二元硼铝复合团簇B_7Al_2^(0/-)和B_7Al_3^(0/-)的结构、成键和芳香性研究  

Binary B_7Al_n and B_7Al_n^-(n=2,3) Clusters:Isovalent Substitution Induced Structural Changes and Double(π and σ)Aromaticity

作　　者：王渊 冯林雁 王康 翟华金[1] WANG Yuan;FENG Linyan;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）》2019年第2期373-383,共11页Journal of Shanxi University(Natural Science Edition)

基　　金：国家自然科学基金(21873058;21573138)

摘　　要：二元复合B—Al团簇有望延续硼的缺电子性和铝的全金属芳香性,从而形成独特团簇结构和新颖化学键。基于密度泛函理论,文章对系列二元B—Al团簇B_7Al_n和B_7Al_n^-(n=2,3)进行量子化学理论研究。通过广泛的全局极小结构搜索以及B3LYP结构优化和CCSD(T)单点计算来确定其最稳定基态结构。团簇B_7Al_2,B_7Al_2^-和B_7Al_3全局极小结构由七边形B_7环和垂直于该环的Al_2中心单元组成。团簇B_7Al_3^-则保持轮状B_7基盘,三个Al原子位于基盘上方或在面内形成桥键。化学键分析结果表明二元B—Al团簇中的所谓"等价Al/B取代"并不是完全等价的,因为Al中心倾向于保留部分定域电子。该成键特征也阐释B_7Al_n^(0/-)(n=2,3)团簇全局极小结构为什么与B_8Al^-/B_9Al^-和B_9-~/B_(10)^-团簇完全不同。本团簇系列的共性是它们都具有双重π/σ芳香性,离域6π和6σ电子计数均满足Hückel规则。Binary B—Al clusters are anticipated to inherit the electron-deficiency of boron and all-metal aromaticity of aluminum,thus leading to unusual structural,electronic,and bonding properties.Here we report on an extensive computational study of a series of binary B—Al clusters:B7Aln and B7Aln-(n=2,3).Their global-minimum structures are identified via computer searches and electronic structure calculations at the B3LYP and single-point CCSD(T)levels.The B7Al2,B7Al2-,and B7Al3 clusters feature a heptagonal B7 ring with a central Al2 unit orienting perpendicular to the ring.In contrast,B7Al3- contains a hexacoordinate B7 disk with one capping and two in-plane bridging Al atoms.The chemical bonding analyses conclude that all B7Aln0/-(n=2,3)clusters are doubly π/σ aromatic with 6π and 6σ electrons,which are the decisive factor that governs the stability of these species.The isovalent Al/B substitution in binary B—Al clusters turns out not to be completely isovalent,because the Al centers preserve a number of localized electrons and/or lone-pairs.This explains why B7Aln0/-(n=2,3)clusters assume different structures than B8Al-/B9Al-and B9-/B10-.One electron alters the potential landscapes of B7Al3 and B7Al3- clusters,due to distinct electron affinities of two-types of neutral structures.

关 键 词：硼铝复合团簇 等价取代 化学键 双重芳香性 适应性自然密度划分 

分 类 号：O641[理学—物理化学]