C<sub>14</sub>H<sub>10</sub>BrNO<sub>2</sub>: A Birefringent Crystal with an Expanded π-Conjugated Group
Yaoguo Shen, Zixiang Chen, Guofa Dong, Junhua Luo
Abstract
The construction and synthesis of novel birefringent materials, particularly those characterized by significant birefringence, are of great importance in the field of optical devices and therefore remain a subject of active research. Herein, a new optical crystal material, C 14 H 10 BrNO 2, was successfully synthesized using a simple solution evaporation method. Its crystal structure comprises two primary structural units, the protonated 9-acridincarboxylic acid hydrate [C 14 H 10 NO 2 ] + and the Br – ion. Notably, C 14 H 10 BrNO 2 exhibits a birefringence of approximately 0.507 at 550 nm, surpassing the birefringence exhibited by commercially birefringent crystals. The first-principles calculations indicate that the large birefringence observed in C 14 H 10 BrNO 2 is primarily attributed to the π-conjugated [C 14 H 10 NO 2 ] + group. In addition, C 14 H 10 BrNO 2 exhibits relatively good thermal stability. This work provides a new insight into the construction of novel birefringent crystals with significant optical anisotropy.