DFT/TD-DFT computational study of the tetrathiafulvalene-1,3-benzothiazole molecule to highlight its structural, electronic, vibrational and non-linear optical properties

Abstract

In this work, we report a computational study of the molecular structure and vibrational spectral analyses of tetrathiafulvalene-1,3-benzothiazole at the DFT level by using the B3LYP method and the 6-31G** basis set. The optimized structure is consistent with the experimental result. The vibrational spectra of tetrathiafulvalene-1,3-benzothiazole (TTF–CH=CH–BTA) are calculated at the same level of theory (DFT/B3LYP/6-31G**), and theoretically calculated vibrational frequencies and assignments are found to agree well with experimental FT-IR and FT-Raman values. Partial atomic charge, molecular electrostatic potential (MEP) map, and global and local reactivity descriptors highlight the reactive sites of the molecule with possible prediction of its reactivity. An analysis of the frontier molecular orbitals provides an estimation of the charge transfer properties of the molecules. In addition, a detailed picture of the intra- and intermolecular interactions shows hyperconjugative interactions based on the charge delocalization that emerges from the natural bond orbital analysis. The non-linear optical properties can be also estimated by the determination of first hyperpolarizabilities of TTF–CH=CH–BTA. For this molecule, the excitation energy, the wavelength and the oscillator strength, derived from a time-dependent DFT method, are presented.