt, Lu, Lv, Lw and Lx) as described above. M is selected from iridium (III), platinum (II), ruthenium (II) or osmium (II). A is a bidentate ancillary ligand or a pair of independently selected monodentate ancillary ligands. Preferably the monodentate ligands are identical.

(30) In one embodiment Cd the metal in Cc is iridium (III).

(31) In one embodiment Ce the ancillary ligands A in complex Cc or Cd are monodentate and are selected from friaryl phosphines (Ar.sub.3P), trialkyl phosphines (R.sub.3P), cyanide ions (CN.sup.−), halides (F.sup.−, Cl.sup.−, Br.sup.−), isocyanides (RNC) and carbonyls (CO).

(32) In one embodiment Cf the ancillary ligand A in complex Cc or Cd is bidentate and is selected from acetylacetonate (acac), R.sup.1COCHCOR.sup.2 where R.sup.1 and R.sup.2 are optionally substituted C.sub.2-C.sub.8 alkyl or C.sub.6-C.sub.10 aryl groups, diphosphines containing two diphenyl phosphines linked by a C.sub.2-C.sub.6 bridging alkyl group and picolinate.

(33) In one embodiment Cg the complex Cc, Cd, Ce or Cf is bis-heteroleptic, i.e. L.sup.1 and L.sup.2 are identical.

(34) In one embodiment Ch the complex Cc, Cd, Ce or Cf is tris-heteroleptic and L.sup.2 is a bidentate ligand selected from 2-phenylpyridine, 2-napthylpyridine, 2-(2,4-difluorophenyl)pyridine, 2,2′-bipyridine, 1,10-phenanthroline, benzo[h]quinoline, 2-(2-thienyl)pyridine, pyridine-1,2,4-triazole, 2-phenylbenzo[d]oxazole, alkenylpyridine, phenylpyrazole, phenylimidazole, phenyltetrazoles and phenylquinoxalines.

(35) In one embodiment Ci the complex Cc, Cd, Ce or Cf is tris-heteroleptic and L.sup.2 is a bidentate ligand selected from 2-phenylpyridine, 2-napthylpyridine, 2-(2,4-difluorophenyl)pyridine, 2,2′-bipyridine, 2-(2-thienyl)pyridine, pyridine-1,2,4-triazole, 2-phenylbenzo[d]oxazole, alkenylpyridine, phenylpyrazole, phenylimidazole and phenyltetrazoles.

(36) In one embodiment there is provided a square planar complex Cj comprising a ligand of structure Lb (e.g. Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp, Lq, Lr, Ls, Lt, Lu, Lv, Lw and Lx) as described above coordinated to platinum (II).

(37) In one embodiment Ck there is provided a complex Cj with one ligand of structure Lb (e.g. Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp, Lq, Lr, Ls, Lt, Lu, Lv, Lw and Lx) and an ancillary ligand A that is a bidentate ancillary ligand or a pair of monodentate ancillary ligands.

(38) In one embodiment Cl the ancillary ligand in Ck is a bidentate ancillary ligand selected from acetylacetonate (acac), R.sup.1COCHCOR.sup.2 where R.sup.1 and R.sup.2 are C.sub.2-C.sub.8 alkyl or C.sub.6-C.sub.10 aryl groups, diphosphines containing two diphenyl phosphines linked by a C.sub.2-C.sub.6 bridging alkyl group and picolinate.

(39) In a further aspect there is provided use of a ligand of structure L, for example La, Lb, Lc, Ld, Le, Lf, Lg, Lh, Lm, Ln, Lo, Lp, Lq, Lr, Ls, Lt, Lu, Lv, Lw and Lx, in the emissive layer of an OLED device.

(40) In one embodiment there is provided use of a complex of structure C, for example Ca, Cb, Cc, Cd, Ce, Cf, Cg, Ch, Ci, Cj, Ck, or Cl, as a phosphor in the emissive layer of an OLED device.

(41) In one aspect there is provided a method for making an OLED device comprising the step of depositing a complex of structure C for example Ca, Cb, Cc, Cd, Ce, Cf, Cg, Ch. Ci, Cj, Ck, or Cl, onto a substrate, optionally a liquid crystalline substrate, and then exposing to radiation, optionally UV light.

(42) In one aspect there is provided an OLED device comprising a complex of structure C, for example Ca, Cb, Cc, Cd, Ce, Cf, Cg, Ch. Ci, Cj, Ck, or Cl, in its emissive layer.

(43) In one embodiment there is provided an OLED device comprising a complex of structure C, for example Ca, Cb, Cc, Cd, Ce, Cf, Cg, Ch. Ci, Cj, Ck, or Cl, aligned on a liquid crystalline material in its emissive layer.

DETAILED DESCRIPTION

(44) Chemical terminology used herein has the normal meaning as defined in the IUPAC Gold Book (http://goldbook.iupac.org/). For ease of reference, simple definitions for some of the terminology used herein is provided below.

(45) In general, the term “Alkyl” is used herein refers to straight chain or branched chain alkyl, such as, without limitation, methyl, ethyl, n-propyl, iso-propyl, butyl, n-butyl and tert-butyl. Straight chain alkyl is generally preferred unless otherwise indicated. In some cases a methylene (CH.sub.2) group in the alkyl chain can be replaced with an heteroatom such as oxygen, sulphur or nitrogen. In the case where a methylene group is replaced by a nitrogen it is preferred that the nitrogen is additionally substituted with a C.sub.1-C.sub.6 alkyl group.

(46) In general, the term “Aryl” as used herein refers to aromatic ring structures. Preferred aromatic ring structures are C.sub.6 to C.sub.18 aromatic groups including phenyl, naphthyl, fluorenyl, anthracenyl, pyrenyl and C.sub.4 to C.sub.12 heteroaromatic groups including imidazole, triazole, tetrazole, pyrazole, pyridine, pyridazine, pyrrole, thiophene, furan, oxazole, isoxazole, benzisoxazole and N-alkylcarbazole. For further examples see the description of Ar.sup.1 and Ar.sup.2 below.

(47) Alkoxy as used herein refers to straight or branched chain alkoxy, for example methoxy, ethoxy, propoxy, butoxy. Alkoxy as employed herein also extends to embodiments in which the or an oxygen atom (e.g. a single oxygen atom) is located within the alkyl chain, for example —C.sub.1-3 alkylOC.sub.1-3 alkyl, such as —CH.sub.2CH.sub.2OCH.sub.3 or —CH.sub.2OCH.sub.3.

