Growth, SHG, Z-scan, optical limiting and quantum chemical investigation of hexamethylenetetraminium hydrogen DL-malate – An organic crystal for optoelectronic applications

Abstract

Single crystals of hexamethylenetetraminium hydrogen dl-malate (HMTM) have been successfully synthesized by slow evaporation method and structurally analyzed by single crystal X-ray diffraction, powder X-ray diffraction, FTIR, FT-Raman, 1H and 13C NMR spectroscopic techniques. These investigations confirm the formation of HMTM crystal which crystallize in the non-centrosymmetric space group Cc with monoclinic crystal system. The N–H⋯O and O–H⋯O intermolecular hydrogen bonding interactions have been investigated by Hirshfeld surface analysis. The optical absorption cut-off wavelength of the grown crystal is observed at 353 nm in the UV–visible spectrum. From the photoluminescence spectrum, two intense emission peaks are identified at 312 nm and 415 nm. Dielectric study reveals low values of dielectric constant and dielectric loss. The positive photoconducting nature of HMTM is identified from the photoconductivity analysis. Second harmonic generation efficiency of the powdered HMTM is found to be 1.25 times greater than that of powdered KDP. The Z-scan and optical limiting results indicate that HMTM exhibits self-defocusing nature and optical limiting response, respectively. In addition, charge transfer interactions, first- and second-order hyperpolarizability values are computed by density functional theory calculations and are discussed in detail.