Synthesis and structural characterization of luminescent gold(I) derivatives with an unsymmetric diphosphine

We have synthesised a series of mono-bridged digold(I) derivatives with an unsymmetric diphosphine, namely, [(AuX)(2)(mu-(PPr2CH2PPh2)-Pr-i)] (X = Cl, Br, I, C6F5, S2CN(CH2Ph)(2)) and the mononuclear gold(III) complex [Au(C6F5)(3)((PPr2CH2PPh2)-Pr-i)]. X-ray diffraction studies show intramolecular gold(I) - gold(I) interactions of 3.4179(2), 3.1660(2) and 3.0926(3) Angstrom, respectively, for X = Cl, Br and C6F5. The pentafluorophenyl derivative emits at 445 nm at room temperature in the solid state; this compound and the halo-derivatives are emissive at low temperature in the range 440 - 486 nm. We have also prepared doubly-bridged diauracycles, namely, [Au2X2(mu- (PPr2CH2PPh2)-Pr-i)(2)] (X = Cl, Br, I) and [Au-2(mu- (PPr2CH2PPh2)-Pr-i)(2)] A(2) (A = CF3SO3, ClO4). The crystal structure of the iodo derivative displays three-coordinated gold centres in a T-shaped geometry, with a gold - gold distance of 2.9931(6) Angstrom and a gold - iodo distance of 3.0999(6) Angstrom, whilst the triflate derivative displays di-coordinated gold centres and a gold - gold distance of 2.9838(5) Angstrom. All the derivatives are intensely photoluminescent in the visible range, with the emission maxima between 480 and 513 nm at 298 K and 459 - 508 nm at 77 K. The emission energies and the gold - gold distances are not directly related.