Theoretical insights into the optoelectronic and charge-transfer characteristics of 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid

This study elucidates the electronic and structural interplay of 5-(1 H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) to assess its potential as a multifunctional heteroaromatic scaffold. Using DFT and TD-DFT calculations at the B3LYP/6-311 + + G(d, p) level, we demonstrate that intramolecular hydrogen bonding locks the triazole and thiophene rings into a highly rigid, planar configuration. This structural coplanarity facilitates extensive π-electron delocalization, which is critical for the molecule's observed optoelectronic behavior. The analysis reveals a dual electronic character: a chemically stable ground state with a HOMO-LUMO gap of 3.13 eV, contrasted by significant visible-light photoactivity evidenced by a narrow optical transition energy of 1.7 eV. Molecular Electrostatic Potential (MEP) and Non-Covalent Interaction (NCI) analyses identify specific nucleophilic sites and weak interactions that empower TTCA to act as a versatile ligand. Validated by high statistical agreement with experimental literature data for structurally related analogs (FT-IR, NMR, UV-Vis), these results confirm TTCA as a promising candidate for charge-transfer applications, coordination chemistry, and optoelectronic material design.