Synthesis, Crystal structure, Spectral characterization and Hirshfeld surface analysis of (E)-N'-(3-ethoxy-4-hydroxybenzylidene)-4-fluorobenzohydrazide single-crystal – A novel NLO active material

Abstract (E)-N'-(3-ethoxy-4-hydroxybenzylidene)-4-fluorobenzohydrazide (3E4H4FB) single crystal was obtained by recrystallization method. Single-crystal X-ray diffraction analysis revealed the crystalline structure, packing, and molecular geometry features of the prepared crystal. The structural parameters such as bond distances and angles of 3E4H4FB crystal were discussed. The B3LYP/6-311G(d,p) level of theory was used to do optimize the structure, and the computed results reveal that the optimized geometry can perfectly replicate the crystal structure. The inter- and intramolecular hydrogen bonding interactions were also interpreted. Hirshfeld surface analysis was used to elucidate and quantify the intermolecular interactions between the molecules in the crystal structure. FTIR analysis was applied to identify the characteristic functional groups of the synthesized crystal. Natural bond orbital (NBO) and Quantum Theory of Atoms in Molecules (QTAIM) analyses of the molecule were also used to quantify interactions present in the molecule. The excitation wavelengths, oscillator strengths, and excitation energies were determined by the TD-DFT calculations and compared to the experimental wavelengths. The charge transfer within the molecule was explained by the frontier molecular orbital analysis. Nonlinear optical (NLO) properties were calculated to predict the electric dipole moment and first-order hyperpolarizability of the compound. The static third-order susceptibility value was measured by the Z-scan technique. Finally, the ecotoxicity impact of the novel NLO material was assessed towards fish, daphnia, and green algae.