Synthesis, luminescence and electrochemical properties of luminescent dinuclear mixed-valence gold complexes with alkynyl bridges

A series of luminescent dinuclear mixed-valence gold alkynyl complexes, [(^tBuC^N^C^tBu)Au^III(CC)Au^I(PPh₃)], [(RC^N^CR)Au^III(CCCC)Au^I(PPh₃)] (R = H, ^tBu), [(RC^N^CR)Au^III(CCC₆H₄CC)Au^I(PPh₃)] (R = H, ^tBu), and [(RC^N^CR)Au^III(CCC₆H₄CC)Au^I(P(C₆H₄R′-p)₃)] (R = H; R′ = OMe, Cl) as well as the precursor complexes, [Au^III(^tBuC^N^C^tBu)(CCSiMe₃)] and [Au^III(^tBuC^N^C^tBu)(CCH)], have been synthesized and their electrochemical properties have been investigated. The molecular structures of a number of dinuclear mixed-valence gold alkynyl complexes have been determined by X-ray crystallography. For complexes with a butadiynyl bridge, the emission was derived from an admixture of metal-perturbed triplet intraligand (³IL) [π–π* (RC^N^CR)] and [π–π* (CC–CC)] states while for complexes with a 1,4-diethynylbenzene bridge, the emission was assigned as derived from the excited state of the ³IL [π → π* (CCC₆H₄CC)] origin. Computational studies have also been performed for selected complexes to support the assignment of the spectroscopic origin and the nature of the photophysical properties.