Structural and Photophysical Study on Heterobimetallic Complexes with d⁸–d¹⁰ Interactions Supported by Carborane Ligands: Theoretical Analysis of the Emissive Behaviour

Heterobimetallic complexes of formula [M{(PPh2)2C2B9H10}(S2C2B10 H10)M'(PPh3)] (M=Pd, Pt; M'=Au, Ag, Cu) and [Ni{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] were obtained from the reaction of [M{(PPh2)2C2B10H10}(S2C2B10H10)] (M=Pd, Pt) with [M'(PPh3)](+) (M'=Au, Ag, Cu) or by one-pot synthesis from [(SH2C2B10H10], (PPh2 )2C2B10H10, NiCl2 ⋅6 H2 O, and [Au(PPh3)](+). They display d(8)-d(10) intermetallic interactions and emit red light in the solid state at 77 K. Theoretical studies on [M{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] (M=Pd, Pt, Ni) attribute the luminescence to ligand (thiolate, L)-to-"P2-M-S2" (ML') charge-transfer (LML'CT) transitions for M=Pt and to metal (M)-to-"P2-M-S2" (ML') charge-transfer (MML'CT) transitions for M=Ni, Pd.