Growth, structural, optical, Z-scan and dielectric analysis of 2-Amino-4-methylpyridinium 2-chloro 4-nitro benzoate crystals for third order non-linear optical applications

Abstract

• AMPCNB was synthesized and grown as crystal by slow evaporation method. The centrosymmetric space group of AMPCNB was concluded as P21/n. • The lower cut-off wavelength of AMPCNB was found to be 318 nm and band gap energy gap was 3.16 eV. • The NLO parameters, refractive index (n2) = 5.610 × 10−8 cm2/W and absorption coefficient = 0.033 × 10−4 cm/W were found. • The dielectric study reveals the phase transition at high temperature. An organic nonlinear optical material 2-Amino-4-methylpyridinium 2-chloro 4-nitro benzoate (AMPCNB) was synthesized and large size single crystals were grown by slow evaporation solution growth method. Single crystal X-ray diffraction study showed that the title compound belongs to monoclinic crystal system with P2 1 /n space group. In the title molecular salt, C 6 H 9 N 2 + ·C 7 H 3 ClNO 4 − , the original pyridine N atom of 2-amino-4-methylpyridine is protonated. The chloro and the carboxylic acid group of nitrobenzoic acid is deprotonated. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxylate O atoms of the anion via a pair of N-H···O hydrogen bonds, forming a R 2 2 (8) ring motif. The ion pairs are further connected via N-H···O and C-H···O hydrogen bonds. The molecules are further stabilized by C-H···π and π-π interactions. The UV–VIS-NIR study was performed to investigate the transparency window and lower cutoff wavelength of the compound. The third harmonic efficiency of title compound has been studied using Z-scan technique using continuous wave Nd:YAG laser to confirm its saturable absorption and self-defocusing effect. Theoretical calculation of molecular polarizability, which is helpful in device fabrication, was carried out from Penn gap, Clausius-Mossotti equations and the obtained results were compared. The Vickers’ micro hardness test was carried out at room temperature and obtained results were investigated using classical Meyer's law.