Homoleptic versus heteroleptic trinuclear systems with mixed l-cysteinate and d-penicillaminate regulated by a diphosphine linker.

Controlled generation of homoleptic versus heteroleptic AuI2M (M = NiII, ZnII) trinuclear complexes, which is achieved by a slight change in the diphosphine P^P linker of digold(i) metalloligands, [Au2(P^P)(d-pen)2]2- (L1P^P; d-pen = d-penicillaminate) and [Au2(P^P)(l-cys)2]2- (L2P^P; l-cys = l-cysteinate), is reported. The reactions of a 1 : 1 mixture of L1dppm and L2dppm (dppm = bis(diphenylphosphino)methane) with M = NiII, ZnII gave the homoleptic AuI2M complexes, [M(L1dppm)] and [M(L2dppm)], which co-crystallized to form [M(L1dppm)]·[M(L2dppm)] (1M). Similar reactions using L1dppe and L2dppe (dppe = bis(diphenylphosphino)ethane), instead of L1dppm and L2dppm, led to the selective production and crystallization of the heteroleptic AuI2M complex, [M(L3dppe)] (2M; L3dppe = [Au2(dppe)(l-cys)(d-pen)]2-), accompanied by the scrambling of L1dppe and L2dppe. The homoleptic 1M and the heteroleptic 2M showed different absorption (green versus blue) and emission (yellow versus orange) colours for M = NiII and ZnII, respectively.