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本文用EHMO方法对C_6H_6·C_2(CN)_4电子施受复合物的电子结构进行了计算,计算时把C_6H_6·C_2(CN)_4看成一个超级分子.计算结果表明,复合物形成的距离3.6A处于能量变化陡峭和趋于平缓的转折点上。室温下C_6H_6平面相对于C_2(CN)_4平面可以自由旋转,自由旋转势垒～0.01kcal/mol,每旋转360°要克服六重势垒.体系能量低的构型是C_2(CN)_4中C—C键与C_6H_6中某一相对C—C键相互垂直的构型,而不是与C_6H_6中某一相对C—C键相互平行的构型、电荷转移随角度而变化与体系能量随角度而变化的倾向相反,能量的极小值对应于电荷转移的极大值.这说明,在此弱电子施受复合物C_6H_6·C_2(CN)_4中电荷转移仍起着决定性的作用。复合物形成时,C_6H_6上的H来参加电荷转移,表征了π-π复合的特性。
In this paper, the electronic structure of C_6H_6 · C_2 (CN) _4 electron-donating complex was calculated by EHMO method, and C_6H_6 · C_2 (CN) _4 was considered as a supermolecule when calculated. The calculated results show that the distance between the complexes formed 3.6 A is at a turning point where the energy changes steeply and gently. The C_6H_6 plane at room temperature can rotate freely with respect to the C_2 (CN) _4 plane, with a free rotation barrier of ~0.01 kcal / mol, which overcomes the six-fold barrier per 360 ° rotation. The C-C bond is perpendicular to the C-C bond in C_6H_6, rather than being parallel to one of the C-C bonds in C_6H_6. The charge transfer varies with the angle and the energy of the system varies with the angle On the contrary, the minimum value of energy corresponds to the maximum value of charge transfer, indicating that charge transfer still plays a decisive role in the weak electron donor complex C_6H_6 · C_2 (CN) _4. When the complex is formed, H on C_6H_6 participates in charge transfer and characterizes the π-π recombination.