Infrared Spectroscopy and Ab Initio Theory of Isolated H5O2+: From Buckets of Water to the Schrödinger Equation and Back

Niedner‐Schatteburg, Gereon

doi:10.1002/anie.200703555

Cited by 34 publications

(22 citation statements)

References 45 publications

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“…Extensive spectroscopic studies [16][17][18][19][20][21][22][23][24][25][26] of the Zundel ion have established that the shared proton has a characteristic vibrational frequency, m sp, of about 1000 cm À1 , corresponding to a red-shift (relative to the free OH stretching band in isolated H 2 O) of $2700 cm À1 [27]. From the quantum mechanical perspective, the strong solvent influence on m sp can be traced to changes in the shallow potential surface that governs the vibrational eigenstates of the shared proton.…”

Section: Introductionmentioning

confidence: 99%

Tuning the intermolecular proton bond in the H5O2+ ‘Zundel ion’ scaffold

Olesen

Guasco

Roscioli

et al. 2011

Chemical Physics Letters

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Section: Introductionmentioning

confidence: 99%

Tuning the intermolecular proton bond in the H5O2+ ‘Zundel ion’ scaffold

Olesen

Guasco

Roscioli

et al. 2011

Chemical Physics Letters

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“…A hydrated proton can be firmly bound to a single water molecule as in H 3 O + or at an equidistant position between two water molecules as in the n = 2 cluster ion H 5 O + 2 [11]. Other forms of binding with different nuclear spacings are found in the higher clusters, with a high degree of symmetry being restored for n = 4.…”

Section: Dissociative X-ray Ionization Of Ionic Water Clustersmentioning

confidence: 99%

“…X-ray photofragmentation measurements on protonated water clusters appear to offer a wide range of opportunities for augmenting the understanding of these systems also because of the tremendous ongoing progress in quantum simulation studies on ion solvation in water [9] and on the dynamics of individual water clusters [11]. Thus, very detailed theoretical simulations were recently used to elucidate the fragmentation of neutral water clusters by highly charged ions [49].…”

Section: Dissociative X-ray Ionization Of Ionic Water Clustersmentioning

confidence: 99%

“…Examples are ion chemistry in the atmosphere [1,2], in space [3,4,5] where it leads to the formation of complex molecules [6,7] in a very cold and dilute environment, or the ubiquitous role played by ions in aqueous solutions [8,9,10,11], including biological systems [12]. For experimental studies of the interaction with radiation, ionic molecules and clusters in well-defined initial states constitute a special group of targets, often only accessible using discharge sources or other dedicated ion preparation techniques.…”

Section: Introductionmentioning

confidence: 99%

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Soft-x-ray fragmentation studies of molecular ions

Wolf¹,

Pedersen²,

Lammich³

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. Imaging of photofragments from molecular ions after irradiation by soft X-ray photons has been realized at the ion beam infrastructure TIFF set up at the FLASH facility. Photodissociation of the two-electron system HeH + at 38.7 eV revealed the electronic excitations and the charge-state ratios for the products of this process, reflecting the non-adiabatic dissociation dynamics through multiple avoided crossings among the HeH + Rydberg potential curves. Dissociative ionization of the protonated water molecules H 3 O + and H 5 O + 2 at 90 eV revealed the main fragmentation pathways after the production of valence vacancies in these ionic species, which include a strong three-body channnel with a neutral fragment (OH + H + + H + ) in H 3 O + photolysis and a significant two-body fragmentation channel (photolysis. The measurements yield absolute cross sections and fragment angular distributions. Increased precision and sensitivity of the technique was realized in recent developments, creating a tool for exploring X-ray excited molecular states under highly controlled target conditions challenging detailed theoretical understanding.

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“…For the mechanisms of reactions in aqueous media, far more important is the observation that species such as H 3 O + (usually called the Eigen cation [22]), H 5 O 2 + (usually called the Zundel cation [23,24], although also strongly preferred by the school of Vinnik and Librovich at the Institute of Physical Chemistry in Moscow [25]), H 9 O 4 + (first postulated by Bell [26], but often (mistakenly) also called the Eigen cation) and the many others which have been proposed [27] (not that there has ever been any believable experimental evidence for any of them [28,29]) do not have lifetimes long enough to exist. Although far less work has been done, recent studies show that HO − cannot exist as such in water either [30–32].…”

Section: Introductionmentioning

confidence: 99%

A Greatly Under-Appreciated Fundamental Principle of Physical Organic Chemistry

Cox

2011

IJMS

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If a species does not have a finite lifetime in the reaction medium, it cannot be a mechanistic intermediate. This principle was first enunciated by Jencks, as the concept of an enforced mechanism. For instance, neither primary nor secondary carbocations have long enough lifetimes to exist in an aqueous medium, so SN1 reactions involving these substrates are not possible, and an SN2 mechanism is enforced. Only tertiary carbocations and those stabilized by resonance (benzyl cations, acylium ions) are stable enough to be reaction intermediates. More importantly, it is now known that neither H3O+ nor HO− exist as such in dilute aqueous solution. Several recent high-level calculations on large proton clusters are unable to localize the positive charge; it is found to be simply “on the cluster” as a whole. The lifetime of any ionized water species is exceedingly short, a few molecular vibrations at most; the best experimental study, using modern IR instrumentation, has the most probable hydrated proton structure as H13O6+, but only an estimated quarter of the protons are present even in this form at any given instant. Thanks to the Grotthuss mechanism of chain transfer along hydrogen bonds, in reality a proton or a hydroxide ion is simply instantly available anywhere it is needed for reaction. Important mechanistic consequences result. Any charged oxygen species (e.g., a tetrahedral intermediate) is also not going to exist long enough to be a reaction intermediate, unless the charge is stabilized in some way, usually by resonance. General acid catalysis is the rule in reactions in concentrated aqueous acids. The Grotthuss mechanism also means that reactions involving neutral water are favored; the solvent is already highly structured, so the entropy involved in bringing several solvent molecules to the reaction center is unimportant. Examples are given.

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Infrared Spectroscopy and Ab Initio Theory of Isolated H₅O₂⁺: From Buckets of Water to the Schrödinger Equation and Back

Cited by 34 publications

References 45 publications

Tuning the intermolecular proton bond in the H5O2+ ‘Zundel ion’ scaffold

Tuning the intermolecular proton bond in the H5O2+ ‘Zundel ion’ scaffold

Soft-x-ray fragmentation studies of molecular ions

A Greatly Under-Appreciated Fundamental Principle of Physical Organic Chemistry

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