Single-Molecule Investigation of Initiation Dynamics of an Organometallic Catalyst
Single-Molecule Investigation of Initiation Dynamics of an Organometallic Catalyst
复制标题
DOI：
10.1021/jacs.6b00357
复制
发表时间：
2016-03-23
影响因子：
15
通讯作者：
Goldsmith, Randall H.
中科院分区：
文献类型：
--
作者：
Ng, James D.;Upadhyay, Sunil P.;Goldsmith, Randall H.
分子催化剂的作用包括多个微观动力学步骤，其性质对于确定催化剂活性和选择性至关重要。单分子显微镜可以直接检查这些步骤，包括阐明分子间的变异性。这种分子多样性对于表面负载的分子催化剂的行为尤其重要。我们首次对可操作的钯交叉偶联催化剂在本体和单分子水平（包括在周转条件下）的引发动力学进行了联合研究。碱引发动力学揭示了高度异质的行为，表明不同的催化剂群体。出乎意料的是，随着碱浓度的增加，这种分布变得更加不均匀。我们用两步饱和机制模拟这种行为，并确定必须存在化学变异性才能产生观察到的行为的特定微观步骤。至关重要的是，我们揭示了表面的结构多样性如何转化为催化剂行为的异质性，同时展示了单分子实验如何有助于理解分子催化剂。
The action of molecular catalysts comprises multiple microscopic kinetic steps whose nature is of central importance in determining catalyst activity and selectivity. Single-molecule microscopy enables the direct examination of these steps, including elucidation of molecule-to-molecule variability. Such molecular diversity is particularly important for the behavior of molecular catalysts supported at surfaces. We present the first combined investigation of the initiation dynamics of an operational palladium cross-coupling catalyst at the bulk and single-molecule levels, including under turnover conditions. Base-initiated kinetics reveal highly heterogeneous behavior indicative of diverse catalyst population. Unexpectedly, this distribution becomes more heterogeneous at increasing base concentration. We model this behavior with a two-step saturation mechanism and identify specific microscopic steps where chemical variability must exist in order to yield observed behavior. Critically, we reveal how structural diversity at a surface translates into heterogeneity in catalyst behavior, while demonstrating how single-molecule experiments can contribute to understanding of molecular catalysts.