DFT Insights into Substituent Effects on Trithiocarbonate Linkages: Electronic Structure, Stability and Reactivity

This study provides a comprehensive theoretical investigation of trithiocarbonate (TTC) linkages, significant in polymerization processes, pharmacological therapies, and biologically active compounds. The focus is on the impact of various substituents on electronic structure, stability, and reactivity using Density Functional Theory (DFT). Key electronic parameters such as HOMO, LUMO, and energy gap were analyzed to evaluate molecular stability and potential reactivity. Compound characterization was performed using UV-visible absorption and IR spectroscopy. Molecular electrostatic potential (MEP) analysis identified nucleophilic and electrophilic regions, while the density of states (DOS) provided additional insights into electronic distribution. Global reactivity descriptors, including chemical potential (µ), chemical softness (s), chemical hardness (ⴄ), and electrophilicity index (ꞷ), were used to assess the stability and reactivity. The electrophilic index of TTC1–TTC11 ranged from 1.5 eV to 4.0 eV, indicating high reactivity, while TTC12, TTC13, and TTC14 were classified as super-electrophilic. MEP analysis highlighted reactive sites, such as the sulfur atom in TTC11 and the C-H bond in TTC13. High bond dissociation energies (BDE) and Gibbs free energies for TTC11, TTC13, and TTC14 suggest strong linkages with their substituents when directly attached to ring-structured substituents without alkyl spacer. In contrast, TTC8, TTC9, TTC10, and TTC12 exhibit weaker linkages when linked with alkyl spacer. These findings offer valuable insights for designing TTC compounds with tailored properties.