Structural, spectroscopic, quantum chemical, and molecular docking investigation of (E)-N'-(2,5-dimethoxybenzylidene)picolinohydrazide

Abstract

Schiff bases and hydrazides are groups of compounds with important biological activities. In this contribution, (E)-N'-(2,5-dimethoxybenzylidene)picolinohydrazide (DBP) was synthesized and characterized by X-ray crystallography, IR, Raman, UV–vis and NMR spectroscopies. The Hirshfeld surface analysis was performed to investigate the interactions within the crystal package. The structure of DBP was optimized by several functionals (B3LYP, CAM-B3LYP, B3PW91, M05-2X, and M06-2X) in conjunction with the 6-311++G(d,p) basis set. The suitable level of theory was determined based on the comparison between experimental and theoretical bond lengths and angles (M06-2X/6-311++G(d,p)). The Natural Bond Orbital (NBO) and Quantum Theory of Atoms in Molecules (QTAIM) approaches were used for the quantification of the interaction strengths within a structure. The experimental IR and Raman peaks were assigned based on the calculated one, with the aid of the Potential Energy Distribution (PED) analysis. The 1H and 13C NMR signals were also assigned when compared to the calculated ones. The reproducibility of the experimental results proved that a suitable level of theory was obtained. The experimental UV–vis spectra consisted of a wide peak between 200 and 450 nm, while the most prominent theoretical transitions were located at 324, 231, and 213 nm. The nonlinear optical (NLO) studies Z-scan experiment allowed the determination of the nonlinear absorption coefficient and nonlinear refractive index, thus proving that DBP can be used as NLO material. Various reactivity descriptors of DBP and its analogs were computed and the reactivity was checked towards Cyclin-Dependent Kinase 2 protein, with the influence of structural parameters explained.