Observation of a mixed-metal transition in a d8–d10 heterobimetallic Pt–Ag cyanide system: Experimental and theoretical study

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 z 2 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).