Quantum chemical study on influence of the substitution effect on the structural and electronic properties and intramolecular hydrogen bonding of 2-nitrophenyl hydrosulfide in ground and electronic excited state

Abstract

A density functional theory (DFT)-based quantum chemical computational study has been carried out to characterize the intramolecular hydrogen bonding (IMHB) interaction in 2-nitrophenyl hydrosulfide. This compound and its 24 derivatives are optimized by B3LYP method using 6-311++G** basis set in the gas phase and the water solution. The following substituents have been taken into consideration: F, Cl, Br, C₂H₅, CH₃, CF₃, NHCOCH₃, NO₂, OH, OCH₃, SH, CH₂F, CH₂Cl, CH₂Br, CH₂OH, SH, SCH₃, SCF₃, SCOCH₃, CH₂CF₃, CH₂OCH₃, CHO, COCH₃, and OCHF₂. The IMHB interaction has been explored by calculation of electron density ρ(r) and Laplacian ∇² ρ(r) at the bond critical point using atoms-in-molecule (AIM) theory. The electron density (ρ) and Laplacian (∇² ρ) properties, estimated by AIM calculations, indicate that H₆···O₁ bond possesses low ρ and positive ∇² ρ values which are in agreement with electrostatic character of the HBs, whereas S₅–H₆ bond has covalent character (∇² ρ < 0). The natural bond orbital analysis is applied to get a more precise insight into the nature of such H₆···O₁ interactions. Vibrational frequencies, several well-established indices of aromaticity, and physical properties such as dipole moment, chemical potential, and chemical hardness of these compounds have been systematically explored. Also, the excited-state properties of intramolecular hydrogen bonding in these systems have been investigated theoretically using the time-dependent DFT method.