Synthesis, Characterization, Linear and NLO Properties of Novel N-(2,4-Dinitrobenzylidene)-3-Chlorobenzenamine Schiff Base: Combined Experimental and DFT Calculations

This study entails two parts: The first reports on the synthesis of a novel N-(2,4-dinitrobenzylidene)-3-chlorobenzenamine Schiff base and its analysis by ultraviolet–visible (UV–vis) spectroscopy, 1 H and 13 C nuclear magnetic resonance (NMR), and infrared (IR) spectroscopy. The UV–vis measurements showed absorption between 264 and 304 nm. The experimental optical gap energy was obtained using the Tauc method, and was estimated to be around 3.1 eV. On the other hand, we calculated optical gap energy using the M06-2X level, which gave a value of 3.20 eV, proving to be very close to the experimental one. The second part of this study focused on the dipole moment, dynamic linear and dynamic nonlinear optical (NLO) properties of this new compound. Theoretical calculations using density functional theory (DFT) were used to optimize the geometry, and to calculate this compound's dynamic polarizability and dynamic first-order hyperpolarizability. For the polarizability, we studied the mean polarizability α and the polarizability anisotropy Δ α . To elucidate the correlation between the molecular architecture of this Schiff base and the dynamic first hyperpolarizability, the dynamic behavior of the hyper-Rayleigh scattering (HRS) first hyperpolarizability β HRS , the dynamic electric field-induced second harmonic generation (EFISHG) β / / , and the depolarization ratios ( DR ) were calculated and analyzed in detail. Moreover, a correlation of β HRS with the optical band gap and between the β HRS and β / / was found. Based on these results, we can conclude that the synthesized Schiff base is a good candidate for the design of organic NLO materials. Graphic Abstract