Yue Rong-Xin, Gao Shu-Juan, Han Peng-Fei, Zhai Hua-Jin
Nanocluster Laboratory, Institute of Molecular Science, Shanxi University Taiyuan 030006 China
Department of Chemistry and Chemical Engineering, Lvliang University Lvliang 033000 China.
RSC Adv. 2023 Jan 11;13(3):1964-1973. doi: 10.1039/d2ra07268h. eCollection 2023 Jan 6.
Despite the isovalency between Al and B elements, Al-doping in boron clusters can deviate substantially from an isoelectronic substitution process. We report herein on a unique sandwich di-Al-doped boron cluster, AlB, using global structural searches and quantum chemical calculations. The cluster features a perfectly planar B molecular wheel, with two isolated Al atoms symmetrically floating above and below it. The two Al atoms are offset from the center of the molecular wheel, resulting in a symmetry for the cluster. The AlB cluster is shown to be dynamically fluxional even at far below room temperature (100 K), in which a vertical Al rod slides or rotates freely within a circular rail on the B plate, although there is no direct Al-Al interaction. The energy barrier for intramolecular rotation is only 0.01 kcal mol at the single-point CCSD(T) level. Chemical bonding analysis shows that the cluster is a charge-transfer complex and can be formulated as [Al][B][Al]. The [B] molecular wheel in sandwich cluster has magic 6π/6σ double aromaticity, which underlies the dynamic fluxionality, despite strong electrostatic interactions between the [Al], [B], and [Al] layers.
尽管铝（Al）和硼（B）元素具有等价位，但在硼团簇中掺杂铝可能会显著偏离等电子取代过程。我们在此报告一种独特的夹心双铝掺杂硼团簇Al₂B₂，采用全局结构搜索和量子化学计算方法。该团簇具有一个完美平面的B分子轮，有两个孤立的Al原子对称地悬浮在其上方和下方。这两个Al原子偏离分子轮中心，导致团簇具有C₂对称性。研究表明，即使在远低于室温（100 K）的温度下，Al₂B₂团簇也是动态易变的，其中一根垂直的Al棒在B板上的圆形轨道内自由滑动或旋转，尽管不存在直接的Al - Al相互作用。在单点CCSD(T)水平下，分子内旋转的能垒仅为0.01 kcal/mol。化学键分析表明，该团簇是一种电荷转移络合物，可表示为[Al₂⁺][B₆²⁻][Al₂⁺]。夹心团簇中的[B₆²⁻]分子轮具有神奇的6π/6σ双芳香性，这是其动态易变性的基础，尽管[Al₂⁺]、[B₆²⁻]和[Al₂⁺]层之间存在强烈的静电相互作用。
