ABSTRACT
Tetrathiafulvalenes (TTFs) 1, redox-controllable electron-rich heterocycles, were employed as building blocks for the construction of molecular receptors and switchable macrocycles. Redox-active calixarene-based molecular receptors 2 with various substituents R1 on the tetrathiafulvalene groups and rigid or flexible attachment of TTF units to the backbone have been prepared using modular construction approach. The addition of planar electron-deficient guests to receptor solutions leads to formation of deeply-colored charge-transfer complexes with high binding constants reaching 2.5 × 105 M−1. TTF substituents display the strong influence on the binding constants and charge transfer intensity. By the synthesis of macrocyclic tetrathiafulvalene-azobenzene (TTF-AB) conjugates 3, we have shown the first example of photochemically controlled macrocyclization, in which the formation of smaller 1 + 1 and larger 2 + 2 cyclization products can be modulated by photoisomerization of one of the reactants. The oxidation potential of the small, structurally rigid, TTF-AB macrocycle is found to depend on the conformation of the AB moiety.