An OLED device comprises a cathode, an anode, and located therebetween a light emitting layer containing a compound represented by formula (I): ##STR00001## wherein M is a d-block transition metal of atomic number greater than 40; the coordination ring C is a triazole ring with the metal as a member of the triazole ring; A is a five- or six-membered ring; B is a five- or six-membered ring; R.sub.1 and R.sub.2 are groups other than hydrogen and may be joined together; n.sub.1 and n.sub.2 are independently an integer from 0 to 6; L is a ligand; n.sub.3 is zero or an integer and n.sub.4 is an integer of at least one.