Design and Synthesis of Calixarene-Based Bis-alkynyl-Bridged Dinuclear Au-I Isonitrile Complexes as Luminescent Ion Probes by the Modulation of Au center dot center dot center dot Au Interactions

Two calixarene-based bis-alkynyl-bridged Au-I isonitrile complexes with two different crown ether pendants, [{calix[4]arene-(OCH2CONH-C6H4C 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=C6H3-(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,CONH-C6H4C CH)(2) has been determined. The cation-binding properties of these complexes with various metal ions have been studied using UV/Vis, emission, H-1 NMR, and ESI-MS techniques, and DFT calculations. A new low-energy emission band associated with Au center dot center dot center dot Au interaction could be switched on upon formation of the metal ion-bound adduct in a sandwich fashion.