Molecular structure, spectroscopic (FTIR, FTIR gas phase, FT-Raman) first-order hyperpolarizability and HOMO-LUMO analysis of 4-methoxy-2-methyl benzoic acid

WOS: 000284023100040Vibrational spectral analysis was carried out for 4-methoxy-2-methyl benzoic acid (4M2MBA) by using Fourier transform infrared (FT-IR) (solid, gas phase) and FT-Raman spectroscopy in the range of 400-4000 and 10-3500 cm(-1) respectively. The effects of molecular association through O-H center dot center dot center dot O hydrogen bonding have been described by the single dimer structure. The theoretical computational density functional theory (DFT) and Hatree-Fock (HF) method were performed at 6-311++G(d,p) levels to derive the equilibrium geometry, vibrational wavenumbers, infrared intensities and Raman scattering activities. The scaled theoretical wavenumbers were also shown to be in good agreement with experimental data. The first-order hyperpolarizability (beta(0)) of this novel molecular system and related properties (beta, alpha(0) and Delta alpha) of 4M2MBA are calculated using the B3LYP/cc-pvdz basis set, based on the finite-field approach. A detailed interpretation of the infrared and Raman spectra of 4M2MBA is reported. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule were also constructed and compared with the experimental one. Copyright (C) 2010 John Wiley & Sons, Ltd.Ministry of Education and Human Resources Development, KoreaMinistry of Education & Human Resources Development (MOEHRD), Republic of Korea; MOST/KOSEFKorea Science and Engineering Foundation [R15-2003-012-02001-0]Dr C. Meganathan was supported by a fellowship from the BK21 program, Ministry of Education and Human Resources Development, Korea and this work was supported by grants from the MOST/KOSEF for the EB-NCRC (grant # R15-2003-012-02001-0)