Noncentrosymmetric versus Centrosymmetric: Halogen Induced Variable Coordination Modes of Sn2+and Structural Transition in Sn3B3O7X (X = Cl and Br)

Two new borate halides, Sn3B3O7X (X = Cl and Br), were successfully synthesized via introducing Sn2+ with lone-pair and halogen into borate. Interestingly, halogen-induced variable coordination modes of Sn2+ and anion frameworks make them crystallize in different space groups, from noncentrosymmetric (Pna21) to centrosymmetric (Pbca). Sn3B3O7Cl possesses an SHG response of about 0.5 times that of KDP, while Sn3B3O7Br exhibits a large birefringence (0.123@1064 nm). The theoretical calculations were performed to elucidate the structure-property relationships.

Automated summary

Two new borate halides, Sn3B3O7X (X = Cl and Br), were synthesized by introducing Sn2+ with lone-pair and halogen into borate. The different coordination modes of Sn2+ and anion frameworks induced by halogen lead to crystallization in different space groups. Sn3B3O7Cl has a SHG response of about 0.5 times that of KDP, while Sn3B3O7Br exhibits a large birefringence (0.123@1064 nm). Theoretical calculations were performed to explain the structure-property relationships.