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

Abstract

Treatment of the (AuC₂R)_<i>n</i> 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⁺ (<b>1</b>) 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 (<b>2</b>), 2-propanolyl (<b>3</b>), 1-cyclohexanolyl (<b>4</b>), diphenylmethanolyl (<b>5</b>), 2-borneolyl (<b>6</b>)). The structures of the compounds <b>1</b>–<b>4</b> and <b>6</b> were determined by single crystal X-ray diffraction analysis. The NMR spectroscopic studies revealed complicated dynamic behavior of <b>1</b>–<b>3</b> in solution. In particular, complexes <b>2</b> and <b>3</b> 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