Study of molecular structure and assignments of fundamental modes of 2-ethylpyridine-4-carbothioamide by density functional methods

Abstract

The FT-IR and UV spectra of 2-ethylpyridine-4-carbothioamide have been recorded. The structure and spectroscopic data of the molecule in ground state have been calculated using AM1, PM3 semi-empirical methods, ab initio Hartree–Fock and density functional theory (B3LYP, B3PW91) methods by employing 6-31+ G (d, p) basis sets. The optimized geometry, vibrational frequencies in the ground state is calculated. The scaled vibrational frequencies are found to coincide with the experimentally observed values. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies show that charge transfer occurs within these molecules. In this work, we have calculated 1H and 13C nuclear magnetic resonance chemical shifts of the molecules using the gauge-including atomic orbital method matches with the experimental values. The natural localized molecular orbital analysis has been made to study the atomic hybrid contribution of the title molecule. Molecular electrostatic potential and total density distribution are constructed to understand the electronic properties and to study the most stable geometry of the compound from the potential energy scan.