Synthesis, Growth, and Characterization of Single-Crystal Benzo[e]indolium for Third-Order Nonlinear Optical Properties

A promising organic third-order nonlinear optical crystal of the benzo[e]indole family 2-(2-(4-(4-hydroxy) phenyl)vinyl)-1, 1,3-trimethyl-1H-benzo[e] indolium iodide (H-BI) has been synthesized and grown by slow evaporation method. The grown crystal’s physicochemical properties have been characterized by several analytical techniques to ensure the suitability for industrial applications. Single-crystal x-ray diffraction has been employed to confirm the crystal structure and space group of the grown crystal and indicated that the title crystal belongs to a monoclinic crystal system with centrosymmetric space group P21/c. The optical absorption of the title crystal has been analyzed by an ultraviolet–visible (UV–Vis) spectrometer, and no significant absorption was found in the entire visible region. The test crystal linear refractive index value has been calculated using standard optical formulations. The dielectric constant and dielectric losses of the test crystal were measured using an impedance analyzer in the temperature range of 40°C to 100°C; no significant changes were found with respect to temperature, and it is highly favorable for device fabrications. The thermal stability assessment of the title crystal was performed by thermogravimetric analysis (TGA) and differential thermal analysis (DTA), which revealed the grown crystal has moderate thermal stability and that the melting point is 266.4°C. Third-order nonlinear optical properties were investigated by the Z-scan technique and determining the refractive index ( n 2 ), absorption coefficient (β), and susceptibility (χ (3) ). Based on the corresponding results, the titled crystal is well suited for photonic device applications. Graphical Abstract