Luminescent Di- and Polynuclear Organometallic Gold(I)-Metal (Au2, {Au2Ag}n and {Au2Cu}n) Compounds Containing Bidentate Phosphanes as Active Antimicrobial Agents (original) (raw)

2012, Chemistry - A European Journal

The reaction of new dinuclear gold(I) organometallic complexes containing mesityl ligands and bridging bidentate phosphanes [Au 2 (mes) 2 (μ-LL)] (LL = dppe: 1,2-Bis(diphenylphosphano)ethane 1a, and water-soluble dppy: 1,2-Bis(di-3-pyridylphosphano)ethane 1b) with Ag + and Cu + lead to the formation of a family of heterometallic clusters with mesityl bridging ligands of the general formula [Au 2 M(μ-mes) 2 (μ-LL)]A (M = Ag, A = ClO 4 − , L-L = dppe 2a, dppy 2b; M = Ag, A = SO 3 CF 3 − , L-L = dppe 3a, dppy 3b; M = Cu, A = PF 6 − , L-L = dppe 4a, dppy 4b). The new compounds were characterized by different spectroscopic techniques and mass spectrometry The crystal structures of [Au 2 (mes) 2 (μ-dppy)] 1b and [Au 2 Ag(μ-mes) 2 (μdppe)]SO 3 CF 3 3a were determined by a single-crystal X-ray diffraction study. 3a in solid state is not a cyclic trinuclear Au 2 Ag derivative but it gives an open polymeric structure instead, with the {Au 2 (μ-dppe)} fragments "linked" by Ag(μ-mes) 2 units. The very short distances of 2.7559(6) Å (Au-Ag) and 2.9229(8) Å (Au-Au) are indicative of gold-silver (metallophillic) and aurophilic interactions. A systematic study of their luminescence properties revealed that all compounds are brightly luminescent in solid state, at room temperature (RT) and at 77 K, or in frozen DMSO solutions with lifetimes in the microsecond range and probably due to the self-aggregation of [Au 2 M(μ-mes) 2 (μ-LL)]+ units (M= Ag or Cu; LL= dppe or dppy) into an extended chain structure, through Au-Au and/or Au-M metallophylic interactions, as that observed for 3a. In solid state the heterometallic Au 2 M complexes with dppe (2a-4a) show a shift of emission maxima (from ca. 430 to the range of 520-540 nm) as compared to the parent dinuclear organometallic product 1a while the complexes with dppy (2b-4b) display a more moderate shift (505 for 1b to a max of 563 nm for 4b). More importantly, compound [Au 2 Ag(μ-mes) 2 (μ-dppy)]ClO 4 2b resulted luminescent in diluted DMSO solution at room temperature. Previously reported compound [Au 2 Cl 2 (μ-LL