DFT/TDDFT investigation on the electronic structures and spectral characteristics of C5H3XOS (X = H,F, Cl or Br)

Halogen and solvent effects on the conformational, vibrational, and electronic characteristics of thiophene-2-carbaldehyde (T2C, C₅H₄OS) and thiophene-2-carbonyl-halogens [C₅H₃XOS, X = F (T2C-F), Cl (T2C-Cl), and Br (T2C-Br)] are analyzed by the density functional theory (DFT) and time dependent density functional theory (TDDFT), using the B3LYP functional and the 6-31++G(d,p) basis set. Computations consider two conformations of the compounds in both gas phase and solution. The present study aims at the exploration of the halogen and medium effects on the stability, structural parameters, dipole moment, carbonyl stretching vibration, frontier molecular orbitals, ultraviolet (UV) and density-of-states spectra of the conformers. The atypical characteristics of fluorine and chlorine affecting the electrical-optical band gaps, chemical hardness, partial density-of-states plot, absorption band, and the highest occupied molecular orbital are observed correspondingly. The findings of this research will provide insight for future studies considering conformations analogous to the compounds studied.