FT-IR, molecular structure, first order hyperpolarizability, NBO analysis, HOMO and LUMO and MEP analysis of 1-(10H-phenothiazin-2-yl)ethanone by HF and density functional methods

Abstract

FT-IR spectrum of 1-(10H-phenothiazin-2-yl)ethanone was recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational wavenumbers were investigated with the help of HF and DFT methods. The normal modes are assigned with the help of potential energy distribution analysis. The observed vibrational wavenumbers were compared with the calculated results. The geometrical parameters of the title compound obtained from XRD studies are in agreement with the calculated (DFT) values. The first hyperpolarizability value is also reported. Natural bond orbital analysis confirms the presence of intra-molecular charge transfer and hydrogen bonding interaction. The HOMO-LUMO gap explains the charge transfer interaction taking place within the molecule. The N-H stretching frequency is red shifted in the IR spectrum with a strong intensity from the computed frequency, which indicates weakening of the N-H bond resulting in proton transfer to the neighboring units. From the MEP analysis it is evident that the negative charge covers the carbonyl and benzene and the positive region is over the NH group.

Keywords: FTIR; Hyperpolarizability; MEP; NBO; PED; Phenothiazine.