Piperazinium ammonium chloride hydrate: growth and physicochemical characterizations of nonlinear optical single crystal

Abstract

A nonlinear optical (NLO) single crystal of piperazinium ammonium chloride hydrate (PACH) was formed at room temperature utilizing the slow evaporation solution growth approach with double distilled water as the solvent. Single crystal X-ray diffraction examination validated the crystal's orthorhombic structure and determined unit cell characteristics (a = 6.52 Å, b = 12.91 Å, and c = 12.83 Å). The appearance of a prominent Bragg's peak in the powder X-ray diffraction pattern proved the developed PACH sample's crystalline nature. Hirshfeld study reveals that intermolecular interactions of N-H⋯Cl, O-H⋯Cl, and H…H contribute significantly to the molecular packing of the title molecule. Fourier transform infrared spectroscopy was used to determine the functional groups in the synthesized molecule. The UV-visible-NIR optical analysis revealed the transparency, band gap (E_g), extinction coefficient (K), and linear refractive index (n₀) of PACH. Using a solid-state laser (632.8 nm), a Z-scan measurement was performed to determine the selected single crystal's third-order optical susceptibility (χ⁽³⁾). A prominent emission peak was seen in the photoluminescence spectrum, indicating yellow (572.8 nm) emission. The thermal stability of the PACH single crystal was examined using thermogravimetric and differential thermal analysis (TG-DTA). The PACH crystal was subjected to Vicker's microhardness testing, and its work-hardening coefficient was determined to be 3.1. The dielectric constant and dielectric loss of the PACH crystal have been investigated. The HOMO-LUMO energy gap was calculated.