Tetrathiafulvalene-Based Phenanthroline Ligands: Synthesis, Crystal Structures, and Electronic Properties

The synthesis and full characterization of three tetrathiafulvalene-based phenanthroline ligands, namely, N-(1,10-phenanthrol-5-yl)-6,7-(ethylenedithio) tetrathiafulvalene-2carboxamide (1), 2-[(1,10-phenanthrol-5-yl) aminocarbonylmethylthio]-3,6,7-tris(methylsulfanyl)tetrathiafulvalene (2), and 2-[(1,10-phenanthrol-5-yl) iminomethyl] tetrathiafulvalene (3), are described. The electronic absorption properties and the electrochemical behavior of the three ligands have been studied. The UV/Vis absorption spectra of these compounds have been rationalized by time-dependent DFT (TD-DFT) calculations, and the single-crystal X-ray structures of 2 and 3 have been determined. The binding properties of these multifunctional systems for various transition metal ions (Ni2+, Zn2+, Cd2+, and Fe2+) have been analyzed in solution by cyclic voltammetry and UV/Vis spectroscopy. The results show that these ligands are suitable candidates for the preparation of electroactive metal complexes and radical cation salts.