Experimental and theoretical investigation of 2-aminopyridinium 6-chloronicotinate: structure, spectroscopy, topology, Hirshfeld analysis, LDT, SHG, and nonlinear optical properties

• Synthesis and crystal growth of 2-aminopyridinium 6-chloronicotinate • N-H ... O hydrogen bonding significantly influences molecular structure • Nonlinear optical properties studied experimentally and theoretically • Detailed photoluminescence and optical property characterization • Hirshfeld analysis shows H … H interactions dominate crystal packing (30.3%) Single crystals of the potential NLO candidate 2-aminopyridinium 6-chloronicotinate (APN) have been successfully grown by the slow evaporation solution growth method. Powder X-ray diffraction studies were done to establish the crystal structure of the grown crystals. Optimized molecular structure and energy assessments for APN occurred via the DFT/B3LYP method employing the 6-311++G(d,p) basis set. Vibration modes of the compound were identified and characterized by using the FT-IR and FT-Raman spectroscopic analyses, which were complemented by the help of VEDA in vibrational mode assignments. The crystal morphological features of the APN were analyzed. Investigation of the second harmonic generation (SHG) of APN was analysed using the Kurtz-Perry powder method. UV–visible spectra supported by TD-DFT and photoluminescence spectra were recorded and analyzed. Both electron localization function (ELF) analysis and local orbital locator (LOL) techniques were used to examine the electron delocalization inside the molecular structure. Van der Waals interactions and steric effects in the molecule were identified by performing Reduced Density Gradient (RDG) study and non-covalent interaction (NCI) analysis. The Hirshfeld surface analysis was made to investigate the 3-D and 2-D interactions within the crystal. The first-order hyperpolarizability value demonstrates that APN has properties suitable for non-linear optics applications. laser damage threshold (LDT) test was also done.