Two Cu(I) complexes constructed by different N-heterocyclic benzoxazole ligands: Syntheses, structures and fluorescent properties

Abstract

Reaction of 2,2-(1,4-butanediyl)bis-1,3-benzoxazole (BBO) or 2-(2′-pyridyl)benzoxazole (PBO) ligands with [Cu(CH3CN)2(PPh3)2](BF4) afforded a copper(I) coordination polymer {[Cu(BBO)(PPh3)](BF4)}n (1) and a mononuclear copper(I) complex [Cu(PBO)(PPh3)2](BF4)·2CH2Cl2 (2) (where PPh3 = triphenylphosphine), which have been characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The structural analysis revealed that in complex 1, copper(I) ions are three-coordinated and the geometric structure around the central copper(I) atom can be described as planar trigonal configuration. Complex 1 exhibits an one-dimensional coordination polymer by two BBO bridging adjacent copper(I) ions, forming a single-stranded meso-helical chain structure. Mononuclear complex 2 is four-coordinated and slightly distorted triangular-pyramid geometry. Solid luminescence properties investigation show that complex 1 has two emission peaks, which attributed to the π*-π and π*-n transitions. However complex 2 only has one emission peak, which may be attributed to MLCT [d10(Cu)→π*]. This indicates that different types of N-heterocyclic ligands have an important influence on the structure and luminescent properties of copper(I) complexes.