title: Complex formation dynamics in a single-molecule electronic device.
abstract: Single-molecule electronic devices offer unique opportunities to investigate the properties of individual molecules that are not accessible in conventional ensemble experiments. However, these investigations remain challenging because they require (i) highly precise device fabrication to incorporate single molecules and (ii) sufficient time resolution to be able to make fast molecular dynamic measurements. We demonstrate a graphene-molecule single-molecule junction that is capable of probing the thermodynamic and kinetic parameters of a host-guest complex. By covalently integrating a conjugated molecular wire with a pendent crown ether into graphene point contacts, we can transduce the physical [2]pseudorotaxane (de)formation processes between the electron-rich crown ether and a dicationic guest into real-time electrical signals. The conductance of the single-molecule junction reveals two-level fluctuations that are highly dependent on temperature and solvent environments, affording a nondestructive means of quantitatively determining the binding and rate constants, as well as the activation energies, for host-guest complexes. The thermodynamic processes reveal the host-guest binding to be enthalpy-driven and are consistent with conventional1H nuclear magnetic resonance titration experiments. This electronic device opens up a new route to developing single-molecule dynamics investigations with microsecond resolution for a broad range of chemical and biochemical applications.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Wen
authors.affiliation: Institute for Molecular Design and Synthesis, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Wengang
authors.initials: W
authors.lastname: Li
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
authors.forename: Jiewei
authors.initials: J
authors.lastname: Chen
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
authors.forename: Gen
authors.initials: G
authors.lastname: He
authors.affiliation: Scientific Research Academy, Jiangsu University, Zhenjiang 212013, China.
authors.forename: Longhua
authors.initials: L
authors.lastname: Li
authors.affiliation: Institute for Molecular Design and Synthesis, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Olson
authors.affiliation: Institute for Molecular Design and Synthesis, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China.; Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
authors.forename: Andrew C-H
authors.initials: AC
authors.lastname: Sue
authors.affiliation: Institute for Molecular Design and Synthesis, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China.; Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.; Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Guo
keywords: Molecular electronics; host-guest chemistry; single-molecule detection; single-molecule device