Synthesis, characterization, and properties of some bisacetylide and binuclear acetylide gold(I) compounds based on the photochromic dithienylethene unit

We report the synthesis and characterization of two new bisacetylide compounds, 1,2-bis(2-ethynyl-5-methyl-3-thienyl)perfluorocyclopentene and 1-[2-methyl-5-phenyl-3-thienyl]-2-[4-methyl-2,5-bis (ethynyl)-3-thienyl]hexafluorocyclopentene together with three dinuclear acetylide gold(I) complexes LAu-C C-dithienylethene-C C-AuL in which L = PPh3 or PCy3, containing the photochromic dithienylethene unit. The photophysical properties of these new complexes are compared and contrasted with those of some previously reported dithienylethene complexes. It has been revealed that these compounds with dithienyletehene units show photochromic behavior, but their absorption spectra, cyclization/cycloreversion quantum yields, and efficiencies of the photochromic process and conversions from the open- to the closed-ring isomers in the photostationary state, are all highly dependent on the substitution sites of the bisalkynyl moiety and whether or not there is bisalkyne metalation. The photochromic process was also found to show complete reversibility by alternating irradiation with UV and visible light. (C) 2013 Elsevier Ltd. All rights reserved.