Transition metal complexes comprising carbene ligands serving as emitters for organic light-emitting diodes (OLED's)

An uncharged transition metal complex of the formula:

• wherein the symbols have the following meanings:
• M1 is Ir in any oxidation state possible;
• L is a monoanionic or dianionic ligand, which may be monodentate or bidentate;
• K is an uncharged monodentate or bidentate ligand;
• n is the number of carbene ligands, wherein n is at least 2 and the carbene ligands in the transition metal complex can be identical or different;
• m is the number of ligands L, wherein m can be 0 or ≧1 and when m>1 the ligands L can be identical or different;
• o is the number of ligands K, wherein o can be 0 or ≧1 and in the case of o>1 the ligands K can be identical or different;
• wherein the sum n+m+o is dependent on the oxidation state and coordination number of the metal atom used and the denticity of the ligands and also on the charge on the ligands, with the proviso that n is at least 2;
• and
• wherein the following symbols have the following meanings:
• Z, Z′ are identical or different and are each CH or N;
• R12, R12′ are identical or different and are each an alkyl, aryl, heteroaryl or alkenyl radical, or 2 radicals R12 or R12′ together form a fused-on ring which may contain at least one heteroatom, or R12 or R12′ is a radical which acts as a donor or acceptor;
• t and t′ are identical or different and are each from 0 to 3, and when t or t′>1 the radicals R12 or R12′ can be identical or different;
• R10 is alkyl, aryl, heteroaryl or alkenyl or 2 radicals R10 together form a fused-on ring which may contain at least one heteroatom, or R10 is a radical which acts as a donor or acceptor;
• and
• v is from 0 to 4 and when v is 0 the four carbon atoms of the aryl radical in the formula c which may be substituted by R10 bear hydrogen atoms.

A light-emitting layer comprising at least one transition metal complex of the formula (I) comprising at least one carbene ligand

• wherein the symbols have the following meanings:
• M1 is Ir in any oxidation state possible;
• carbene is a carbene ligand selected from the group consisting of the following formulae
• wherein Z, Z′ are identical or different and are each CH or N;
• R12,R12′ are identical or different and are each an alkyl, aryl, heteroaryl or alkenyl radical, or 2 radicals R12 or R12′ together form a fused-on ring which may contain at least one heteroatom, or R12 or R12′ is a radical which acts as a donor or acceptor;
• t and t′ are identical or different and are each from 0 to 3, and when t or t′ >1 the radicals R12 or R12′ can be identical or different;
• R4, R5, R6, and R7 are each hydrogen, alkyl, aryl, heteroaryl or alkenyl or a radical which acts as a donor or acceptor;
• R10 is alkyl, aryl, heteroaryl or alkenyl or 2 radicals R10 together form a fused-on ring which may contain at least one heteroatom, or R10 is a radical which acts as a donor or acceptor;
• and
• v is from 0 to 4 and when v is 0 the four carbon atoms of the aryl radical in the formula c which may be substituted by R10 bear hydrogen atoms;
• L is a monoanionic or dianionic ligand, which may be monodentate or bidentate;
• K is an uncharged monodentate or bidentate ligand selected from the group consisting of phosphines;
• phosphonates and derivatives thereof, arsenates and derivatives thereof;
• phosphites;
• CO;
• pyridines;
• nitriles and conjugated dienes which form a π complex with M1;
• n is the number of carbene ligands, wherein n is at least 1 and when n>1 the carbene ligands in the complex of the formula I can be identical or different;
• m is the number of ligands L, wherein m can be 0 or ≧1 and when m>1 the ligands L can be identical or different;
• o is the number of ligands K, wherein o can be 0 or ≧1 and when o>1 the ligands K can be identical or different;
• wherein the sum n+m+o is dependent on the oxidation state and coordination number of the metal atom and on the denticity of the ligands carbene, L and K and also on the charge on the ligands carbene and L, with the proviso that n is at least 1.