Three Polyborates with High-Symmetry [B12O24] Units Featuring Different Dimensions of Anion Groups.

Abstract

Three polyborates, namely, LiNa11B28O48, Li1.45Na7.55B21O36, and Li2Na4Ca7Sr2B13O27F9, were synthesized via the high-temperature solution method. All of them feature high-symmetry [B12O24] units, yet their anion groups exhibit distinct dimensions. LiNa11B28O48 features a three-dimensional anionic structure of 3[B28O48]∞ framework, which is composed of three units: [B12O24], [B15O30], and [BO3]. Li1.45Na7.55B21O36 possesses a one-dimensional anionic structure of 1[B21O36]∞ chain consisting of [B12O24] and [B9O18] units. The anionic structure of Li2Na4Ca7Sr2B13O27F9 is composed of two zero-dimensional isolated units, namely, [B12O24] and [BO3]. The novel FBBs [B15O30] and [B21O39] are present in LiNa11B28O48 and Li1.45Na7.55B21O36, respectively. The anionic groups in these compounds exhibit a high degree of polymerization, thereby augmenting the structural diversity of borates. And the crystal structure, synthesis, thermal stability, and optical properties were meticulously discussed to guide the synthesis and characterization of novel polyborates.