Exploration of nonlinear optical properties of 4-methyl-4H-1,2,4-triazol-3-yl)thio)- N -phenylpropanamide based derivatives: experimental and DFT approach

Triazoles, nitrogen-containing heterocycles, have gained attention for their applications in medicinal chemistry, drug discovery, agrochemicals, and material sciences. In the current study, we synthesized novel derivatives of N-substituted 2-((5-(3-bromophenyl)-4-methyl-4H-1,2,4-triazol-3-yl)thio)-N-phenylpropanamide and conducted a comprehensive investigation using density functional theory (DFT). These novel structural hybrids of 1,2,4-triazole were synthesized through the multi-step chemical modifications of 3-bromobenzoic acid (1) . Initially, compound 1 was converted into its methyl-3-bromobenzoate (2) which was then transformed into 3-bromobenzohydrazide (3) . The final step involved the cyclization of compound 3, producing its 1,2,4-triazole derivative (4) . This intermediate was then coupled with different electrophiles, resulting in the formation of the final derivatives (7a–7c) . Additionally, the characterization of these triazole-based compounds ( 7a, 7b , and 7c ) were carried out using techniques such as IR, HNMR, and UV–visible spectroscopy to understand their structural and spectroscopic properties. The DFT study utilized M06/6-311G(d,p) functional to investigate geometrical parameters, HOMO–LUMO energies, natural bond orbital analyses, transition density matrix (TDM), density of states, and nonlinear optical (NLO) properties. The FMO analysis revealed that compound 7c exhibited the lowest band gap value (4.618 eV). Notably, compound 7c exhibited significant linear polarizability (4.195 > × 10 –23 ) and first and second hyperpolarizabilities (6.317 > × 10 –30 , 4.314 × 10 –35 ), signifying its potential for nonlinear optical applications. These NLO characteristics imply that each of our compounds, especially 7c , plays a crucial part in fabricating materials showing promising NLO properties for optoelectronic applications.