Manipulation of organic polyradicals in a single-molecule transistor

Abstract

Inspired by cotunneling spectroscopy of spin-states in a single OPE5-based molecule, we investigate the prospects for electric control of magnetism in purely organic molecules contacted in a three-terminal geometry. Using the gate electrode, the molecule is reversibly switched between three different redox states, with magnetic spectra revealing both ferromagnetic and antiferromagnetic exchange couplings on the molecule. These observations are shown to be captured by an effective low-energy Heisenberg model, which we substantiate microscopically by a simple valence bond description of the molecule. These preliminary findings suggest an interesting route towards functionalized all-organic molecular magnetism.

Synthesis of Covalently Linked Oligo(phenyleneethynylene) Wires Incorporating Dithiafulvene Units: Redox‐Active “H‐Cruciforms”

“…Importantly, irreversible oxidations only present a problem in solution where radical cations can react in an intermolecular manner and not necessarily in a molecular electronics junction. Thus, successful conductance measurements on several charge states of an OPE5‐TTF cruciform motif (molecule 1 ) were previously achieved, where unpaired electrons provided Kondo effect behavior. Single‐molecule conductance studies on the new series of H‐cruciform molecules will be the focus of future work.…”

“…π‐Conjugated molecules such as oligo(phenyleneethynylene)s (OPEs) have been widely examined as molecular wires for electron transport in molecular electronics Functionalization of the OPE by donor and/or acceptor groups offers a way to tune its electronic properties, providing, for example, molecules exhibiting rectification or zero‐bias conductance behavior upon charging (Kondo effect, resulting from unpaired spins) in molecular junctions. The electron‐donor tetrathiafulvalene (TTF; Figure ) has also played a significant role in the field of molecular electronics since the proposal by Aviram and Ratner of the possibility for rectification in donor–acceptor systems with an aliphatic bridge between donor (TTF) and acceptor (tetracyanoquinodimethane) units .…”

“…The electron‐donor tetrathiafulvalene (TTF; Figure ) has also played a significant role in the field of molecular electronics since the proposal by Aviram and Ratner of the possibility for rectification in donor–acceptor systems with an aliphatic bridge between donor (TTF) and acceptor (tetracyanoquinodimethane) units . Inspired by the molecular‐wire properties of OPEs and redox‐active properties of TTF, we have developed a class of cruciform‐like molecules, such as 1 (Figure ), incorporating an extended TTF unit orthogonal to an OPE wire with thioacetate electrode anchoring groups, and we have shown how this unit influenced molecular conductance in self‐assembled monolayers, break‐junctions, and gated three‐terminal junctions . For OPE5 ( 1 ) interesting Kondo effect behavior was observed for three different charge/spin states.…”

Forty years of molecular electronics: Non‐equilibrium heat and charge transport at the nanoscale

“…However, in order to distinguish spin species, time‐reversal symmetry must be broken (e.g., via a magnetic field or chemical structure). The role of molecular chirality on spin transport has been investigated , as has excitation by polarized light (), molecules with asymmetric twists (e.g., in DNA ), and transport through molecular radicals with an applied magnetic field (). The realization that, for elements beyond the first row of the periodic chart, the Rashba Hamiltonian suggests that the spin orbit mixing will be even greater than might otherwise be expected, coupled with the availability of specially designed molecules with chiral properties and spin localization, promises to make this a vibrant part of the molecular electronics field going forward.…”

Interference enhanced thermoelectricity in quinoid type structures

“…[13][14][15][16][17] Cruciform oligo(phenylene ethynylene)s (OPEs) with a conjugated and extended tetrathiafulvalene (TTF) donor moiety have recently been synthesised 18,19 and shown to be redox active as well as having interesting spin properties in the Coulomb blockade regime. 20 Cruciform type molecules have a) Electronic mail: strange@chem.ku.dk also been synthesised with substituent side groups, such as TTF, dithiofulvalene (DTF), and atomic oxygen, forming crossconjugated OPEs. Such structures can be referred to as quinoid, since the central core corresponds to a quinone, with the substituents replacing the oxygen atoms, see Figures 1(a) and 5.…”