Abstract: A metal complex of formula (I): M(L1)x(L2)y (I) wherein: M is a second or third row transition metal; L1 in each occurrence is independently a light-emitting ligand; L2 is an auxiliary ligand; x is at least 1; y is at least 1; each L1 is a group of formula (IIa) or (IIb): wherein R1-R10 are each independently H or a substituent with the proviso at least one of R3, R5 and R9 of at least one L1 is a group of formula —(Ar)p wherein Ar in each occurrence is independently an aryl or heteroaryl group that may be unsubstituted or substituted with one or more substituents, and p is at least 2.