The viologens

Monk, Paul; Mortimer, Roger J.; Rosseinsky, David R.

doi:10.1017/cbo9780511550959.013

Cited by 35 publications

(79 citation statements)

References 116 publications

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“…Comparing the potentials of the characteristic redox-processes V 21 2 V 1d and V 1d 2 V for HS-6V6-SH and HS-6V6-H under the present experimental conditions with literature data [51][52][53][54][56][57][58][59][60]63 indicates that co-adsorbed bromide ions are partially replaced by perchlorate ions, which are in excess in the supporting electrolyte chosen in this study.…”

Section: Resultssupporting

confidence: 63%

“…The differences between the results of the Liverpool group and those reported in this paper might be attributed to the different electrolytes used and/or to the presence of oxygen which is known to significantly alter the association and redox-properties of dithiol-functionalized viologens. 52 We tentatively attribute the sigmoidal-type increase of the molecular conductance current to the higher electron density and the higher conjugation of V 1d compared to V 21 . This view is supported by force field calculations of Hester et al 78 They reported that the inter-ring bond order increases when the viologen dication transforms into the radical upon reduction, which implies that the aromatic character extends across both rings for the latter compound.…”

Section: Symmetric Molecular Junctions Au(t)|hs-6v6-sh|au(s)mentioning

confidence: 83%

“…P1 (E ¼ À0.440 V) and P1 0 (E ¼ À0.428 V) are assigned to the one-electron reaction V 21 2 V 1d . 51,52 The peak-to-peak separation is rather constant up to 2 V s À1 , and the peak height scales linearly with the scan rate. The peak FWHM (P1, P1 0 ) is 0.091 V. These observations indicate a fairly reversible process.…”

Section: Stm and Sts Measurementsmentioning

confidence: 99%

“…59 Attempts to estimate a rate constant from the variation of the peak separation on the scan rate and based on chronoamperometric experiments 72 with microelectrodes indicated that k o (at E P1/P1 0 ) 4 150 s À1 . 76 The second pair of peaks P2 (E ¼ À0.920 V) and P2 0 (E ¼ À0.900 V) is assigned to V 1d 2 V. 51,52 The peak-to-peak separation is constant up to 1 V s À1 and the peak height scales linearly with the scan rate. The peak FWHM of P2 and P2 0 are estimated to be 0.110 V and 0.132 V, respectively.…”

Section: Stm and Sts Measurementsmentioning

confidence: 99%

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Two-dimensional assembly and local redox-activity of molecular hybrid structures in an electrochemical environment

et al. 2006

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The self-assembly and redox-properties of two viologen derivatives, N-hexyl-N 0 -(6-thiohexyl)-4,4 0 -bipyridinium bromide (HS-6V6-H) and N,N 0 -bis(6-thiohexyl)-4,4 0 -bipyridinium bromide (HS-6V6-SH), immobilized on Au(111)-(1 Â 1) macro-electrodes were investigated by cyclic voltammetry, surface enhanced infrared spectroscopy (SEIRAS) and in situ scanning tunneling microscopy (STM). Depending on the assembly conditions one could distinguish three different types of adlayers for both viologens: a low coverage disordered and an ordered ''striped'' phase of flat oriented molecules as well as a high coverage monolayer composed of tilted viologen moieties. Both molecules, HS-6V6-H and HS-6V6-SH, were successfully immobilized on Au(poly) nano-electrodes, which gave a well-defined redox-response in the lower pA-current range. An in situ STM configuration was employed to explore electron transport properties of single molecule junctions Au(T)|HS-6V6-SH(HS-6V6-H)|Au(S). The observed sigmoidal potential dependence, measured at variable substrate potential E S and at constant bias voltage (E T À E S ), was attributed to electronic structure changes of the viologen moiety during the one-electron reduction/re-oxidation process V 21 2 V 1d . Tunneling experiments in asymmetric, STM-based junctions Au(T)-S-6V6-H|Au(S) revealed current (i T )-voltage (E T ) curves with a maximum located at the equilibrium potential of the redox-process V 21 2 V 1d . The experimental i T À E T characteristics of the HS-6V6-H-modified tunneling junction were tentatively attributed to a sequential two-step electron transfer mechanism.

