Evaluation of Geometrical, Vibrational, Electronic and Other Molecular Parameters of Two Vinyl Sulfone Derivatives Using Experimental Spectroscopic and Computational Density Functional Theory Analyses

The goal of this article is to characterize 2-(phenylsulfonyl)vinylbenzene(PVB) and 1-chloro-4-(phenylsulfonyl)vinylbenzene(CVB), using experimental spectroscopic techniques (FT-IR, FT Raman, UV-Vis) and computational tools (DFT, TD-DFT, Gauss View, MOLVIB, NBO software ORIGIN). Density functional theory formalism at DFT/B3LYP/6-311++G(d,p) level was employed to determine barrier hights around (C1-S12), (S12-C15) and (C17-C19) bonds, ground state geometry, general valence force field, harmonic vibrational fundamentals, and vital molecular electronic parameters (FMO,NLO, NBO, MESP), whereas, in combination with MOLVIB, it provided scaled values for force field and vibrational frequencies, along with eigenvectors, potential energy distribution (PED), infrared and Raman intensities, and simulated vibrational spectra, while its time dependent variant computed absorption maxima (λmax) and oscillator strengths and simulated UV-Vis spectra for electron transitions in various solvents for the target molecules. Experimental and corresponding theoretical parameters for structure, and vibrational wavenumbers, and measured and simulated spectra agreed very well. Experimental and scaled vibrational frequencies agreed with rms error 9.0 and 5.4 cm−1 for PVB and CVB, respectively. PED and eigenvectors helped in the assignment of all the eighty-one fundamentals of each of the two molecules unambiguously. Comparative study made for frontier molecular orbital (FMO) parameters revealed that PVB is less reactive and more stable, in comparison with CVB, with energy gap (ΔE) values 3.60 and 3.23 eV, for PVB and CVB, respectively. Nonlinear optical (NLO) investigation ascertained their utility for NLO applications. Natural bond orbital (NBO) analysis made it clear that the highest contribution of stabilization energy comes from (C3–C4)π→(C1–C2)π* interaction which were 23.40 and 23.50 kcal/mol for PVB and CVB, respectively. MESP mapping confirmed that sulfone moiety was an electrophilic group and identified its oxygen atoms as sites for an electrophilic attack. The most significant aspect of these investigations was, that we tried to explain major changes observed for vibrational and electronic parameters of CVB in terms of the increased mass, and inductive and resonance effects of the chlorine atom, in comparison with PVB, to the extent possible.