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Properties of intramolecular H-bond (IHB) for a chemical system can affect the changes in geometrical/electronic features in the vicinity of the bridge. Substitution of an atom (H) in benzene with OH/SH groups forming IHB has little effect on its aromaticity. This report is devoted to the depiction of the effect of OH/SH substituent on stability/aromaticity of multi-substituted benzene rings via IHB formation. The computational studies on the stability/aromaticity in the homo (OH/SH) and hetero (OH and SH) substituted form of the benzene systems have been investigated using B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ approaches with the aid of aromaticity indices (AIs) descriptors (NICS, HOMA, AIBIC, and PDI) and IHB/stability diagnostics; relative energy, QTAIM based interaction energy acquired from the potential energy density and electron density, HBSBIC, and HOMO-LUMO gap including NCI plots. The IHBs formed by different OH/SH substituents have a vital role as an aromaticity modulator and deploying the above-said tools, it turns out that the cyclic 4n+2 I�-electrons delocalization is weakened/strengthened depending on the number and types of OH/SH substituents forming the IHBs. Here, all the AIs vary in a small amount and indicative of the modulator of the I�-electron structure to the substituent effect via IHB formation. As in practical applications, the diagnostics based on different criteria do not speak with the same voice, hence interestingly, in many cases, the changes in AIs notably correlate with their stability. © 2021 Wiley-VCH GmbH

This work presents the synthesis and characterization as well as crystal structure determination of a biologically relevant, chemically and medicinally interesting isolated solids-state crystal structure of its ethanol inclusion compound, 2-(5,5-dimethyl-3-oxocyclohex-1-en-1-yl) Hydrazinecarbothioamide for the first time in the literature. The molecules pack itself in the crystal lattices via intermolecular interactions. The stability due to the role of H-bond(s) in the title compound and its packed cell, were quantitatively investigated by topological analysis based on Bader′s quantum theory of atoms in molecules (QTAIM) to characterize these interactions. The chemical, as well as topological properties of the electron densities, ρ(r) of the title system and its packed cell have been studied using DFT approach. Chemical reactivity of both species has also been calculated using HOMO-LUMO, ionization energy, hardness, and chemical potential along with their molecular electrostatic potential and total electron density plots. In order to gain better insight into the role of H-bonding interaction(s), the theoretically investigated binding energies revealed that crystal within the lattice unit (packed cell) having more intermolecular stabilizing interactions has been found to be more stable than its molecular unit using DFT method and ab initio modeling which is fairly supported by the experimentally predicted H-bonding interaction(s) and QTAIM based topological parameters.