Resolving orbital pathways for intermolecular electron transfer

Abstract

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.

π covalency in the halogen bond

“…The Dye-X compounds were adsorbed to a solid mesoporous TiO 2 thin film with a common molecular orientation ( Supplementary Fig. 2), thereby facilitating the study of halogen bonding interactions with a solution-phase species while suppressing selfinteraction between Dye-X molecules 45 . For our XAS experiments, the surface-anchored Dye-X compounds were oxidized with an acetonitrile solution of nitrosonium tetrafluoroborate (NOBF 4 ) then immersed in an acetonitrile solution of tetrabutylammonium chloride (NBu 4 Cl) and frozen at 77 K 37 .…”

Mediated Inner‐Sphere Electron Transfer Induces Homogeneous Reduction of CO2 via Through‐Space Electronic Conjugation**

“…[7] Indeed, the existence of an inner-sphere electron transfer pathway involving a non-covalently linked RM and a photoredox catalyst was only recently demonstrated experimentally. [19] Other examples of mediated electron transfer in homogeneous catalysis are proposed to proceed largely through outer-sphere pathways. [20] In conclusion, we report what is, to the best of our knowledge, the only example of an inner-sphere electron transfer RM in a co-electrocatalytic system.…”

Activation of H2O tailored by interfacial electronic states at nanoscale interface for enhanced electrocatalytic hydrogen evolution

“…The concept of SWS dominated surface transient states to tune the concerted electron and proton enables optimization of the entire electrochemical interface as opposed to only catalysts structure to improve activity for the hydrogen evolution reaction, which is critical to designing more active electrochemical interfaces for energy storage and conversion reactions. This unique reaction mechanism may not only provide an important guidance for the design/selection of catalysts/electrolytes for the nanomaterial-catalyzed reactions in an aqueous environment, including CO 2 /CO reduction [85][86][87][88][89] , nitrogen reduction 17,90,91 , and other electrocatalytic reduction reactions 92 , but also shed new light on the nanoscale-range electron and proton transfer through the water-line 'bridge' in the biological macromolecule system [93][94][95] , which could follow the out sphere electron transfer model of Marcus theory with connected SWs as a bridge [96][97][98] . Author Contributions PYW and JFZ performed the main experiments and equally contribute to this research.…”