Construction of tetrahedral chiral-at-metal complexes towards asymmetric light-driven redox catalysis

在一年的研究中，我主要研究了氧化还原活性手性-镍（II）和手性-钴（II）配合物的构建和拆分。首先，我用不对称的非手性三叉配体构建了两个四面体手性-镍（II）配合物，并通过NMR， ESI-MS，单晶XRD和UV-vis吸收光谱对其进行了表征。结构信息被仔细地阐明了。配合物采用四面体的几何形状，并表现出氧化还原活性以及可见光吸收。此外，它们能够交换配体以激活底物。其次，我成功地在低温下将S/R-[NiL(ClLi(thf)2)]配合物自发分解为砾岩晶体。优化了结晶条件，阐明了晶体结构。我发现氢键是实现自发分辨的关键。配体和镍离子从非手性构建块开始，以高度不对称的方式组装手性金属配合物、一维手性螺旋、三维手性上结构和最后的同手性晶体。这与古地球生物系统中同手性的起源有关，并揭示了晶体工程的概念。我还成功构建了一个四面体手性钴（II）配合物，并通过NMR， ESI-MS，单晶XRD， UV-vis吸收光谱对其进行了表征。与银盐一起，发现该配合物能够裂解1,2-二乙基乙二胺的碳-碳键。目前反应条件还在优化中。

In one year research, I mainly focus on construction and resolution of redox-active chiral-at-nickel(II) and chiral-at-cobalt(II) complexes.First, I constructed two tetrahedral chiral-at-nickel(II) complexes using an unsymmetrical, achiral tridentate ligand and characterized them by NMR, ESI-MS, single-crystal XRD and UV-vis absorption spectroscopy. The structural information was carefully elucidated. The complexes adopt a tetrahedral geometry and exhibit redox activity as well as visible-light absorption. Also, they are capable of ligand exchange for substrate activation.Second, I succeeded in spontaneous resolution of S/R-[NiL(ClLi(thf)2)] complex to conglomerate crystals at low temperature. I optimized the crystallization conditions and elucidated the crystallographic structure. I found that hydrogen bondings are essential to achieve spontaneous resolution. Starting from achiral building blocks, the ligands and nickel ions assemble chiral-at-metal complexes, 1D chiral helices, 3D chiral suprastructure and finally homochiral crystals in a highly asymmetric manner. This is related to the origin of homochirality in biological systems in ancient earth and sheds light on the concept of crystal engineering.I also successfully constructed a tetrahedral chiral-at-cobalt(II) complex and charactered it by NMR, ESI-MS, single-crystal XRD, UV-vis absorption spectroscopy. Together with silver salts, the complex was found to be capable for carbon-carbon bond cleavage of 1,2-diarylethylenediamine. The reaction condition is under optimization currently.