Stable Near-Infrared Anionic Polymethine Dyes: Structure, Photophysical, and Redox Properties

International audienceThe concept of cyanine has been successfully extended to anionic heptamethine dye featuring tricyanofuran (TCF) moieties in terms of structure, reactivity and photophysical properties. Importantly, absorption and emission are red-shifted compared to its classical cationic analog without any cost in term of thermal stability. In addition to its "cyanine" behavior, this molecule exhibits further redox properties: oxidation and reduction led to the reversible formation of radical species whose absorption is in marked contrast with that of cyanines

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

International audienceThe 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 cou d achieve a redox-triggered magnetic switch

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 “Cyanine−Cyanine” Salt Exhibiting Photovoltaic Properties

International audienceAssociation between cationic and anionic heptamethine dyes led to the formation of a new organic salt (3) displaying exceptional light harvesting properties in the NIR spectral range and having amphoteric redox character. Preliminary results of molecular bulk heterojunction solar cells based on the title compound 3 and [60]PCBM as the only active layer reveal this new dye as a promising light harvesting material for photovoltaics

Fully Delocalized (Ethynyl)(vinyl)phenylene Bridged Triruthenium Complexes in up to Five Different Oxidation States

Triruthenium [(dppe)₂Ru­{−CC–1,4-C₆H₂–2,5-R₂–CHCH–RuCl­(CO)­(P^<i>i</i>Pr₃)₂}₂]^<i>n</i>+ (<b>4a</b>, R = H; <b>4b</b>, R = OMe) containing unsymmetrical (ethynyl)­(vinyl)­phenylene bridging ligands and displaying five well-separated redox states (<i>n</i> = 0–4) are compared to their bis­(alkynyl)ruthenium precursors (dppe)₂Ru­{−CC–1,4-C₆H₂–2,5-R₂–CCR′} (<b>2a</b>,<b>b</b>: R′ = TMS; <b>3a</b>,<b>b</b>: R′ = H) and their symmetrically substituted bimetallic congeners, complexes {Cl­(dppe)₂Ru}₂{μ-CC–1,4-C₆H₂–2,5-R₂–CC} (<b>A</b>_<b>a</b>, R = H; <b>A</b>_<b>b</b>, R = OMe) and {RuCl­(CO)­(P^<i>i</i>Pr₃)₂}₂{μ-CHCH–1,4-C₆H₂–2,5-R₂–CHCH} (<b>V</b>_<b>a</b>, R = H; <b>V</b>_<b>b</b>, R = OMe) as well as the mixed (ethynyl)­(vinyl)­phenylene bridged [Cl­(dppe)₂Ru–CC–1,4-C₆H₄–CHCH–RuCl­(CO)­(P^<i>i</i>Pr₃)₂] (<b>M</b>_<b>a</b>). Successive one-electron transfer steps were studied by means of cyclic voltammetry, EPR and UV–vis–NIR–IR spectroelectrochemistry. These studies show that the first oxidation mainly involves the central bis­(alkynyl) ruthenium moiety with only limited effects on the appended vinyl ruthenium moieties. The second to fourth oxidations (<i>n</i> = 2, 3, 4) involve the entire carbon-rich conjugated path of the molecule with an increased charge uniformly distributed between the two arms of the molecules, including the terminal vinyl ruthenium sites. In order to assess the charge distribution, we judiciously use ¹³CO labeled analogues to distinguish stretching vibrations due to the acetylide triple bonds and the intense and charge-sensitive Ru­(CO) IR probe in different oxidation states. The comparison between complex pairs <b>4a,b</b>^{<b><i>n</i>+</b>} (<i>n</i> = 0–3), <b>A</b>_<b>a,b</b>^{<b><i>n</i>+</b>} and <b>V</b>_<b>a,b</b>^{<b><i>n</i>+</b>} (<i>n</i> = 0–2) serves to elucidate the effect of the methoxy donor substituents on the redox and spectroscopic properties of these systems in their various oxidation states and on the metal/ligand contributions to their frontier orbitals

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

Fully Delocalized (Ethynyl)(vinyl)phenylene Bridged Triruthenium Complexes in up to Five Different Oxidation States

