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In the present study, we use a dual approach comprising of experimental and computational techniques to report the syntheses, characterizations (1H NMR, 13C NMR, FT-IR, UV–visible spectroscopy and X-ray structure determination) and theoretically evaluated the third order NLO response properties of the new organic compounds; 1-((E)-(2-methoxy-4-nitrophenylimino)methyl)naphthalen-2-ol hydrate (HL1), (E)- N -(ethoxy(2,3-dichlorophenyl)methyl))-2-methoxy-4-nitrobenzenamine(L2) and copper(II) complex [Cu(L3)(py)] of (E)- N '-(3,5-dichloro-2-hydroxybenzylidene)benzohydrazide(H 2 L3). The HL1 and L2 were crystallized in the triclinic system of the space group P-1 with two molecules in the unit cell, whereas complex [Cu(L3)(py)] was crystallized in the monoclinic system in the space groups P2 1 / c with eight molecules in the unit cell. The thermal properties (DSC and TG-DTG analysis) of these compounds were also investigated. State of the art quantum computational methods are performed at molecular and bulk levels to get structure-property relationships from molecule to materials. For HL1, L2 and complex [Cu(L3)(py)], their isotropic (anisotropic) values are found to be 55.46 × 10−24 esu (71.69 × 10−24 esu), 44.67 × 10−24 esu (26.92 × 10−24 esu) and 60.73 × 10−24 esu (69.71 × 10−24 esu), respectively. The differences in isotropic and anisotropic values are 16.23 × 10−24 esu, 17.75 × 10−24 esu and 9.00 × 10−24 esu, respectively. The NLO response properties including third-order polarizability (γ) are calculated using density functional theory (DFT) methods. The calculated γ amplitudes for the synthesized HL1, L2 and complex [Cu(L3)(py)] are found to be 801.54 × 10−36, 77.81 × 10−36 and 311.17 × 10−36 esu, respectively. These γ amplitudes of HL1, L2 and complex [Cu(L3)(py)] are about 44, 4 and 17 times larger than that of standard para -nitroaniline (PNA, a prototype NLO molecule), respectively, which show the potential of these compounds as efficient NLO materials. Their electronic parameters and NLO properties were also evaluated using TD-DFT calculations. The HL1, L2 and complex [Cu(L3)(py)] showed maximum absorptions with oscillator strengths of 0.749, 0.393 and 0.368 at 2.751 3.476 and 3.214 eV, respectively. Image 1 • Syntheses and characterizations of new organic compounds and Cu(II) complex. • The electronic structures were studied by X-ray crystallography. • The DFT calculations showed the good NLO response properties. • The FMOs and MEPs were used to reveal structure-property relationship. • NMR, FT-IR and UV–Vis spectral analysis were carried out. [ABSTRACT FROM AUTHOR]

• Synthesis growth and molecular interaction of organic nonlinear optical single crystals of (E)-N′-(2,3-dimethoxybenzylidene)−4-fluorobenzohydrazide (DMB-FBH) were discussed. • X-ray single-crystal diffraction analysis confirmed the structure. • Vibrational analysis and various electronic properties of the compound were studied using density functional theory (DFT) calculations. • Hirshfeld surface analyses and fingerprint plots confirmed the O...H, N...H, C...C and C...H intermolecular hydrogen bonds interaction. • UV–visible and the fluorescence emission spectra of the DMB-FBH in aqueous solutions were recorded. • Third order nonlinear optical susceptibility (χ3) of DMB-FBH was determined by Z-scan measurement. Organic nonlinear optical single crystals of (E)-N′-(2,3-dimethoxybenzylidene)-4-fluorobenzohydrazide (DMB-FBH) were synthesized and grown using slow evaporation crystallization from ethanol solution. The single crystal X-ray diffraction scattering revealed that the DMB-FBH crystallised in the tetragonal crystal system with a centro symmetric space group of I 4 1 /a. The crystallographic bond lengths and bond angles were compared with the values generated from optimized molecular geometry based on quantum chemical calculations. The functional group vibrations were identified theoretically by density functional theory with B3LYP 6–311 G (d,p) basis set using Gaussian 09 software package and their vibrations were compared with the experimental FT-IR spectra. The UV-visible and the fluorescence emission spectra of the DMB-FBH in aqueous solutions were recorded. The HOMO-LUMO energy level pictogram addressed the intramolecular charge transfer (ICT) interaction between donor and acceptor moieties and their impact on the energy gap was determined. Different interactions such as O···H, N···H, C···C and C···H in DMB-FBH were quantified via fingerprint plots and these results were compared with that of similar structure. The detailed molecular docking simulation was carried out with M. tuberculosis protein [PDB ID:2 × 22]. The third order nonlinear optical susceptibility (χ3) of DMB-FBH was confirmed experimentally by Z-scan method and their conversion efficiency was higher than the other hydrazones derivatives. In short, this work discusses the crystal structure, identification and quantification of the molecular interactions, thermal, antimycobacterial and optical properties of new hydrazone derivative. Energy frameworks (left) coloumb dispersion (center) and total energy (right) of DMB-FBH crystal structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, two new thiazole derivatives: ethyl2-(2-benzylidenehydrazinyl)thiazole-4-carboxylate (3) and ethyl2-(2-(2-hydroxybenzylidene)hydrazinyl)thiazole-4-carboxylate (4) were synthesized by cyclization of 1-benzylidenethiosemicarbazide with ethyl bromopyruvate. The synthesis was validated by spectroscopic techniques like FTIR, 1H- NMR, 13C-NMR and chemical structure of title compounds 3 and 4 has been determined using SC-XRD. Ancillary to experimental analysis, DFT calculations with B3LYP/6-311 + G (d,p) level were performed for comparative analysis of FT-IR spectroscopic data, optimized geometry, frontier molecular orbitals (FMOs), natural bond orbital (NBO) analysis and nonlinear optical (NLO) properties. Overall, experimental findings were supported by corresponding DFT computed results. TDDFT calculations were executed at M06/6-311 + G (d,p) level of theory to calculate the vertical electronic transition states. NBO analysis disclosed that intramolecular charge transfer and hyper-conjugative interactions among bonds provide stability to the investigated compounds 3 and 4. The global reactivity parameters calculated from energy of FMOs indicates that 3 and 4 enclose larger softness and fewer hardness values. NLO results of 3 and 4 were observed better than standard molecule recommended the NLO activity of said compounds. We hope that this joint experimental and computational insight may provide new ways for the utilization of title molecules as NLO material for optoelectronic applications. Image 1 • Two novel ethyl 2-(2-(2-substitutedbenzylidene)hydrazinyl)thiazole-4-carboxylate crystals were synthesized. • XRD, 1H NMR, 13C NMR, FT-IR and UV–Vis were performed for the characterization. • Computational study was done at B3LYP/6-311 + G (d,p) level for comparative analysis. • Comparative study reveals a good agreement between experimental and DFT results. • FMOs, NBO analysis and nonlinear optical (NLO) properties were calculated. [ABSTRACT FROM AUTHOR]