Luminescent gold-silver complexes derived from neutral bis(perfluoroaryl)diphosphine gold(I) precursors

Complex [Au{4-C6F4(4-C6BrF4)}(tht)] reacts with diphosphines (L-L) such as bis(diphenylphosphino)methane (dppm) or 1,2-bis(diphenylphosphino) benzene (dppb) in a 2 : 1 molar ratio in dichloromethane, leading to neutral products of stoichiometry [(Au{4-C6F4(4-C6BrF4)})(2)(mu-L-L)] (L-L = dppm (1), dppb (2)). In the crystal structure of complex 2 short Au center dot center dot center dot Au interactions of 2.9367(5) and 2.9521(5) angstrom appear. This complex displays an orange emission, which is assigned to arise from a charge transfer transition from a metal centered Au-Au orbital to an orbital located at the diphosphine ligand. Addition of silver trifluoroacetate to these complexes in a 1 : 1 or a 2 : 1 molar ratio generates polymeric heterometallic gold-silver compounds of stoichiometry [Ag2Au2{4-C6F4(4-C6BrF4)}(2)(CF3CO2)(2)(mu-L-L)](n) (L-L = dppm (3), dppb (4)), which confirms the capability of the neutral [(Au{4-C6F4(4-C6BrF4)})(2)(mu-diphosphine)] units to act as electron density donors when treated with a Lewis acid substrate. These heterometallic derivatives show blue emissions indicating large HOMO-LUMO band gaps, due to the stabilization that the gold-based HOMO orbitals suffer when the electron withdrawing silver trifluoroacetate fragments interact with them.