Insight into the theoretical approach to calculate molecular geometries, absorption, and IR spectra of Vat Orange 7

•Theoretical investigation of VOG has been done and optimized by DFT/B3LYP method.•The IR and UV–visible data has been compared with the experimental results.•The chemical reactivity and the stability of the compounds were also examined.•Mulliken charge investigation and MESP shows the reactive site of the compound.•Thermodynamic parameters were studied, which confirmed the stability of compound. In this paper, the computational investigation of Vat orange 7 has been studied. Vat dyes have high color fatness, due to which the investigation into the geometric properties should be studied and can be helpful in various applications, therefore the geometric parameters i.e., bond angles, bond length, energies, dipole moment, dihedral angles, Mulliken, atomic polar tensor (APT) atomic charges, and thermodynamics energies were calculated for the titled compound. The potential energy surface of vat orange dyes was computed at the quantum mechanical calculation level by using the Density functional theory, DFT/B3LYP/6311/6–311++G) basic set. The molecular absorption and IR spectra of vat orange 7 were computed in both the gaseous state and various solvent environments i.e., water, ethanol, DMSO, heptane, and acetonitrile. A comparison was also made with the experimental spectra of UV/visible and FTIR studies. Computer programs such as Gaussian 16 W and Hyperchem are used to perform calculations. The line shape of the emission spectrum of the computed spectra is correlated with the experimentally observed spectra. The effect of solvent shift, protonic shift, and other parameters for different solvents according to their polarity and prototype were thoroughly investigated. By polarized continuum model (PCM) coupled with time-dependent density functional theory (TD-DFT) along DFT/B3LYP/6–311G++ basic sets were calculated, which shows perfect converges to excitation spectra and geometries. To understand the intermolecular and intramolecular interaction of compounds and the transfer of density from filled to unfilled orbitals, NBO analysis was performed. The analysis of the intramolecular charge transfer mechanism involved the determination of HOMO-LUMO energies. The calculations show that Vat Orange 7 exhibits higher reactivity in the medium with the smallest HOMO-LUMO gap. [Display omitted] Representation of energy levels and molecular orbital surfaces of Vat Orange 7 computed by DFT/B3LYP/6311++G (d,p) method.