Redox responsive molecular tweezers with tetrathiafulvalene units: synthesis, electrochemistry, and binding properties

Several new molecular tweezers with tetrathiafulvalene (TTF) arms as well as mono-TTF derivatives bearing 3,5-di-tert-butylbenzylthio groups to provide enhanced solubility were prepared starting from a bis-cyanoethyl-protected tetrathiafulvalene derivative. The X-ray crystallographic analysis of 3 and 7a showed highly distorted TTF groups and absence of close TTF–TTF contacts in the crystalline state. Comparative cyclic voltammetry (CV) measurements demonstrated that through space distance-dependent TTF–TTF interactions take place in the TTF-containing molecular tweezers, leading to electronic pairing with formation of mixed valence [TTF]2+radical dot species and splitting of the first oxidation wave. TTF-containing molecular tweezers were successfully tested as receptors for several electron-deficient substances.