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Topic 1: Carbon-Rich Systems and Molecular Electronics

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Pr Stéphane Rigaut / Dr. Lucie Norel

The aim of our current project is to develop novel fundamental issues for (i) conducting and (ii) switching molecular materials.
We previously demonstrated that ruthenium organometallic compounds are particularly suitable for this purpose as they promote exceptionally efficient intramolecular electronic delocalization over long length scale, and in which both the metals and the intervening bridging ligands provide a linear conduit for electron transfer up to at least 28 Å.
(J. Am. Chem. Soc. (2010) 130, 5638; Inorg. Chem. (2012) 51, 1902; Organometallics (2014) 33, 4672)

Consequently, electrical transport characteristics of linear ruthenium(II) bis(σ-arylacetylide) molecular wires probed with atomic force microscopy (CP-AFM) show a weak length dependence of the wire resistance, indicating a high degree of electronic coupling between the redox centers and a charge transport via direct tunneling or thermally activated hopping, depending on the length of the molecule.
(J. Phys. Chem. C (2011) 115, 19955)

Therefore, our current interest is also related to the building of switching devices based on these redox active ruthenium carbon-rich organometallics associated with specific units with special properties, and to the modulation of the properties of those news architectures with light or electron transfers. Further grafting of these systems on substrates will allow the building of experimental operating devices for molecular optoelectronics and spintronics.

Luminescence redox switch: the association between an ytterbium ion and a ruthenium carbon-rich complex enables the first switching of the near-IR Yb(III) luminescence by taking advantage of the redox commutation of the carbon-rich antenna.
(J. Am. Chem. Soc. (2011) 133, 6174; Organometallics (2014) 33, 4824)

Single Molecule Magnet (SMM) switching: association of a carbon-rich ruthenium complex with an anisotropic dysprosium ion leads also to a unique complex showing SMM behaviour with multiple relaxation processes. Long-distance perturbation of the 4f ion is achieved upon oxidation, resulting in an overall enhancement of the magnetic slow relaxation.
(Chem. Commun. (2012) 48, 3948; Inorg. Chem. (2014) 53, 2361)

Control of a photochromic unit: perturbation of a dithienylethene system with a ruthenium carbon-rich system is also a targeted mean to provide unique light- and electro-triggered multifunctional switches featuring multicolor electrochromism and electrocyclization at remarkably low voltage, thus addressable with a combination of electrochemical and optical stimuli.
(Org. Lett. (2012) 14, 4454; Inorg. Chem. (2014) 53, 8173)

Optical and redox control of conductivity: those systems appeared to be unique to achieve the first photo- and electromodulable molecular transport junctions. The addressable and stepwise control of molecular isomerization can be repeatedly and reversibly completed in nanograps with a judicious use of the orthogonal optical and electrochemical stimuli to reach the controllable switching of conductivity of the junction between two distinct states. The differences in electronic structure between the two isomers (open and closed states) are responsible for conductivity switching.
(Chem. Sci. (2012) 3, 3113; Nat. Commun. (2014) 5, 3023)