Structural, photoluminescence, and theoretical DFT studies of gold(I) and silver(I) metallacycle dinuclear complexes of 1-methylbenzimidazolediphenyl phosphine (MBDP) ligand

The synthesis and structural characterization of the bridging ligand, 1-methyl benzimidazole diphenylphosphine (MBDP) and its coordination with Au(I) and Ag(I) metal ions is reported. Two ligands coordinate to the metal ions in head to tail fashion forming a metallacycle coordination consisting of strong M-M bonding interaction with Au-Au = 2.808 and Ag-Ag = 3.017 angstrom. Linear coordination is observed for the gold, while the silver shows distorted tetrahedral arrangement. X-ray crystal data of [(MBDP)(2)Au-2](CH3CN)(BF4)(2) (2) crystallizes in the monoclinic system with the space group of P2(1)/n with cell constants of a = 8.9993 (8) angstrom, b = 19.6166 (18) angstrom, c = 13.4484 (12) angstrom, beta = 100.966 (2)degrees, R = 0.026, and R-w = 0.064. The structure of [(MBDP)(2)(CH3CN)(4)Ag-2](BF4)(2), (3) crystallizes in the P (-)1 space group and the unit cell is a = 10.5423 (10)angstrom, b = 10.7638 (10)angstrom, c = 12.3530 (12) angstrom; alpha = 88.592 (3)degrees, beta = 73.097 (3)degrees, gamma = 84.422 (3)degrees, V = 1334.8 (2) angstrom(3) with Z = 1, R = 0.034 and R-w = 0.093. The coordinating ligand as well as both dinuclear compounds reported here are luminescent in the near UV region. As supported by the DFT theoretical work, the emission is suggested to be primarily ligand based pi-pi* transition. (C) 2016 Elsevier B.V. All rights reserved.