Commutation par voies redox et optique de la luminescence de complexes d'ions lanthanides et synthèse de nouveaux fils moléculaires organométalliques

Ce travail est consacré à la synthèse, à la caractérisation et aux études photophysiques de nouveaux commutateurs moléculaires luminescents et de fils moléculaires thermoélectriques. Après une étude bibliographique concernant la modulation de la luminescence dans le proche infrarouge avec des ions lanthanide, la deuxième partie de ce manuscrit décrit la synthèse d'un complexe macrocyclique de lanthanide portant deux unités photochromiques. Les complexes sont entièrement caractérisés et leurs études photophysiques sont démontrées. Ils présentent une stabilité optique et chimique améliorée et montrent une émission photo-modulable dans les domaines du visible et du proche infrarouge. La troisième partie de ce travail vise à obtenir des commutateurs multifonctionnels. La synthèse de nouveaux complexes de lanthanides portant trois unités photochromiques et une unité redox-active à base de ruthénium est décrite. La caractérisation complète des complexes est également démontrée. Les études photophysiques révèlent la possibilité de commuter la luminescence dans le proche infrarouge de l'ion Yb(III) à la fois optiquement et électrochimiquement. La quatrième partie de ce manuscrit décrit la synthèse et la caractérisation de complexes robustes à base de lanthanide pour des applications en technologies anti-contrefaçon. Il est montré que la commutation de l’émission de l’europium(III) ou de l’ytterbium(III) respectivement dans les domaines du visible et du proche infrarouge se produit en solution et dans les matrices polymère solides. La dernière partie décrit la synthèse et la caractérisation de complexes d’ions de transition prometteurs devant présenter des propriétés d'interférences quantiques.This work is devoted to the synthesis, characterization, and photophysical studies of novel luminescent molecular switches and thermoelectric molecular wires. After a bibliographic survey concerning the modulation of near-infrared (NIR) luminescence with lanthanide ions, the synthesis of macrocyclic lanthanide-based systems bearing two photochromic units is described. The key complexes are fully characterized and their photophysical studies are demonstrated. These complexes display enhanced optical and chemical stability and show photo-tunable emission in the visible and the NIR regions. The third part of this work aims at obtaining multifunctional lanthanide-based switches. The synthesis of new lanthanide complexes bearing three photochromic units and a redox-active ruthenium-based moiety is described. Full characterization of the complexes are further demonstrated. The photophysical studies reveal the possibility to switch the NIR luminescence of the ytterbium(III) ion both optically and electrochemically. The fourth part of this manuscript describes the synthesis and characterization of robust lanthanide-based complexes toward anticounterfeiting technologies. It is shown that switching europium(III) and ytterbium(III) luminescences in the visible and NIR regions could occur in both solution and solid polymer matrices. The last part of this work concerns molecular wires for thermoelectric applications. It describes the synthesis and characterization of promising transition metal complexes that should display quantum interferences in order to reach thermoelectric properties in molecular devices

Remote Control of Near Infrared Emission with Lanthanide Complexes

International audienceMolecular luminescent switches form a unique and fascinating class of compounds whose luminescence response can be toggled with chemical or physical stimuli. Switchable near-infrared (NIR) emitters are of major interest since they are compatible with in vivo imaging and have potential for advanced materials such as security tags. Of particular interest are the NIR emitting lanthanides, which feature narrow, sharp and intense emission lines originating from the f-f Laporte forbidden transitions. Although, these "fingerprints" are in general rather insensitive to surrounding media, they can be manipulated thanks to a proper engineering of the complex first or second coordination spheres. The resulting switching systems may thus find usefulness in various application fields. In this review, we selected representative examples of switchable lanthanide NIR emitters based on the most relevant stimuli, such as chemical, environmental, thermal, electrochemical and photochemical inputs

Efficient Photomodulation of Visible Eu(III) and Invisible Yb(III) Luminescences using DTE Photochromic Ligands for Optical Encryption

International audienceThis work describes a class of complex combining three dithienylethene units and a lanthanide ion used as an optical system displaying a double encryption method i) a colorful code, drawn and erased under UV and visible irradiations respectively, due to coloration and discoloration of the photochromic entities, and ii) a concomitant gradual disappearance and progressive restoration of the associated lanthanide ion luminescence triggered with the same stimuli. The innovation of the system stems from the emission color tunability, i.e., with either a lanthanide ion emitting only in the visible range (Eu3+) or with another lanthanide ion emitting only in the near infrared (NIR) range (Yb3+), therefore observable, or not, to the naked eye. This system is the very first one to achieve efficient repeatable modulation of pure NIR luminescence on photochemical command. Furthermore, it is proven to be highly efficient when embedded in a PDMS polymer opening real opportunities for practical applications as anti-counterfeiting

Efficient luminescence control in dithienylethene functionalized cyclen macrocyclic lanthanide complexes

