Department of Chemistry, 2036 Main Mall, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada.
Department of Chemistry, University of North Carolina at Chapel Hill, Murray Hall 2202B, Chapel Hill, NC, 27599-3290, USA.
Nat Commun. 2018 Nov 21;9(1):4916. doi: 10.1038/s41467-018-07263-1.
Over 60 years have passed since Taube deduced an orbital-mediated electron transfer mechanism between distinct metal complexes. This concept of an orbital pathway has been thoroughly explored for donor-acceptor pairs bridged by covalently bonded chemical residues, but an analogous pathway has not yet been conclusively demonstrated for formally outer-sphere systems that lack an intervening bridge. In our present study, we experimentally resolve at an atomic level the orbital interactions necessary for electron transfer through an explicit intermolecular bond. This finding was achieved using a homologous series of surface-immobilized ruthenium catalysts that bear different terminal substituents poised for reaction with redox active species in solution. This arrangement enabled the discovery that intermolecular chalcogen⋯iodide interactions can mediate electron transfer only when these interactions bring the donor and acceptor orbitals into direct contact. This result offers the most direct observation to date of an intermolecular orbital pathway for electron transfer.
自 Taube 推导出不同金属配合物之间的轨道介导电子转移机制以来，已经过去了 60 多年。这个轨道途径的概念已经被彻底探索了用于通过共价键化学残基桥接的供体-受体对，但对于没有中间桥的形式上的外球系统，类似的途径尚未得到明确证明。在我们目前的研究中，我们在原子水平上实验解决了通过明确的分子间键进行电子转移所需的轨道相互作用。这一发现是通过使用一系列带有不同末端取代基的表面固定化钌催化剂实现的，这些取代基准备与溶液中的氧化还原活性物质反应。这种排列方式使我们能够发现只有当分子间的硫属元素···碘化物相互作用使供体和受体轨道直接接触时，才能介导电子转移。这一结果提供了迄今为止对电子转移的分子间轨道途径的最直接观察。
