Spectroscopic (FTIR, FT-Raman, 1H NMR and UV–Vis) and DFT/TD-DFT studies on cholesteno [4,6-b,c]-2′,5′-dihydro-1′,5′-benzothiazepine

Abstract

The density functional theory calculations and spectroscopic characterization (FTIR, FT-Raman, 1H NMR and ultraviolet–visible) of the pharmaceutically active compound Cholesteno [4,6-b,c]-2′,5′-dihydro-1′,5′-benzothiazepine (CHBT) have been carried out. The recorded Vibrational, proton NMR and electronic spectra have been compared with the simulated one and they are found in well agreement. The bands appearing in FTIR and FT-Raman spectra are assigned with great accuracy using animated modes. The ultraviolet–visible (UV–Vis) absorption bands are assigned using molecular orbitals data obtained by TD-B3LYP/PCM calculations with 6-311G(d,p) basis set. Proton NMR signal peaks have been assigned using GIAO-B3LYP/6-311G(d,p)/PCM method. The hyperconjugative interactions and charge delocalization within the molecule have been studied using natural bond orbital (NBO) analysis. The non-linear optical (NLO) behavior of the present compound has been investigated using theoretical dipole moment, polarizability and first static hyperpolarizability values. The thermodynamic functions (entropy, heat capacity and enthalpy) obtained from harmonic force field calculations for the range of temperature 100–1000 K are reported. Moreover, highest occupied molecular orbital – lowest unoccupied molecular orbital (HOMO-LUMO) analysis, molecular electrostatic potential (MEP) diagram, global reactivity descriptors and condensed or atomic Fukui Functions have been also presented.