Synthesis, crystal structure, Hirshfeld surface analysis, spectral characterization, reduced density gradient and nonlinear optical investigation on (E)-N'-(4-nitrobenzylidene)-2-(quinolin-8-yloxy) acetohydrazide monohydrate: A combined experimental and DFT approach

• A novel quinoline derivative was synthesized and characterized. • FT-IR, NMR, UV–Vis techniques and DFT method were used for spectroscopic analysis. • Conformational analysis was performed to determine the stable geometry. • The HS, NBO and RDG analyses explained the intramolecular hydrogen bonding. • First hyper polarizability and HOMO-LUMO energy gap were theoretically predicted. In this work, (E)-N'-(4-nitrobenzylidene)-2-(quinolin-8-yloxy) acetohydrazide monohydrate (NBQA) crystal was synthesized and its structural characterization was carried out by single-crystal X-ray diffraction. The intermolecular interactions in the crystal were investigated through the Hirshfeld surface analysis and the 2D-fingerprint plot. In the solid phase, the spectroscopic characterization was also carried out using FT-IR, 1H NMR, and 13C NMR experimental spectroscopies. To support experimental results, DFT calculations have been accomplished on the NBQA molecule in the ground state. First, theoretical calculations were performed using BPV86 and GGA-PBE functionals with the 6-311G(d,p) basis set to obtain the stable conformer of the molecule. Likewise, harmonic vibrational frequencies, 1H and 13C chemical shifts, and NBO analysis were also calculated using the same level of theory and compared to available experimental data. Furthermore, the molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, HOMO-LUMO energies, energy band gap, density of state (DOS), global chemical reactivity descriptors, and some thermodynamic functions were studied and discussed. UV–Vis spectrum was predicted by the TD-DFT method in chloroform solvent and compared with the experimental spectrum for displaying the involved electronic transitions in the compound. The repulsive, attractive, and Van der Waals strong and weak interactions in NBQA were investigated via the RDG analysis. The NLO properties of NBQA have also investigated in different available solvents by DFT and compared to the most important compounds in the field. The first hyperpolarizability values of NBQA have been increased with increasing solvent polarity and decreasing the energy band gap. Image, graphical abstract [ABSTRACT FROM AUTHOR]