(48) Halo or halogen includes fluoro, chloro, bromo or iodo, in particular fluoro, chloro or bromo, especially fluoro or chloro.

(49) Heteroleptic, as used herein, refers to an organometallic compound having two or more types of ligand. Bis-heteroleptic complexes feature two different types of ligand and tris-heteroleptic complexes feature three different types of ligand.

(50) Organometallic compounds are compounds having at least one metal-to-carbon bond. Organometallic complexes are complexes containing a metal atom that is coordinated to at least one carbon ligand centre. A ligand centre is the atom of a ligand that chemically binds to a metal atom in a complex. An sp.sup.2-hybridised carbon ligand centre is a carbon atom that is covalently double bonded to an adjacent atom in the ligand and that forms a chemical bond to a metal atom in the overall organometallic complex. Preferred ligands of the inventions form complexes with useful light emitting properties. Preferred materials of the invention are complexes of iridium (III), platinum (II), osmium (II) and ruthenium (II).

(51) In most preferred examples the metal complex is an iridium (III). Iridium (III) and platinum (II) possess the most attractive properties for OLED applications due to their higher triplet quantum yield (Φ.sub.P), relatively short triplet state lifetime (τ.sub.P), and tunable emission colour.

(52) Monodentate ligands are ligands that can form a chemical bond to a metal atom through a single ligand centre. Examples of monodentate ligands described herein that are useful as ancillary ligands include but are not limited to triaryl phosphines (Ar.sub.3P), trialkyl phosphines (R.sub.3P), cyanide ions (CN.sup.−), halides (F.sup.−, Cl.sup.−, Br.sup.−), isocyanides (RNC) and carbonyls (CO).

(53) Bidentate ligands are ligands that, when part of a ligand-metal complex, have two ligand centres that can form chemical bonds to a metal atom. 1,4-Bidentate ligands are bidentate ligands with two ligand centres separated by three chemical bonds. An example of a 1,4-bidentate ligand is given below with the ligand centres indicated by an asterisk.

(54) ##STR00011##

(55) The 5- or 6-membered aromatic ring structures of the bidentate ligands referred to herein are 6□-electron conjugated nitrogen heterocycles that optionally contain one or more further heteroatoms. Examples of 5-membered nitrogen heterocycles described herein include pyrrole, imidazole, pyrazole, triazole, tetrazole, oxazole, isoxazole, isothiazole, oxadiazole and thiadiazole and all of the isomeric forms of these structures. Examples of 6-membered nitrogen heterocycles described herein include pyridine, pyridazine, pyrimidine, pyrazine, triazine and tetrazine and all of the isomeric forms of these structures. Benzo derivatives of these 5- and 6 membered are also encompassed in the description, such benzo-derivatives feature a 6-membered aromatic ring fused to the 5- or 6-membered nitrogen heterocycles described above and include, by way of example, quinoline, isoquinoline, quinazoline, quinoxaline, phthalazine, indole, benzimidazole and benzisoxazole. 2-Phenyl pyridine systems and analogues are most preferred.

(56) The term ancillary ligand refers to a ligand or ligands that fulfil the valency and electronic requirements required to stabilise the organometallic complex but have no considerable influence on the chemistry of the complex. Examples of bidentate ancillary ligands include acetylacetonate (acac) and related ligands described by the general structure R.sup.1COCHCOR.sup.2 where R.sup.1 and R.sup.2 are alkyl or aryl groups, diphosphines containing two diphenyl phosphines linked by a bridging C.sub.2-C.sub.6 alkyl group such as dppe, dppp and dppb (with ethyl, propyl and butyl bridging groups respectively), quinolinate and picolinate.

(57) Exemplary ancillary ligands are:

(58) ##STR00012##

(59) The term “arm” is used to refer to a linear structure of formula 1:
—Ar.sup.1.sub.a—Y.sup.1.sub.b—Ar.sup.2—[Y.sup.2.sub.c—Ar.sup.2].sub.d—S—B  (1)

(60) attached to Q.sup.5 or Q.sup.6 (i.e. the ring containing the second ligand centre having 5 or six constituent atoms) as appropriate, wherein (1) is attached to the ring by X, wherein X is a bond, a methylene group, a substituted methylene group, an oxygen atom or a sulphur atom.

(61) Each Ar.sup.1 and Ar.sup.2 are independently selected from the group of C.sub.6 to C.sub.20 aromatic and C.sub.4 to C.sub.20 heteroaromatic groups. Y.sup.1 and each Y.sup.2 is independently an optionally substituted C.sub.2 or acetonitrile trans double-bond linking moiety. a is 0, 1, 2 or 3. b is 0, 1 or 2. Each c is independently 0, 1 or 2. d is 0, 1, 2, 3 or 4. S is a flexible spacer, and B represents a moiety having one or more cross-linkable functionalities

(62) The Ar.sup.1 and Ar.sup.2 groups are connected to adjacent members of the arm to maintain the linear character of the arms. As well as providing alignment properties with e.g. liquid crystalline host materials or liquid crystalline aligned substrate layers derived from e.g. π-π interactions, these groups can be used to tailor the electron and hole transport characteristics of the material. Thus Ar.sup.1 and Ar.sup.2 can be used to optimise the efficiency of the light emission of complexes of the invention in e.g. an OLED device. In addition, the electronic properties of the Ar.sup.1 group, and to a lesser extent the Ar.sup.2 group can alter the wavelength of light emitted by the complexes of the invention as they influence the energy levels of the molecular orbitals of the overall complex and the energy gap between the metal-ligand orbitals through which excited complexes degrade and release light.

(63) In cases where Ar.sup.1 or Ar.sup.2 are 5-membered rings they are substituted by adjacent components of the arm at the 1,3- or 1,4-positions (e.g. when the heteroatom is N) or at 2,4- or 2,5-positions (e.g. where the heteroatom is S, N or O). Where the Ar.sup.1 or Ar.sup.2 groups are 6-membered rings such as phenyl they are substituted by adjacent components of the arm at the 1- and 4-positions. In the case where the Ar.sup.1 and Ar.sup.2 groups are 10-membered bicycles such as naphthyl they are substituted by adjacent components of the arm at the 1,4-, 1,5- or 2,6-positions. In the case where the Ar.sup.1 and Ar.sup.2 groups are linear 14-membered tricycles such as anthracenyl they are substituted by adjacent components of the arm at the 2,6-positions. In the case where the Ar.sup.1 and Ar.sup.2 group are linear 14-membered tricycles such as phenanthracenyl they are substituted by adjacent components of the arm at the 1,4- and 1,7-positions. In the case where the Ar.sup.1 and Ar.sup.2 group are 16-membered tetracycles such as pyrenyl they are substituted by adjacent components of the arm at the 1,4- and 1,7-positions. As will be appreciated, the presence of heteroatoms would change the official numbering of the locations in the molecule—for consistency, the numbering should be approached as if the molecules are entirely carbon atom structures.

