Physicochemical and computational perspectives of 8-hydroxyquinoline 5-chloro-2-hydroxybenzoic acid: a novel second-order nonlinear optical crystal

In recent times, there has been considerable research and constant development on second-order nonlinear optical (NLO) materials owing to their potential applications in optical information processing, THz imaging and spectroscopy, telecommunication and optical data storage. A novel organic material 8-hydroxyquinoline 5-chloro-2-hydroxybenzoic acid (8HQ5C) was synthesized, and the single crystals were grown by solution technique. The crystal structure (8HQ5C) was confirmed by single-crystal (SCXRD) X-ray diffraction, and it crystallized in orthorhombic structure with non-centrosymmetric P212121 space group. The different functional groups were identified from Fourier transform infrared (FTIR) spectroscopy. The proton NMR spectral study was helpful to understand the various protons of 8HQ5C structure in its chemical environment. The % of transmittance and absorbance of light by the title crystal was estimated by UV–visible spectral study, and the cutoff wavelength was observed at 460 nm. The thermal nature of the 8HQ5C crystal has been identified by TG-DSC analysis. The mechanical strength of the grown crystal was analyzed through microhardness. Second harmonic generation (SHG) was confirmed through the Kurtz–Perry method, and the efficiency was compared with the value of the prominent KDP crystal. The theoretical computation was made with density functional theory (DFT) B3LYP method 6–311 +  + G (d,p) as a basis set. The charge property of the title crystal was described by frontier molecular orbital (FMO) test. The first hyperpolarizability of 8HQ5C was analyzed, and the hydrogen bond of a given molecule was determined through natural bond analysis (NBO).