Functional molecular architectures based on tetrathiafulvalene building blocks

GRAPHICAL ABSTRACT

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.

KEYWORDS:

• Tetrathiafulvalenes
• molecular recognition
• molecular devices
• macrocyclization
• calixarenes
• azobenzenes