Oxidation-state changes of molecules irreversibly adsorbed on electrode surfaces as monitored by in situ Fourier transform infrared reflection absorption spectroscopy

Sasaki, Takeshi; Bae, In Tae; Scherson, Daniel Alberto; Bravo, Beatriz G.; Soriaga, Manuel P.

doi:10.1021/la00097a007

Cited by 21 publications

(16 citation statements)

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“…The downward bands at 1662 cm À1 are assigned to C=O stretching in the anthraquinone moiety. Bands at similar frequencies were previously reported for the C=O stretch in benzoquinone (BQ) species in solution (1672 cm À1 ), [44] C=O in the oxidized form of thiolated hydroquinone SAMs, that is, H 2 QSH (1647 cm À1 ), [18] H 2 QC 1 SH (1650 cm À1 ) [45] and 2-(11-mercaptoundecyl) hydroquinone (1660 cm À1 ) [14] SAMs are both assigned to the aromatic C=C skeletal stretch of the benzene ring in the anthrahydroquinone form (species appearing). The wavenumbers are close to those reported for an aromatic ring C=C stretching of 1626 [46] and 1580, 1598 cm À1 [47] for anthrahydroquinone derivatives in solution and to the 1580 cm À1 upward band corresponding to the C= C of SAMs formed from 2-(11-mercaptoundecyl) hydroquinone on a gold surface by using in situ IR spectroscopy.…”

supporting

confidence: 74%

Electroactive Self‐Assembled Monolayers of Unique Geometric Structures by Using Rigid Norbornylogous Bridges

Darwish

Eggers

Silva

et al. 2011

Chemistry A European J

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Herein, we describe the synthesis of straight (S) and L-shaped (L) norbornylogous bridges (NBs) with an anthraquinone moiety at the distal end as the redox-active head group and two thiol feet at the proximal end, by which the molecules assemble on gold surfaces. The NB molecules were shown to form self-assembled monolayers (SAMs) with a well-behaved surface redox process. The SAMs were characterized by using in situ IR spectroscopy, cyclic voltammetry, scanning tunnelling microscopy and electrochemical impedance spectroscopy. The surface selection rules associated with the IR band intensities allowed the estimation of the position of the anthraquinone moiety with respect to the surface and the tilt of the bridge with respect to the surface normal, both in pure and diluted monolayers. It is shown that the S- and L-NBs hold the plane of the anthraquinone moiety close to the surface normal or the surface tangent, respectively. Neither NB molecule changes its orientation if spaced by diluents on the surface. The difference in the structure of the S- and L-NB SAMs provides a suitable framework for the investigation of factors that govern electron transfer of anthraquinone moieties across self-assembled monolayers with limited structural ambiguity, as compared with the commonly used structurally flexible alkanethiol monolayers.

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confidence: 74%

Electroactive Self‐Assembled Monolayers of Unique Geometric Structures by Using Rigid Norbornylogous Bridges

Darwish

Eggers

Silva

et al. 2011

Chemistry A European J

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“…This question is important because, for instance, dissociation reactions (e.g., ester hydrolysis) or redox chemistry of alkanethiol-derivatized SAMs can lead to a rearrangement of the polymethylene chain structure which may affect the targeted performance. 4a,5a, 6,7 Ferrocene is a prototypical redox group that has frequently been incorporated at the terminal site of alkanethiol-derivatized electroactive SAMs on various electrodes. In this light, a wealth of information has been gathered by several research groups on the reactivity and stability of ferrocene-terminated alkanethiol SAMs on gold.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical and Vibrational Spectroscopic Characterization of Self-Assembled Monolayers of 1,1‘-Disubstituted Ferrocene Derivatives on Gold

et al. 2000

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Self-assembled monolayers (SAMs) of 1,1′-disubstituted ferrocene derivatives, i.e., 1,1′-bis(11-mercaptoundecyl)ferrocene (1) and 1-decyl-1′-(11-mercaptoundecyl)ferrocene (2), on a gold surface were prepared, and their structural and electrochemical properties were characterized by reflection-absorption infrared spectroscopy (RAIRS), ellipsometry, cyclic voltammetry (CV), and subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS). From the RAIR spectral features, both molecules, 1 and 2, were found to chemisorb on gold as thiolates after deprotonation. The peak positions of the methylene stretching modes indicated that the alkyl chains of 1 and 2 assume disordered structures on the gold surface. The thicknesses of the monolayers 1 and 2 on gold were determined by ellipsometry to be 2.27 ( 0.10 and 2.30 ( 0.10 nm, respectively. In the CV experiments, symmetric redox peaks were identified at ca. 0.32 and 0.30 V versus saturated calomel electrode (SCE) for the SAMs of 1 and 2, respectively. The surface coverage values determined from the CV of 1 and 2 were 3.4 × 10 -10 and 3.2 × 10 -10 mol/cm 2 , respectively. Both SAMs at full-coverage limits were stable in neutral (0.2 M NaClO4) as well as in acidic (0.2 M HClO4) medium, suggesting that hardly any decomposition of the ferricinium cation occurred for the SAMs prepared from disubstituted ferrocene derivatives. In particular, the SAMs of 1 were stable irrespective of the surface coverage, displaying the bonding capability of dithiols to gold; the submonolayer of 2 was slightly unstable in neutral medium. The SNIFTIR spectral data suggested that the alkyl chain of the two SAMs takes a more upright orientation when the ferrocene moiety is oxidized to a ferricinium cation.

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“…The in situ electrochemical cell for FTIRRAS measurements as well as the electrochemical and spectroscopic instrumentation have been described elsewhere. 4 For the FTIRRAS spectroscopic experiments, the layer was formed directly in the spectroelectrochemical cell by potential cycling. The EOB containing solution was drained and the cell washed (three times) and later filled with neat supporting electrolyte.…”

Section: Methodsmentioning

confidence: 99%

“…This can be explained on the basis that the alkyl chains in the dication are in a collapsed (or unstretched) form adopting a more stretched configuration (with the skeletal axis pointing away from the surface) when in the reduced state, leading to a net decrease in the C-H stretching contribution to the spectra. The experimental approach employed in this work has followed very closely that described by Sasaki et al 4 to monitor modifications in the vibrational properties of 2,5-dihydroxythiophenol irreversibly adsorbed on Au and Pt surfaces engendered by changes in the redox state.…”

mentioning

confidence: 99%

In-Situ Spectroscopic Studies of Redox Active Self-Assembled Monolayers on Gold Electrode Surfaces

Bae¹,

Huang²,

Yeager³

et al. 1990

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Oxidation-state changes of molecules irreversibly adsorbed on electrode surfaces as monitored by in situ Fourier transform infrared reflection absorption spectroscopy

Cited by 21 publications

References 0 publications

Electroactive Self‐Assembled Monolayers of Unique Geometric Structures by Using Rigid Norbornylogous Bridges

Electroactive Self‐Assembled Monolayers of Unique Geometric Structures by Using Rigid Norbornylogous Bridges

Electrochemical and Vibrational Spectroscopic Characterization of Self-Assembled Monolayers of 1,1‘-Disubstituted Ferrocene Derivatives on Gold

In-Situ Spectroscopic Studies of Redox Active Self-Assembled Monolayers on Gold Electrode Surfaces

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