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.

Two calixarene-based bis-alkynyl-bridged Au(I) isonitrile complexes with two different crown ether pendants, [{calix[4]arene-(OCH(2)CONH-C(6)H(4)C[triple bond]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(6)H(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(2)CONH-C(6)H(4)C[triple bond]CH)(2) has been determined. The cation-binding properties of these complexes with various metal ions have been studied using UV/Vis, emission, (1)H NMR, and ESI-MS techniques, and DFT calculations. A new low-energy emission band associated with AuAu interaction could be switched on upon formation of the metal ion-bound adduct in a sandwich fashion.