Teixeira Filipe, Mosquera Ricardo A, Melo André, Freire Cristina, Cordeiro M Natália D S
REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciê ncias, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal.
Phys Chem Chem Phys. 2014 Dec 14;16(46):25364-76. doi: 10.1039/c4cp00721b. Epub 2014 Oct 22.
The theoretical study of Mn(salen) catalysts has been traditionally performed under the assumption that Mn(acacen') (acacen' = 3,3'-(ethane-1,2-diylbis(azanylylidene))bis(prop-1-en-olate)) is an appropriate surrogate for the larger Mn(salen) complexes. In this work, the geometry and the electronic structure of several Mn(salen) and Mn(acacen') model complexes were studied using Density Functional Theory (DFT) at diverse levels of approximation, with the aim of understanding the effects of truncation, metal oxidation, axial coordination, substitution on the aromatic rings of the salen ligand and chirality of the diimine bridge, as well as the choice of the density functional and basis set. To achieve this goal, geometric and structural data, obtained from these calculations, were subjected to Principal Component Analysis (PCA) and PCA with orthogonal rotation of the components (rPCA). The results show the choice of basis set to be of paramount importance, accounting for up to 30% of the variance in the data, while the differences between salen and acacen' complexes account for about 9% of the variance in the data, and are mostly related to the conformation of the salen/acacen' ligand around the metal centre. Variations in the spin state and oxidation state of the metal centre also account for large fractions of the total variance (up to 10% and 9%, respectively). Other effects, such as the nature of the diimine bridge or the presence of an alkyl substituent in the 3,3 and 5,5 positions of the aldehyde moiety, were found to be less important in terms of explaining the variance within the data set. A matrix of discriminants was compiled using the loadings of the principal and rotated components that best performed in the classification of the entries in the data. The scores obtained from its application to the data set were used as independent variables for devising linear models of different properties, with satisfactory prediction capabilities.
传统上，对Mn(salen)催化剂的理论研究是在假设Mn(acacen')（acacen' = 3,3'-（乙烷-1,2-二基双（氮亚基））双（丙-1-烯醇盐））是较大的Mn(salen)配合物的合适替代物的前提下进行的。在这项工作中，使用密度泛函理论（DFT）在不同的近似水平下研究了几种Mn(salen)和Mn(acacen')模型配合物的几何结构和电子结构，目的是了解截断、金属氧化、轴向配位、salen配体芳环上的取代以及二亚胺桥的手性的影响，以及密度泛函和基组的选择。为了实现这一目标，将从这些计算中获得的几何和结构数据进行主成分分析（PCA）以及成分正交旋转的PCA（rPCA）。结果表明，基组的选择至关重要，占数据方差的30%，而salen和acacen'配合物之间的差异占数据方差的约9%，并且主要与金属中心周围salen/acacen'配体的构象有关。金属中心的自旋态和氧化态的变化也分别占总方差的很大比例（分别高达10%和9%）。发现其他影响，如二亚胺桥的性质或醛部分3,3和5,5位上烷基取代基的存在，在解释数据集中的方差方面不太重要。使用在数据条目的分类中表现最佳的主成分和旋转成分的载荷编制了一个判别矩阵。将其应用于数据集所获得的分数用作设计不同性质线性模型的自变量，具有令人满意的预测能力。
