The Ionic Work Function and its Role in Estimating Absolute Electrode Potentials

Fawcett, W. Ronald

doi:10.1021/la7038976

Cited by 167 publications

(270 citation statements)

References 38 publications

Supporting

Mentioning

246

Contrasting

Order By: Relevance

“…The free energy value of the reference electrode half-cell reaction is calculated using the relevant species involved in the redox reaction of the reference electrode system. There are experimentally determined absolute values available for these reference electrodes in different solvents; for example, the absolute values of the SHE in H 2 O, methanol, ethanol, acetonitrile, and dimethylsulfoxide (DMSO) are different, these absolute values were derived from thermodynamic parameters [6,7,26,27,35,37] (see Table 1). In addition, the absolute value of the Fc/Fc + reference electrode with respect to the SHE is also known.…”

Section: Direct Methodsmentioning

confidence: 99%

“…Although during the experiment the value of the SHE is considered zero, its absolute value is not zero; a range of absolute reference values for the SHE have been reported from 4.24 to 4.73 eV [25][26][27][28][29]. However, the IUPAC had recommended a value of 4.44 eV as the absolute value of the SHE in 1986 [26], a value that has been recently confirmed by an experimental study [27]. It should be noted that the absolute value for the SHE has been in debate for years.…”

Section: Aqueous Solutionsmentioning

confidence: 99%

See 1 more Smart Citation

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Arumugam

Becker

2014

Minerals

View full text Add to dashboard Cite

Abstract:Applications of redox processes range over a number of scientific fields. This review article summarizes the theory behind the calculation of redox potentials in solution for species such as organic compounds, inorganic complexes, actinides, battery materials, and mineral surface-bound-species. Different computational approaches to predict and determine redox potentials of electron transitions are discussed along with their respective pros and cons for the prediction of redox potentials. Subsequently, recommendations are made for certain necessary computational settings required for accurate calculation of redox potentials. This article reviews the importance of computational parameters, such as basis sets, density functional theory (DFT) functionals, and relativistic approaches and the role that physicochemical processes play on the shift of redox potentials, such as hydration or spin orbit coupling, and will aid in finding suitable combinations of approaches for different chemical and geochemical applications. Identifying cost-effective and credible computational approaches is essential to benchmark redox potential calculations against experiments. Once a good theoretical approach is found to model the chemistry and thermodynamics of the redox and electron transfer process, this knowledge can be incorporated into models of more complex reaction mechanisms that include diffusion in the solute, surface diffusion, and dehydration, to name a few. This knowledge is important to fully understand the nature of redox processes be it a geochemical process that dictates natural redox reactions or one that is being used for the optimization of a chemical process in industry. In addition, it will help identify materials that will be useful to design catalytic OPEN ACCESSMinerals 2014, 4 346 redox agents, to come up with materials to be used for batteries and photovoltaic processes, and to identify new and improved remediation strategies in environmental engineering, for example the reduction of actinides and their subsequent immobilization. Highly under-investigated is the role of redox-active semiconducting mineral surfaces as catalysts for promoting natural redox processes. Such knowledge is crucial to derive process-oriented mechanisms, kinetics, and rate laws for inorganic and organic redox processes in nature. In addition, molecular-level details still need to be explored and understood to plan for safer disposal of hazardous materials. In light of this, we include new research on the effect of iron-sulfide mineral surfaces, such as pyrite and mackinawite, on the redox chemistry of actinyl aqua complexes in aqueous solution.

show abstract

Section: Direct Methodsmentioning

confidence: 99%

Section: Aqueous Solutionsmentioning

confidence: 99%

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Arumugam

Becker

2014

Minerals

View full text Add to dashboard Cite

show abstract

“…Gas-phase proton affinities (PAs) and basicities (GBs) were calculated as protonation enthalpies and free-energies, respectively, employing the M06-2X/6-311++G(2df,2pd)//M06-2X/6-31+G (d, 23 All calculations were performed using the Gaussian 09 24 software. Calculated basicity constants are given in Table 1.…”

mentioning

confidence: 99%

Engineering exceptionally strong oxygen superbases with 1,8-diazanaphthalene di-N-oxides

Despotović

Vianello

2014

Chem. Commun.

View full text Add to dashboard Cite

DFT calculations revealed that 1,8-diazanaphthalene di-N-oxides provide extraordinary oxygen superbases, whose gas-phase and acetonitrile basicities surpass those of classical naphthalene-based nitrogen proton sponges. Such high basicity is almost entirely a consequence of a large strain-induced destabilization in neutral forms, while only a small contribution is offered by the intramolecular [O-HÁ Á ÁO] À hydrogen bonding upon protonation.For more than four decades, the design and synthesis of neutral organic superbases have attracted much attention 1-3 because their unique characteristics allow deprotonation of a wide range of weak acids resulting in weakly coordinated and highly reactive anionic species. Although usually weaker than their inorganic counterparts, uncharged organobases have become broadly used standard reagents in organic synthesis. Their practical usefulness involving mild reaction conditions, very good stability at low temperatures, efficient solubility in most organic solvents, and excellent recycling possibilities makes them superior to their ionic alternatives, 2,4 having an expansive range of applications in base-mediated transformations, 2 carbon dioxide storage, 5,6 and polymerization. 7 In 1968, Alder's discovery of the exceedingly high basicity of 1,8-bis(dimethylamino)naphthalene 8 (DMAN 1, Fig. 1) spurred interest in the area of neutral organic superbases, in particular, promoting a quest to create compounds with the highest basicity. 1-3 Since then, numerous diverse new superbases containing amines, imines, guanidines, phosphazenes, quinoimines, or cyclopropenimines have been synthesized, mostly by Staab, 9 Alder, 10 Schwesinger, 11 Verkade, 12 and other groups, 13 and their properties broadly characterized by means of experimental and computational methods. The extensive investigations by Koppel, Leito and their co-workers 14 should be highlighted, since they include both experimental and theoretical results in designing, preparing and measuring basicities of a huge variety of organic bases and superbases.A general feature of a large number of organic superbases is the presence of two (or more) basic centers that are placed close to each other and oriented in such a way that the incoming proton forms a strong stabilizing intramolecular hydrogen bond (Fig. 1). The favorable influence of multiple hydrogen bonds on enhancing the basicity (and acidity) of simple organic amines and alcohols has recently been particularly emphasized by Bachrach 15 and Kass. 16 Basic centers are usually nitrogen moieties due to their strongly attractive interactions with protons, since nitrogen lone pair orbitals are energetically higher-lying compared to, for example, those of oxygen in ethers and ketones, 17 in line with reports that ketones 18 and aldehydes 19 are less basic than the corresponding imines. 20 Yet, herein we wish to demonstrate that the oxygen basicity of N-oxides surpasses that of the related nitrogen compounds and that molecules containing two neighboring N-oxide moieties are sev...

show abstract

“…Basic questions linger about the thickness of interfacial layers (12), how acidity changes through the interfacial region (13), and the mechanistic differences between proton transfer (PT) across interfacial (IF) versus in bulk (B) water (10,14). Because aqueous surfaces are usually charged relative to the bulk liquid (15), the thermodynamic requirement of uniform electrochemical activity throughout (including the interfacial regions) implies that the chemical activity of protons (pH) in IF could be different from that in the B liquid. Reduced hydration of ionic species at the interface could force acids and bases toward their undissociated forms (16).…”

mentioning

confidence: 99%

Brønsted basicity of the air–water interface

Mishra

Enami

Nielsen

et al. 2012

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

168

203

View full text Add to dashboard Cite

Differences in the extent of protonation of functional groups lying on either side of water-hydrophobe interfaces are deemed essential to enzymatic catalysis, molecular recognition, bioenergetic transduction, and atmospheric aerosol-gas exchanges. The sign and range of such differences, however, remain conjectural. Herein we report experiments showing that gaseous carboxylic acids RCOOH(g) begin to deprotonate on the surface of water significantly more acidic than that supporting the dissociation of dissolved acids RCOOH(aq). Thermodynamic analysis indicates that > 6 H 2 O molecules must participate in the deprotonation of RCOOH(g) on water, but quantum mechanical calculations on a model air-water interface predict that such event is hindered by a significant kinetic barrier unless OH − ions are present therein. Thus, by detecting RCOO − we demonstrate the presence of OH − on the aerial side of on pH > 2 water exposed to RCOOH(g). Furthermore, because in similar experiments the base (Me) 3 N(g) is protonated only on pH < 4 water, we infer that the outer surface of water is Brønsted neutral at pH ∼3 (rather than at pH 7 as bulk water), a value that matches the isoelectric point of bubbles and oil droplets in independent electrophoretic experiments. The OH − densities sensed by RCOOH(g) on the aerial surface of water, however, are considerably smaller than those at the (>1 nm) deeper shear planes probed in electrophoresis, thereby implying the existence of OH − gradients in the interfacial region. This fact could account for the weak OH − signals detected by surface-specific spectroscopies.gas-liquid reactions | surface potential | water surface acidity | interfacial proton transfer A cid-base chemistry at aqueous interfaces lies at the heart of major processes in chemistry and biology. Changes in the degree of dissociation of the acidic/basic residues upon translocation between aqueous and hydrophobic microenvironments orchestrate enzyme catalysis (1), drive proton/electron transport across biomembranes (2, 3), and mediate molecular recognition and self-assembly phenomena (4-6). Despite its importance, the characterization of acid-base chemistry at aqueous interfaces remains fraught with uncertainties (7-11). Basic questions linger about the thickness of interfacial layers (12), how acidity changes through the interfacial region (13), and the mechanistic differences between proton transfer (PT) across interfacial (IF) versus in bulk (B) water (10,14). Because aqueous surfaces are usually charged relative to the bulk liquid (15), the thermodynamic requirement of uniform electrochemical activity throughout (including the interfacial regions) implies that the chemical activity of protons (pH) in IF could be different from that in the B liquid. Reduced hydration of ionic species at the interface could force acids and bases toward their undissociated forms (16).These fundamental issues have been extensively investigated via electrostatic (17) and electrokinetic experiments (11), surface tension studies and analysis (1...

show abstract

The Ionic Work Function and its Role in Estimating Absolute Electrode Potentials

Cited by 167 publications

References 38 publications

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Engineering exceptionally strong oxygen superbases with 1,8-diazanaphthalene di-N-oxides

Brønsted basicity of the air–water interface

Contact Info

Product

Resources

About