Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.
ACS Nano. 2013 Jul 23;7(7):6138-45. doi: 10.1021/nn401971g. Epub 2013 Jun 12.
We report a disproportionation mechanism identified in the transformation of rod-like biicosahedral Au38(SCH2CH2Ph)24 to tetrahedral Au36(TBBT)24 nanoclusters. Time-dependent mass spectrometry and optical spectroscopy analyses unambiguously map out the detailed size-conversion pathway. The ligand exchange of Au38(SCH2CH2Ph)24 with bulkier 4-tert-butylbenzenethiol (TBBT) until a certain extent starts to trigger structural distortion of the initial biicosahedral Au38(SCH2CH2Ph)24 structure, leading to the release of two Au atoms and eventually the Au36(TBBT)24 nanocluster with a tetrahedral structure, in which process the number of ligands is interestingly preserved. The other product of the disproportionation process, i.e., Au40(TBBT)m+2(SCH2CH2Ph)24-m, was concurrently observed as an intermediate, which was the result of addition of two Au atoms and two TBBT ligands to Au38(TBBT)m(SCH2CH2Ph)24-m. The reaction kinetics on the Au38(SCH2CH2Ph)24 to Au36(TBBT)24 conversion process was also performed, and the activation energies of the structural distortion and disproportionation steps were estimated to be 76 and 94 kJ/mol, respectively. The optical absorption features of Au36(TBBT)24 are interpreted on the basis of density functional theory simulations.
我们报告了在棒状双二十面体 Au38(SCH2CH2Ph)24 向四面体 Au36(TBBT)24 纳米团簇的转变中发现的歧化机制。时间分辨质谱和光谱分析明确描绘了详细的尺寸转换途径。Au38(SCH2CH2Ph)24 与较大体积的 4-叔丁基苯硫醇（TBBT）的配体交换，直到一定程度开始引发初始双二十面体 Au38(SCH2CH2Ph)24 结构的结构变形，导致两个 Au 原子的释放，并最终形成具有四面体结构的 Au36(TBBT)24 纳米团簇，在此过程中配体的数量保持不变。歧化过程的另一个产物，即 Au40(TBBT)m+2(SCH2CH2Ph)24-m，同时作为中间体被观察到，这是由于 Au38(TBBT)m(SCH2CH2Ph)24-m 中加入了两个 Au 原子和两个 TBBT 配体的结果。还对 Au38(SCH2CH2Ph)24 到 Au36(TBBT)24 转化过程的反应动力学进行了研究，结构变形和歧化步骤的活化能分别估计为 76 和 94 kJ/mol。基于密度泛函理论模拟，解释了 Au36(TBBT)24 的光学吸收特征。
