Chen Fuqiang, Wu Hongping, Hu Zhanggui, Wang Jiyang, Wu Yicheng, Yu Hongwei
Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystal, College of Materials Science and Engineering, Tianjin University of Technology Tianjin 300384 China
Chem Sci. 2024 Dec 18;16(4):2015-2023. doi: 10.1039/d4sc05747c. eCollection 2025 Jan 22.
Non-centrosymmetric (NCS) compounds can exhibit many symmetry-dependent functional properties, yet their rational structure design remains a great challenge. Herein, a strategy to introduce F-centered octahedra to construct a perovskite-type framework filled by π-conjugated [BO] dimers is proposed to obtain NCS compounds. The first examples of antiperovskite or double antiperovskite borate fluorides, [(M/Ba)Ca]F[BO] (M = K, Rb) and [CsBaCa]F[BO], have been successfully designed and synthesized. All three compounds exhibit a novel three-dimensional framework constructed from [F(M/Ba)Ca] (M = K, Rb), [FCsCa] and [FBaCa] octahedra, which are further filled by [BO] dimers to form antiperovskite-type structures. They all crystallize in the NCS space group 4̄2 , and can exhibit moderate second harmonic generation (SHG) responses (∼0.5 × KDP@1064 nm) and short UV cut-off edges (∼190 nm), as well as suitable birefringence (Δ = 0.0405-0.0548@532 nm). This suggests their potential as UV nonlinear optical crystals.
非中心对称（NCS）化合物可展现出许多与对称性相关的功能特性，但其合理的结构设计仍然是一个巨大挑战。在此，提出一种引入以F为中心的八面体来构建由π共轭[BO]二聚体填充的钙钛矿型框架的策略，以获得NCS化合物。反钙钛矿或双反钙钛矿硼氟化物[(M/Ba)Ca]F[BO]（M = K，Rb）和[CsBaCa]F[BO]的首个实例已成功设计并合成。所有这三种化合物均展现出由[F(M/Ba)Ca]（M = K，Rb）、[FCsCa]和[FBaCa]八面体构建的新型三维框架，这些八面体进一步由[BO]二聚体填充以形成反钙钛矿型结构。它们均结晶于NCS空间群4̄2 ，并可展现出适度的二次谐波产生（SHG）响应（∼0.5 × KDP@1064 nm）和短的紫外截止边（∼190 nm），以及合适的双折射（Δ = 0.0405 - 0.0548@532 nm）。这表明它们作为紫外非线性光学晶体的潜力。
