- Light harvesting and energy transfer in a ruthenium-coumarin-2 copolymer
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Copolymers containing Ru(bpy)3 and coumarin-2 chromophores prepared using both grafting and copolymerization approaches exhibit Foerster-type energy-transfer efficiencies ranging from 70% to above 98%.
- Schultze,Serin,Adronov,Frechet
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- Organic Diodes Based on Redox-Polymer Bilayer-Film-Modified Electrodes
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The synthesis of four electropolymerizable 2,2'-bipyridinium salts with tuned reduction potential (E01) is described (N,N'-ethylene-4-methyl-4'-vinyl-2,2'bipyridinium dibromide (4: E01=-0.48 V), 4-methyl-N,N'-(trimethylene)-4'-vinyl-2,2'-bipyridinium dibromide (5: E01=-0.66 V), N,N'-ethylene-4-methyl-4'--2,2'-bipyridinium bis(hexafluorophosphate) (6b: E01=-0.46 V), and 4-methyl-4'--N,N'-(trimethylene)-2,2'-bipyridinium bis(hexafluorophosphate) (7b: E01=-0.66 V)).E01-Tuning is based on the torsional angle C(3)-C(2)-C(2')-C(3'), imposed by the N,N'-ethylene and N,N'-(trimethylene) bridge.The vinylic compounds 4 and 5 undergo cathodic, the pyrrole derivatives 6b and 7b anodic electropolymerization on glassy carbon electrodes from MeCN solutions, yielding thin, surface-confined films with surface concentrations of redox-active material in the range 5*10-9-8 mol/cm2, depending on experimental conditions.T he modified electrodes exhibit reversible 'diquat' electrochemistry in pure solvent/electrolyte.Copolymerization of 6b and 7b with pyrrole yields most stable electrodes.Bilayer-film-modified electrodes were prepared by sequential electropolymerization of the monomers.The assembly electrode/poly-6b/poly-7b behaves as a switch, it transforms -as a Schmitt trigger- an analog input signal (the electrode potential) into a digital output signal (redox state of the outer polymer film).Forward-(electrode/poly-7b/poly-6b) and reverse-biased assemblies (electrode/poly-6b/poly-7b) were coupled to the electrochemical reduction of redox-active solution species, e.g.N-(cyanomethyl)-N'-methyl-4,4'-bipyridinium bis(hexafluorophosphate) (8).Zener-diode-like behavior was observed.Aspects of redox-polymer multilayer-film assemblies, sandwiched between two electronic conductors, are discussed in terms of molecular electronic devices.
- Zhao, Wenyuan,Marfurt, Judith,Walder, Lorenz
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- Electropolymerization of Ruthenium Bis(1,10-phenanthroline)(4-methyl-4'-vinyl-2,2'-bipyridine) Complexes through Direct Attack on the Ligand Ring System
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Mixed ligand complexes of the general type RuP2(4-methyl-4'-vinyl-2,2'-bipyridine)2+ (where P represents phenanthroline or a substituted phenanthroline) undergo rapid electropolymerization following initial two-electron reduction.The polymerization yields redox-conductive electrode coatings and appears to proceed via radical-radical coupling between the vinyl moiety and a phenanthroline carbon, with the 4- and 7-positions of the phenanthroline being the most reactive.When the phenanthroline ligands possess substituents in the 4- and 7-positions, polymerization still proceeds, but an unexpected reversible electrochemical response near -0.2 V vs.SSCE is generated.The response is attributed to an intermediate which can exist in a stable ligand-centered free-radical form.This radical species has been observed by EPR spectroscopy and is stabilized by 4,7-disubstitution and/or the presence of proton donors.The mechanistic pathways involved in the electropolymerization are complex and lead to multiple products.Polymerized films display unusual electrochemistry, including prominent "charge-trapping" peaks for which a mechanistic system is proposed.
- Guarr, Thomas F.,Anson, Fred C.
