Ce(2,2′-bipyridyl)3(SCN)3: Lanthanide Coordination- and Hydrogen-Bond-Directed Binary π-Conjugated Assemblies with Synergistic Large Birefringence and Broad Transparency

Exploring high-performance birefringent crystals holds paramount significance in modern optics, yet traditional candidates generally struggle to reconcile substantial birefringence with broad spectral transparency. To circumvent this long-standing bottleneck, a synergistic multifunctional-group assembly strategy has been devised to guide the rational design of birefringent crystals. Correspondingly, driven by lanthanide coordination and hydrogen bonding, two kinds of π-conjugated units were successfully incorporated into a new birefringent crystal, Ce(2,2'-bipyridyl)3(SCN)3. Synthesized via a facile solution evaporation method, Ce(2,2'-bipyridyl)3(SCN)3 was characterized by a large birefringence of 0.18@546 nm, broad transmission windows (nearly spanning 0.445-25 μm), and moderate thermal stability (up to 270 °C), making it favorable for practical applications.