E_4^(2-),[CoE_4]^+和[P_4CoE_4]^-(E=N～Bi)结构和芳香性的理论预测

Theoretical Predictions on Structures and Aromaticities of E_4^(2-),[CoE_4]^+and[P_4CoE_4]^-(E=N～Bi)

用密度泛函理论杂化密度泛函B3LYP方法研究了E24-,[CoE4]+和[P4CoE4]-(E=N,P,As,Sb,Bi)几何结构、键能及芳香性.结果表明,E42-,[CoE4]+和[P4CoE4]-的基态结构分别具有D4h,C4v和C4v(交错型)对称性.三明治配合物中,金属与配体间存在σ,π和δ三种成键方式,P4与E4间相互影响较小.E4对P4中的P—P键长影响随着N,P,As,Sb,Bi顺序逐渐变长,中心Co离子与E4间的键合能随N,P,As,Bi,Sb的顺序增大.N42-的环外具有弱芳香性,其它E42-环中心及环外均为反芳香性.除[CoN4]+外,其它[CoE4]+中的E4环均具有较强的中心和内芳香性及弱的外反芳香性.[P4CoE4]-中的P4和E4均具有较大的中心、内和外芳香性,且P4环芳香性随N,P,As,Sb,Bi顺序逐渐递增.

The equilibrium geometries,bonding energies and aromaticity of the E 24-,[CoE4]＋ and [P4CoE4]-（E=N,P,As,Sb and Bi） were predicted with the hybrid density functional method B3LYP within density functional theory.The calculations showed that the ground states of E 24-,[CoE4]＋ and [P4CoE4]-were in D4h,C4v and C4v（staggered） symmetries,respectively.There are three types of interactions σ,π and δ between the ligands and metal for the [P4CoE4]-complexes.There is a little influence between P4 and E4,and the P—P bond length of P4 is longer with the order of N,P,As,Sb and Bi.The binding energies between Co3＋ and E4 in [P4CoE4]-increase with the order N,P,As,Bi and Sb.All of the center and inner side of E 42-rings are anti-aromatic excluding that the outer of isolated N 24-is aromatic.Except for [CoN4]＋,all of E4 rings of [CoE4]＋ have strong center and inner aromaticity,and weak outer anti-aromaticity.All of center,inner and outer of P4 and E4 rings in [P4CoE4]-are aromatic,and the aromaticity of P4 ring increases with the order of N,P,As,Sb and Bi in [P4CoE4]-.