Departamento de Química Física, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
Molecules. 2022 Mar 3;27(5):1678. doi: 10.3390/molecules27051678.
Recently, we reported a new approach to develop pairwise analytical corrections to improve the description of noncovalent interactions, by approximate methods of electronic structures, such as semiempirical quantum mechanical (SQM) methods. In particular, and as a proof of concept, we used the PM6 Hamiltonian and we named the method PM6-FGC, where the FGC acronym, corresponding to Functional Group Corrections, emphasizes the idea that the corrections work for specific functional groups rather than for individual atom pairs. The analytical corrections were derived from fits to B3LYP-D3/def2-TZVP (reference). PM6 interaction energy differences, evaluated for a reduced set of small bimolecular complexes, were chosen as representatives of saturated hydrocarbons, carboxylic, amine and, tentatively, amide functional groups. For the validation, the method was applied to several complexes of well-known databases, as well as to complexes of diglycine and dialanine, assuming the transferability of amine group corrections to amide groups. The PM6-FGC method showed great potential but revealed significant inaccuracies for the description of some interactions involving the -NH group in amines and amides, caused by the inadequate selection of the model compound used to represent these functional groups (an NH molecule). In this work, methylamine and acetamide are used as representatives of amine and amide groups, respectively. This new selection leads to significant improvements in the calculation of noncovalent interactions in the validation set.
最近，我们报道了一种新的方法，通过电子结构的近似方法，如半经验量子力学（SQM）方法，开发成对分析修正来改进非共价相互作用的描述。特别是，作为概念验证，我们使用了 PM6 哈密顿量，并将该方法命名为 PM6-FGC，其中 FGC 是功能组修正（Functional Group Corrections）的缩写，强调了修正适用于特定功能组而不是单个原子对的思想。分析修正来自于对 B3LYP-D3/def2-TZVP（参考）的拟合。选择了 PM6 相互作用能差异的较小双分子复合物的简化集合，作为饱和烃、羧酸、胺以及暂时的酰胺功能组的代表。为了验证，该方法应用于几个已知数据库的复合物，以及二甘氨酸和二丙氨酸的复合物，假设胺基团修正可转移到酰胺基团。PM6-FGC 方法显示出很大的潜力，但对于描述涉及胺和酰胺中-NH 基团的一些相互作用，显示出明显的不准确性，这是由于用于代表这些功能组的模型化合物的选择不当（一个 NH 分子）造成的。在这项工作中，甲胺和乙酰胺分别用作胺和酰胺基团的代表。这种新的选择导致验证集中非共价相互作用计算的显著改进。
