Non-covalent interactions in neutral and oxidized tetrathiafulvalenes

Abstract

Tetrathiafulvalenes (TTFs) functionalized with groups able to increase non-covalent intermolecular interactions through either hydrogen, halogen or chalcogen bonding were investigated. For that purpose, we designed several appropriate precursors, fused dithiole-2-one/thiazoles, which under homocoupling led to symmetrically substituted TTFs or through heterocoupling to dissymmetrically substituted TTFs. The electrochemical investigations allowed the assessment of the electronic effect of these substituents on the overall donating ability of the TTFs. In addition two charge transfer salts have been prepared involving two of these TTFs with TCNQF4 as the electron acceptor, (4c)2(TCNQF4) and (4b)(TCNQF4). Furthermore the crystal structures of the neutral TTFs and of the charge transfer salts allowed us to study the stacking mode and the different non-covalent interactions taking place in the crystals, in connection with the calculated electrostatic surface potential (ESP) of the investigated molecules. All the data provide information about non-covalent bonding interactions in the solid state and about their potential contribution to direct to some extent crystallographic intermolecular organization.