Synthesis, Structure, and Electroluminescence of BR2q (R = Et, Ph, 2-Naphthyl and q = 8-Hydroxyquinolato)

Three 8-hydroxyquinolato (q) boron compounds B(C2H5)2q (1), BPh2q (2), and B(2-naph)2q (3) have been synthesized by the reaction of 8-hydroxyquinoline with an appropriate BR3 compound. Compounds 1−3 have a tetrahedral geometry as demonstrated by the structure of 1 determined by a single-crystal X-ray diffraction analysis. Compounds 1−3 emit a green-blue color at λmax = 495−500 nm when irradiated by UV light. The electroluminescent (EL) properties of 2 and 3 were examined by fabricating EL devices using 2 and 3 as the light-emitting layer, respectively. The devices of 2 produce a yellow-green light with broad emission spectra, attributed to the formation of an exciplex of 2 with the N,N ‘-di-1-naphthyl-N,N ‘-diphenylbenzidine (NPB) in the hole transport layer while the intrinsic EL emission of compound 3 was observed. Both 2 and 3 were found to be good electron transport materials in EL devices.