HgCl₂(C₃N₆H₆), a layered hybrid material, is obtained by combining mercury(II) chloride and melamine in a hydrothermal synthesis. It crystallizes in a non-centrosymmetric structure and exhibits strong second-harmonic generation. The thermally stable compound features a distorted octahedral coordination environment of mercury ions. Structural, spectroscopic, and density functional theory analyses highlight its potential as a nonlinear optical material.

The pursuit of efficient nonlinear optical materials is critical for advancing optoelectronic applications. This study focuses on the synthesis and characterization of HgCl₂(C₃N₆H₆), a melamine-based hybrid metal halide. Structural analysis reveals a non-centrosymmetric lattice facilitated by large asymmetric secondary building units and a π-conjugated system. The compound exhibits a strong second-harmonic generation efficiency. Density functional theory calculations, optical band gap measurements, and photoluminescence measurements specify the electronic properties. For completeness and analytical comparison, the centrosymmetric compound Hg₂Cl₂(C₃N₆H₆)₂ is also introduced.