Synthesis, structural characterization and third-order nonlinear optical properties of 1,1-diphenylmethanaminium 4-aminobenzene-sulfonate hydrate

Single crystals of 1,1-diphenylmethanaminium 4-aminobenzene-sulfonate hydrate (DPASH), were successfully synthesized. Single crystals were grown in a mixed solvent of ethanol and water (1:1) using a gradual evaporation method at room temperature. The crystal structure was determined via single-crystal X-ray diffraction analysis, revealing a monoclinic system (P2₁/c). The vibrational bands were examined using FT-IR analysis, and the bandgap was estimated using the Kubelka–Munk algorithm. Crystal cohesion was facilitated by N⋯O, O⋯O, and π–π stacking interactions. The compound exhibits a significant third-order nonlinear optical susceptibility (χ⁽³⁾), measured to be 2.06 × 10⁻⁶ esu. This value underscores the material’s potential for applications in nonlinear optical devices. The Vickers hardness number of the DPASH crystal increased with the applied load. The characteristics of the complex, including shape, size, chemical reactivity sites, and charge density distribution, were analyzed through electron density mapping with electrostatic potential. Molecular surfaces and interactions were further examined via fingerprint plots generated from Hirshfeld surfaces. Additionally, theoretical investigations using the density functional theory method were conducted to determine polarizability and dipole moment.