Gray Centre for Advanced Materials, School of Mathematics and Physical Sciences, University of Hull, Cottingham Road, Hull HU6 7RX, UK.
Institute of Inorganic Chemistry, University of Vienna, Faculty of Chemistry, Währinger Strasse 42, 1090 Vienna, Austria.
J Inorg Biochem. 2019 Oct;199:110707. doi: 10.1016/j.jinorgbio.2019.110707. Epub 2019 May 10.
N-Heterocyclic carbene-stabilized metal nanoparticles have drawn much attention over the last decade due their strong carbon metal bond. Although several reports show increased stability of such N-heterocyclic carbene-stabilized metal nanoparticles, only limited examples of water-soluble N-heterocyclic carbene stabilized metal nanoparticles are known to date. However, water dispersibility and stability in biologically relevant solvents would be a prerequisite for any biological applications. Drawing from the natural amino acid chiral pool, L-histidine was utilized for preparing chiral NHC ligands in the synthesis of water soluble NHC-stabilized gold nanoparticles. For this purpose, N-acetyl-L-histidine ethyl ester was converted into its imidazolium salt either using methyl iodide or 2-iodopropane as alkylation agent. Subsequent reaction of the imidazolium salt with [Au(SMe)Cl] yielded the corresponding organometallic gold chloride complex. Histidine-2-ylidene stabilized gold nanoparticles were first generated in organic solvents; the histidine derived capping ligand bore ethyl ester moieties which were saponified, affording water soluble pH-responsive NHC-stabilized gold nanoparticles. These gold nanoparticles show remarkable stability in aqueous solutions, with gold nanoparticle solutions remaining stable after months of storage.
N-杂环卡宾稳定的金属纳米粒子由于其强的碳-金属键在过去十年中引起了广泛关注。尽管有几篇报道表明这种 N-杂环卡宾稳定的金属纳米粒子的稳定性有所提高，但迄今为止，只有有限的水溶性 N-杂环卡宾稳定的金属纳米粒子的例子是已知的。然而，在生物相关溶剂中的水分散性和稳定性将是任何生物应用的前提条件。从天然氨基酸手性池中，L-组氨酸被用于制备手性 NHC 配体，以合成水溶性 NHC 稳定的金纳米粒子。为此，N-乙酰-L-组氨酸乙酯要么使用碘甲烷，要么使用 2-碘丙烷作为烷基化试剂，转化为其咪唑鎓盐。随后，咪唑鎓盐与[Au(SMe)Cl]反应生成相应的有机金属金氯化物配合物。首先在有机溶剂中生成组氨酸-2-亚基稳定的金纳米粒子；衍生自组氨酸的封端配体带有乙酯部分，这些部分可以皂化，得到水溶性 pH 响应性 NHC 稳定的金纳米粒子。这些金纳米粒子在水溶液中表现出显著的稳定性，金纳米粒子溶液在储存数月后仍保持稳定。
