Theoretical Insights into the Optoelectronic and Charge-Transfer Characteristics of 5-(1H- 1,2,4-triazol-1-yl)-2-thiophenecarboxylic Acid

The structural, spectroscopic, and electronic characteristics of 5-(1H-1,2,4-triazol-1-yl)-2-thiophenecarboxylic acid (TTCA) were investigated using DFT and TD-DFT approaches at the B3LYP/6-311 + + G(d,p) level. Geometry optimization confirmed a planar π-conjugated structure stabilized by intramolecular hydrogen bonding. The computed HOMO–LUMO energy gap (3.13 eV) and optical transition energy (1.7 eV) revealed chemical stability and visible-light photoactivity. Simulated FT-IR, NMR, and UV–Vis spectra agreed with experimental analogs, validating the theoretical approach. Global reactivity descriptors (IP, EA, η, S, χ, ω) further elucidated the charge-transfer capacity and electronic softness of the molecule. Density of states, molecular electrostatic potential, and non-covalent interaction analyses revealed strong π-delocalization and donor–acceptor interaction within the triazole–thiophene framework. These results provide new theoretical insights into the optoelectronic tunability of heteroaromatic systems, highlighting TTCA as a promising scaffold for future coordination and photoactive material design.