Synthesis, spectroscopy and excited-state redox properties of novel luminescent trinuclear three-co-ordinate gold(I) phosphine complexes

Abstract

Reaction of [Au₃(dmmp)₂][CIO₄]₃ with an excess of dmmp [bis(dimethylphosphinomethyl)methylphosphine] in methanol yielded [Au₃(dmmp)₃][CIO₄]₃ in almost quantitative yield. Excitation of a degassed acetonitrile solution of [Au₃(dmmp)₃]³⁺ at λ > 350 nm resulted in intense phosphorescence (λ_em= 625 nm, τ₀= 2.2 ± 0.2 µs). A comparison between the electronic absorption and emission spectra of [Au₃(dmmp)₃]³⁺ and [Au₂(dmpm)₃]²⁺[dmpm = bis(dimethylphosphino)methane] has been made. The assignment of the lowest electronic excited state in the (AuP₃)_n system has been suggested to be ³[(d_δ*)(p_σ)]. The excited-state redox potentials of [Au₃(dmmp)₃]^3+* and [Au₂(dmpm)₃]^2+* have been determined through oxidative quenching experiments with a series of pyridinium acceptors of variable reduction potential.