Vibrational spectroscopic, NBO, AIM, and multiwfn study of tectorigenin: A DFT approach

Abstract Tectorigenin (5,7-dihydroxy-3-(4-hydroxyphenyl)-6-methoxy-4H-chromen-4-one), a plant isoflavonoid, is a potential bioactive compound having antioxidant, anti-inflammatory, anti-osteoarthritis, anti-microbiotic, and antiplatelet activity. A combined experimental and theoretical approach was used to investigate the structural properties of the title compound. The optimized structure was obtained using B3LYP with 6–311++G(d,p) basis set. Two stable structural motifs in addition to the initially optimized form were obtained by the one-dimensional potential energy surface scan. The calculated 1H and 13C nuclear magnetic resonance spectra revealed good agreement with the available experimental data. Stability of the structure has been predicted by natural bond orbital analysis, which also confirmed the presence of lone pair and bonding to antibonding orbital interactions in the molecule. The reactive sites of the molecule were predicted using the molecular electrostatic potential surface. The weak and strong hydrogen bonds between non bonded atoms of the molecule have been analyzed by the quantum theory of atom in molecule. The reduced density gradient (RDG) and iso-surface defining long-range forces such as van der Waal and steric effect have been plotted and explained using multiwave function (Multiwfn) program. The vibrational assignment and interpretation of the spectra (FT-IR and FT-Raman) have been performed with the potential energy distribution (PED) analysis.