Spectroscopic and quantum chemical investigation of hexamethylenetetraminium 3, 5-dinitrobenzoate hemihydrate single crystals for optical limiting applications

The slow evaporation method has been used to grow hexamethylenetetraminium 3,5-Dinitrobenzoate hemihydrate (HMTNB) single crystals. The single crystal X-ray diffraction investigation confirmed the centrosymmetric space group P 1¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{1 }$$\end{document} and triclinic crystalline system of grown HMTNB crystals. The powder X-ray diffraction, 1H, 13C NMR, FTIR, and FT-Raman analysis validated the crystalline nature, molecular arrangement, and functional groups in HMTNB. The intermolecular hydrogen bonding interactions of the HMTNB system have been well understood with the help of Hirshfeld surface study. Lower cutoff wavelength (386 nm) and emission peaks (312, 438, and 482 nm) have been reported in optical absorption and photoluminescence investigations. The dielectric study has revealed that HMTNB has low values of dielectric constant and loss. The photoconductivity study showed that HMTNB has a negative photoconducting nature. The HMTNB has a negative refractive index, and the Z-scan study revealed self-defocusing nature. Optical limiting studies indicate the HMTNB crystal's optical limiting response. Quantum chemical calculations were used to establish inter- and intra-molecular charge transfer mechanisms, as well as the presence of N–H···O, O–H···O and C–H···O hydrogen bonding in HMTNB are discussed in detail.