Looking for novel UV birefringent units with great birefringence and discovering new candidates that are constructed by them have always been a hotspot in the field of optical materials. Here, a new imidazole-based [C₃N₂H₅]₂C₂O₄·H₂O crystal is synthesized with a cutoff edge (274 nm). According to achieve the well-directed alignment, the millimeter-sized single crystal [C₃N₂H₅]HC₂O₄ is obtained and possesses a larger birefringence than [C₃N₂H₅]₂C₂O₄·H₂O with a similar band gap. What’s more, the [C₃N₂H₅]HC₂O₄ crystals can be grown by a simple aqueous solution volatilization method, and the difference in the measured refractive index of [C₃N₂H₅]HC₂O₄ is 0.119@546 nm which is similar to the birefringence of the famous α-BBO crystal. The birefringence originates from the π-conjugated [C₃N₂H₅] units and [HC₂O₄] units, which implies [C₃N₂H₅]HC₂O₄ is promising candidates for exploring UV materials with large birefringence.

寻找具有高双折射性能的新型紫外双折射单元并发现由其构建的新候选材料一直是光学材料领域的热点。这里，合成了一种新的咪唑基[C ₃ N ₂ H ₅ ] ₂ C ₂ O ₄ ·H ₂ O晶体，具有截止边缘（274 nm）。通过良好的定向排列，获得了毫米级单晶[C ₃ N ₂ H ₅ ]HC ₂ O _{4 ，并且具有比[C 3} N ₂ H ₅ ] ₂ C ₂ O ₄ ·H更大的双折射₂ O 具有相似的带隙。此外，通过简单的水溶液挥发法即可生长出[C ₃ N ₂ H ₅ ]HC ₂ O _{4晶体，测得的[C 3} N ₂ H ₅ ]HC ₂ O ₄折射率差异为0.119@546 nm，类似于著名的α -BBO晶体的双折射。双折射源自π共轭的[C ₃ N ₂ H ₅ ]单元和[HC ₂ O ₄ ]单元，这意味着[C ₃ N ₂ H ₅ ]HC ₂ O ₄是探索具有大双折射的UV材料的有希望的候选者。