Bridging the Interlayer Binding to Ordered π‐Conjugated Units for Constructing High‐Performing Light Polarization Crystals

The light polarization modulation involves the capacity to respond selectively to light-mater interaction and is dependent on the optical anisotropy of crystalline materials. The π-conjugated component is almost typically utilized to produce such materials in the short-wave ultraviolet region; however, the conflicting link between high optical anisotropy and strong layered habit is difficult to reconcile. As a result, many anisotropic crystals are limited to tiny crystals rather than processing optical devices. This study designs crystals with beneficial but easy-to-grow layered structure and strong optical anisotropy by bridging the interlayer binding to ordered π-conjugated units. To this end, two new hybrid crystals Na₂[C(NH₂)₃][HCOO]₃ (1Na) and K₂[C(NH₂)₃][HCOO]₃ (2K) are reported by combining cationic regulation and π-conjugated units. The strong interlayer interaction and stable crystal structure of 1Na have been found to be caused by the orbital hybridization and Lewis acidity of Na⁺ and [HCOO] groups. This allows for the easy growth of centimeter-large, high optical quality 1Na single crystals, providing crystal assurance for all-around testing for a practical crystal. Using the most accurate minimal deviation angle method, the birefringence is measured to be 0.174-0.258 @253-1013 nm, surpassing all reported crystals with the same components of [HCOO] or [C(NH₂)₃] in the applied short-wave ultraviolet region as well as the corresponding commercial crystals. More importantly, preliminary Glan-Taylor prism is designed to test its light polarization ability. This work will serve as a guide for future research on innovative short-wave ultraviolet birefringent crystals.