(64) Each Ar.sup.1 and Ar.sup.2 are independently selected from the group of optionally substituted C.sub.6 to C.sub.20 aromatic and C.sub.4 to C.sub.20 heteroaromatic groups. Preferably each Ar.sup.1 and Ar.sup.2 are optionally substituted aromatic diradicals independently selected from the group consisting of 1,4-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, perylene-3,10-diyl, pyrene-2,7-diyl, fluorene-2,7-diyl, fluorene-3,6-diyl, 9,9-dialkylfluorene-2,7-diyl, 9,9-dialkylfluorene-3,6-diyl, 9-(1′-alkylidiene)fluorene-2,7-diyl, 2,5-dialkoxybenzene-1,4-diyl, m-xylene, p-xylene, durene and/or optionally substituted heteroaromatic diradicals independently selected from the group consisting of benzo[1,2-b:4,5-b′]bis[1]benzothiophene-3,9-diyl, dibenzothiophene-3,7-diyl, [1]benzothieno[3,2-b][1]benzothiophene-2,7-diyl, 1,3,4-oxadiazole-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl, 2,1,3-benzothiadiazole-4,7-diyl, 2,2′-dithiophene-5,5′-diyl, 4,7-dithien-2-yl-2,1,3-benzothiazole-5′,5″-diyl, 4-alkyl-1,2,4-triazole-3,5-diyl, 4-thien-2-yl-2,1,3-benzothiazole-7,5′-diyl, 5,5-dioxodibenzothiophene-3,7-diyl, 5,11-dialkylindolo[3,2-b]carbazole-3,9-diyl, 5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl, 9-alkylcarbazole-2,7-diyl, 9-alkylcarbazole-3,6-diyl, benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl, benzo[1,2-b:5,4b′]dithiophene-2,6-diyl, benzo[1,2-d:4,5-d]bisoxazole-2,6-diyl, benzo[1,2-d:5,4-d]bisoxazole-2,6-diyl, dithieno[3,2-b:2′,3′-d]thiophene-2,6-diyl, imidazo[4,5-d]imidazole-2,5-diyl, oxazole-2,5-diyl, oxazolo[4,5-d]oxazole-2,5-diyl, oxazolo[5,4-d]oxazole-2,5-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 5,5-dialkyl-5H-dibenzo[b,d]silole, pyridine-2,5-diyl, pyrimidine-2,5-diyl, thiazolo[4,5-d]oxazole-2,5-diyl, thiazolo[4,5-d]thiazole-2,5-diyl, thiazolo[5,4-d]oxazole-2,5-diyl, thiazolo[5,4-d]thiazole-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl, thiophene-2,5-diyl, furan-2,5-diyl and 1,2,4,5-tetrazine-3,6-diyl.

(65) If hole transporting properties are desired then indole and thiophene containing moieties such as those presented below may be preferred, * denotes the typical site of attachment.

(66) ##STR00013##

(67) If electron transporting properties are desired then oxazole containing moieties such as those presented below may be preferred, * denotes the typical site of attachment.

(68) ##STR00014##

(69) The Ar.sup.1 and Ar.sup.2 groups of each arm may be optionally substituted with one to four halogens or alkyl groups. Preferred substituents are F, Cl, CF.sub.3 and C.sub.1-5 alkyl groups. It is preferred that the Ar.sup.1 and Ar.sup.2 groups of each arm are selected independently from the group of C.sub.6 to C.sub.18 aromatic groups with no intrinsic fluorescence properties of their own—for this reason aromatic groups such as anthracene and phenanthracene are generally not preferred. Examples of preferred Ar.sup.1 and Ar.sup.2 groups are phenyl, biphenyl, naphthyl, terphenyl, 9,9-dialkylfluorene, thiophene and N-alkyl carbazole. In some cases it is preferred that Ar.sup.1 and Ar.sup.2 are optionally substituted phenyl or naphthyl. In preferred cases Ar.sup.1 and Ar.sup.2 are optionally substituted phenyl. In most preferred cases Ar.sup.1 and Ar.sup.2 are phenyl.

(70) Such moieties provided as substituents which do not extend the arm length are not counted in the formula of the arm (1). That is, moieties in the arm may be substituted with other aromatic or heteroaromatic rings. For example, due to the position of the attachment, each of the following structures would constitute a single moiety in the arm.

(71) ##STR00015##

(72) The trans-alkene group of each arm, where present, is a group of the formula

(73) ##STR00016##

(74) wherein R.sup.3 and R.sup.4 are trans to each other and are each either H, C.sub.1-4 alkyl or CN groups. Where R.sup.3 or R.sup.4 are alkyl, methyl and ethyl groups are preferred.

(75) The composition of the arm is such that overall the arm is a linear conjugated system terminating in an insulating spacer group S, optionally with a site of branching Z, and a cross-linkable group B (or in the case where Z is present in two cross-linkable groups B and B.sup.1. The linear character and the presence of a number of aromatic and/or heteroaromatic rings in the arm confers the ability to of the ligand, and by extension the complexes it forms to align with liquid crystalline materials that surround them in the device thus providing the opportunity to obtain OLED device structures wherein the emitter cores are substantially all aligned in the same direction, for example by aligning with a liquid crystalline host material. This advantageously allows the possibility to deliver emitter layers with anisotropic emission characteristics and improved light output due to a reduction in the light absorbed by the device.

(76) In some preferred embodiments the integer a is 0, b is 1, each c is 1, d is from 1 to 5, and X is a bond. An example of an arm unit with this structure is

(77) ##STR00017##

(78) wherein the asterisk indicates the site of attachment to the rest of the ligand and benzene is used to represent each Ar group.

(79) In some preferred embodiments the integer d is from 2 to 5. In some preferred embodiments the integer d is from 3 to 5. In some preferred embodiments d is either 2 or 3.

(80) In some preferred embodiments the integer a is 1, b is 1, each c is 0, d is from 1 to 5 and X is a methylene. An example of an arm unit with this structure is

(81) ##STR00018##

(82) wherein the asterisk indicates the site of attachment to the rest of the ligand and benzene is used to represent each Ar group.