Triruthenium [(dppe)₂Ru­{−CC–1,4-C₆H₂–2,5-R₂–CHCH–RuCl­(CO)­(P^<i>i</i>Pr₃)₂}₂]^<i>n</i>+ (<b>4a</b>, R = H; <b>4b</b>, R = OMe) containing unsymmetrical (ethynyl)­(vinyl)­phenylene bridging ligands and displaying five well-separated redox states (<i>n</i> = 0–4) are compared to their bis­(alkynyl)ruthenium precursors (dppe)₂Ru­{−CC–1,4-C₆H₂–2,5-R₂–CCR′} (<b>2a</b>,<b>b</b>: R′ = TMS; <b>3a</b>,<b>b</b>: R′ = H) and their symmetrically substituted bimetallic congeners, complexes {Cl­(dppe)₂Ru}₂{μ-CC–1,4-C₆H₂–2,5-R₂–CC} (<b>A</b>_<b>a</b>, R = H; <b>A</b>_<b>b</b>, R = OMe) and {RuCl­(CO)­(P^<i>i</i>Pr₃)₂}₂{μ-CHCH–1,4-C₆H₂–2,5-R₂–CHCH} (<b>V</b>_<b>a</b>, R = H; <b>V</b>_<b>b</b>, R = OMe) as well as the mixed (ethynyl)­(vinyl)­phenylene bridged [Cl­(dppe)₂Ru–CC–1,4-C₆H₄–CHCH–RuCl­(CO)­(P^<i>i</i>Pr₃)₂] (<b>M</b>_<b>a</b>). Successive one-electron transfer steps were studied by means of cyclic voltammetry, EPR and UV–vis–NIR–IR spectroelectrochemistry. These studies show that the first oxidation mainly involves the central bis­(alkynyl) ruthenium moiety with only limited effects on the appended vinyl ruthenium moieties. The second to fourth oxidations (<i>n</i> = 2, 3, 4) involve the entire carbon-rich conjugated path of the molecule with an increased charge uniformly distributed between the two arms of the molecules, including the terminal vinyl ruthenium sites. In order to assess the charge distribution, we judiciously use ¹³CO labeled analogues to distinguish stretching vibrations due to the acetylide triple bonds and the intense and charge-sensitive Ru­(CO) IR probe in different oxidation states. The comparison between complex pairs <b>4a,b</b>^{<b><i>n</i>+</b>} (<i>n</i> = 0–3), <b>A</b>_<b>a,b</b>^{<b><i>n</i>+</b>} and <b>V</b>_<b>a,b</b>^{<b><i>n</i>+</b>} (<i>n</i> = 0–2) serves to elucidate the effect of the methoxy donor substituents on the redox and spectroscopic properties of these systems in their various oxidation states and on the metal/ligand contributions to their frontier orbitals

Divinylphenylene- and Ethynylvinylphenylene-Bridged Mono‑, Di‑, and Triruthenium Complexes for Covalent Binding to Gold Electrodes

In this work, we describe the preparation and the properties of the novel bis­(vinylphenylene)-bridged diruthenium complexes {Ru­(CO)­(η²-O₂C-<i>p-</i>C₆H₄SAc)­(P^<i>i</i>Pr₃)₂}₂(μ-CHCH-C₆H₄-CHCH-1,3 and -1,4) (<b>6</b> and <b>7</b>), the bis­(ethynylphenylene)-bridged complex <i>trans</i>-[AcS-<i>p</i>-C₆H₄-CC-Ru­(dppe)₂-CC-<i>p</i>-C₆H₄-CC-Ru­(dppe)₂-CC-<i>p</i>-C₆H₄-SAc] (<b>11</b>), the bis­(1-ethynyl-4-vinylphenylene)-bridged triruthenium complex <i>trans</i>-[{Ru­(dppe)₂}­{−CC-<i>p</i>-C₆H₄-CHCH-Ru­(CO)­(η²-O₂C-<i>p-</i>C₆H₄SAc)­(P^<i>i</i>Pr₃)₂}₂] (<b>8</b>), and the monometallic congeners Ru­(CHCH-<i>p</i>-C₆H₄SAc)­(CO)­(η²-O₂C-<i>p-</i>C₆H₄SAc)­(P^<i>i</i>Pr₃)₂ (<b>4</b>) and <i>trans</i>-[Ru­(dppe)₂(−CC-<i>p</i>-C₆H₄-SAc)₂] (<b>10</b>). These mono-, bi-, and trimetallic complexes feature terminal acetyl-protected thiol functions for covalent binding to gold surfaces or for bridging the gaps of gold nanoelectrodes. All complexes display low oxidation potentials, and IR studies of the neutral complex <b>8</b> and of its various oxidized forms <b>8</b>^{<b><i>n</i>+</b>} indicate the high vinyl/ethynyl bridging ligand contribution to the oxidation processes and complete charge delocalization in all available oxidation states (<i>n</i> = 1–3). Strong delocalization of the relevant occupied frontier MOs over the entire π-conjugated {Ru}–bridge–{Ru′}–bridge–{Ru} backbone is also supported by DFT calculations on the parent complexes <b>V8</b> and <b>V8</b>_<b>OMe</b>. The benzoate ligand bearing the functional group for gold binding is outside the conjugation path and insulates the wirelike central portion of these molecules from their periphery. Upon insertion into molecular junctions, these molecules are expected to enhance sequential tunneling and to facilitate Coulomb blockade behavior. They will thus contribute to our understanding of structure–property relationships for metal-containing molecular wires

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 <i>trans</i> 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