A Comparative Study on the Molecular Structures and Vibrational Spectra of 2-, 3- and 4-Cyanopyridines by Density Functional Theory

The optimized molecular structures, harmonic vibrational wavenumbers, and corresponding vibrational assignments of 2-, 3and 4-cyanopyridines have been calculated using Gaussian 03 set of quantum chemistry code. Calculations were carried out at Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) level using the standard 6-311++G(d,p)basis set. The geometrical parameters, thermodynamic parameters, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), Infrared intensities, Raman activities and molecular electrostatic potentials results are reported. Reliable vibrational assignments have been made on the basis of Potential Energy Distribution (PED) using VEDA4 program. Theoretical results have been successfully compared with the available experimental data.