(83) S is a flexible spacer connected at two distal ends to the adjacent moieties which in each occurrence is independently selected from the group of straight chain or branched achiral C.sub.4-C.sub.14 alkyl and ether groups linked to adjacent components of the arm through a bond or an ether, ester or carbonate linkage. The spacer group serves, to a degree, to electrically isolate the emitter complex and also allows the cross-linkable groups B the requisite flexibility to efficiently cross-link with other cross-linkable groups in adjacent molecules. The compounds of the present invention are chemically stable enough to be used in OLED devices, spacer structures featuring relatively unstable groups such as acetals, ketals and peroxide groups do not form part of the present invention.

(84) In some preferred embodiments the flexible spacer group S is a straight chain C.sub.5-12 alkyl group. In some preferred embodiments the flexible spacer group S is a straight chain C.sub.4-11 alkoxyalkyl group. In some preferred embodiments the flexible spacer group S is a straight chain C.sub.3-10 polyether group.

(85) Preferably S has the formula 2:
—K—S.sup.1—K—  (2)

(86) wherein S.sup.1 is a straight chain or branched C.sub.4-C.sub.14 alkyl group, wherein from 1 to 10 CH.sub.2 groups are optionally each replaced by an oxygen, provided that no acetal, ketal, peroxide or vinyl ether is present in the S group, and wherein each K is independently selected from a bond, or an ether, ester or carbonate linkage. Preferably S is achiral.

(87) Preferably B is of the formula 3 or the formula 4:
—B.sup.1  (3)
—Z(—S—B.sup.1).sub.2  (4)

(88) wherein B.sup.1 is a cross-linkable functionality selected from the group consisting of ethylenic, diene, thiol and oxetane cross-linkable groups, wherein Z is a straight-chain C.sub.1-C.sub.12 alkyl, C.sub.1-C.sub.12 haloalkyl, C.sub.3-C.sub.8 cycloalkyl, C.sub.6-C.sub.16 aryl or C.sub.4-C.sub.15 heteroaryl group, and wherein S has the formula 2.

(89) Branching, as in structure (4) can be advantageous when the metal complex contains a single ligand of structure L as a higher degree of cross-link can be obtained.

(90) Preferably S or S.sup.1 is a linear C7 alkyl chain and/or wherein B is methacrylate.

(91) Exemplary —S—B groups are presented below by way of illustration wherein the asterisk indicates the site of attachment to the rest of the ligand.

(92) ##STR00019##

(93) Exemplary —B groups of the formula 4 are presented below by way of illustration wherein the asterisk indicates the site of attachment to the rest of the ligand through the flexible spacer S. The integers m, n and p are selected are chosen to match the preferred S structures described herein.

(94) ##STR00020##

(95) Preferred cross-link groups B (also referred to as cross-linkable groups herein) are selected from the group of alkene, diene, thiol and oxetane cross-linkable groups. Alkene or “ethylenic” cross-linkable groups are cross-linkable groups containing a carbon-carbon double bond. In a preferred aspect, all of the cross-link groups independently represent an alkene cross-link group. Favoured alkene cross-link groups include electron rich and electron poor ethylenic cross-link groups.

(96) The compounds of the invention therefore comprise a first cross-link group B, and optionally a second cross-link group B, and form, when cross-linked, network polymers. This is because preferred cross-link groups react with two other cross-link groups to yield a chain reaction and a polymer matrix.

(97) If the compounds of the present invention only have a single cross-linking group, then they will be unable to form a network polymer, except when provided in combination with a secondary monomer (or polymer) having two or more cross-linking grounds.

(98) In a preferred aspect, polymerisable cross-linking groups are selected from the group of ethylenic, diene, thiol and oxetane polymerisable cross-linking groups. Ethylenic cross-linking groups are cross-linkable groups containing a carbon-carbon double bond. In a preferred aspect, all of the cross-link groups independently represent an ethylenic cross-link group. Favoured ethylenic cross-link groups include electron rich and electron poor ethylenic cross-link groups.

(99) In a preferred aspect the cross-linkable groups undergo cross-link reactions on exposure to radiation. In a preferred aspect the cross-linkable groups are photo cross-linkable groups, i.e. those groups that undergo cross-link reactions on exposure to ultra-violet (UV) light.

(100) Examples of preferred cross-linking groups are straight chain and cyclic □□□-unsaturated esters and □□□-unsaturated amides, straight chain terminal alkenes, bridged cyclic alkenes, thiols, vinyl ethers, cyclic ethers and non-conjugated dienes. Favoured cross-linking groups therefore include acrylate, methacrylate, monomethylmaleate, monoethylmaleate, monomethylfumarate, monoethylfumarate, 4,4,4-trifluorocrotonate, N-maleimide, ethenyl, N-vinylpyrrolidone, N-substituted-N-vinylformamide, N-substituted-N-vinylalkylamide, norbornene, sulfhydryl, vinyloxy, methylvinyloxy, 1,3-propylene oxide (oxetane), 1,4-pentadiene, 1,6-heptadiene and diallylamine as these groups are particularly suitable for photo cross-linking, especially with UV-light.

(101) In a preferred aspect the cross-linking groups are electron-rich ethylenic cross-linkable groups. Electron rich ethylenic cross-linkable groups contain an ethylene group substituted with one or more electron donating groups. The electron donating group can comprise a heteroatom such as O, N or S. In a preferred aspect the electron rich cross-linkable group is a vinyloxy group. Other electron donating group substituted crosslinking groups are 1-alkenyl ethers such as propen-1-yloxy groups and buten-1-yloxy groups; cyclic vinyl ethers such as cyclohexen-1-yloxy and cyclopenten-1-yloxy; bicyclic vinyl ethers such as 2-norbornen-2-yloxy groups and groups in which the vinyl ether function is connected to the spacer S or the branches of Z through an intervening hydrocarbyl structure such as 4-vinyloxybenzene and 2-vinyloxyethyl groups.

(102) ##STR00021##

(103) The above groups show examples of cross-linking groups, with the former also including a portion of the spacer group S.

(104) ##STR00022##

(105) In a preferred aspect the cross-link groups are electron-poor ethylenic cross-linkable groups. Electron deficient ethylenic cross-linkable groups contain an ethylene group substituted with one or more electron withdrawing groups. The electron withdrawing group may comprise a carbonyl group and may for example be an ester or an amide. In a preferred aspect the electron deficient cross-linkable group comprises a monoalkylmaleate group, a monoalkylfumarate group, a monoarylmaleate group, a monoarylfumarate group or a maleimide group. Other examples of electron deficient crosslinking groups are acrylate groups, methacrylate groups, 4,4,4-trifluorocrotonate groups, Z- and E-3-cyanoacrylates, Z- and E-3-cyanomethacrylates, monoalkyl cyclohexene-1,2-dicarboxylates, and monoalkyl cyclopentene-1,2-dicarboxylates.

