title: Synthesis and Single-Molecule Conductance Study of Redox-Active Ruthenium Complexes with Pyridyl and Dihydrobenzo[b]thiophene Anchoring Groups.
abstract: The ancillary ligands 4'-(4-pyridyl)-2,2':6',2''-terpyridine and 4'-(2,3-dihydrobenzo[b]thiophene)-2,2'-6',2"-terpyridine were used to synthesize two series of mono- and dinuclear ruthenium complexes differing in their lengths and anchoring groups. The electrochemical and single-molecular conductance properties of these two series of ruthenium complexes were studied experimentally by means of cyclic voltammetry and the scanning tunneling microscopy-break junction technique (STM-BJ) and theoretically by means of density functional theory (DFT). Cyclic voltammetry data showed clear redox peaks corresponding to both the metal- and ligand-related redox reactions. Single-molecular conductance demonstrated an exponential decay of the molecular conductance with the increase in molecular length for both the series of ruthenium complexes, with decay constants of βPY =2.07±0.1 nm(-1) and βBT =2.16±0.1 nm(-1) , respectively. The contact resistance of complexes with 2,3-dihydrobenzo[b]thiophene (BT) anchoring groups is found to be smaller than the contact resistance of ruthenium complexes with pyridine (PY) anchors. DFT calculations support the experimental results and provided additional information on the electronic structure and charge transport properties in those metal|ruthenium complex|metal junctions.
authors.affiliation: Department of Applied Chemistry, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, 112-8551, Tokyo, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ozawa
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freistrasse 3, 3012, Bern, Switzerland.
authors.forename: Masoud
authors.initials: M
authors.lastname: Baghernejad
authors.affiliation: Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK. o.al-owaedi@lancaster.ac.uk.|Department of Laser Physics, Women Faculty of Science, Babylon University, Hillah, Iraq. o.al-owaedi@lancaster.ac.uk.
authors.forename: Oday A
authors.initials: OA
authors.lastname: Al-Owaedi
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freistrasse 3, 3012, Bern, Switzerland. kaliginedi@dcb.unibe.ch.
authors.forename: Veerabhadrarao
authors.identifier: http://orcid.org/0000-0002-4361-741X
authors.initials: V
authors.lastname: Kaliginedi
authors.affiliation: Department of Applied Chemistry, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, 112-8551, Tokyo, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Nagashima
authors.affiliation: Departamento de Física, Universidad de Oviedo and CINN, 33007, Oviedo, Spain.
authors.forename: Jaime
authors.initials: J
authors.lastname: Ferrer
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freistrasse 3, 3012, Bern, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wandlowski
authors.affiliation: Departamento de Física, Universidad de Oviedo and CINN, 33007, Oviedo, Spain.
authors.forename: Víctor M
authors.initials: VM
authors.lastname: García-Suárez
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freistrasse 3, 3012, Bern, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Broekmann
authors.affiliation: Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Lambert
authors.affiliation: Department of Applied Chemistry, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, 112-8551, Tokyo, Japan. mhaga@kc.chuo-u.ac.jp.
authors.forename: Masa-Aki
authors.initials: MA
authors.lastname: Haga
keywords: STM-break junction; anchoring groups; electrochemistry; molecular wires; ruthenium