Li X L, Kuznetsov A E, Zhang H F, Boldyrev A I, Wang L S
Department of Physics, Washington State University, 2710 University Drive, Richland, WA 99352, USA.
Science. 2001 Feb 2;291(5505):859-61. doi: 10.1126/science.291.5505.859.
Aromaticity is a concept invented to account for the unusual stability of an important class of organic molecules: the aromatic compounds. Here we report experimental and theoretical evidence of aromaticity in all-metal systems. A series of bimetallic clusters with chemical composition MAl4- (M = Li, Na, or Cu), was created and studied with photoelectron spectroscopy and ab initio calculations. All the MAl4- species possess a pyramidal structure containing an M+ cation interacting with a square Al4(2-) unit. Ab initio studies indicate that Al4(2-) exhibits characteristics of aromaticity with two delocalized pi electrons (thus following the 4n + 2 electron counting rule) and a square planar structure and maintains its structural and electronic features in all the MAl4- complexes. These findings expand the aromaticity concept into the arena of all-metal species.
芳香性是为解释一类重要有机分子（即芳香化合物）的异常稳定性而提出的概念。在此，我们报告了全金属体系中芳香性的实验和理论证据。通过光电子能谱和从头算计算，制备并研究了一系列化学组成为MAl4-（M = 锂、钠或铜）的双金属簇合物。所有的MAl4-物种都具有金字塔结构，包含一个M+阳离子与一个方形Al4(2-)单元相互作用。从头算研究表明，Al4(2-)表现出芳香性特征，有两个离域π电子（因此遵循4n + 2电子计数规则）且呈平面正方形结构，并且在所有MAl4-配合物中保持其结构和电子特征。这些发现将芳香性概念扩展到了全金属物种领域。
