Cs3Na(H2C3N3O3)4•3H2O: A Mixed Alkali-Metal Hydroisocyanurate Nonlinear Optical Material Containing π-Conjugated Six-Membered-Ring Units

Practical ultraviolet nonlinear optical (NLO) crystals are indispensable in modern scientific equipment and solar-blind communication systems. Herein, a new hydroisocyanurate NLO crystal, Cs3Na(H2C3N3O3)(4)center dot 3H(2)O (1), was grown by a facile aqueous solution method. It features a two-dimensional layered structure composed of coplanar large pi-conjugated (2)(infinity)[H2C3N3O3](-) isocyanurate ribbons. More importantly, it exhibits concurrently short ultraviolet phase-matching capability (lambda(pm) approximate to 227 nm) and considerable second-harmonic-generation response (d(eff) approximate to 2/3 KDP) resulting from the pi-conjugated (H2C3N3O3)(-) six-membered ring units. First principles calculations were employed to elaborate its delocalized pi-bonds and strong interaction between the Cs+ cations and (H2C3N3O3)(-) anionic groups. Consequently, 1 will be a promising ultraviolet NLO material for the fourth harmonic generation of Nd-based lasers. Successful synthesis of the title compound also provides a new roadmap to discover new ultraviolet linear optical or NLO materials in metal hydroisocyanurates.