A single crystal of piperazinium tetrabromozincate(II) (PTBZ) was successfully grown using the slow evaporation solution technique. The crystal structure was elucidated by single-crystal X-ray diffraction (SXRD), revealing that PTBZ crystallizes in the orthorhombic system with the non-centrosymmetric space group P212121. Powder X-ray diffraction analysis was employed to determine the corresponding Miller indices. Structurally, the piperazinium moieties act as cations \(\left[ {C_{4} N_{2} H_{12} ]^{2 + } } \right.\) , while isolated zinc tetrabromide units serve as anions \(\left[ {ZnBr_{4} ]^{2 - } } \right.\) , collectively stabilizing the crystal lattice. Hirshfeld surface (HF) analysis provides a clear visualization of the various intermolecular interactions governing the crystal packing. Fourier transform infrared (FTIR) spectroscopy confirms the presence of characteristic functional groups in the synthesized compound. UV–Vis–NIR spectral analysis indicates a wide optical transparency with an estimated optical band gap of 5.87 eV. The third-order nonlinear optical (NLO) response of PTBZ was evaluated, and the measured third-order nonlinear susceptibility χ(3) (2.195 × 10−7 esu) is found to be significantly higher than that of the benchmark potassium dihydrogen phosphate (KDP) crystal (8.34 × 10−14 esu), highlighting its strong NLO potential. Photoluminescence (PL) studies reveal an intense emission centered at 491 nm. Thermal analysis demonstrates that the crystal remains stable up to 300 °C. The dielectric behaviour was investigated by measuring the dielectric permittivity \(\left( {\varepsilon_{r} } \right)\) and dielectric loss (tan δ) as functions of frequency, providing insight into its electrical response. Mechanical properties were assessed using Vickers microhardness testing, and the hardness value was found to be 148 kg/mm2 under an applied load of 100 g on the (110) plane.
