Lucie Norel

Orthogonally modulated molecular transport junctions for resettable electronic logic gates

Individual molecules have been demonstrated to exhibit promising applications as functional components in the fabrication of computing nanocircuits. Based on their advantage in chemical tailorability, many molecular devices with advanced electronic functions have been developed, which can be further modulated by the introduction of external stimuli. Here, orthogonally modulated molecular transport junctions are achieved via chemically fabricated nanogaps functionalized with dithienylethene units bearing organometallic ruthenium fragments. The addressable and stepwise control of molecular isomerization can be repeatedly and reversibly completed with a judicious use of the orthogonal optical and electrochemical stimuli to reach the controllable switching of conductivity between two distinct states. These photo-/electro-cooperative nanodevices can be applied as resettable electronic logic gates for Boolean computing, such as a two-input OR and a three-input AND-OR. The proof-of-concept of such logic gates demonstrates the possibility to develop multifunctional molecular devices by rational chemical design.

Metallahelicenes: Easily Accessible Helicene Derivatives with Large and Tunable Chiroptical Properties†

Enantiopure metallahelicenes have been prepared by cyclometalation of 2-pyridyl-substituted benzophenanthrenes followed by resolution using chiral HPLC. They are red phosphors at room temperature and their chiroptical properties can be modulated by oxidation of the metal center to the oxidation state IV.

d―f Heterobimetallic Association between Ytterbium and Ruthenium Carbon-Rich Complexes: Redox Commutation of Near-IR Luminescence

We describe how 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.

Multifunctional and reactive enantiopure organometallic helicenes: tuning chiroptical properties by structural variations of mono- and bis(platinahelicene)s.

Acetylacetonato-platina[6]- and -platina[7]helicenes have been prepared from 2-pyridyl-substituted benzophenanthrene ligands by following a two-step cycloplatination reaction. The photophysical properties (UV-visible absorption and emission behavior) and chiroptical properties (circular dichroism and molar rotation) of the resolved enantiomers have been measured. These metallahelicenes constitute a novel family of easily accessible helicene derivatives that exhibit large and tuneable chiroptical properties that can be rationalized theoretically and compared to the parent [6]- and [7]carbohelicenes. Furthermore, they are red phosphors at room temperature and their large chiroptical properties can be modulated by oxidation of the metal center to Pt(IV). Hetero- and homochiral diastereomeric bis(metallahelicene)s that possess a rare Pt(III)-Pt(III) scaffold bridged by benzoato ligands have also been prepared. It is shown that the heterochiral (P,M)-bis(Pt(III)-[6]helicene) 9a(1) can isomerize into the homochiral (P,P)- and (M,M)-bis(Pt(III)-[6]helicene) 9a(2). Spectral assignments and an analysis of the optical rotation of these systems were made with the help of time-dependent density functional theory. The calculations highlight the contributions of the metal centers to the chiroptical properties. For 9a(1) and 9a(2), σ-π conjugation between the helicenes and the Pt-Pt moiety may contribute strongly to the optical rotation and electronic circular dichroism.

Controlling the Stepwise Closing of Identical DTE Photochromic Units with Electrochemical and Optical Stimuli

The full or stepwise controlled closing of identical photochromic dithienylethene units in the same molecule was addressed with a combination of electrochemical and optical stimuli in a trimetallic carbon-rich ruthenium complex.

A carbon-rich ruthenium decorated dysprosium single molecule magnet.

The association of a carbon-rich ruthenium complex with an anisotropic dysprosium ion leads to a unique complex showing SMM behaviour with multiple relaxation processes.

Redox modulation of magnetic slow relaxation in a 4f-based single-molecule magnet with a 4d carbon-rich ligand.

A ruthenium carbon-rich-based ligand that brings redox reversibility to a dysprosium-based single-molecule magnet is reported. Long-distance perturbation of the 4f ion is achieved upon oxidation, resulting in an overall enhancement of the magnetic slow relaxation.

Spin transition and exchange interaction: Janus visions of supramolecular spin coupling between face-to-face verdazyl radicals.

In both cases, they can exhibit versatile interactionsbetween their unpaired electrons spins. These interactionsare mediated through intramolecular covalent or coordina-tion bonds or through intermolecular interactions. Thisduality is well exemplified in one of the first organicferromagnetsbuiltfromadamantane-basedferromagneticallycoupled diradicals. It displays intramolecular exchange cou-pling while the packing favors weak intermolecular ferro-magnetic interactions, thus leading to a long-range magneticorder below 1.48 K.

Diarylethene-Containing Carbon-Rich Ruthenium Organometallics: Tuning of Electrochromism

The association of a dithienylethene (DTE) system with ruthenium carbon-rich systems allows reaching sophisticated and efficient light- and electro-triggered multifunctional switches R-[Ru]-C≡C-DTE-C≡C-[Ru]-R, featuring multicolor electrochromism and electrochemical cyclization at remarkably low voltage. The spin density on the DTE ligand and the energetic stabilization of the system upon oxidation could be manipulated to influence the closing event, owing to the noninnocent behavior of carbon-rich ligands in the redox processes. A combination of spectroscopic (UV-vis-NIR-IR and EPR) and electrochemical studies, with the help of quantum chemical calculations, demonstrates that one can control and get a deeper understanding of the electrochemical ring closure with a slight modification of ligands remote from the DTE unit. This electrochemical cyclization was established to occur in the second oxidized state (EEC mechanism), and the kinetic rate constant in solution was measured. Importantly, these complexes provide an unprecedented experimental means to directly probe the remarkable efficiency of electronic (spin) delocalization between two trans carbon-rich ligands through a metal atom, in full agreement with the theoretical predictions. In addition, when no cyclization occurs upon oxidation, we could achieve a redox-triggered magnetic switch.

Improved slow magnetic relaxation in optically pure helicene-based DyIII single molecule magnets

Racemic and optically pure [Dy(hfac)3(L)] complexes with L = 3-(2-pyridyl)-4-aza[6]-helicene have been synthesized and characterized. Both the racemic and enantiopure forms behave as single molecule magnets in their crystalline phase, while electronic circular dichroism activity is evidenced. Ab initio calculations on isolated complexes followed by the determination of intermolecular dipolar couplings allowed the rationalization of the different low-temperature magnetic behaviours. The enantiopure SMM differs from the racemic one by the presence of a hysteresis loop in the former system.