吡啶甲酸分子平衡构型的ab initio理论研究

本文用能量梯度法TEXAS从头计算程序,选取4-21G(,N原子含极化d轨道)基组,对α-,β-吡啶甲酸分子的平衡几何构型进行了全优化计算,二套基组的理论优化表明,三个吡啶甲酸分子都具有平面的平衡构型,其计算键长经4-21G 基组的标准经验校正值校正后,所得的理论预测平衡几何构型与X射线单晶衍射实验结果有很好的一致性.对部分键长以及羧基与吡啶华平面的二面角中出现的差异进行了讨论.

theoretical studies on molecular equilibrium geometries of picolinic acid with ab initio calculations

The equilibrium geometries of a-, b- and g-picolinic acid mols. have been optimized by the ab initio gradient program TEXAS using the 4-21G and 4-21G* (with d functions on N and O atoms) basis sets. Theor. optimizations with both basis sets show that the equilibrium geometries of the three picolinic acid mols. are completely planar. The theor. predicted geometries, in which the bond lengths were determine according to the 4-21G optimized results together with some corresponding empirical corrections, are basically in agreement with the experiment results from X-ray crystallog. Deviations in some bond lengths and dihedral angle between planes of carboxyl group and pyridine have been discussed.