Core-Structure-Dependent Luminescence of Thiolato-Bridged Copper(I) Cluster Complexes

Thiolato-bridged dinuclear, tetranuclear, and hexanuclear Cu(I) complexes [Cu2(P∧S)2(PPh3)2], [Cu4(P∧S)4(CH3CN)2], and [Cu6(P∧S)6] (abbreviated as Cu2, Cu4, and Cu6, respectively, P∧S = 2-(diphenylphosphino)benzenethiolate, PPh3 = triphenylphosphine) were synthesized and characterized by elemental analyses and single-crystal X-ray diffraction measurements. These complexes had {Cu2S2}, {Cu4S4}, and {Cu6S6} cluster cores and exhibited strong luminescence at room temperature in solid states. Different luminescence properties were observed depending on the core structure. Cu2, Cu4, and Cu6 exhibited blue-green (λmax = 482 nm, Φem = 0.52), green (λmax = 526 nm, Φem = 0.19), and yellow (λmax = 553 nm, Φem = 0.49) luminescence, respectively, at 298 K in the solid state; among them, only Cu6 showed luminescence thermochromism. Different radiative rate constants at room temperature and 78 K derived from the emission lifetimes and quantum yields indicate that the luminescence from Cu2 and Cu4 at room temperature or...