A combined experimental and theoretical analysis on molecular structure and vibrational spectra of 2,4-dihydroxybenzoic acid

Abstract

The FT-IR and FT-Raman spectra of 2,4-dihydroxybenzoic acid (2,4-DHBA) in the solid phase have been recorded in the regions 4000-400 cm(-1) and 3700-100 cm(-1), respectively. The total energies of sixteen stable conformers for 2,4-DHBA have been calculated by density functional theory (DFT) using the B3LYP method with 6-311++G (d, p) basis set, and the C1 conformer with the lowest energy was obtained, the geometrical parameters between X-ray experiment diffraction and DFT calculation show good consistency. Furthermore, the vibrational frequencies of 2,4-DHBA were computed, and the detailed analysis of vibrational spectra was made on the basis of the potential energy distribution (PED) by combining experimental with theoretical data. In addition, frontier molecular orbitals, atomic charge distribution and molecular electrostatic potential (MEP) were also given.

Keywords: 2,4-Dihydroxybenzoic acid; DFT; FT-IR; FT-Raman; Vibrational analysis.