Carboxylic acid derivatives of tetrathiafulvalene: key intermediates for the synthesis of redox-active calixarene-based anion receptors

A series of calixarene–TTF (TTF=tetrathiafulvalene) receptors incorporating amide binding units for anion recognition have been synthesized and characterized. For this purpose, two synthetically versatile new TTF carboxylic acid derivatives were prepared and characterized by X-ray diffraction, these structures demonstrating the critical role of the carboxylic function in the solid-state organization. Some of the calixarene–amide–TTF assemblies exhibit strong binding of various anions, as shown by 1H NMR titration studies, and one receptor is able to electrochemically respond in the presence of H2PO4−, C6H5CO2− or CH3CO2− anion.