Phosphite materials have aroused widely attention for their diverse open-frameworks and promising magnetic and optical performances. Here, the first barium scandium phosphite, BaSc2(HPO3)4(H2O)2, was obtained via a facile hydrothermal route....

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Compounds constructed by mixed anions are widely favorable for their diverse crystal structures and physical performances. Here, two lead phosphite halides, Pb2Cl2(HPO3)(H2O) (1) and Pb3Br2(HPO3)2 (2), were obtained by facile hydrothermal reactions. Both compounds crystallize in the space group Pnma. 1 exhibits a 3D structure composed of HPO3 units, PbCl4O3 pentagonal bipyramids, and PbO3 pyramids. 2 also shows a 3D framework built by HPO3 units, PbO2Br4 octahedron, PbO5 and PbO3Br2 square pyramids. By introducing halogen anions to the lead phosphite system, 1 and 2 show enhanced birefringences of 0.083 and 0.072 at 1064 nm, respectively, compared with 0.023@1064 nm for Pb2(HPO3)2. In this work, syntheses, crystal structures, optical properties, and theoretical calculation results have been studied in detail.

Oxide nonlinear optical (NLO) crystals have drawn wide interest for their comprehensive physical performances including wide infrared (IR) transparency ranges, large band gaps, and good stability in open air. Here, two isostructural germanate oxides, Pb 5 (GeO 4 )(Ge 2 O 7 ) (1) and Pb 3.32 Ca 1.68 (GeO 4 )(Ge 2 O 7 ) (2), adopting the noncentrosymmetric (NCS) space group P6̅ , were composed via a conventional solidstate reaction. The latter was designed by the partial cation substitution strategy based on parent 1. The whole structures of 1 and 2 are composed of isolated distorted GeO 4 tetrahedra, Ge 2 O 7 dimers, and diverse M (M = Pb, Ca, or Pb/Ca)-centered polyhedra. They exhibit second-harmonic generation (SHG) responses around 3.3 and 1.4 times that of KH 2 PO 4 (KDP) under 1.064 μm laser radiation, respectively. Theoretical calculation results reveal that the Pb 2+ cations with stereoactive long pair (SCALP) electrons of 1 favor the large SHG response, while Pb-based polyhedra showing inert SCALP electrons make predominant contributions to the moderate SHG effect of 2.

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