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- Controlled electropolymerization of ruthenium(II) vinylbipyridyl complexes in mesoporous nanoparticle films of TiO2
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Surface-initiated, oligomeric assemblies of ruthenium(II) vinylpolypyridyl complexes have been grown within the cavities of mesoporous nanoparticle films of TiO2 by electrochemically controlled radical polymerization. Surface growth was monitored by cyclic voltammetry as well as UV/Vis and X-ray photoelectron spectroscopy. Polymerization occurs by a radical chain mechanism following cyclic voltammetry scans to negative potentials where reduction occurs at the π* levels of the polypyridyl ligands. Oligomeric growth within the cavities of the TiO2 films occurs until an average of six repeat units are added to the surface-bound initiator site, which is in agreement with estimates of the internal volumes of the pores in the nanoparticle films.
- Fang, Zhen,Keinan, Shahar,Alibabaei, Leila,Luo, Hanlin,Ito, Akitaka,Meyer, Thomas J.
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- Asymmetric Elelctron Transfer from a Chiral Ruthenium Complex Donor to an Atropisometric Chiral 2,2'-Bipyridine Acceptor
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We report asymmetric light-induced electron transfer (ET) in water in the system (Λ)-Ru(methylvinylbipyridine)32+/(+)- and (-)-1,1'-tetramethylene-2,2'-bipyridine-3,3'-dicarboxylic acid at pH => 5 (zwitterionic form).This reaction is activation controlled; ΔG0 was made nearly zero by manipulation of molecular structure, pH, and solvent.Then reverse ET to the excited donor occurs which renders the quenching reaction asymmetric.The asymmetry of ET is small as expected for high-DK solvents.From our results we infer that chiral recognition takes place in a diastereomeric exciplex.
- Woerner, Michael,Greiner, Gerhard,Rau, Hermann
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- Rectifying interfaces using two-layer films of electrochemically polymerized vinylpyridine and vinylbipyridine complexes of ruthenium and iron on electrodes
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Polymerization of the complexes [Ru(bpy)2(vinyl-py)2]2+ (I), [Ru(vinyl-bpy)3]2+ (II), [Ru(bpy)2(vinyl-bpy)]2+ (III), [Ru(bpy)2(vinyl-py)Cl]+ (IV), and [Fe(vinyl-bpy)3]2+ (V) can be initiated by electrochemical reduction in CH3CN solvent to produce stable, adherent, electrochemically active films on Pt, vitreous carbon, SnO2, and TiO2 electrodes. Randomly site-mixed copolymer (one-layer) and spatially segregated two-layer films of the pairs I and IV and II and V can be prepared by simultaneous and sequential polymerization of the appropriate monomers, respectively. The spatial features were confirmed by variable-angle X-ray photoelectron spectroscopy. Cyclic voltammetry of the copolymers is the additive response of the two redox components. In the two-layer films, however, oxidation state changes of the outer polymer films are constrained to occur via electron-transfer mediation by the inner polymer film. The result is a rectifying property of the polymer two-layer interface which should be useful in mimicking electronic device behaviors such as Zener diodes.
- Abruna,Denisevich,Umana,Meyer, Thomas J.,Murray, Royce W.
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- A self-deformable gel system with asymmetric shape change based on a gradient structure
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A self-deformable gel system is constructed by coupling a gradient structured gel with a chemical oscillating reaction. The system exhibits periodic and asymmetric shape change. The asymmetric shape change of the gel is based on the gradient structure.
- Li, Jie,Li, Xiuchen,Xu, Guohe,Zheng, Zhaohui,Deng, Jinni,Ding, Xiaobin
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supporting information
p. 11594 - 11597
(2018/11/10)
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- Robust photocatalytic water reduction with cyclometalated Ir(iii) 4-vinyl-2,2′-bipyridine complexes
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Novel [Ir(CN)2(NN)]+ complexes with NN ligands containing vinyl groups were synthesized resulting in quintupled turn-over numbers for the photocatalytic hydrogen production compared to the analogous non-vinyl compounds.
