Photo-physical properties of donor-acceptor-radical triad based on functionalized tetrathiafulvalene and nitronyl nitroxide radical

Abstract

An acceptor-donor-radical triad based on tetrathiafulvalene (TTF)-fused (benzimidazol-2-yl)-pyridine (bzip) which is alkylated with a nitronyl nitroxide (NIT) radical derivative, has been designed and synthetized. Its X-ray structure has been refined showing a complex arrangement of head-to-tail dimers of the TTF-bzip moieties and a 1D network of short contacts between the NIT radicals. Its electrochemical behavior has been studied by cyclic voltammetry (CV) showing that the TTF and NIT moieties can be reversibly and independently oxidized. The occurrence of intramolecular ligand charge transfers (ILCT) of both TTF → bzip and TTF → NIT nature has been evidenced by UV–visible electronic absorption spectroscopy coupled to TD-DFT calculations. Moreover, these calculations and RPE measurements confirmed the radical form (S = ½) of the compound as well as the spin density mainly localized on the methyl-benzo-[1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolin-2-yl] unit. Both emissions of the NIT radical and TTF-based molecular skeleton have been observed with a tunable intensity ratio depending on the irradiation energy. Finally, this new triad may be a valuable candidate for the construction of multi-property compounds by coordination of metallic ions either on the TTF-based molecular skeleton or on the NIT moieties.