(106) The ligands of the invention as described above are useful for forming complexes with light emitting properties that find application for example as light emitters in OLED devices amongst other applications. The emission properties of the complex can be tailored to the intended application by varying the nature of the ligand and the metal.

(107) The presence of cross-linkable groups B allow complexes formed from the ligands of the present invention to be deposited in layers from solution processing, then once the solvent is removed they can be fixed in place by cross-link to form a relatively insoluble network polymer. The complexes formed between the ligands of the present invention as described below and the preferred metals are soluble in common organic solvents. This is significant as the solubility of the complexes of the invention provides distinct advantages in terms of device fabrication relative to e.g. polymeric materials. In more detail, these complexes are suitable for a solution processing approach to OLED device fabrication. In outline, this involves first dissolving the complex in an organic solvent, applying the resultant solution to a substrate and then evaporating to generate a film coating on the substrate. Once the material is deposited as a film the material can be polymerised in situ. This polymerisation may be initiated by exposure to radiation, for instance ultraviolet light, which causes the cross-linkable groups of one molecule to cross-link with those in an adjacent molecule to form a network polymer. Regions of the deposited film can be masked from the initiating radiation to give zones of non-cross-linked material while zones exposed to radiation undergo polymerisation. If desired the unexposed, non-cross-linked material can be washed off to leave behind a patterned structure of cross-linked material due to the cross-linked material having negligible or reduced solubility relative to that of the monomer. Iterative cycles of solution deposition and polymerisation can be used to generate structures with complex architectures.

(108) Sequentially deposited polymerised structures can be assembled in a side by side or stacked/layered manner. In one example, sequential deposition and polymerisation of red, green and blue emitting material in a side by side manner can be used to generate pixels for colour displays. In another example, a stack of red, green and blue emitter materials can be used to give a white light source. In another example, two or more emitter structures can be arranged in a stack to give a coloured light source.

(109) The ability to cheaply and economically produce multilayer devices in which adjoining layers have different highest occupied or lowest unoccupied molecular orbital (HOMO and LUMO) energy levels as well as different charge carrier mobilities is of general utility in plastic electronics. For instance, the equivalent of p-n junctions may be formed using the materials and processes of this invention and these may find utility in diodes, transistors, and photovoltaic devices. The propensity of the complexes of the invention to be photo lithographically patterned allows large arrays of plastic electronic devices of virtually any size and description to be fabricated.

(110) Complexes according to this invention may be mixed together with a liquid crystalline host material to form layers in which the emitter cores with a high degree of directional order. This can be very advantageous from the standpoint of optimising the material properties for OLED as noted above. This directional order can be fixed in place by cross-link the components of the deposited films, for example by exposing the deposited film to radiation such as ultraviolet light. For example, linearly polarised emission uniaxial molecular orientation of the phosphor (i.e. the metal complexes of the invention) is achieved using a nematic photo-crosslinkable liquid crystal host on either a rubbed polymer surface (i.e., PEDOT, polyimide or nylon 6,6) or by photoalignment of coumarin derivatives. The nematic liquid crystal acts as a host and the organometallic material (the phosphor) acts as the emissive dopant. For multi-layer OLED capability, the host-dopant system is preferably photo-crosslinkable in which a solution deposited film can be rendered insoluble to common organic solvents after UV-curing. The resulting insolubility of the film allows layers to be solution processed on top without damaging or washing away the phosphorescent host-dopant layer below.

(111) The potential to obtain highly ordered device structures can be exploited to generate polarised light emitting structures in which the emitter cores are aligned in the same direction and therefore emit light in the same direction. Ultimately, the properties of the materials described herein afford the possibility to fabricate 3D-displays through sequential deposition of aligned layers of uniformly aligned liquid crystalline fluid or glass, sequential polymerisation of patterned areas of each layer in turn, and sequentially washing away of unpolymerised areas of each layer in turn so as to provide light emitting structures such that the polarisation axis of light emission of each respective layer is in a different direction. For linearly polarised emission uniaxial molecular orientation of the phosphorescent emitter can be achieved using a nematic photo-crosslinkable liquid crystal host on either a rubbed polymer surface (i.e., PEDOT, polyimide or nylon 6,6) or by photoalignment of coumarin derivatives. The nematic liquid crystal acts as a host and the organometallic material (the phosphor) acts as the emissive dopant.

(112) The materials of the present invention also possess a number of additional desirable properties that render them useful for the production of electronic devices such as OLEDs. In organic light emitting devices it is often also desirable to reduce the self-absorption of emitted light by organic luminescent materials. This self-absorption occurs because the spectral absorbance and emission bands of organic luminescent materials overlap to a greater or lesser extent in various materials. A solution to this problem well known, for instance, in the field of dye lasers is to dissolve the luminescent material in a host with that absorbs light at a shorter wavelength than the luminescent solute. If the solution is dilute, for instance one to two percent, the self-absorption of the luminescent solute is nearly completely suppressed. The facile mutual miscibility of the various compounds of this invention makes the preparation of solutions of this type very easy. The materials of the present invention therefore are useful as host materials as well as light emitting materials.

(113) In organic light emitting device applications it is necessary that there be facile excitation energy transfer from the host material to the solute luminescent material. This is because charge carriers (electrons and holes) must be transported through the host medium to recombine to form the excitons (electrically excited molecular orbital states) that radiate light. In a mixture composed mainly of component host molecules this recombination and exciton formation will mainly occur in the host molecules. The excitation energy then needs to be transferred from the host molecules into the luminescent solute molecules. It is a requirement for this energy transfer that the spectral luminescent emission band(s) of the host material overlap the absorption band of the luminescent solute. Thus an important aspect of the invention is the preparation of mixtures of the compounds of the invention that have this spectral relationship between the constituent components. For instance, a compound which emits in the blue region of the spectrum can serve as a host for a compound which is a green light emitter. A polymer film prepared by the UV induced crosslinking of a solution of 5% blue emitter compound in green emitter compound will exhibit considerably less self-absorption of the green light emitted by the green emitter than will a film prepared by UV crosslinking of pure green emitter.

