Experimental and Quantum Chemical Approaches for Hydrazide-based Crystalline Organic Chromophores: Synthesis, SC-XRD, Spectroscopic and Nonlinear Optical Properties

Abstract

Crystalline organic compounds, (E)-N-(2-(2-(2-hydroxybenzylidene)hydrazinecarbonyl)-phenyl) benzamide (NHBPB) and (E)-4-chloro-N-(2-(2-(2-hydroxybenzylidene)hydrazine-carbonyl) phenyl)benzene sulfonamide (CNHBP), were prepared through condensation of hydrazide derivatives of N-benzoylated and N-4-chlorobenzenesulfonylated derivatives of anthranilic acid with 2-hydroxybenzaldehyde. The structural interpretations were accomplished distinctly by single-crystal X-ray diffraction (SC-XRD) analysis and NMR studies. Accompanying the experimental studies, quantum chemical computations were employed to determine the non-linear optical (NLO) properties using the M06 and M06-2X functionals along with 6-311G (d,p) basis set. A comparative analysis was made in order to compare the geometrical parameters between XRD and DFT calculations and a good agreement was found. Frontier molecular orbital (FMO) analysis found a narrower HOMO/LUMO energy gap for NHBPB than CNHBP. Further, UV-Vis investigation revealed a red-shifted behavior for NHBPB (297.894 and 311.594 nm at M06-2X and M06 levels, respectively) owing to its smaller HOMO/LUMO energy gap. From the FMOs findings, Global Reactivity Parameters (GRPs) were also calculated and a relatively lower ionization potential and hardness with larger softness were found for NHBPB. The FMO and UV results indicated the greater polarizability in NHBPB as compared to CNHBP. Therefore, greater second hyperpolarizability response was noticed for NHBPB (2.749 ×105 and 1.945×105a.u at M06-2X and M006 functional, respectively). Additionally, comparative study with urea molecule showed good NLO responses for the foresaid compounds. These findings revealed that hydrazide-based compounds possess extremely high linear and nonlinear polarizabilities compared to most of the previously synthesized compounds which highlights their excellent properties for use in NLO materials.