Blue light-emitting electroluminescent devices with 2,9-disubstituted 1,10-phenanthrolines

2,9-Diphenyl-1,10-phenanthroline derivatives 1 and 2, containing N,N-dimethylamino and tert-butyl groups at the p-positions of their phenyl units, respectively, were synthesized as the emitting materials for the electroluminescent (EL) devices. The emission band of the device containing 1 was observed at 485 nm, and that of 2 was at 460 nm. These emissions were visible under ordinary room lighting. The EL emission of the device containing 1 was identical to the photoluminescence but that of the device containing 2 was revealed to be the exciplex emission.