Synthesis and Single-Molecule Conductances of Neutral and Cationic Indenofluorene-Extended Tetrathiafulvalenes

Synthesis and Single-Molecule Conductances of Neutral and Cationic Indenofluorene-Extended Tetrathiafulvalenes: Kondo Effect Molecules

Mansø, Mads (University of Copenhagen)
Koole, M.A. (TU Delft Solutions; Kavli institute of nanoscience Delft)
Mulder, M. (TU Delft ImPhys/Practicum support; Kavli institute of nanoscience Delft)
Olavarria Contreras, I.J. (TU Delft QN/van der Zant Lab; Kavli institute of nanoscience Delft)
Andersen, Cecilie Lindholm (University of Copenhagen)
Jevric, Martyn (University of Copenhagen)
Broman, Søren Lindbæk (University of Copenhagen)
Kadziola, Anders (University of Copenhagen)
Hammerich, Ole (University of Copenhagen)
van der Zant, H.S.J. (TU Delft QN/van der Zant Lab; Kavli institute of nanoscience Delft)
Nielsen, Mogens Brøndsted (University of Copenhagen)

2016-09-16

Development of molecules that can switch between redox states with paired and unpaired electrons is important for molecular electronics and spintronics. In this work, a selection of redox-active indenofluorene-extended tetrathiafulvalenes (IF-TTFs) with thioacetate end groups was prepared from a readily obtainable dibromo-functionalized IF-TTF building block using palladium-catalyzed cross-coupling reactions, such as the Suzuki reaction. The end groups served as electrode anchoring groups for single-molecule conductance studies, and the molecules were subjected to mechanically controlled break-junction measurements with gold contacts and to low-bias charge transport measurements in gated three-terminal electromigration junctions. The neutral molecules showed clear conductance signatures, and somewhat surprisingly, we found that a meta-meta anchoring configuration gave a higher conductance than a para-meta configuration. We explain this behavior by "through-space" coupling between the gold electrode and the phenyl on which the anchoring group is attached. Upon charging the molecule in a gated junction, we found reproducibly a Kondo effect (zero-bias conductance) attributed to a net spin. Ready generation of radical cations was supported by cyclic voltammetry measurements, revealing stepwise formation of radical cation and dication species in solution. The first oxidation event was accompanied by association reactions as the appearance of the first oxidation peak was strongly concentration dependent.

http://resolver.tudelft.nl/uuid:2c37578e-4d09-4296-939a-544a831d32db

https://doi.org/10.1021/acs.joc.6b01579

0022-3263

The Journal of Organic Chemistry, 81 (18), 8406-8414

Institutional Repository

journal article

© 2016 Mads Mansø, M.A. Koole, M. Mulder, I.J. Olavarria Contreras, Cecilie Lindholm Andersen, Martyn Jevric, Søren Lindbæk Broman, Anders Kadziola, Ole Hammerich, H.S.J. van der Zant, Mogens Brøndsted Nielsen