Integrated computational and experimental examination of Schiff base (E)-2-methoxy-6-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol: Synthesis, structural elucidation, and nonlinear optical characteristics for optoelectronics and photonics applic

This study explores the nonlinear optics (NLO) properties of the Schiff base molecule ( E )-2-methoxy-6-((2-phenyl-2-(pyridin-2-yl)hydrazineylidene)methyl)phenol “ OP1 ,” synthesized via the condensation of hydrazine hydrate, 2-chloropyridine, and benzaldehyde. OP1 exhibits UV–visible absorption bands at 368 nm (n–π* transition) and 330 nm (π–π* transition). Z -scan measurements under continuous-wave laser illumination reveal third-order NLO parameters including a nonlinear absorption coefficient ( β ) of ∼10 −3 cm/W, nonlinear refractive index ( n ₂) of ∼10 −7 cm 2 /W, and third-order susceptibility ( χ 3 ) of ∼10 −6 esu, highlighting its optical limiting capabilities. DFT/TD-DFT calculations at the B3LYP/6–311++G(d,p) level confirm electronic structure properties, with HOMO-LUMO gap analysis via Conceptual DFT identifying key reactivity descriptors (chemical hardness, electrophilicity index). The compound's enhanced NLO response stems from π-conjugation and charge-transfer interactions, validated by natural bond orbital (NBO) and frontier molecular orbital (FMO) analyses. The convergence of experimental and computational findings highlights the robust third-order NLO performance and optical stability of OP1 , positioning it as a strong molecular scaffold for applications in optoelectronics, photonic devices, and radiation protection technologies. Collectively, these results demonstrate the critical role of molecular design—specifically π-conjugation and charge-transfer pathways—in optimizing the NLO characteristics of Schiff base systems. • Schiff base ( E )-2-methoxy6-((2-phenyl-2-(pyridin-2-yl)hydrazono) methyl) phenol ( OP1 ) synthesized and characterized, showing strong n–π* and π–π* transitions. • Z-scan technique revealed high third-order nonlinear optical coefficients for OP1. • DFT and TD-DFT studies confirmed OP1's electronic and vibrational properties. • FMO and NBO analyses indicated efficient charge transfer and π-conjugation. • OP1 shows promise for optoelectronic, photonic, and radiation protection uses.