The electrochemical oxidation of ruthenocene in various room temperature ionic liquids

Rogers, Emma I.; Lawrence, Nathan S.; Compton, Richard G.

doi:10.1016/j.jelechem.2011.04.007

Cited by 8 publications

(4 citation statements)

References 27 publications

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“…The mechanism in [14][15][16][17] has been corroborated by TD-DFT excitation energies showing that ½Cp 2 Os IV ðH − Þ þ is much easier to photoexcite than Cp 2 Os. The vertical excitation energy for ½Cp 2 Os IV ðH − Þ þ corresponds to a wavelength of 266 nm (∼107 kcal∕mol) and is associated with a HOMO to LUMO transition.…”

Section: Dft Computationsmentioning

confidence: 79%

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Biphasic water splitting by osmocene

Todorova

Patır

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The photochemical reactivity of osmocene in a biphasic waterorganic solvent system has been investigated to probe its water splitting properties. The photoreduction of aqueous protons to hydrogen under anaerobic conditions induced by osmocene dissolved in 1,2-dichloroethane and the subsequent water splitting by the osmocenium metal-metal dimer formed during H 2 production were studied by electrochemical methods, UV-visible spectrometry, gas chromatography, and nuclear magnetic resonance spectroscopy. Density functional theory computations were used to validate the reaction pathways.S olar water splitting is undoubtedly a key challenge (1-3), and in the quest for solar fuels, hydrogen is definitely a major target with many industrial applications ranging from transportation to carbon dioxide mitigation (4).Interestingly, some transition metal complexes like metallocenes have been reported to reduce protons to hydrogen. In 1988, cobaltocene was found to produce hydrogen in strong acidic solutions. The mechanism was investigated by pulse radiolysis, and it was found that the reaction kinetics was first order with respect to cobaltocene and the protons pointing to a protonation of the metal as the primary step (5). In 2009, Kunkely and Vogler reported that osmocene dissolved in strong acidic solutions could photogenerate hydrogen and that ½Cp 2 Os IV ðOH − Þ þ could photogenerate oxygen (6). Proton reduction was shown to proceed also by the formation of a hydride followed under UV light by the formation of H 2 and the dimer ½Cp 2 Os III -Os III Cp 2 2þ .One of the major difficulties in studying water splitting by metallocenes is their very poor solubility in aqueous or even acidic solutions. When investigating the reduction of protons in organic phases where metallocenes are soluble, the other major drawback is the low solubility and dissociation of acids in organic solvents. One way to circumvent these issues is to carry out these reactions in biphasic systems.In 2008, we studied the reduction of aqueous protons by decamethylferrocene (DMFc) in 1,2-dichloroethane (1,2-DCE), and, here again the data suggested that the first step is the protonation of the metal (7). In particular, we have shown that hydrogen bubbles can form at the interface and that hydrogen production is associated to the oxidation of the electron donor DMFc. More generally, we have shown that voltammetry at the interface between two immiscible electrolyte solutions (ITIES) is a very useful tool to study proton coupled electron transfer reactions involving aqueous protons and organic electron donors (8-10). This methodology has been also applied to molecular electrocatalysis where an amphiphilic catalyst is used to complex oxygen to facilitate its reduction as recently reviewed (10-13).In this study, the photochemical reactivity of osmocene with water in biphasic systems has been investigated by electrochemical methods on solid electrodes and soft liquid-liquid interfaces to unravel the multistep reaction mechanisms. Density functional theory (DFT)...

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Section: Dft Computationsmentioning

confidence: 79%

“…Indeed, ½Cp 2 Os IV 2þ can be readily reduced to osmium (III) on the electrode surface, considering the respective redox potentials (16). A recent chronopotentiometric study by the Compton's group on ruthenocene clearly shows that the anion can play a role in stabilizing the oxidized species, namely Ru III and Ru IV (17).…”

Section: Redox Voltammetrymentioning

confidence: 99%

Biphasic water splitting by osmocene

Todorova

Patır

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Moreover, although ruthenium(III) undergoes a facile addition of one-electron ligands to form 18 e – complexes, delocalization of the positive charge makes the formation of a monomer more energetically favorable than that of a dimer. For the same reason, mono-oxidized porphyrin was not found to react with BF 4 – or I – to form a Ru IV species as previously reported for ruthenocene or biruthenocene. − …”

Section: Discussionmentioning

confidence: 99%

Similar, Yet Different: Long-Range Metal–Metal Coupling and Electron-Transfer Processes in Metal-Free 5,10,15,20-Tetra(ruthenocenyl)porphyrin

et al. 2021

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The electronic structure, redox properties, and long-range metal–metal coupling in metal-free 5,10,15,20-tetra(ruthenocenyl)porphyrin (H2TRcP) were probed by spectroscopic (NMR, UV–vis, magnetic circular dichroism (MCD), and atmospheric pressure chemical ionization (APCI)), electrochemical (cyclic voltammetry, CV, and differential pulse voltammetry, DPV), spectroelectrochemical, and chemical oxidation methods, as well as theoretical (density functional theory, DFT, and time-dependent DFT, TDDFT) approaches. It was demonstrated that the spectroscopic properties of H2TRcP are significantly different from those in H2TFcP (metal-free 5,10,15,20-tetra(ferrocenyl)porphyrin). Ruthenocenyl fragments in H2TRcP have higher oxidation potentials than the ferrocene groups in the H2TFcP complex. Similar to H2TFcP, we were able to access and spectroscopically characterize the one- and two-electron oxidized mixed-valence states in the H2TRcP system. DFT predicts that the porphyrin π-system stabilizes the [H2TRcP]+ mixed-valence cation and prevents its dimerization, which is characteristic for ruthenocenyl systems. However, formation of the mixed-valence [H2TRcP]2+ is significantly less reproducible than the formation of [H2TRcP]+. DFT and TDDFT calculations suggest the ruthenocenyl fragment dominance in the highest occupied molecular orbital (HOMO) energy region and the presence of the low-energy MLCT (Rc → porphyrin (π*)) transitions in the visible region with energies higher than the predominantly porphyrin-centered Q-bands.

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“…Because of their high electrochemical stability, good ionic conductivity, negligible vapor pressure, and wide electrochemical windows [19], IL have received much attention in many areas including electrochemistry [20,21] organic synthesis [22], catalysis [23], liquid-liquid extraction [24], etc. In the field of electroanalysis, IL can be used as binders for carbon paste electrodes [25], supporting electrolytes for electrochemical measurements [26] and membrane materials for modified electrodes [27].…”

Section: Introductionmentioning

confidence: 99%

Application of multi wall carbon nanotube–graphene hybrid for voltammetric determination of naproxen

Sarhangzadeh

2015

J IRAN CHEM SOC

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The electrochemical oxidation of ruthenocene in various room temperature ionic liquids

Cited by 8 publications

References 27 publications

Biphasic water splitting by osmocene

Biphasic water splitting by osmocene

Similar, Yet Different: Long-Range Metal–Metal Coupling and Electron-Transfer Processes in Metal-Free 5,10,15,20-Tetra(ruthenocenyl)porphyrin

Application of multi wall carbon nanotube–graphene hybrid for voltammetric determination of naproxen

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