Birefringent crystals with optical anisotropy, which are employed to modulate the polarization of light, play a vital role in many fields of the optical industry. In this Communication, two mixed… Click to show full abstract
Birefringent crystals with optical anisotropy, which are employed to modulate the polarization of light, play a vital role in many fields of the optical industry. In this Communication, two mixed alkali metal hydroisocyanurates, RbLi(H2C3N3O3)2·2H2O (I) and CsLi(H2C3N3O3)2·2H2O (II), were synthesized by a simple aqueous solution method, and they feature layered structures composed of ∞2[H2C3N3O3]- ribbons through hydrogen bonds with the separation of water molecules and alkali cations. They exhibit a simultaneously short ultraviolet cutoff and giant birefringence, resulting from the perfect parallel alignment of π-conjugated (H2C3N3O3)- anions. Interestingly, the first-principles calculations elucidated that the electronic states and optical properties are slightly different owing to the distinct p-π interaction between alkaline metals and the (H2C3N3O3)- group despite the isostructural crystallographic lattice.
               
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