(114) Complexes

(115) The ligands of the present invention are useful for making both octahedral and square planar transition metal complexes. Octahedral complexes of iridium (III), osmium (II), ruthenium (II) and square planar complexes of platinum (II) are preferred.

(116) The octahedral complexes of the invention feature a metal selected from iridium (III), osmium (II) and ruthenium (II) listed above and either one ligand of the invention and a 1,4-bidentate ligand and ancillary ligand(s) or two ligands of the invention and ancillary ligand(s). Exemplary complexes of the present invention wherein the second ligand centres of L.sup.1 and L.sup.2 are nitrogen, first ligand centres are sp.sup.2-hybridised carbons, and the arm, of each of L.sup.1 and L.sup.2, optionally terminate in one or two cross-linkable groups B (and B.sup.1).

(117) The invention also relates to square planar complexes of platinum (II) two with a single ligand according to the invention of type Lb and a bidentate ancillary ligand or a pair of monodentate ancillary ligands.

(118) Complexes according to the invention can be formed under standard conditions, for example by heating the appropriate ligand of structure La and metal salt in the appropriate solvent and then adding in the appropriate ancillary ligand. This process is shown schematically for octahedral iridium complexes and square planar platinum complexes in the Schemes below.

(119) ##STR00023##

(120) The bis-heteroleptic octahedral complexes, i.e. those containing two ligands according to the present invention, form in such a manner that the second ligand centres of each ligand (a nitrogen in each case) and the metal are in substantially linear alignment. The complex thus has arms projecting along this same linear axis as can be seen in the crystal structure of Ir(4-pepe-2-ppy).sub.2(acac) shown below. This linear character and the □-stacking interaction potential provided by the aromatic rings in the ligand arms allows the complexes of the invention to align with liquid crystalline host materials and thus deliver the possibility of making emitter layers (phosphor layers) with molecular aligned emitter cores and anisotropic emission properties.

(121) ##STR00024##

(122) While the present invention has been described with reference to ligands comprising at least one arm of the structure:
—Ar.sup.1.sub.a—Y.sup.1.sub.b—Ar.sup.2—[Y.sup.2.sub.c—Ar.sup.2].sub.d—S—B

(123) and complexes comprising said ligands, it will be appreciated that during synthesis several intermediates will be produced. In particular the ligands may be produced with one or two arms of the structure:
—Ar.sup.1.sub.a—Y.sup.1.sub.b—Ar.sup.2—[Y.sup.2.sub.c—Ar.sup.2].sub.d—S-LG

(124) Wherein LG is a leaving group, such as a hydroxy group (—OH), a halide (—Cl or —Br or —I), a sulfonate ester (such as a -mesylate or -tosylate), a carboxylate, phenoxide or any other conventional leaving group as would be known in the art.

(125) Producing complexes from ligands including cross-linkable groups can cause complication during synthesis. In particular, reactions to form the complexes are often performed at increased temperature. Cross-linkable groups are often unstable at increased temperature. Therefore, it may be advantageous to form the complexes using ligands comprising one or more arms of the above intermediate structure and then add the cross-linking group to the already metallated ligand complex by reaction with the leaving group.

(126) Examples of addition of the cross-linking groups both before and after metallation are provided in the non-limiting examples below.

SYNTHETIC EXAMPLES

(127) The compounds and complexes of the present invention may be synthesised by common techniques in organic synthesis and organometallic chemistry well known to those of ordinary skill in the art. Illustrative examples of how these compounds can be synthesised are presented below. As can be appreciated, the nature of these materials allows a modular approach to synthesis to be adopted. The examples provided below are by way of example only and in no way limit the scope of the invention.

Scheme 1: Synthesis of Bis-Heteroleptic Cross-linkable Iridium Complex Ir(4-dpe-2-ppy).SUB.2.(acac)

(128) ##STR00025##

(129) Suzuki coupling of 4-bromo-2-phenylpyridine (1) with phenylboronic acid, using Pd(PPh.sub.3).sub.4 as the catalyst, gave good selectivity at the pyridine 2-position and afforded compound (2) in good yield. This allowed a remaining Ar—Br bond to be utilised in a second Suzuki coupling using (4-vinylphenyl)boronic acid to afford compound (3). Heck coupling using Pd(PPh.sub.3).sub.2Cl.sub.2 as the catalyst at 130° C. in DMF with 5-(4-bromophenoxy)pentan-1-ol yielded compound (4), which was esterified with methacrylic acid by a Steglich esterification to afford (E)-5-(4-(4-(2-phenylpyridin-4-yl)styryl)phenoxy)pentyl methacrylate (5). Subsequent cyclometalation using bis(1,5-cyclooctadiene)diiridium(I) dichloride ([Ir(cod)Cl].sub.2) as the iridium source in refluxing THF (dry and degassed) afforded DIMER-1 that was converted to the cross-linkable bis-heteroleptic acac phosphor Ir(4-dpe-2-ppy).sub.2(acac) using acetylacetone with tetrabutylammonium hydroxide in DCM at 40° C.

4-bromo-2-phenylpyridine (2)

(130) 2,4-Dibromopyridine (compound 1, 4.35 g, 0.0184 mol), phenylboronic acid (2.24 g, 0.0184 mol), Na.sub.2CO.sub.3 (5.84 g, 0.0551 mol), dimethoxyethane (50 mL) and water (20 mL) were all added to a 3-neck round bottomed flask. The system was degassed with the aid of two freeze-pump-thaw cycles using nitrogen as the inert gas. Subsequently, Pd(PPh.sub.3).sub.4 (1.06 g, 0.92 mmol) was added and the reaction mixture was again degassed by one freeze-pump-thaw cycle. The reaction mixture was heated under reflux for 2 days and then poured into a separating funnel. Work-up was conducted using ethyl acetate (200 mL) and the organic extract washed with water (200 mL), dried (MgSO.sub.4) and filtered. The filtrate was concentrated under reduced pressure and the crude product was purified by column chromatography (dry loaded, silica gel, 100% DCM) to yield a pale-yellow oil (2.85 g, 66.3%).

2-phenyl-4-(4-vinylphenyl)pyridine (3)

(131) 4-Bromo-2-phenylpyridine (compound 2, 2.00 g, 0.0085 mol), (4-vinylphenyl)boronic acid (1.52 g, 0.0103 mol), Na.sub.2CO.sub.3 (2.72 g, 0.0256 mol), tetrahydrofuran (30 mL) and water (10 mL) were all added to a 3-neck round bottomed flask. The system was degassed with the aid of two freeze-pump-thaw cycles using nitrogen as the inert gas. Subsequently, Pd(PPh.sub.3).sub.4 (0.99 g, 0.85 mmol) was added and the reaction mixture was again degassed by one freeze-pump-thaw cycle. The reaction mixture was heated under reflux for 2 days and then poured into a separating funnel. Work-up was conducted using diethyl ether (2×150 mL) and the organic extracts washed with water (2×200 mL), dried (MgSO.sub.4) and filtered. The filtrate was concentrated under reduced pressure and the crude product was purified by column chromatography (dry loaded, silica gel, 100% DCM) to yield a powder.

