Molecular Assemblies Based on Strong Axial Coordination in Metal Complexes of Saddle-Distorted Dodecaphenylporphyrins
Molecular Assemblies Based on Strong Axial Coordination in Metal Complexes of Saddle-Distorted Dodecaphenylporphyrins
复制标题
基于鞍形扭曲十二苯基卟啉金属配合物强轴向配位的分子组装
DOI：
10.1142/s1088424615500273
复制
发表时间：
2015
影响因子：
1.5
通讯作者：
T. Kojima
中科院分区：
文献类型：
--
作者：
T. Ishizuka;S. Fukuzumi;T. Kojima
本文综述了以鞍形十二苯基卟啉（DPP）及其衍生物为配体的金属配合物的研究工作，主要是为了提高卟啉配位的金属中心的刘易斯酸性。通过这个小的审查的重要一点是平面外的吡咯氮原子的孤对与鞍形扭曲的卟啉核结合的金属中心的σ-轨道的不良重叠。中心金属离子的增强的刘易斯酸性使我们能够通过使用金属DPP（M（DPP））部分（M = MoV或SnIV）和具有路易斯碱性配位位点的分子或离子实体（包括Keggin型聚氧乙烯醚（POM））的轴向配位来构建稳定的分子络合物，已知Keggin型聚氧乙烯醚具有弱刘易斯碱性，因此难以与金属离子配位。与Ru取代的POM的离散1：2络合物在有机溶剂中进行催化底物氧化反应。SnIV（DPP）和Keggin型POM之间的1：1络合物表现出光诱导电子转移，其中SnIV（DPP）部分作为电子供体，POM作为电子受体。除POM外，其他以羧基为连接单元的电子受体，如μ3-氧代三核RuIII簇合物和蒽醌，也能与DDP-金属配合物形成稳定的配合物，进行光诱导电子转移。成功的光反应的M（DPP）受体配合物的主要是通过增强的刘易斯酸性的DPP-金属配合物的组装体的稳定性，也通过降低卟啉配体的氧化电位，以获得更大的电子转移的驱动力，形成电子转移状态，避免系统间的交叉。其稳定性和光化学行为与以平面卟啉为配体的金属配合物形成鲜明对比。
In this mini-review, we have highlighted our works on metal complexes having saddle-distorted dodecaphenylporphyrin (DPP) and its derivative as ligands in the light of enhancement of the Lewis acidity of a metal center coordinated by the porphyrin. The important point through this mini-review is ill-overlap of the out-of-plane lone pairs of pyrrole nitrogen atoms with σ-orbitals of the metal center bound to the saddle-distorted porphyrin core. The enhanced Lewis acidity of the central metal ions enabled us to construct stable molecular complexes through axial coordination using metal–DPP (M(DPP)) moieties (M = MoVor SnIV) and molecular or ionic entities with Lewis-basic coordination sites, including Keggin-type polyoxometallates (POM), which are known to have weak Lewis basicity and thus hard to coordinate to metal ions. A discrete 1:2 complex with a Ru-substituted POM performs catalytic substrate oxidation reactions in organic solvents. A 1:1 complex between SnIV(DPP) and a Keggin-type POM exhibited photoinduced electron transfer, in which the SnIV(DPP) moiety acts as an electron donor and the POM as an electron acceptor. Besides POM, other electron acceptors, including μ3-oxo trinuclear RuIIIclusters and anthraquinone, having carboxyl groups as a linker unit also formed stable complexes with DPP-metal complexes as axial ligands to perform photoinduced electron transfer. Successful photoreactions of the M(DPP)-acceptor complexes are mainly enabled by the enhanced Lewis acidity of the DPP-metal complexes for the stabilization of the assemblies and also by lowering the oxidation potential of the porphyrin ligand to gain larger driving force of electron transfer to form an electron-transfer state with avoiding intersystem crossing. The stability and photochemical behavior are in sharp contrast to those for metal complexes with planar porphyrins as ligands.