Copper(i)-assisted red-shifted phosphorescence in Au(i)⋯Cu(i) heteropolynuclear complexes

Abstract

Reactions between [Au(C₆Cl₂F₃)(tht)] and P,N-donor bridging ligands of the type PPh₂py and (PPh₂)₂phen lead to the homonuclear gold complexes [Au(C₆Cl₂F₃)(PPh₂py)] (1) and [Au₂(C₆Cl₂F₃)₂{(PPh₂)₂phen}] (2). Subsequent addition of [Cu(CH₃CN)₄](BF₄) leads to the formation of the corresponding gold–copper heterometallic complexes [Au₂Cu(C₆Cl₂F₃)₂(PPh₂py)₂](BF₄) (3) and [Au₂Cu(C₆Cl₂F₃)₂{(PPh₂)₂phen)}(CH₃CN)](BF₄) (4). The four complexes have been structurally characterized and are luminescent. The gold precursors show emissions arising from metal-perturbed intraligand transitions. The heterometallic complexes show a red shift of the emissions that is proposed to arise from an admixture of IL (intraligand) and MLCT (metal-to-ligand-charge-transfer) transitions. DFT and TD-DFT calculations agree well with these results.