Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Heverlee-Leuven, Belgium.
Inorg Chem. 2010 Nov 15;49(22):10316-29. doi: 10.1021/ic100866z. Epub 2010 Oct 21.
In this paper, the results are presented from a comparative study of the electronic and geometric structure of copper corroles by means of either density functional theory (DFT, using both pure and hybrid functionals) and multiconfigurational ab initio methods, starting from either a complete active space (CASSCF) or restricted active space (RASSCF) reference wave function and including dynamic correlation by means of second-order perturbation theory (CASPT2/RASPT2). DFT geometry optimizations were performed for the lowest singlet and triplet states of copper corrole, both unsubstituted and meso-substituted with three phenyl groups. The effect of saddling on the electronic structure was investigated by comparing the results obtained for planar (C(2v)) and saddled (C(2)) structures. With DFT, the origin of the saddling distortion is found to be dependent on the applied functional: covalent Cu 3d-corrole π interactions with pure functionals (BP86, OLYP), antiferromagnetic exchange coupling between an electron in the corrolate (C(2)) b type π orbital, and an unpaired Cu(II) 3d electron with hybrid functionals (B3LYP, PBE0). The CASPT2 results essentially confirm the suggestion from the hybrid functionals that copper corroles are noninnocent, although the contribution of diradical character to the copper-corrole bond is found to be limited to 50% or less. The lowest triplet state is calculated at 0-10 kcal/mol and conform with the experimental observation (variable temperature NMR) that this state should be thermally accessible.
在本文中，通过密度泛函理论（DFT，使用纯函数和混合函数）和多组态从头算方法，对铜叶啉的电子和几何结构进行了比较研究，得到了结果。从头算方法的参考波函数是完全活性空间（CASSCF）或受限活性空间（RASSCF），并通过二阶微扰理论（CASPT2/RASPT2）包括动态相关。对铜叶啉的最低单重态和三重态进行了未取代和三个苯基取代的平面（C(2v))和马鞍（C(2))结构的最低 singlet 和 triplet 态的 DFT 几何优化。通过比较平面（C(2v))和马鞍（C(2))结构的结果，研究了马鞍畸变对电子结构的影响。对于 DFT，马鞍畸变的起源被发现取决于所应用的函数：纯函数（BP86、OLYP）中铜 3d-叶啉π 键的共价相互作用、处于叶啉（C(2)) b 型 π 轨道中的电子与混合函数（B3LYP、PBE0）中未配对的 Cu(II) 3d 电子之间的反铁磁交换耦合。尽管认为铜叶啉是非无辜的，但从头算方法的 CASPT2 结果基本上证实了混合函数的这一说法，尽管双自由基特征对铜-叶啉键的贡献被发现限制在 50%或以下。最低三重态计算在 0-10 kcal/mol，与实验观察（变温 NMR）一致，表明该态应该是热可及的。
