Synthesis, crystal structures and photophysical properties of novel copper(I) complexes with 4-diphenylphosphino-1,5-naphthyridine ligands

Abstract Two new copper(I) complexes [Cu( L 1 ) 2 ]PF 6 ( L 1  = 4-diphenylphosphino-1,5-naphthyridine, 1) and [Cu( L 2 ) 2 ]PF 6 ( L 2  = 4-diphenylphosphino-8-methyl-1,5-naphthyridine, 2 ), have been prepared and characterized. In each of them, the coordinate geometry of Cu atom is a distorted square planar configuration with bond distances and angles in the normal range. Moreover, compound 2 features one-dimensional zigzag chains which are cross-linked by the metal complex cations and PF 6 − anions through hydrogen bonding interactions. The HOMO–LUMO energy gaps of 1 – 2 estimated by the cyclic voltammetry (CV) show values in the order of 1  >  2 . Both 1 and 2 show low-energy bands ranging from 360 to 430 nm and available florescence in the solid state at room temperature with λ max  = 532–541 nm. The UV–vis absorption spectra of 1 – 2 show obvious red-shifts compared with those of the corresponding quinoline containing Cu(I) complexes [Cu(QN) 2 ]PF 6 (QN = 8-diphenylphosphino quinoline), exhibiting the HOMO–LUMO energy gaps of 1 – 2 should be narrower than that of [Cu(QN) 2 ]PF 6 .