Probing the structure–property relationship of a new semiorganic nonlinear optical crystal: catena-poly[bis(4-methylbenzylammonium) [[dibromidocadmate(II)]-di-l-bromido]]

A new semiorganic single crystal, catena-Poly[bis(4-methylbenzylammonium) [[dibromidocadmate(II)]-di-l-bromido]],[4MLBDCB], has been developed by evaporating the solvent at a 37 °C. It crystallizes in centrosymmetric space group Pnma. In the crystal structure, 4-methylbenzylammonium cation and tetrabromido cadmate anion are connected by N–H⋯Br and C-H⋯Br hydrogen bonds. Functional groups vibrations of 4MLBDCB were analysed by FT-Raman and FTIR spectroscopy. The stretching vibration of NH and CH shifted towards lower frequency side and their bending vibrations (–NH, –CH) to higher frequency when compared with pure 4 methylbenzylamine (4MLBA) vibrations. The observed variations in CH bond length are discussed. Presence of Raman active CdBr₄²⁻ vibrations ensures the formation of the molecule. Transmittance bandwidth of the crystal extends from 260 and 1100 nm. In ¹H and ¹³C NMR spectra, the observed variations in the chemical shifts are interpreted through intermolecular interactions. The presence of hydrogen bonds enhances the third order nonlinear susceptibility (χ³) value of the grown crystal and found to be 5.04 × 10⁻⁶ esu. The third order nonlinear optical parameters such as absorption coefficient (β) and refractive index (n₂) are also determined using Z-scan technique.