Synthesis, physicochemical characterization, and TD-DFT calculations of monothiocarbohydrazone derivatives

Abstract

Derivatives of thiocarbohydrazone studied so far have shown great biological activity such as antioxidant, antimicrobial, and anticancer. Most of these compounds are bis-substituted derivatives, while monothiocarbohydrazones are much less investigated. Eighteen monothiocarbohydrazones were synthesized and subjected to physicochemical characterization in order to facilitate the examination of their potential biological activity and application in future studies. The structure of synthesized derivatives was confirmed with NMR and FT-IR spectroscopy, and with elemental analysis. For one of the compounds, single-crystal X-ray diffraction analysis was performed. Specific and non-specific molecular interactions were interpreted by LSER principles, using Catalan's model. For additional information about the dominance and influence of the interactions presented, correlations with Hansen's solubility parameters were calculated. Influence of the type and position of the substituent on absorption maxima was determined with LFER (linear free-energy relationship) principles, using Hammett's equation. Acidity constants of the synthesized compounds were theoretically calculated and experimentally determined. Moreover, the excitation of a molecule by a photon of UV-Vis light was interpreted by time-dependent density functional theory (TD-DFT) calculations of UV absorption bands, and intramolecular charge transfer (ICT) was quantified by calculations of the charge transfer distances (D-CT).