Theoretical and experimental studies on 2-(2-methyl-5-nitro-1-imidazolyl)ethanol

Abstract

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational spectra, natural bond orbital (NBO) and UV spectral analysis of [2-(2-methyl-5-nitro-1-imidazolyl) ethanol] (Metronidazole-MTD). The FT-IR solid phase (4000-400 cm-1) liquid phase, and FT-Raman spectra (3500-50 cm-1) of MTD were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of MTD in the ground state have been calculated using the density functional method B3LYP with 6-311G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of the Gauss view program package. Stability of the molecule arising from hyperconjugative interactions and charge delocalization have been analyzed using natural bond orbital analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order stabilization energies E2 confirms the occurrence of Intramolecular Charge Transfer (ICT) within the molecule. The UV spectrum was measured in ethanol solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complement the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge Independent Atomic Orbital (GIAO) method and compared with experimental results.  Finally the results of calculations were applied to simulate Infrared and Raman spectra of the title compound which show good agreement with observed spectra.