Molecular structure and vibrational analysis of 2,5-pyridine-dicarboxylic acid using experimental and theoretical methods

Abstract

The FTIR and FT-Raman spectra of 2,5-pyridine-dicarboxylic acid (PDA) has been recorded in the range 4000-450 cm-1 and 4000-50 cm-1, respectively. The optimized geometry and vibrational frequencies were computed using density functional theory (DFT) employing B3LYP functional with 6-311++G(d,p) basis set. The rms error between observed and calculated frequencies is obtained as 10.8 cm-1. A normal coordinate analysis was carried out for all the vibrations of this molecule by solving inverse vibrational problem (IVP) using a 74-parameter modified valence force field employing overlay technique. This reproduced 35 observed frequencies of this molecule with an error of 9.28 cm-1 in the zero-order calculations, demonstrating the transferability of the force field obtained in our earlier work on some related pyridine-dicarboxylic acids. PED and eigen vectors calculated in the process were used to make unambiguous vibrational assignments of all the fundamentals of the molecule.