Luminescent gold–silver complexes derived from neutral bis(perfluoroaryl)diphosphine gold(i) precursors

Abstract

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(μ-L–L)] (L–L = dppm (1), dppb (2)). In the crystal structure of complex 2 short Au⋯Au interactions of 2.9367(5) and 2.9521(5) Å 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(μ-L–L)]_n (L–L = dppm (3), dppb (4)), which confirms the capability of the neutral [(Au{4-C₆F₄(4-C₆BrF₄)})₂(μ-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.