Chen Meihui, Wei Wei, Zhao Jiawei, An Donghai, Chen Yanna
Changji University, Changji 831100, China.
Dalton Trans. 2024 May 28;53(21):8898-8904. doi: 10.1039/d4dt01130a.
Birefringent materials with high optical anisotropy have been identified as a research hotspot owing to their significant scientific and technological significance in modern optoelectronics for manipulating light polarization. Researchers studying borate systems have discovered that adding π-conjugated units placed in parallel can significantly increase the birefringence of crystalline solids; some examples include [BO] units, [BO] units, and [BO] units. However, there are not many borates with strictly parallel configurations of π-conjugated [BO] units. In this study, a new bimetallic borate SrCd(BO) with near-parallel arrangement of π-conjugated [BO] units was discovered. SrCd(BO) possesses the maximum number density of [BO] units, shortest dihedral angle of [BO] units (between the two [BO]), and largest degree of [CdO] octahedral distortion among all the currently known Sr-Cd-B-O tetragonal system borates, making it demonstrate a large birefringence of 0.102 at 532 nm. Theoretical analysis proves that π-conjugated [BO] anions are the primary source of the large birefringence of SrCd(BO).
由于具有高光光学各向异性的双折射材料在现代光电子学中对光偏振的操纵具有重大的科学和技术意义，已成为研究热点。研究硼酸盐体系的研究人员发现，添加平行排列的π共轭单元可以显著提高晶体固体的双折射；一些例子包括[BO]单元、[BO]单元和[BO]单元。然而，具有严格平行构型的π共轭[BO]单元的硼酸盐并不多。在本研究中，发现了一种新的双金属硼酸盐SrCd(BO)，其π共轭[BO]单元近乎平行排列。在所有目前已知的Sr-Cd-B-O四方系硼酸盐中，SrCd(BO)具有最大的[BO]单元数密度、最短的[BO]单元二面角（两个[BO]之间）和最大的[CdO]八面体畸变程度，使其在532nm处表现出0.102的大双折射。理论分析证明，π共轭[BO]阴离子是SrCd(BO)大双折射的主要来源。
