Application of NHC-modified Gold Nanoclusters in Photoredox Catalysis

近年来，N-杂环卡宾(NHCS)作为硫醇或膦的有价值的替代品出现在金属表面、纳米粒子和簇合物的稳定方面。中性的、富含电子的NHC与金属形成强烈的共价键，这对于提供金属纳米簇的稳定性非常重要。到目前为止，我们已经能够通过直接还原邻二甲基连接的双-N-杂环卡宾(BisNHC)配体连接的非手性双核Au(I)卤化物配合物来合成一系列手性AU13纳米簇。广泛的官能团被允许作为翼尖取代基，允许合成各种功能化的手性AU13纳米簇。我们用单晶X射线结晶学确定了分子式为[AU13(BisNHC)5Cl2]Cl3，其中五个双齿NHC配体以手性螺旋排列在二十面体AU13核周围。这种AU13纳米团簇具有很高的发光，量子产率为23%。手性高效液相色谱可分离AU13簇的两个对映体，圆二色谱对分离得到的对映体进行了表征。我们合成的团簇表现出了显著的稳定性，包括构型稳定性，为进一步研究手性对这些团簇的影响打开了大门。我们的初步结果表明，该双NHC AU13纳米簇对细胞友好，可用于细胞成像。

N-heterocyclic carbenes (NHCs) have recently emerged as valuable alternatives to thiols or phosphines for the stabilization of metal surfaces, nanoparticles, and clusters. The neutral, electron-rich NHCs form a strong covalent bond with the metal, which is important in providing stability to metal nanoclusters.Thus far we have been able to synthesize a series of chiral Au13 nanoclusters via the direct reduction of achiral dinuclear Au(I) halide complexes ligated by ortho-xylyl-linked bis-N-heterocyclic carbene (bisNHC) ligands. A broad range of functional groups are tolerated as wingtip substituents, allowing for the synthesis of a variety of functionalized chiral Au13 nanoclusters. We have used single-crystal X-ray crystallography to confirm the molecular formula to be [Au13(bisNHC)5Cl2]Cl3, with a chiral helical arrangement of the five bidentate NHC ligands around the icosahedral Au13 core. This Au13 nanocluster is highly luminescent, with a quantum yield of 23%. The two enantiomers of the Au13 clusters can be separated by chiral HPLC, and the isolated enantiomers characterized by circular dichroism spectroscopy. The clusters synthesized by us show remarkable stability, including configurational stability, opening the door to further investigation of the effect of chirality on these clusters. Our preliminary results showed that this bisNHC Au13 nanocluster is friendly to cells and can be used for the cell imaging.