Structural and Photophysical Properties of (Phosphane)gold(I)-Decorated 4,4′-Diethynyl-2,2′-bipyridine Ligands

Treatment of 4,4'-diethynyl-2,2'-bipyridine with R3PAuCl (R = Ph, 4-Tol, Et, iPr) leads to the formation of a family of (phosphane)gold(I)-decorated 4,4'-diethynyl-2,2'-bipyridine ligands. The solid-state structures of the compounds are significantly affected by the change from aryl- to alkyl-substituted phosphanes, whereas the progression from ethyl to isopropyl substituents leads to a subtle change in the packing that results in the propagation of two different polymeric chain motifs, both supported by close Au center dot center dot center dot Au contacts [3.1239(1) angstrom for R = Et, and 3.395(1) angstrom for R = iPr]. In CH2Cl2 solution, each of the compounds 1-4 is a dual emitter at room temperature. When the excitation wavelength is approximately 238 nm, the emission spectra of I and 2 exhibit new bands at 288 and 570 nm at the expense of the original emissions. The photodegradation is not inconsistent with the formation of gold nanoclusters.