Design and synthesis of calixarene-based bis-alkynyl-bridged dinuclear Au I isonitrile complexes as luminescent ion probes by the modulation of Au⋯Au interactions

Abstract

Two calixarene-based bis-alkynyl-bridged Au I isonitrile complexes with two different crown ether pendants, [{calix[4]arene-(OCH 2CONHC 6H 4C ≡ C) 2}Au(CNR)} 2] (R = benzo[15]crown-5 (1); R=benzo[18]crown-6 (2)), together with their related crown-free analogue 3 (R = C 6H 3(OMe) 2-3,4) and a mononuclear gold(I) complex 4 with benzo[15]-crown-5 pendant, have been designed and synthesized, and their photophysical properties have been studied. The X-ray structure of the ligand, calix[4]arene-(OCH 2CONH-C 6H 4C≡CH) 2 has been determined. The cation-binding properties of these complexes with various metal ions have been studied using UV/Vis, emission, 1H NMR, and ESI-MS techniques, and DFT calculations. A new low-energy emission band associated with Au⋯Au interaction could be switched on upon formation of the metal ion-bound adduct in a sandwich fashion. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.