硼基B_(6)Al_(2)^(-/0/+)合金团簇结构和成键理论研究(英文)  

Al-B Substitution in Boron-based Alloy Clusters is Not Completely Isoelectronic: Structures and Bonding of B_(6)Al_(2)^(-/0/+) Clusters

作　　者：张洁琼 王康 翟华金[1] ZHANG Jieqiong;WANG Kang;ZHAI Huajin(Institute of Molecular Science,Shanxi University,Taiyuan 030006,China)

机构地区：[1]山西大学分子科学研究所,山西太原030006

出　　处：《山西大学学报（自然科学版）》2022年第5期1281-1291,共11页Journal of Shanxi University(Natural Science Edition)

基　　金：国家自然科学基金(21873058,21573138)。

摘　　要：硼和铝团簇分别呈现独特的结构与化学成键。二元B-Al复合团簇研究通常遵循所谓的等电子B-Al取代概念。然而这纯粹是一种假设。文章利用全局极小结构搜索和量子化学电子结构计算对不同电荷态的系列二元B_(6)Al_(2)^(-/0/+)团簇进行结构、成键和芳香性等理论研究。在PBE0和CCSD(T)单点理论水平上对低能量异构体的相对能量进行比较,确定了全局极小结构。文章主要讨论的团簇结构1-4有两种不同结构模式:反三明治和杂环分子轮。中性团簇的全局极小结构1略微倾向于反三明治结构,而分子轮结构2是低能量异构体。阴离子团簇结构3也是分子轮结构,然而阳离子团簇结构4却强烈的倾向于反三明治构型。在从阳离子、中性到阴离子的逐级还原过程中分子轮逐步获得优势。在成键方面,团簇1和2具有6π/4σ冲突芳香性,这导致它们拉长的形状。阳离子团簇4和阴离子团簇3具有3σ/5σ电子离域,它们偏离严格的4σ反芳香性。因此,团簇3/4相对而言是更圆形的结构。掺杂Al原子在特定B-Al复合团簇结构中会呈现形式上的3个、2个、1个价电子等不同状态;剩余价电子则处于非键或孤对状态。基于此,掺杂Al可以被分为三类,只有一类复合严格的等电子Al-B取代。上述认知对任意复合B-Al团簇都具有借鉴意义。Elemental boron and aluminum clusters show unique structures and chemical bonding. Consequently,binary B-Al clusters are normally studied following the idea of isoelectronic Al-B substitution. However,the concept is purely an assumption. We report on the structures,bonding,and aromaticity of a series of binary B_(6)Al_(2)^(-/0/+)clusters in their different charge states,using computational global-minimum(GM)searches and electronic structure calculations. Relative energies of top low-lying structures are systematically assessed at the PBE0 and single-point CCSD(T)levels of theory,offering useful methodological information for this and relevant systems. The key cluster structures(1—4)have two distinct motifs:inverse sandwich versus heteroatomic molecular wheel. Neutral GM cluster 1 slightly favors the inverse sandwich,with molecular wheel structure 2 being a low-lying isomer. Anionic GM cluster 3 is also a molecular wheel,whereas cationic GM cluster 4 strongly favors the inverse sandwich. Upon the sequential reduction from cation,neutral,to anion,the molecular wheel monotonically gains a relative advantage,and a structural transition from inverse sandwich to molecular wheel takes place in the anion. In terms of bonding,clusters 1/2 feature the 6π/4σconflicting aromaticity,leading to elongated structural shapes. The cationic cluster 4 and anionic cluster 3 have the 3σ/5σ frameworks,which deviate from strict 4σ antiaromaticity. Thus,clusters 3/4 are relatively circular. The doping Al sites fall into three distinct categories,being chemically valence three/two/one,respectively. Only one out of three categories conforms to the isoelectronic B-Al substitution.

关 键 词：硼基B-Al合金团簇 等电子取代 反三明治团簇 分子轮团簇 冲突π/σ芳香性 

分 类 号：O641.4[理学—物理化学]