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Section: Resultssupporting

confidence: 63%

Section: Symmetric Molecular Junctions Au(t)|hs-6v6-sh|au(s)mentioning

confidence: 83%

Section: Stm and Sts Measurementsmentioning

confidence: 99%

Section: Stm and Sts Measurementsmentioning

confidence: 99%

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Two-dimensional assembly and local redox-activity of molecular hybrid structures in an electrochemical environment

et al. 2006

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“…6) 8) A typical example is seen for the combination of these oxides with methylviologen dication (MV 2+ ) that has been utilized as an electron relay in photoenergy conversion systems because of its characteristic redox behavior. 9) When MV 2+ cations are intercalated in the interlayer spaces of the layered niobates and titanates, electron transfer from the photocatalytically active semiconducting oxide layers to the incorporated MV 2+ cations occurs to yield methylviologen radical cations (MV +• ) upon UV irradiation. 10) 12) In addition, our recent study has demonstrated that the photoinduced electron transfer also occurs even when the MV 2+ cations are not intercalated in the interlayer spaces but adsorbed on the external surfaces.…”

Section: Introductionmentioning

confidence: 99%

Visible-light-induced electron transfer in intercalation-type composites organized on photocatalytically active layered niobate

Nakato¹,

Kamase²,

Shinozaki³

2011

J. Ceram. Soc. Japan

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We prepared multicomponent composites of layered hexaniobate, a photocatalytically active layered semiconductor, with cationic organic species of methylviologen as an electron acceptor, proflavine as a photosensitizing dye, and triethanolammonium as a sacrificial donor. Two types of composites with different location of methylviologen, which was incorporated in the interlayer spaces or adsorbed on the external surfaces, were obtained. Visible light irradiation caused photoreduction of methylviologen in the composites, which was ascribed to the photoinduced electron transfer initiated by the photoexcitation of the proflavine dye. The location of methylviologen affected aggregation of the photoreduced methylviologen. A mixture of the three organic species without the niobate did not cause the reduction of viologen but self-decomposition of the proflavine dye under the same irradiation conditions, which indicated that the semiconducting niobate layers were indispensible for transferring electrons from the photoexcited dye to the acceptor.

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Redox-Connected Multilayers of Discrete Gold Particles: A Novel Electroactive Nanomaterial

et al. 1999

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using the inkjet printing technology. Built-in shadow masks for the cathode deposition can be easily fabricated using this technology. Finally, the fabrication of multicolor organic displays with fine pixels can be achieved if an inkjet printer capable of a better lateral control of the ink materials is available. [11] Experimental The pinhole-free PVK buffer layer was fabricated by spin-casting a 2 % w/v solution of PVK at 1500 rpm, which yielded a film thickness of approximately 1500 as determined by an Alphastep profilometry. The thin films were subsequently dried in a vacuum oven at 70 C for two hours. For the orange-red-emission devices, DCM was printed onto the PVK layer using a commercially available printer (Epson Stylus II) with the capability of handling solid substrates. For the green-emission device, Almq 3 was inkjet-printed onto the PVK buffer layer using the same printer. The spin-casting of PVK and the inkjet printing process of DCM and Almq 3 was carried out in air. The volatile nature of methanol permits the localized deposition of the Almq 3 and DCM droplets and hence no smearing of these droplets occurred on printing. In order to remove the solvent and moisture from the DCM and Almq 3 , the films were further dried inside a vacuum oven at 70 C for two hours before being loaded into an evaporator for the deposition of calcium (500 ) and aluminum (1000 ) bilayer electrodes. The devices were tested in a nitrogen environment. The current-voltage characteristics were measured using a HP 4145A Semiconductor Parameter Analyzer. The photoluminescence and electroluminescence spectra were measured using an Ocean Optics Spectrometer. For the purpose of comparison, a regular organic LED with the structure ITO/PEDOT/PVK/Almq 3 /Ca was also prepared, with Almq 3 deposited by vacuum sublimation.

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The viologens

Cited by 35 publications

References 116 publications

Two-dimensional assembly and local redox-activity of molecular hybrid structures in an electrochemical environment

Two-dimensional assembly and local redox-activity of molecular hybrid structures in an electrochemical environment

Visible-light-induced electron transfer in intercalation-type composites organized on photocatalytically active layered niobate

Redox-Connected Multilayers of Discrete Gold Particles: A Novel Electroactive Nanomaterial

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