Insights into structural and vibrational characteristics of 1-methoxy-4-[2-(phenylsulfonyl)vinyl]benzene: An application of experimental vibrational spectroscopy and density functional theory

Fourier transform infrared and Raman spectra, in the spectral range 4000-400 and 4000-50 cm(-1), respectively, were measured for 1-methoxy-4-[2-(phenylsulfonyl)vinyl]benzene (MPB). Initial values of torsion angles around five flexible bonds C1-S, S-C15, C17-C19, C22-O and O-C30 (see Fig. 1 for numbering), essential for starting geometry optimization, were determined using "bond-pairing method" proposed earlier by us. Optimized structure parameters, harmonic general valence force field, vibrational fundamentals, potential energy distribution and infrared and Raman band intensities were determined using density functional theory, employing B3LYP/ 6-311++G(d,p) formalism. Good agreement was found, between measured and computed quantities investigated here. The r.m.s error between experimental and theoretical vibrational wavenumbers was 8.6 cm(-1), for MPB. With the help of PED and eigenvectors, all vibrational fundamentals of the molecule were assigned unambiguously for the first time.