Low-Dimensional Organic–Inorganic Hybrid Metal Halide with Large Optical Anisotropy

Birefringent crystals exhibit strong light modulation and polarization capabilities, playing a crucial role in optical components. By optimizing crystal structures, particularly through the design of low-dimensional materials, the birefringence properties can be significantly enhanced. In this work, 1,10-phenanthroline is selected as the organic ligand, and d¹⁰ electronic configuration cation Zn²⁺ as the metal center, combined with Cl⁻ anions for structural regulation. Through this rational design, a novel 0D organic–inorganic hybrid metal halide (OIMH), (C₁₂H₈N₂)ZnCl₂, was successfully synthesized. (C₁₂H₈N₂)ZnCl₂ exhibits a large birefringence of 0.70@546 nm. First-principles calculations and structural analysis indicate that the anomalous birefringence originates predominantly from C−H···Cl hydrogen bonding between the [C₁₂H₈N₂] and [ZnCl₂], as well as their highly ordered spatial arrangement. Furthermore, (C₁₂H₈N₂)ZnCl₂ exhibits remarkable thermal stability (431 °C) and a short-wavelength UV cutoff edge (368 nm), achieving an optimal balance between birefringence and bandgap properties. This work provides fundamental insights into the rational design of high-performance birefringent crystals in low-dimensional OIMHs.