Substituent influence on the structural, vibrational and electronic properties of 2,5-dihydrothiophene-1,1-dioxide by experimental and DFT methods

• FTIR and FT-Raman spectra of 25DHT and 3M25DHT were analysed.
• The 25DHT possesses C2v point group symmetry.
• The ELUMO–EHOMO of 25DHT and 3M25DHT is found to be 7.2625 and 7.0968 eV.
• The nO → σSO∗ interactions have strong stabilization of 23.3 kcal mol−1.

Spectroscopic and theoretical quantum chemical studies of 2,5-dihydrothiophene-1,1-dioxide and 3-methyl-2,5-dihydrothiophene-1,1-dioxide have been carried out by FTIR and FT-Raman spectral techniques along with B3LYP methods. The geometry of the compounds have been optimised by B3LYP method with 6-311++G∗∗ and cc-pVTZ basis sets. The geometrical parameters obtained at B3LYP levels have been compared with the experimental values. Molecular electrostatic potential surface, total electron density distribution and frontier molecular orbital are constructed at B3LYP/cc-pVTZ level to understand the electronic properties. The charge density distribution and sites of chemical reactivity of the molecules have been obtained by mapping electron density isosurface with electrostatic potential surfaces. Natural bond orbital analysis of the molecules are carried out and the occupancies and the atomic hybrid contributions are calculated.

The FT-IR and FT-Raman spectral measurements of 2,5-dihydrothiophene-1,1-dioxide and 3-methyl-2,5-dihydrothiophene-1,1-dioxide and complete assignments of the observed spectra have been elaborated. DFT calculations have been performed and the structural parameters of the compound were determined from the optimised geometry with 6-311++G(d, p) and cc-pVTZ basis sets and giving energies, harmonic vibrational frequencies, depolarisation ratios, IR and Raman intensities. Detailed bond pair-band pair and bond pair-lone pair interaction analysis was carried out.Figure optionsDownload as PowerPoint slide