The spectroscopic (FT-IR, FT-Raman and NMR), NCA, Fukui function analysis first order hyperpolarizability, TGA of 6-chloro-3,4dihydro-2H-1,2,4-benzothiazine-7-sulphonamide1,1-dioxide by ab initio HF and Density Functional method

•FT-IR, and FT-Raman spectra of 6CDBSD in solid phase were recorded and analyzed.•The vibrations were assigned with PED.•The NBO analysis explained the intramolecular hydrogen bonding.•Fukui function was calculated to identify changes in the reactivity of molecule.

The Fourier-Transform Infrared and Fourier-Transform Raman spectra of 6-Chloro-3,4dihydro-2H-1,2,4-benzothiazine-7sulphonamide1,1-dioxide(6CDBSD) was recorded in the region 4000–450 cm−1 and 4000–100 cm−1respectively. Quantum chemical calculations of energies, geometrical structure and vibrational wave numbers of 6CDBSD were carried out by HF and DFT (B3LYP) method with 6-31G (d,p) basis set. The difference between the observed and scaled wavenumber value of most of the fundamentals is very small. The assignments of the vibrational spectra have been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The linear polariazability (α) and the first order hyperpolarizability (βtot) values of the investigated molecule have been computed using HF and DFT with 6-31G (d,p) basis set. Stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The 1H and 13C Nuclear Magnetic Resonance (NMR) chemical shifts of the molecules were calculated using the Gauge-Invariant Atomic orbital (GIAO) method, confirms with the experimental values. The calculated HOMO and LUMO energies also confirm that charge transfer occurs within the molecule. Thermal stability of 6CDBSD was studied by thermo gravimetric analysis (TGA). Next Fukui functions was calculated to identify changes in the reactivity of molecule. Finally molecular electrostatic potential (MEP) and other molecular properties were performed.

Graphical abstract6-Chloro-3,4dihydro-2H-1,2,4-benzothiazine-7-sulphonamide1,1-dioxide is diuretic which is commonly referred to as a water pill. The equilibrium geometry harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by HF and DFT method with 6-31G(d,p) basis set using Gaussian 03W program. The 1H and 13C Nuclear Magnetic Resonance (NMR) chemical shifts of the molecules were calculated using GIAO method.Figure optionsDownload full-size imageDownload as PowerPoint slide