(E)-5-(4-(4-(2-phenylpyridin-4-yl)styryl)phenoxy)pentan-1-ol (4)

(132) 2-Phenyl-4-(4-vinylphenyl)pyridine (compound 3, 2.00 g, 0.0078 mol), 5-(4-bromophenoxy)pentan-1-ol (3.02 g, 0.0117 mol), K.sub.2CO.sub.3 (1.07 g, 0.0078 mol) and dry DMF (50 mL) were all added to a 3-neck round bottomed flask. The system was degassed with the aid of two freeze-pump-thaw cycles using nitrogen as the inert gas. Subsequently, Pd(PPh.sub.3).sub.2Cl.sub.2 (0.27 g, 0.39 mmol) was added and the reaction mixture was heated at 130° C. for 24 h. The reaction mixture was then poured into a separating funnel, DCM was added (200 mL), followed by water (200 mL), the aqueous layer extracted with more DCM (100 mL) and the combined organics were washed with water (200 mL), dried (MgSO.sub.4) and filtered. After evaporating the filtrate to dryness under reduced pressure, the crude product was purified by column chromatography (dry loaded, silica gel, 30% ethyl acetate in hexanes) to yield a powder.

(E)-5-(4-(4-(2-phenylpyridin-4-yl)styryl)phenoxy)pentyl methacrylate (5)

(133) DCC (0.95 g, 0.0046 mol) was added portion wise to a solution of compound 4 (1.00 g, 0.0023 mol), methacrylic acid (0.40 g, 0.0046 mol) and DMAP (0.28 g, 0.0023 mol) in dry CH.sub.2Cl.sub.2 (25 mL) at room temperature under a nitrogen atmosphere. The reaction mixture was stirred for 24 h and the formed DCU was filtered and CH.sub.2Cl.sub.2 was removed under reduced pressure. The resulting residue was purified by column chromatography (wet loaded, silica gel, 100% DCM) to yield a powder.

Ir(4-dpe-2-ppy).SUB.2.(acac)

(134) A solution of compound 5 (0.50 g, 0.99 mmol) in dry THF (20 ml) was degassed by 3×freeze-pump-thaw cycles and [Ir(cod)Cl].sub.2 (0.32 g, 0.48 mmol) was added. The reaction mixture was heated under reflux for 2 days, cooled to room temperature and the formed precipitate filtered. After drying under vacuum DIMER-1 was obtained as a solid. Subsequently, a solution of DIMER-1 (0.30 g, 0.12 mmol), TBAOH (30-hydrate, 0.97 g, 1.22 mmol) and acetylacetone (5 ml) in DCM (50 ml), was heated to 40° C. overnight. The reaction mixture was then poured into a separating funnel, DCM was added (100 mL), followed by water (150 mL), the aqueous layer extracted with more DCM (100 mL) and the combined organics were washed with water (200 mL), dried (MgSO.sub.4) and filtered. After evaporating the filtrate to dryness under reduced pressure, the crude product was purified by column chromatography (dry loaded, silica gel, 50% DCM in hexanes) to yield a powder.

Scheme 2: Synthesis of Bis-Heteroleptic Cross-linkable Iridium Complex Ir(4-durph-2-pyrpy).SUB.2.(acac)

(135) ##STR00026##

(136) The Suzuki coupling reaction of 4-bromo-2-phenylpyridine (1) with N-Boc-2-pyrroleboronic acid, using Pd(OAc).sub.2 as the catalyst, was carried out in a glove box due to the air sensitivity of PtBu.sub.3, and afforded 4-bromo-2-(N-Boc-pyrrol-2-yl)pyridine (6) with good selectivity. This allowed the remaining Ar—Br bond to be utilised and converted into a boronic ester functional group (7) and mono-Suzuki coupled to 1,4-diiododurene to yield compound (8). The cross-linking group was attached to compound (8) via Suzuki coupling reaction with (4-(non-8-en-1-yloxy)phenyl)boronic acid to yield compound (9). Boc deprotection to give (10) and subsequent cyclometalation using IrCl.sub.3.3H.sub.2O in 2-ethoxyethanol/H.sub.2O at 110° C. afforded DIMER-2 that was converted to the cross-linkable bis-heteroleptic acac phosphor Ir(4-durph-2-pyrpy).sub.2(acac) using acetylacetone and sodium carbonate in 2-ethoxyethanol at 90° C.

Scheme 3: Synthesis of Square Planar Cross-linkable Platinum Complex Pt(3-ph-4-ph)-(2-ppy)(acac)

(137) ##STR00027##

(138) Suzuki coupling reaction of 5-bromo-2-iodopyridine (11) with (4-bromophenyl)boronic acid, using Pd(PPh.sub.3).sub.4 as the catalyst, afforded compound (12) in moderate yield. 5-Bromo-2-(4-bromophenyl)pyridine (12) was then converted to compound (13) by Suzuki coupling with (4-(octyloxy)phenyl)boronic acid, which was followed by octyloxy deprotection using BBr.sub.3 to afford the corresponding bis-phenol (14). The cross-linking group was attached to compound (14) via Williamson-ether reaction in refluxing butanone using potassium carbonate as the base with 8-bromo-1-vinyloxy octane to yield compound (15). Subsequent cyclometalation of 15 using K.sub.2PtCl.sub.4 in 2-ethoxyethanol at 80° C. afforded DIMER-3 that was converted to the cross-linkable acac phosphor Pt(3-ph-4-ph)-(2-ppy)(acac) using acetylacetone and sodium carbonate in 2-ethoxyethanol at 100° C.

Scheme 4: Synthesis of Bis-Heteroleptic Non-Cross-Linkable Iridium Complex's Ir(4-p-2-ppy).SUB.2.(acac) and Ir(4-bp-2-ppy).SUB.2.(acac)

(139) ##STR00028##

(140) Scheme 4 demonstrates the synthesis of the central portion of the ligands to which spacers can be attached to arrive at the ligands of the invention as defined in the claims.

