LUMINESCENT MONONUCLEAR GOLD(I) PHOSPHINES

Crystals of Au(PPh3)2Cl, Au(PPh3)3BPh4, and other three-coordinate bis(phosphine)gold(I) compounds are luminescent. Solutions of [Au(tht)2]PF6 (tht = tetrahydrothiophene) with added PPh3 in CH3CN luminesce with lambda(max) = 512 nm and an excited-state lifetime of 10-mu-s. The emission intensity is sensitive to the phosphine concentration. The lumine-scent species is postulated to be the tris(phosphine)gold(I) cation, Au(PPh3)3+, in equilibrium with Au(PPh3)2+. Other PR3 Phosphine complexes (R = n-octyl, n-butyl, ethyl) also luminesce in solution when excess (>3:1 PR3:Au) phosphine is present. The emission is attributed to a metal-centered P(z) --> (d(x2-y2), d(xy)) transition which can be dipole allowed under spin-orbit coupling or by Jahn-Teller splitting of the 3E" excited state.