The first measurement of the hydrogen bond basicity of monomeric water, phenols and weakly basic alcohols

Laurence, Christian; Berthelot, M.; Helbert, Maryvonne; Sraidi, Khadija

doi:10.1021/j100346a083

Cited by 61 publications

(39 citation statements)

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“…This observation is supported by ab initio calculations (22)(23)(24)(25)(26). This is a surprising analogy with the oxygen complex of 3: (i) 4 molecules of water are found in the pocket surrounding the superoxide, (ii) the concentration of superoxide-bound porphyrin is low, and (iii) the network of hydrogen bonds are known to increase the basicity of water, a condition that is known to increase the kinetic stability of superoxide (27,28). Moreover, water is held above the superoxide on the distal upper portion of the pocket in 1-3 through hydrogen bonding with the nitrogens in the imidazole pickets in 3, or through coordinating to the Cu in 1 and 2.…”

Section: Resultsmentioning

confidence: 83%

Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Collman

Decréau

Lin

et al. 2009

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

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Five iron porphyrins with different superstructures were immobilized on self-assembled-monolayer (SAM)-coated interdigitatedarray (IDAs) gold-platinum electrodes. The selectivity of the catalysts i.e., limited formation of partially reduced oxygen species (PROS) in the electrocatalytic reduction of dioxygen, is a function of 2 rates: (i) the rate of electron transfer from the electrode to the catalyst, which is controlled by the length, and conjugation of the linker from the catalyst to the electrode and (ii) the rate of bound oxygen (superoxide) hydrolysis, which correlates with the presence of a water cluster in the gas-binding pocket influencing the rate of oxygen binding; these factors are controlled by the nature of the porphyrin superstructure. The structurally biomimetic Trisimidazole model is the most selective.electron transfer rate ͉ oxygen binding rates ͉ water cluster ͉ oxygen complex stabilization ͉ partially reduced oxygen species A recent report showed that water may inhibit oxygen binding in hemoprotein models (1). This echoes the ''water displacement model'' proposed for oxygen binding in myoglobin (2-4). This finding is relevant to cytochrome c oxidase (CcO) for 2 reasons: (i) CcO binds and reduces oxygen to form water (5) and (ii) the hydrolysis of the oxygen complex in CcO and in other enzymes is an issue and occurs when water, protons, and electrons are present (6, 7). This reaction releases partially reduced oxygen species (PROS) that are toxic to organisms (Fig. 1). The study herein examines the formation of PROS during the electrocatalytic reduction of oxygen by several site-isolated CcO models ( Fig. 2) as a function of (i) the oxygen association rate [k on (O 2 )] and the rate of hydrolysis, both associated with the presence of water in the gas binding pocket, and (ii) the availability of electrons at the oxygen reduction site associated with the rate of electron arrival from the electrode to the catalyst [k(eT)] and/or the presence of redox active species in the vicinity of the heme. The latter aspects were specifically addressed in previous studies by immobilizing the active-site models onto self-assembled-monolayer (SAM)-coated rotating ring disk gold electrodes (RRDE) (8-10): k(eT) was controlled by the length and conjugated character of the linker between the catalyst and the gold electrode, and immobilization allowed site isolation. To get better collection efficiencies for the detection of PROS and to prevent damage to the SAM associated with high rotation rates, the present study used Au-Pt interdigitated array electrodes (IDAs). The collection efficiency of these IDA electrodes is in the 65-90% range as compared with Ͻ20% in RRDE (8).IDAs have 2 sets of alternating arrays of electrodes. The electrode widths and spacing are on similar dimensions, and this distance is within diffusion layers for typical electroactive species in solution. This results in diffusion gradients of adjacent microband electrodes that overlap with each other. Redox products created at the Au generator ...

