Pharmaceutica Analytica Acta

Abstract

Spectroscopic Investigation (FT-IR, FT-Raman, NMR and UV-Vis),Conformational Stability, NBO and Thermodynamic Analysis of 1-(2-Methoxyphenyl) Piperazine and 1-(2-Chlorophenyl) Piperazine by DFT Approach

Prabavathi N, Senthil Nayaki N and Krishnakumar V

The Vibrational and electronic properties of phenyl substituted compounds 1-(2-methoxyphenyl)piperazine and 1-(2-chlorophenyl)piperazine have been investigated by FT-IR, FT-Raman, NMR and UV-Vis spectral measurements. Density functional theory (DFT) method, using B3LYP functional, with 6-311++G (d,p) basis set, has been performed for assigning vibrational frequencies of the title compounds, which also helps to derive useful information about the structure of the chosen compounds. A detailed interpretation of the Infrared and Raman spectra of the two molecules were reported based on potential energy distribution (PED). 13C and 1H NMR chemical shifts of the molecules were calculated using the gauge independent atomic orbital (GIAO) method. These studies satisfactorily agree the experimental data. Charge density distribution and site of chemical reactivity of the molecule have been studied by mapping electron density isosurface with molecular electrostatic potential (MEP). Stability of the molecules arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The compounds have similar HOMO (Highest Occupied Molecular Orbitals) - LUMO (Lowest Unoccupied Molecular Orbitals) gap due to similarity in their structures. The compounds show (π→ π*) transitions in the UVVisible range.