Gies Anthony P, Hercules David M, Gerdon Aren E, Cliffel David E
Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA.
J Am Chem Soc. 2007 Feb 7;129(5):1095-104. doi: 10.1021/ja0639057.
Electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS) and gel permeation chromatography (GPC) were used to study the synthesis of a series of tiopronin monolayer-protected gold nanoclusters (MPCs) and to monitor their postsynthesis peptide ligand place-exchange reactions. All mass spectra identified the presence of cyclic gold(I)-thiolates with a strong preference for tetrameric species. During the synthesis of pre-monolayer-protected nanoclusters (pre-MPCs), esterified gold(I)-thiolate tetramers were initially observed in minor abundance (with respect to disulfide bridged tiopronin species) before dramatically increasing in abundance and precipitating from solution. After conversion of pre-MPCs to MPCs, ESI-TOF mass spectra demonstrated an overall predominance of tetrameric species with conversion from ester-terminated end groups to carboxyl-terminated end groups. Further modifications were performed through postsynthesis ligand place-exchange reactions to validate the existence of the tetramers. This work suggests that monolayer protection is accomplished by cyclized gold(I)-thiolate tetramers on the gold core surface, and/or that gold(I)-thiolates are a basic building block within the nanoparticles.
采用电喷雾电离飞行时间质谱（ESI-TOF MS）和凝胶渗透色谱（GPC）研究了一系列硫普罗宁单层保护金纳米簇（MPCs）的合成，并监测其合成后肽配体的位置交换反应。所有质谱均鉴定出存在环状金（I）硫醇盐，且强烈倾向于四聚体物种。在合成单层前保护的纳米簇（pre-MPCs）过程中，最初观察到酯化的金（I）硫醇盐四聚体含量较低（相对于二硫键桥连的硫普罗宁物种），随后其含量急剧增加并从溶液中沉淀出来。将pre-MPCs转化为MPCs后，ESI-TOF质谱表明四聚体物种总体占优势，且末端基团从酯基转化为羧基。通过合成后配体位置交换反应进行了进一步修饰，以验证四聚体的存在。这项工作表明，单层保护是通过金核表面的环状金（I）硫醇盐四聚体实现的，和/或金（I）硫醇盐是纳米颗粒中的基本结构单元。
