The idea to use a single organic molecule with tailored electronic structure as an electronic device was first proposed by Aviram and Ratner in 1974. Although the challenge of integrating a single molecule into a macroscopic electric circuit seemed insurmountable at the time, recent developments in nanotechnology allow us to explore this idea experimentally.
The original Aviram-Ratner rectifier molecule consisted of a very strong electron donor (tetrathiafulvalene, TTF) and a very strong electron acceptor (tetracyanoquinodimethane, TCNQ) covalently linked in one molecule. Such a structure should have a very low HOMO-LUMO gap which was considered essential for effective current rectification (that is, asymmetric current flow through the molecule). However, synthesis of such molecules has been an elusive goal for a long time, since strong donor-acceptor interaction and electron transfer between the two parts of the molecule complicated the coupling reaction and subsequent purification. We have pioneered the synthesis of organic molecules with HOMO-LUMO gap below 0.3 eV, including the long-sought TTF-TCNQ dyad.
Using Langmuir-Blodgett deposition technique of the synthesized donor-acceptor amphiphiles, we have prepared molecular monolayers on a surface of gold, and, employing mercury drop as a second electrode, have demonstrated diode-like properties (current rectification) in such molecules.
We continue exploring the field by synthesis of more robust rectifying molecules, molecules with switching capabilities, embedding "sticky" groups (such as thiols) for selective self-assembly on electrodes, making molecules with controlled dipole moment for fundamental studies of electron injection at the molecule/electrode interface, etc (see below). In collaboration with other groups, we use scanning probe techniques to interrogate the electrical and electronmechanic properties of single molecules.
New Stable Donor-Acceptor Dyads for Molecular Electronics,
M. Kondratenko, A. Moiseev, D.F. Perepichka*, J. Mater. Chem. 2011, 21, 1470-1478.
Self-Assembled Monolayers of Strong Electron Acceptors: Polynitrofluorenes on Gold,
D.F.Perepichka, M.Kondratenko, M.R.Bryce , Langmuir 2005 , 21, 8824-8831.
The first studies of a tetrathiafulvalene -σ- acceptor molecular rectifier,
G. Ho, J. Heath, M. Kondratenko, D. F. Perepichka, K. Arseneault, M. Pezolet, M. R. Bryce, Chem. Eur . J. 2005, 11 , 2914-2922. ( VIP and cover article )
Molecules With Exceptionally Low HOMO-LUMO Gap,
D.F.Perepichka, M.R.Bryce, Angew. Chem. Int. Ed. 2005 , 44 , 5370-5373.
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