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

Manso, Mads; Koole, Max; Mulder, Maarten; Olavarria-Contreras, Ignacio J.; Andersen, Cecilie Lindholm; Jevric, Martyn; Broman, Soren Lindbaek; Kadziola, Anders; Hammerich, Ole; van der Zant, Herre S. J.; Nielsen, Mogens Brondsted

Abstract

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.

Más información

Título según WOS: ID WOS:000383639500030 Not found in local WOS DB
Título de la Revista: JOURNAL OF ORGANIC CHEMISTRY
Volumen: 81
Número: 18
Editorial: AMER CHEMICAL SOC
Fecha de publicación: 2016
Página de inicio: 8406
Página final: 8414
DOI:

10.1021/acs.joc.6b01579

Notas: ISI