轮烯稳定性的价键理论研究

Valence Bond Study of the Stability of Cyclenes

采用键表方法对两个最典型的轮烯即苯和环丁二烯进行了价键计算，并绘制苯和环丁二烯的定量共振结构相关图。为讨论π电子离域对构型的影响，设计一个假想粒子Ｍ，其核电荷为３．１８，并且核外层仅有一个电子在２Ｐ＿ｚ上，用Ｍ＿ｎ模拟讨论（ＣＨ）＿ｎ中π电子的离域行为。计算表明共轭体系中π电子倾向于长短键交替，但σ骨架将阻止这种变形，两者力量对比决定构型是等边的（如苯）还是长短交替的（如环丁二烯）。

Tow most prominent cyclenes,namely benzene and cyclobutadiene are calculatedwith the Bonded Tableau Unitary Group Approach(BTUGA)and the energy correlation diagrams fortheir resonance structures are depicted,In order to investigate the effect of π electronic delocalizationon the molecular structure, we devise a hypothetical particle,whose core charge is 3.18 and there isonly one electron on the atomic orbital 2p_π around the core, Thus the π-component of(CH)_n can beimitated by M_n. The results show that in a conjugated system,π electrons distortive,while the σ-frameprefers are regular geometry with tha same C-C bond lengths. The competition between the above twoforces determines whether the system takes a regular(e.g. benzene)or an alternant geometry(e,g.cyclobutadiene).