Patent ID: 7393599

Claim:
An organic light emitting device, comprising: (a) an anode; (b) a cathode; (c) an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a compound comprising one or more carbene ligands coordinated to a metal center, wherein the carbene ligand has a structure selected from: the dotted lines between A and R 1 and between A or A′ and adjacent carbon atoms represent optional double bonds; each Z 1 , Z 2 , A, and A′ is C, N, O, P, or S; R 1 , R 2 , and R 3 are independently selected from H, alkyl, aryl or heteroaryl, and additionally or alternatively, one or more of R 1 and R 2 and R 2 and R 3 together form independently a 5 or 6-member cyclic group, wherein the cyclic group is cycloalkyl, cycloheteroalkyl, aryl or heteroaryl, and wherein said cyclic group is optionally substituted by one or more substituents J; each substituent J is independently selected from the group consisting of R′, O—R′, N(R′) 2 , SR′, C(O)R′, C(O)OR′, C(O)NR′ 2 , CN, NO 2 , SO 2 , SOR′, or SO 3 R′, and additionally, or alternatively, two J groups on adjacent ring atoms form a fused 5- or 6-membered aromatic group; each R′ is independently selected from H, alkyl, alkenyl, alkynyl, heteroalkyl, aralkyl, aryl and heteroaryl; and a is 0, 1, or 2.