Design of D‒π‒A stilbazolium crystal growth of 4-[2-(3-nitro-phenyl)-vinyl]-1-methyl-pyridinium iodide (NMPI) single crystal: investigation of their structural, physiochemical, and third-order nonlinear optical activity

A novel extended π-conjugated Stilbazolium chromophore NMPI material was synthesized and grown via solvent evaporation solution growth. Structural analysis indicated that the title material is crystallized in the centrosymmetric space group P-1 and triclinic crystal pattern. The material composition was identified using proton NMR analysis, and the FTIR results demonstrate the presence of vinyl groups through their respective vibrational modes. UV‒Vis‒NIR can be used to analyse the linear optical properties. The photoluminescence spectrum reveals a broad emission peak observed at 543 nm indicating green-light emission with a band gap value is 2.28 eV. The DSC, TG, and DTA analyses were used to examine the thermal behaviour of the NMPI crystal. The intermolecular interactions in the crystal structure were examined using the Hirshfeld surface. The Etching analysis reveals the rectangular etch pits with minor dislocations. The Z-scan methodology was employed to figure out that the grown ionic NMPI crystal possessed an enhanced third-order NLO susceptibility. It establishes the self-defocus nature and reverses saturation absorption.