Disclosed is an electroluminescent device comprising a light emitting layer comprising a boron complex wherein the boron is bonded to a nitrogen atom of a first 5-membered heteroaromatic ring group and to a nitrogen atom of a second 5-membered heteroaromatic ring group, provided that the 5-membered rings are further connected by a methene or an imine bridge to form a six-membered ring, and provided further that at least one of the 5-membered rings contains at least one additional heteroatom that is divalent or trivalent.