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

Abstract 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 d 10 electronic configuration cation Zn 2+ 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. (C 12 H 8 N 2 )ZnCl 2 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 [C 12 H 8 N 2 ] and [ZnCl 2 ], 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.