- Metz, Stefan,Bernhard, Stefan
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supporting information; experimental part
p. 7551 - 7553
(2010/12/19)
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- Intramolecular Energy Transfer in Covalently Linked Polypyridine Ruthenium(II)/Osmium(II) Binuclear Complexes. Ru(II)(bpy)2Mebpy(CH2)n-MebpyOs(II)(bpy)2 (n=2, 3, 5, and 7)
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A novel series of polymethylene-linked heterobinuclear complexes of polypyridine ruthenium(II)/osmium(II) complex Ru(II)(bpy)2Mebpy-(CH2)n-MebpyOs(II)(bpy)2(bpy=2,2'-bipyridine and N=2, 3, 5, and 7), 1, was prepared.The photophysical behavior was examined in various solvents.The emission spectra of 1 (excitation wavelength: 455 nm) showed a nearly complete quenching of Ru(II) -> ?*(bpy) metal-to-ligand charge transfer (MLCT) emission and the enhancement of Os(II) -> ?*(bpy) MLCT emission.The luminescence lifetime measurements by a time-correlated single photon-counting method provided evidence that intramolecular energy transfer is a significant pathway for the observed emission quenching.The rate constants of the intramolecular energy transfer in ethanol are 5.3 * 108, 3.3 * 108, 1.3 * 108, and 1.0 * 108 s-1 for 1 (n=2, 3, 5, and 7), respectively.They were found to be proportional to the inverse sixth power on the center-to-center distance of the two complexes.The mechanisms is discussed in terms of the Foerster (a dipole-dipole interaction) mechanism.
- Furue, Masaoki,Yoshidzumi, Toshiyuki,Kinoshita, Shuichi,Kushida, Takashi,Nozakura, Shun-ichi,Kamachi, Mikiharu
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p. 1632 - 1640
(2007/10/02)
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- Vinyl-substituted 2,2'-bipyridine compounds
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Vinyl-substituted 2,2'-bipyridine compounds of the formula STR1 and complexes thereof with metals or metal compounds other than alkali metals or alkaline earth metals, or alkali metal compounds, or alkaline earth metal compounds are described, R1 and R2 being as defined in patent claim 1 and the vinyl group being bonded in the 4-position or 6-position. The 2,2'-bipyridine compounds (I) are suitable for the preparation of complex-forming or complexed, crosslinked or uncrosslinked polymers. Complexed polymers, obtainable from these, are used, for example, as catalysts, in particular for transvinylation reactions. Uncomplexed polymers, which can be prepared from compounds (I), are suitable as metal ion scavengers in various applications.
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- Photoelectrochemistry of Tris(bipyridyl)ruthenium(II) Covalently Attached to n-Type SnO2
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Ru(bpy)32+ (bpy = 2,2'-bipyridyl) has been covalently attached to n-type SnO2 via condensation of surface hydroxyl groups with ruthenium (4-(trichlorosilylethyl)-4'-methyl-2,2'-bipyridine)bis(2,2'-bipyridine) bis(hexafluorophosphate)).A thick coating (ca. 1000 layers, based on the surface hydroxyl group concentration) was produced, presumably via oligomerization of hydrolyzed -SiCl3 groups.The coating, which was stable to organic solvents as well as to aqueous acids and bases, gave reversible cyclic voltammograms, with peak potentials shifted slightly from those of aqueous Ru(bpy)32+, but the number of electroactive molecules corresponding only to a few layers.The coated electrode gave a photocurrent about twice that observed for SnO2 in contact with aqueous 4mM Ru(bpy)32+, with a slightly red-shifted excitation spectrum.Only a small fraction of the electroactive molecules appeared to participate in excited-state electron transfer, although a steady-state current was supported, presumably by slow electron transfer from the outer layers.Prolonged illumination produces extensive hydrolysis of the outer layers of the coating, but a modest reduction of electroactivity, and only a slight decrease in photocurrent.The photocurrent increases with applied potential, then reaches a plateau, and falls off again near the reduction potential of Ru(bpy)32+*; the falloff is attributed to back-electron transfer via tunnelling through the thin space charge layer.
- Ghosh, Pushpito K.,Spiro, Thomas G.
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p. 5543 - 5549
(2007/10/02)
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