Synthesis and cation-binding studies of gold(i) complexes bearing oligoether isocyanide ligands with ester and amide as linkers
Abstract
A series of dinuclear gold(I) isocyanide complexes of bis(alkynyl)calix[4]arene was designed and synthesized, and their photophysical and cation recognition properties were studied. Complex 1, [{calix[4]arene-(OCH2CONH-C6H4CC)2}{Au(CN-C6H4O(CH2CH2O)2CH3)}2], was found to show a high selectivity towards Al3+ in CH2Cl2–MeCN (1 : 1 v/v). Upon addition of Al3+, drastic changes in the electronic absorption, emission and 1H NMR spectra were observed. These changes have been attributed to the formation of Au(I)⋯Au(I) interactions induced by the high binding affinity of the amide site for the Al3+ ion, instead of the high binding affinity expected of the oligoether site for alkali and alkaline earth metal ions. Further studies with the control complex, [{calix[4]arene-(OOC-C6H4CC)2}{Au(CN-C6H4O(CH2CH2O)2CH3)}2] (4), indicated that the amide carbonyl oxygen in the flexible pendants is crucial for the binding of Al3+.
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