Structural characterization, quantum chemical calculations and Hirshfeld surface analysis of a new third order harmonic organic crystal: 2-Amino-4-methylpyridinium benzilate

Abstract

A new organic non-linear optical crystal, 2-amino-4-methylpyridinium benzilate (2-A4MPB) was synthesized and single crystals were grown by slow evaporation-solution growth method at 30 °C using methanol as solvent. The FT-IR spectroscopic analysis confirmed the presence of characteristic functional groups in the title compound. The 1H and 13C NMR spectra were recorded to establish the molecular structure. The thermogravimetric and differential thermal analyses were carried out to assess the thermal stability of the 2-A4MPB crystal. The structure of the 2-A4MPB crystal was determined by single crystal X-ray diffraction analysis and the crystal belongs to monoclinic system with centrosymmetric space group P21/n. The stable structure of 2-A4MPB was optimized by Gaussian 09 program using B3LYP method at 6-311 + G(d,p) level of theory. Molecular electrostatic potential analysis confirmed the proton transfer during the formation of 2-A4MPB. The first order hyperpolarizability value confirms that 2-A4MPB is NLO active. The natural bond orbital and Mulliken atomic charge analyses predicted N–H⋯O hydrogen bonding as predominant interaction. Hirshfeld surface analysis was carried out to estimate different types of non-covalent and inter atomic interactions. The effective third-order nonlinear optical susceptibility and nonlinear refractive index were calculated using Z-scan technique to confirm the suitability of the title compound for optical applications.