Synthesis, spectroscopy and excited-state redox properties of novel luminescent trinuclear three-co-ordinate gold(I) phosphine complexes
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 (λem= 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[(dδ*)(pσ)]. 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.