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≡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 CCH) 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 Au⋅⋅⋅Au interaction could be switched on upon formation of the metal ion‐bound adduct in a sandwich fashion.