Heteroleptic light emitting complexes having the general formula M(L1)n(L2)m wherein a) L1 has the formula E1 -E2, wherein E1 is a 6-membered heteroaryl ring bound to the metal atom M by a dative bond and containing at least one donor hetero atom and E2 is bound to the metal atom by covalent or dative bonds and is selected from the group consisting of substituted or un-substituted C5-C30 aryl and substituted or un-substituted C2-C30 heteroaryl groups, b) ligand L2 is selected from the group consisting of 1 -(2,6 disubstituted phenyl)-2- phenyl-1 H- imidazole ligands or 5-(2,6 disubstituted phenyl)-1-phenyl-1 H- pyrazole ligands, and c) M is a non-radioactive transition metal with an atomic number of at least 40 and the sum of m and n is equal to half of the bond valency of metal M
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