Facile synthesis, crystal growth, characterization and computational study of new pyridine-based halogenated hydrazones: Unveiling the stabilization behavior in terms of noncovalent interactions

The pyridine-based halogenated hydrazone derivatives (E)-N '-benzylidene-2-[(6 ''-chloroazin-2 ''-yl)oxy]acetohydrazide (6a), (E)-N '-(3 '-chlorobenzylidene)-2-[(6 ''-chloroazin-2 ''-yl)oxy]acetohydrazide (6b) and (E)-N '-(3 '-bromobenzylidene)-2-[(6 ''-chloroazin-2 ''-yl)oxy]acetohydrazide (6c) have been obtained using 6-chloro-2-hydroxypyridine. The structure of the products (6a-c) has been verified using X-ray crystallography and spectroscopic approaches. A single-crystal X-ray diffraction (SC-XRD) investigation showed that the structures are stabilized by intermolecular attractive forces. Additionally, density functional theory (DFT) has been adopted to explore the structural properties, vibrational spectra, noncovalent interactions and frontier molecular orbitals using the B3LYP/6-311 + G(d,p) level. The nonlinear optical properties of the title compounds were calculated using the CAM-B3LYP/6-311 + G(d,p) level. Frequency analysis confirmed the stability of the molecules, and an excellent correlation was observed between the DFT- and SC-XRD-based structural parameters. The SC-XRD analysis confirmed that the dimers of 6a, 6b and 6c are linked by hydrogen-bonding interactions. Natural bond orbital (NBO) analysis also reconfirmed the strength of intermolecular hydrogen-bonding and hyperconjugative interactions. NBO investigation was also utilized to analyze the atomic charges. Moreover, Fourier transform infrared and natural population analyses endorsed that there are significant N bond H... O & dbond;C hydrogen-bonding linkages in dimeric structures of the compounds. The hydrogen-bonding network and different sorts of hyperconjugative interactions are the main reasons for the stability of the products in the solid state. The highest occupied and lowest unoccupied molecular orbital energies and first-order nonlinear optical properties of these molecules are reported. The quantum chemical parameters were derived using frontier molecular orbital energies.