Dong Xue, Liu Yu-Qian, Tiznado William, Cabellos-Quiroz Jose Luis, Zhao Jijun, Pan Sudip, Cui Zhong-Hua
Institute of Atomic and Molecular Physics, Jilin University, Changchun 130023, China.
Computational and Theoretical Chemistry Group, Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello, República 270, Santiago 7550196, Chile.
Inorg Chem. 2022 Sep 19;61(37):14553-14559. doi: 10.1021/acs.inorgchem.2c01179. Epub 2022 Sep 8.
Tubular boron clusters represent a class of extremely unusual geometries that can be regarded as a key indicator for the 2D-to-3D boron structural evolution as well as the embryos for boron nanotubes. While a good number of pure boron or metal-doped boron tubular clusters have been reported so far, most of them are two-ring tubular structures, and their higher-ring analogues are very scarce. We report herein the first example of a four-ring tubular boron motif in the cagelike global minimum of BeB. Global-minimum searches of MB and MB (M = alkali/alkaline-earth metals; = 1+, 0, 1-) reveal that the most stable structure of BeB is a -symmetric cage having a four-ring tubular boron moiety, whereas it is a high-lying isomer for those having a two/three-ring tubular boron motif for all other systems. The B framework in BeB can be viewed as consisting of two two-ring B tubular structures linked together at one side of the B rings along the high-symmetry axis and two offside B rings capped by two Be atoms. The Be-B bonding is best described as Be in an excited triplet state, forming two highly polarized covalent bonds with B in a quartet spin state. The unique ability of beryllium to make strong covalent and electrostatic interactions makes the BeB cluster stable in such an unusual geometry.
管状硼簇代表了一类极其特殊的几何结构，可被视为二维到三维硼结构演化的关键指标以及硼纳米管的雏形。尽管到目前为止已经报道了大量的纯硼或金属掺杂的硼管状簇，但其中大多数是双环管状结构，其更高环的类似物非常稀少。我们在此报告了在笼状全局最小值BeB中首次出现的四环管状硼 motif 的例子。对MB和MB（M = 碱金属/碱土金属； = 1 +、0、1 -）的全局最小值搜索表明，BeB最稳定的结构是具有四环管状硼部分的 - 对称笼状结构，而对于所有其他系统中具有双/三环管状硼 motif 的那些结构来说，它是一个高能异构体。BeB中的B框架可以看作是由两个双环B管状结构沿着高对称轴在B环的一侧连接在一起，以及两个由两个Be原子封顶的外侧B环组成。Be - B键最好描述为处于激发三重态的Be与处于四重态自旋状态的B形成两个高度极化的共价键。铍形成强共价和静电相互作用的独特能力使得BeB簇在这种不寻常的几何结构中稳定存在。
