M2B7^-(M=Mg,Zn)团簇的双重芳香性促进Mg-Mg和Zn-Zn单键的形成

Designer Mg-Mg and Zn-Zn Single Bonds Facilitated by Double Aromaticity in the M2B7^-(M=Mg,Zn)Clusters

本文使用密度泛函理论设计了两个无需配体的具有Mg-Mg和Zn-Zn单键的团簇M(g2)B7^-和Zn2B7^-.这两种团簇的全局能量最低构型均以M2^2+(B7^3-)的形式存在,其中M-M单键处于准平面六边形形状的B7部分的上方.化学键分析证实了这些团簇中Mg-Mg和Zn-Zn单键的存在,这些单键是在异常稳定的B7^3-的驱动下生成的.该B7^3-部分同时具有σ和7π双重芳香性.计算得到Mg2B7^-和Zn2B7^-的垂直跃迁能分别为2.79 eV和2.94 eV.

The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design the M^+-M^+single bond.Existing studies generally use sterically bulky organic ligands L^-to synthesize the compounds in the L^--M^+-M^+-L-manner.However,here we report the design of Mg-Mg and Zn-Zn single bonds in two ligandless clusters,Mg2B7-and Zn2B7-,using density functional theory methods.The global minima of both of the clusters are in the form of M2^2+(B7^3-),where the M-M single bonds are positioned above a quasi-planar hexagonal B7 moiety.Chemical bonding analyses further confirm the existence of Mg-Mg and Zn-Zn single bonds in these clusters,which are driven by the unusually stable B7^3-moiety that is bothσandπaromatic.Vertical detachment energies of Mg2B7-and Zn2B7-are calculated to be 2.79 e V and 2.94 e V,respectively,for the future comparisons with experimental data.