A comparative study on metal–metal interaction in binuclear two- and three-coordinated d10-metal complexes

An overview of an UV–vis spectroscopic and resonance Raman investigation of the lowest energy dipole-allowed absorption band of [M 2 (dcpm) 2 ] 2+ (M = Au, Ag, Cu) and [M 2 (dmpm) 3 ] 2+ (M = Au, Ag, Cu) complexes is presented. The UV–vis absorption spectra of [M 2 (dcpm) 2 ] 2+ and [M 2 (dmpm) 3 ] 2+ feature intense low energy n dσ* → ( n + 1)pσ transition with transition energy increase from two- to three-coordinated complexes and for [M 2 (dcpm) 2 ] 2+ falls in the order: Ag > Au > Cu. A resonance Raman intensity analysis of the spectra allows estimation of the structural changes of the 1 [dσ*pσ] excited states relative to the ground state. The structural changes in these compounds are compared with each other and with other related compounds. The metal–metal bonds are found to be very similar for the ground and excited states of the [Au 2 (dcpm) 2 ] 2+ and [Au 2 (dmpm) 3 ] 2+ complexes but significantly different for the [Cu 2 (dcpm) 2 ] 2+ and [Cu 2 (dmpm) 3 ] 2+ complexes that have weaker metal–metal bonding.