Observation of a mixed-metal transition in a d~8-d~(10) heterobimetallic Pt-Ag cyanide system: Experimental and theoretical study

摘要

Photoluminescence spectra of synthesized crystals of the mixed-metal heterobimetallic Ba{[Ag(CN)_2]_(2-2x)[Pt(CN)_4] _x} (x = 0 → 1) were recorded at 300, 150 and 77 K. Emission of the mixed-metal system containing both [Pt(CN)_4]~(2-) and [Ag(CN)_2]- ions shows an emission band due to Pt-Ag interaction. This new peak (424 nm) is not seen for pure Ba[Pt(CN)_4] or Ba[Ag(CN)_2]_2. Theoretical DFT and extended Hückel molecular orbital population calculations shows that in heterometallic dimers, the HOMO correspond to d_z2 of the metals with a weakly antibonding interaction between the moieties while the LUMO π*(CN) orbital shows a stronger bonding character between monomers. This indicate that the 424 nm emission peak corresponds to a MLCT (d →π*) transition with some metal to metal charge transfer character (Pt to Ag).