Electroluminescent devices based on phosphorescent iridium and related group VIII metal multicyclic compounds

A phosphorescent material comprising a complex of a metal atom M selected from Ir, Pt, Rh, Pd, Ru and Os and at least one ligand L, wherein the ligand L is represented by formula (1):

• wherein:
• ring A is a substituted or unsubstituted 5-membered heterocycle containing at least one ring nitrogen atom bound to the metal atom at the asterisk (*);
• wherein ring A may be substituted with one or more substituents from the group consisting of:
• halogen, cyano, amide, imine, imide, amidine, amine, nitro, hydroxy, ether, carbonyl, carboxy, carbonate, carbamate, phosphine, phosphate, phosphonate, sulphide, sulphone, sulphoxide, silyl, substituents containing a functional group that can be polymerised or a polymer chain, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, and substituted or unsubstituted alkynyl wherein:
• one or more of the carbon atoms in the alkyl may be replaced, wherein each carbon atom that is replaced is independently replaced with an atom or group selected from the group consisting of:
• —C(═O)—, —O—, —S—, —N—, —C═N—, —Si— and —P—;
• ring B is a substituted or unsubstituted 5- or 6-membered carbocycle or heterocycle containing a carbon atom as represented in formula (1) which is bound to the metal atom at the asterisk (*),
• rings A and B are joined by a direct covalent bond as represented in formula (1),
• rings A and B are joined via a tether Q, wherein
• Q is a tether of between 3 and 30 atoms in length, and is selected from the group consisting of:
• linear, branched, or cyclic alkyl;
• linear or branched alkenyl;
• linear or branched alkynyl;
• aryl;
• alkyl-aryl, wherein one or more of the carbon atoms in the alkyl, aryl or alkyl-aryl may be replaced, wherein each carbon atom that is replaced is independently replaced with an atom or group selected from:
• —C(═O)—, —O—, —S—, —N—, ═N—, —Si— and —P—, wherein when the atom is ═N—, the nitrogen double bond is to an adjacent carbon atom in the alkyl, aryl, or alkyl-aryl so as to form a —C═N— group;
• and wherein the tether may contain one or more substituents selected from the group consisting of halogen, cyano, amide, imine, imide, amidine, amine, nitro, hydroxy, ether, carbonyl, carboxy, carbonate, carbamate, phosphine, phosphate, phosphonate, sulphide, sulphone, sulphoxide, alkenyl, aryl, alkyl, heteroaryl, alkynyl, silyl, and substituents containing a functional group that can be polymerised, a polymer chain, or two substituents may together form a ring or fused ring system.

A method for the production of a phosphorescent material comprising:

• reacting a precursor complex of a metal M, with a ligand L, in a ratio suitable to result in a product containing the desired number of ligands L being co-ordinated to the metal M, optionally followed by:
• reacting the product with another ligand L′ in a ratio suitable to introduce the desired number of ligands L′ into the product,
• wherein:
• M is a metal atom selected from Ir, Pt, Rh, Pd, Ru and Os,
• L is a ligand represented by formula (1):
• wherein:
• ring A is a substituted or unsubstituted 5-membered heterocycle containing at least one ring nitrogen atom bound to the metal atom at the asterisk (*);
• wherein ring A may be substituted with one or more substituent selected from the group consisting of:
• halogen, cyano, amide, imine, imide, amidine, amine, nitro, hydroxy, ether, carbonyl, carboxy, carbonate, carbamate, phosphine, phosphate, phosphonate, sulphide, sulphone, sulphoxide, silyl, substituents containing a functional group that can be polymerised or a polymer chain, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, and substituted or unsubstituted alkynyl, wherein:
• one or more of the carbon atoms in the alkyl may be replaced wherein each carbon atom that is replaced is independently replaced with an atom selected from the group consisting of:
• —C(═O)—, —O—, —S—, —N—, —C═N—, —Si— and —P—;
• ring B is a substituted or unsubstituted 5- or 6-membered carbocycle or heterocycle containing a carbon atom as represented in formula (1) which can bind to the metal atom at the asterisk (*),
• rings A and B are joined by a direct covalent bond as represented in formula (1),
• rings A and B are joined via a tether Q, wherein
• Q is a tether of between 3 and 20 atoms in length, and is selected from the group consisting of:
• linear, branched, or cyclic alkyl;
• linear or branched alkenyl;
• linear or branched alkynyl;
• aryl alkyl-aryl;
• wherein one or more of the carbon atoms in the alkyl, aryl or alkyl-aryl may be replaced, wherein each carbon atom that is replaced is independently replaced with an atom or group selected from:
• —C(═O), —O—, —S—, —N—, ═N—, —Si— and —P—, wherein when the atom is ═N—, the nitrogen double bond is to an adjacent carbon atom in the alkyl, aryl, or alkyl-aryl so as to form a —C═N— group;
• and wherein the tether may contain one or more substituents selected from the group consisting of halogen, cyano, amide, imine, imide, amidine, amine, nitro, hydroxy, ether, carbonyl, carboxy, carbonate, carbamate, phosphine, phosphate, phosphonate, sulphide, sulphone, sulphoxide, alkenyl, aryl, alkyl, heteroaryl, alkynyl, silyl, and substituents containing a functional group that can be polymerised, a polymer chain, or two substituents may together form a ring or fused ring system, and
• L′ is a bidentate ligand of a different identity to L.