Graduate School of Information Sciences, Hiroshima City University, 3-4-1 Ozuka-Higashi, Asa-Minami-Ku, Hiroshima 731-3194, Japan.
Molecules. 2018 Dec 15;23(12):3332. doi: 10.3390/molecules23123332.
We report a reparameterization of PM6 parameters for fluorine and chlorine using our training set containing transition metal complexes. Spin unrestricted calculations with the resulting rPM6 (UrPM6) were examined quantitatively using two test sets: (i) the description of magnetic interactions in 25 dinuclear metal complexes and (ii) the prediction of barrier heights and reaction energies for epoxidation and fluorination reactions catalyzed by high-valent manganese-oxo species. The conventional UPM6 and UPM7 methods were also evaluated for comparison on the basis of either experimental or computational (the UB3LYP/SVP level) outcomes. The merits of UrPM6 are highlighted by both the test sets. As regards magnetic exchange coupling constants, the UrPM6 method had the smallest mean absolute errors from the experimental data (19 cm), followed by UPM7 (119 cm) and UPM6 (373 cm). For the epoxidation and fluorination reactions, all of the transition state searches were successful using UrPM6, while the success rates obtained by UPM6 and UPM7 were only 50%. The UrPM6-optimized stationary points also agreed well with the reference UB3LYP-optimized geometries. The accuracy for estimating reaction energies was also greatly remedied.
我们报告了使用包含过渡金属配合物的训练集对氟和氯的 PM6 参数进行重新参数化。使用两个测试集定量检查了由此产生的 rPM6（UrPM6）的无自旋限制计算：（i） 描述 25 个双核金属配合物中的磁相互作用，（ii） 预测高价锰氧物种催化的环氧化和氟化反应的能垒高度和反应能。还根据实验或计算（UB3LYP/SVP 水平）结果对常规 UPM6 和 UPM7 方法进行了评估，以进行比较。两个测试集都突出了 UrPM6 的优点。就磁交换耦合常数而言，UrPM6 方法的实验数据的平均绝对误差最小（19 cm），其次是 UPM7（119 cm）和 UPM6（373 cm）。对于环氧化和氟化反应，所有过渡态搜索都成功使用 UrPM6 进行，而 UPM6 和 UPM7 的成功率仅为 50%。UrPM6 优化的稳定点也与参考 UB3LYP 优化的几何形状吻合良好。估计反应能的准确性也得到了很大的改善。
