DFT/TDDFT studies of the structural, electronic and NBO properties of some complexes with the tetrathiafulvalene-1,3-benzothiazole ligand

Abstract

In this work, the electronic structures and derived properties (UV, NBO and more) of the three know and relevant Cu-based complexes of tetrathiafulvalene (TTF) are reported. The experimentally available structures of formulas [Cu(hfac)2(L)2]0,2+ and [Cu(L)2]2+ (L = TTF-1,3-benzothiazole and hfac = hexafluoroacetylacetonate are characterized by variable π-π stacking in the crystals. Since the latter depends on the spin unpairing at the TTF portions of L, we have optimized with the DFT method the single units as potential building blocks of the solid state compounds. The geometric parameters appear to be in a satisfactory agreement with the available experimental data and, by taking into account the various spin distributions (possible ground states), we analyzed the corresponding MO features. The APT atomic charges were evaluated and the coordination bond strengths were evaluated by the Natural Bond Orbital (NBO) analysis, which also confirmed the π electron delocalization at the TTF portion of L. The theoretical UV–visible spectra, computed with the time-dependent DFT/TDDFT method, show that the charge transfer bands in all complexes are red-shifted with respect to the corresponding free ligand.