(141) 4-Bromo-2-phenylpyridine (2) was prepared according to the previous procedure with 0.54 g of 2,4-diphenylpyridine (16) obtained as a by-product. Suzuki coupling reaction of 4-bromo-2-phenylpyridine (2) with 1,1′-biphenyl]-4-ylboronic acid, using Pd(PPh.sub.3).sub.4 as the catalyst, afforded compound (17) in good yield. Subsequent cyclometalation of compound (17) using IrCl.sub.3.3H.sub.2O in 2-ethoxyethanol/H.sub.2O at 110° C. afforded DIMER-5 that was converted to the bis-heteroleptic acac phosphor Ir(4-bp-2-ppy).sub.2(acac) using acetylacetone and sodium carbonate in 2-ethoxyethanol at 90° C. Finally, cyclometalation of compound (16) using IrCl.sub.3.3H.sub.2O afforded DIMER-4 that was converted to the bis-heteroleptic acac phosphor Ir(4-p-2-ppy).sub.2(acac) using acetylacetone and sodium carbonate in 2-ethoxyethanol at 90° C.

4-([1,1′-Biphenyl]-4-yl)-2-phenyl pyridine (17)

(142) 1,1′-Biphenyl-4-ylboronic acid (0.99 g, 0.0050 mol), 4-bromo-2-phenylpyridine (0.90 g, 0.0038 mol), K.sub.2CO.sub.3 (2.65 g, 0.0192 mol), toluene (30 ml) ethanol (5 ml) and water (15 ml) were all added to a 3-neck round bottomed flask and the system was evacuated, with the aid of a vacuum pump, and filled with nitrogen 3 times. Subsequently, Pd(PPh.sub.3).sub.4 (0.22 g, 0.19 mmol) was added and the reaction mixture was stirred under reflux overnight. The reaction mixture was poured into a separating funnel, in which more water (50 ml) and toluene (50 ml) were both added, the water layer washed with toluene (20 ml) and the combined organic layers washed with water (50 ml), dried (MgSO.sub.4) and filtered. The crude product was purified by column chromatography (dry loaded, silica gel, 100% DCM to 5% ethanol/DCM) to yield a white powder (0.59 g, 50%). .sup.1H-NMR (400 MHz, CDCl.sub.3): δ (ppm) 8.76 (1H, dd, J=5.0 and 0.6 Hz), 8.06-8.08 (2 H, m), 7.99 (1 H, dd, J=1.6 and 0.8 Hz), 7.80 (2 H, d, J=8.4 Hz), 7.75 (2 H, d, J=8.8 Hz), 7.66 (2 H, m), 7.46 (7 H, m).

Ir(4-p-2-ppy).SUB.2.(acac)

(143) A suspension of compound 16 (0.54 g, 2.33 mmol) in 2-ethoxyethanol (20 ml) and water (7 ml) was purged with nitrogen and IrCl.sub.3.3H.sub.2O (0.41 g, 1.13 mmol) was added. The reaction mixture was heated to 110° C. overnight (20 h), cooled to room temperature and precipitated with water (40 ml). The precipitate was filtered, washed with water and dried (dissolved in DCM with MgSO.sub.4). After evaporating the solvent using a rotary evaporator and drying under vacuum a red powder (DIMER-4) was obtained (0.56 g, 71.8%). Subsequently, a reaction mixture containing the DIMER-4 (0.54 g, 0.39 mmol), Na.sub.2CO.sub.3 (0.60 g, 5.66 mmol) and acetylacetone (5 ml) in 2-ethoxyethanol (50 ml), was heated to 90° C. overnight. The reaction mixture was cooled to room temperature and precipitated with water (50 ml), filtered and dried (dissolved in DCM with MgSO.sub.4). The crude product was purified by column chromatography (dry loaded, silica gel, 50% DCM/hexanes) to yield a yellow-orange powder (0.17 g, 28.8%). .sup.1H-NMR (400 MHz, CDCl.sub.3): δ (ppm) 8.56 (2 H, d, J=6.0 Hz), 8.06 (2 H, d, J=2.0 Hz), 7.80-7.81 (4 H, m), 7.65 (2 H, dd, J=8.0 and 1.2 Hz), 7.48-7.59 (6H, m), 7.38 (2 H, dd, J=6.0 and 2.0 Hz), 6.84 (2 H, td, J=7.2 and 1.2 Hz), 6.73 (2 H, td, J=7.2 and 1.2 Hz), 6.38 (2H, dd, J=7.6 and 0.8 Hz), 5.26 (1H, s), 1.83 (6H, s), ASAP-MS: 753.2 ([M+1].sup.+).

Ir(4-bp-2-ppy).SUB.2.(acac)

(144) A suspension of compound 17 (0.56 g, 1.82 mmol) in 2-ethoxyethanol (35 ml) and water (10 ml) was purged with nitrogen and IrCl.sub.3.3H.sub.2O (0.32 g, 0.89 mmol) was added. The reaction mixture was heated to 110° C. overnight (20 h), cooled to room temperature and precipitated with water (50 ml). The precipitate was filtered, washed with water and dried (dissolved in DCM with MgSO.sub.4). After drying under vacuum a red powder (DIMER-5) was obtained (0.75 g, 100%). Subsequently, a reaction mixture containing the DIMER-5 (0.75 g, 0.45 mmol), Na.sub.2CO.sub.3 (0.47 g, 4.43 mmol) and acetylacetone (5 ml) in 2-ethoxyethanol (50 ml), was heated to 90° C. overnight. The reaction mixture was cooled to room temperature and precipitated with water (50 ml), filtered and dried (dissolved in DCM with MgSO.sub.4). The crude product was purified by column chromatography (dry loaded, silica gel, 50% DCM/hexanes to 100% DCM) to yield an orange powder (0.33 g, 40.7%). ASAP-MS: 905.3 ([M+1].sup.+).

Scheme 5: Synthesis of Bis-Heteroleptic Cross-Linkable Iridium Complex Ir(4-dpe-2-ppy).SUB.2.(acac) (Cross-Linking Groups Added after Metalation)

(145) ##STR00029##

Examples of Platinum Complexes

(146) The following structures provide specific embodiments of square planar platinum complexes according to the invention.

(147) ##STR00030## ##STR00031##

Examples of Octahedral Iridium Complexes

(148) The following structures are examples of bis-heteroleptic octahedral complexes of the invention:

(149) ##STR00032## ##STR00033## ##STR00034## ##STR00035##

(150) Although preferred embodiments of the invention have been described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the scope of the invention or of the appended claims.