Sn3B8O15: A Ternary Tin(II) Borate with Flexible [B8O18]12– Fundamental Building Block Formed by [B7O16]11– and [BO3]3– Groups

Owing to the tendency to form the glass state in growing crystals in the ternary tin­(II) borate system, hitherto, very few single crystals in ternary tin­(II) borate were reported. In this paper, a single crystal of Sn3B8O15 was obtained via a high temperature solution method in a closed system. The structure features a flexible fundamental building block [B8O18]12– constructed by one [BO3]3– unit and one [B7O16]11– group that contains three hexatomic rings, which further connect to compose a two-dimensional 2 ∞[B8O15] layer structure. The connection mode and flexibility of the three hexatomic B-O rings were analyzed, verifying the structural diversity of the B-O configuration. Moreover, the synthesis, crystal structure, and various characterizations were comprehensively presented. Also, theoretical calculations were employed to discuss structure-property relationships, and we use the real-space atom-cutting techniques to explain the origin of the birefringence of Sn3B8O15.