Sky-Blue Luminescent Au-I-Ag-I Alkynyl-Phosphine Clusters

Treatment of the (AuC2R)(n) acetylides with phosphine ligand 1,4-bis(diphenylphosphino)butane (PbuP)) and Ag+ ions results in self-assembly of the heterobimetallic clusters of three structural types depending on the nature of the alkynyl group. The hexadecanuclear complex [Au12Ag4(C2R)(12)(PbuP)(6)](4+) (1) is formed for R = Ph, and the octanuclear species [Au6Ag2(C2R)(6)(PbuP)(3)](2+) adopting two structural arrangements in the solid state were found for the aliphatic alkynes (R = Bu-t (2), 2-propanolyl (3), 1-cyclo-hexanolyl (4), diphenylmethanolyl (5), 2-borneolyl (6)). The structures of the compounds 1-4 and 6 were determined by single crystal X-ray diffraction analysis. The NMR spectroscopic studies revealed complicated dynamic behavior of 1-3 in solution. In particular, complexes 2 and 3 undergo reversible transformation, which involves slow interconversion of two isomeric forms. The luminescence behavior of the titled clusters has been studied. All the compounds exhibit efficient sky-blue room-temperature phosphorescence both in solution and in the solid state with maximum quantum yield of 76%. The theoretical DFT calculations of the electronic structures demonstrated the difference in photophysical properties of the compounds depending on their structural topology.