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Section: Resultsmentioning

confidence: 83%

Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Collman

Decréau

Lin

et al. 2009

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

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“…Berthelot and Laurence have developed an experimentally accessible means of quantitating hydrogen-bond-accepting tendencies through the measurement of the IR frequency shift of the methanol 0-H peak when the hydrogen is complexed with a hydrogen-bond-accepting molecule (40)(41)(42)(43)(44)(45)(46). This O-H frequency shift is designated AVOH.…”

Section: Methanol Infrared 0-h Frequency Shiftmentioning

confidence: 99%

Family-independent relationships between computed molecular surface quantities and solute hydrogen bond acidity/basicity and solute-induced methanol O–H infrared frequency shifts

Hagelin¹,

Murray²,

Politzer³

et al. 1995

Can. J. Chem.

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165

140

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Family-independent relationships between computed molecular surface properties and solute hydrogen bond aciditylbasicity and solute-induced methanol 0-H infrared frequency shifts are presented. The molecular surface quantities, computed at the ab initio HFl6-31G* level, are primarily related to the electrostatic potential of the molecule, but also include the average local ionization energy on its surface.

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“…We have already measured pK HB for nitrogen [7] , oxygen, sulfur [8] , and π [9] bases. In the case of oxygen bases, alcohols [10] , esters [11] , amides [12] , ketones [13] , nitro bases [14] , sulfonyl bases [15] , and amidates [16] have already Eur. J. Org.…”

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confidence: 99%

The Hydrogen-Bond Basicity pKHB Scale of Peroxides and Ethers

1998

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Using 4‐fluorophenol as a reference hydrogen‐bond donor, equilibrium constants, Kf, for the formation of 1:1 hydrogen‐bonded complexes have been obtained by FTIR spectrometry for 39 ethers of widely different structure (cyclic and acyclic ethers, crown ethers, glymes, acetals, orthoesters, and disiloxane) and 3 peroxides, in CCl4 at 298 K. The pKHB scale of monoethers extends from 1.44 for 2,3‐diadamant‐2‐yloxirane to –0.53 for hexamethyldisiloxane. The main effects explaining the variation of the hydrogen‐bond basicity of sp3 oxygen atoms are (i) the electron‐withdrawing field‐inductive effect [e.g. in (CF3)2CHOMe], (ii) the electron‐withdrawing resonance effect (e.g. in EtOCH=CH2) (iii) the steric effect (e.g. in tBu2O), (iv) the lone‐pair–lone‐pair repulsion (e.g. in cyclic peroxides), and (v) the cyclization giving the basicity order: oxetane > tetrahydrofuran > tetrahydropyran > oxirane. A spectroscopic scale of hydrogen‐bond basicity is constructed from the infrared frequency shift Δν(OH) of methanol hydrogen‐bonded to peroxides and ethers. The thermodynamic pKHB scale does not correlate with the ν(OH) scale because of (i) statistical effects in polyethers and peroxides (ii) secondary hydrogen‐bond acceptor sites (e.g. in benzyl ether), (iii) variations of the s character of oxygen lone pairs either by conjugation or cyclization, (iv) steric effects, (v) lone‐pair–lone‐pair repulsions, and (vi) anomeric effects. The ν(OH···O) band shape reveals two stereoisomeric complexes, the most stable being tetrahedral at the ether oxygen atom.

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The first measurement of the hydrogen bond basicity of monomeric water, phenols and weakly basic alcohols

Cited by 61 publications

References 3 publications

Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Family-independent relationships between computed molecular surface quantities and solute hydrogen bond acidity/basicity and solute-induced methanol O–H infrared frequency shifts

The Hydrogen-Bond Basicity pKHB Scale of Peroxides and Ethers

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The first measurement of the hydrogen bond basicity of monomeric water, phenols and weakly basic alcohols

Cited by 61 publications

References 3 publications

Role of a distal pocket in the catalytic O 2 reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Role of a distal pocket in the catalytic O 2 reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Family-independent relationships between computed molecular surface quantities and solute hydrogen bond acidity/basicity and solute-induced methanol O–H infrared frequency shifts

The Hydrogen-Bond Basicity pKHB Scale of Peroxides and Ethers

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Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes