Bi2[B2(SeO3)6]: A Metal Boroselenite with a Unique Zero-Dimensional [B2(SeO3)6]6- Anionic Group and Large Birefringence.

Explorations of new types of borates are important because of their promising application in diverse fields. A new bismuth-containing boroselenite, Bi2[B2(SeO3)6], has been obtained through high-temperature solid-state reaction in a closed system. Bi2[B2(SeO3)6] possesses a zero-dimensional [B2(SeO3)6]6- anionic group that does not belong to any types of reported boroselenites. Besides, Bi2[B2(SeO3)6] is the first boroselenite with lone-pair electrons containing a metal ion as the countercation. More interestingly, on the basis of the first-principles calculations, this compound displays a large birefringence (0.090) at 1064 nm.