A comprehensive investigation into the effect of substitution on electronic structure, charge transfer, resonance, and strength of hydrogen bond in 3–amino-propene thial and its analogous: a DFT calculation

In this study, the effect of substitution (CH2OCH3, Cl, F, NHCH3, NO2, OH, Ph, PhOCH3, and SH) on the hydrogen bonding energies of N-H···S intramolecular bridges in the 3-amino-propene thial and its analogous compound, 2-hydrazineylidene-ethane thial, is examined using density functional theory (DFT). The outcomes reveal that the compounds containing the Ph and F substitutions possess the strongest and weakest hydrogen bonds. In other words, the electron-donating substitutions strengthen the hydrogen bond, whereas electron-withdrawing ones weaken it. The hydrogen bonding formation can cause elongation of the N-H bond and shortening of the H∙∙∙S distance. The findings derived from atoms in molecules (AIM) calculations show characteristics of closed-shell interactions and also the electrostatic nature of the H∙∙∙S bonding. Moreover, the natural bond orbital (NBO) approach is employed to compute the interaction between the LPS and the σ∗N−H, which reveals that the largest interaction is related to the strongest hydrogen bond. Finally, to investigate the effect of the environment on the strength of hydrogen bonding, the calculations are conducted in two solvents, namely water and CCl4. The outcomes indicate that hydrogen bonding strength is lower in the solution as compared to the gas phase.