International audienceWe report the synthesis of an original ligand scaffold and the corresponding yttrium(III), europium(III) and ytterbium(III) complexes. All three compounds show reversible photochromism with high photo-conversions. Photoluminescence experiments demonstrate that this design is adapted for both europium and ytterbium emission switching. The OFF/ON luminescence ratio are excellent in the case of europium (4 to 8 %) and still quite good in the case of ytterbium (around 13 %)Nous présentons la synthèse d'un ligand original et ses complexes d'yttrium (III), d'europium (III) et d'ytterbium (III). Les trois composés présentent un photochromisme réversible avec des photo-conversions élevées. Les expériences de photoluminescence démontrent que le conception est adapté tant pour la commutation de l’émission de l'europium et de l'ytterbium. Le rapport de luminescence OFF/ON est excellent dans le cas de l'europium (4 à 8%) et encore assez bon dans le cas de l'ytterbium (environ 13%

Efficient Luminescence Control in a Dithienylethene Functionalized Cyclen Macrocyclic Complex

We report the synthesis of an original ligand scaffold based on a dimethyl-cyclen platform Medo2pa with two dithienylethene units attached to each picolinate arms and the corresponding yttrium(III), europium(III) and ytterbium(III) complexes. All three complexes show reversible photochromism with high photo-conversions. Photoluminescence experiments demonstrate that this design is versatile and adapted for both europium and ytterbium emission switching when measured in frozen organic glasses at 77 K.<br /

Self-Assembled Monolayers of Redox-Active 4d-4f Heterobimetallic Complexes

International audienceIn this work, we report the preparation of functional interfaces incorporating heterobimetallic systems consisting in the association of an electroactive carbon-rich ruthenium organometallic unit and a luminescent lanthanide ion (Ln = Eu and Yb). The organometallic systems are functionalized with a terminal hexylthiol group for subsequent gold surface modification. The formation of self-assembled monolayers (SAMs) with these complex molecular architectures are thoroughly demonstrated by employing a combination of different techniques, including infrared reflection absorption spectroscopy, ellipsometry, contact angle, and cyclic voltammetry measurements. The immobilized heterobimetallic systems show fast electron-transfer kinetics and, hence, are capable of fast electrochemical response. In addition, the characteristic electrochemical signals of the SAMs were found to be sensitive to the presence of lanthanide centers at the bipyridyl terminal units. A positive shift of the potential of the redox signal is readily observed for lanthanide complexes compared to the bare organometallic ligand. This effect is equally observed for preformed complexes and on-surface complexation. Thus, an efficient ligating recruitment of europium and ytterbium cations at gold-modified electrodes is demonstrated, allowing for an easy electrochemical detection of the lanthanide ions along with an alternative preparative method of SAMs incorporating lanthanide cations compared to the immobilization of the preformed complex

Electronic transport through single-molecule oligophenyl-diethynyl junctions with direct gold-carbon bonds formed at low temperature

International audienceWe report on the first systematic transport study of alkynyl-ended oligophenyl-diethynyl (OPA) single-molecule junctions with direct Au-C anchoring scheme at low temperature using the mechanically controlled break junction technique. Through quantitative statistical analysis of opening traces, conductance histograms and density functional theory studies, we identified different types of junctions, classified by their conductance and stretching behavior, for OPA molecules between Au electrodes with two to four phenyl rings. We performed inelastic electron tunneling spectroscopy and observed the excitation of Au-C vibrational modes confirming the existence of Au-C bonds at low temperature and compared the stability of molecule junctions upon mechanical stretching. Our findings reveal the huge potential for future functional molecule transport studies at low temperature using alkynyl endgroups

Dual Light and Redox Control of NIR Luminescence with Complementary Photochromic and Organometallic Antennae

International audienceWith the help of a judicious association between dithienylethene (DTE) units, an ytterbium ion, and a ruthenium carbon-rich complex, we describe (i) the efficient (on/off) switching of pure NIR luminescence with a photochromic unit absorbing in the UV range and (ii) the association of electrochemical and photochemical control of this NIR emission in a single system with nondestructive readout

Hysteresis Photomodulation via Single-Crystal-to-Single-Crystal Isomerization of a Photochromic Chain of Dysprosium Single-Molecule Magnets

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Dual-gated single-molecule field-effect transistors beyond Moore's law

International audienceAs conventional silicon-based transistors are fast approaching the physical limit, it is essential to seek alternative candidates, which should be compatible with or even replace microelectronics in the future. Here, we report a robust solid-state single-molecule field-effect transistor architecture using graphene source/drain electrodes and a metal back-gate electrode. The transistor is constructed by a single dinuclear ruthenium-diarylethene (Ru-DAE) complex, acting as the conducting channel, connecting covalently with nanogapped graphene electrodes, providing field-effect behaviors with a maximum on/off ratio exceeding three orders of magnitude. Use of ultrathin high-k metal oxides as the dielectric layers is key in successfully achieving such a high performance. Additionally, Ru-DAE preserves its intrinsic photoisomerisation property, which enables a reversible photoswitching function. Both experimental and theoretical results demonstrate these distinct dual-gated behaviors consistently at the single-molecule level, which helps to develop the different technology for creation of practical ultraminiaturised functional electrical circuits beyond Moore's law