α- and β-(C 4 H 5 N 2 O)(IO 3 )·HIO 3 : Two SHG Materials Based on Organic-Inorganic Hybrid Iodates.

Organic-inorganic hybrid nonlinear optical (NLO) materials are highly anticipated because of the integration of both merits of the organic and inorganic moieties. Herein, the 2-pyrimidinone cation (C 4 H 5 N 2 O) + has been incorporated into the iodate system to form two polymorphic organic-inorganic hybrid iodates, namely, α- and β-(C 4 H 5 N 2 O)(IO 3 )·HIO 3 . They crystallize in different polar space groups ( Ia and Pca 2 1 ), and their structures feature one-dimensional (1D) chain structures composed of (C 4 H 5 N 2 O) + cations, IO 3 - anions, and HIO 3 molecules interconnected via hydrogen bonds. α- and β-(C 4 H 5 N 2 O) (IO 3 )·HIO 3 exhibit strong and moderate second-harmonic-generation (SHG) responses of 6.4 and 0.9 × KH 2 PO 4 (KDP), respectively, the same band gaps of 3.65 eV, and high powder laser-induced damage threshold (LIDT) values [51 and 57 × AgGaS 2 (AGS)]. The results of theoretical calculations revealed that the large SHG effect of α-(C 4 H 5 N 2 O)(IO 3 )·HIO 3 originated from the IO 3 and HIO 3 groups. This work indicates that (C 4 H 5 N 2 O) + is a potential group for designing new NLO materials with brilliant optical performances.