氮杂多环芳烃^(13)C-NMR化学位移的理论探讨

Theoretical Calculation of^(13)C-NMR Chemical Shifts of Some Polycyclic Aromatic Heterocycles

本文主要是对氮原子以ｓｐ~２杂化，孤氮电子占据ｓｐ~２杂化轨道，以这种形式成键的氮杂交变多环芳烃中的１１个化合物的^（１３）Ｃ－ＮＭＲ的化学位移进行了计算。该计算依据ＣＮＤＯ方法一个联系分子电荷密度，键级和键长等参数的半经验公式。同时利用环电流、空间效应以及针对氮原子的屏蔽效应和去屏蔽效应的影响，通过分子动力学的考虑，得到理论上计算的化学位移，该计算结果与实验值吻合得很好，通过时^（１３）Ｃ－ＮＭＲ化学位移的回归分析表明，回归系数达到０．９９，非常好地反映了氮杂多环芳烃^（１３）Ｃ－ＮＭＲ化学位移与分子微观结构之间的关系，同时表明我们在处理诸多化学位移时考虑到的因素是合理可行的。

We hare studied eleven polycyclic aromatic heterocycles with their￣(13)C-NMR chemical shifts,especially to those that the lone pair electrons form sp 2occupy the orbital of nitrogen.The calcutation is mainly based on CNDO method,an equation that we proposed previously that considered electron density,bond length and bond polarization,etc.factors and many other influences to carbon atom especially produced by shielding and deshielding effect of nitrogen.From the studying,it can be observed that the correlation coefficient calculated 13 C-NMR chemical shifts w over 0.99.It well reflects the relationship between the microstructure of polycyclic aromatic heterocycles and their 13 C-NMR Chemical shifts.