ESR Spectroscopy of Nitroxides: Kinetics and Dynamics of Exchange Reactins

Grampp, Günter; Rasmussen, Kenneth

doi:10.5772/39131

Cited by 3 publications

(5 citation statements)

References 114 publications

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“…Nitroxides are a broad family of organic free radicals which have been of constantly growing interest to researchers for many decades [1][2][3]. The relative simplicity of chemical modification of nitroxide structures resulted in the synthesis of countless numbers of derivatives, allowing for tuning of their chemical and physical properties and spectral parameters for specific applications in various fields of science and technology [4][5][6][7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

2,5-Di-tert-butyl-2,5-diethylpyrrolidine-1-oxyls: Where Is a Reasonable Limit of Sterical Loading for Higher Resistance to Reduction?

Zhurko,

Dobrynin,

Glazachev

et al. 2024

Molecules

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The pyrrolidine nitroxides with four bulky alkyl substituents adjacent to the N–O∙ group demonstrate very high resistance to reduction with biogenic antioxidants and enzymatic systems. This makes them valuable molecular tools for studying the structure and functions of biomolecules directly in a living cell and for functional EPR and NMR tomography in vivo. The first example of highly strained pyrrolidine nitroxides with both ethyl and tert-butyl groups at each of the α-carbon atoms of the nitroxide moiety with cis-configuration of the tert-butyl groups was prepared using a three-component domino reaction of tert-leucine and 2,2-dimethylpentan-3-one with dimethyl fumarate with subsequent conversion of the resulting strained pyrrolidine into 1-pyrroline-1-oxide and addition of EtLi. The nitroxide has demonstrated unexpectedly fast reduction with ascorbate, the rate constant k2 = (2.0 ± 0.1) × 10−3 M−1s−1. This effect was explained by destabilization of the planar nitroxide moiety due to repulsion with the two neighboring tert-butyl groups cis to each other.

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Section: Introductionmentioning

confidence: 99%

2,5-Di-tert-butyl-2,5-diethylpyrrolidine-1-oxyls: Where Is a Reasonable Limit of Sterical Loading for Higher Resistance to Reduction?

Zhurko,

Dobrynin,

Glazachev

et al. 2024

Molecules

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“…An alternative way of measuring the rate of solute exchange is to use ESR and spin probes, , the essential idea being that the spin probe shows different ESR parameters, specifically hyperfine interactions, in water, interface regions, and hydrocarbon as solvent. Exchange of the spin probe between these environments leads to the averaging of the ESR parameters, in a process known as “chemical exchange” . By simulating the spectral changes, it is possible to derive the exchange rate between the environments.…”

Section: Introductionmentioning

confidence: 99%

“…Exchange of the spin probe between these environments leads to the averaging of the ESR parameters, in a process known as "chemical exchange". 15 By simulating the spectral changes it is possible to derive the exchange rate between the environments. Thus in the case of the spin probe 2,2,6,6,-tetramethyl-4-piperidone N-oxide in an AOT w/o microemulsion in heptane a rate of exchange of 4 x 10 6 s -l was deduced.…”

Section: Introductionmentioning

confidence: 99%

Rate of Molecular Transfer of Allyl Alcohol across an AOT Surfactant Layer Using Muon Spin Spectroscopy

et al. 2016

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ABSTRACT:The transfer rate of a probe molecule across the interfacial layer of a water-in-oil (w/o) microemulsion was investigated using a combination of Transverse Field muon spin rotation (TF-μSR), Avoided Level Crossing muon spin resonance (ALC-μSR) and Monte Carlo simulations. Reverse microemulsions consist of nanometer sized water droplets dispersed in an apolar solvent separated by a surfactant monolayer. Although the thermodynamic, static model of these systems has been well described, our understanding of their dynamics is currently incomplete. For example, what is the rate of solute transfer between the aqueous and apolar solvents, and how this is influenced by the structure of the interface? With an appropriate choice of system and probe molecule, SR offers a unique opportunity to directly probe these interfacial transfer dynamics. Here, we have employed a well characterized w/o microemulsion stabilized by bis(2-ethylhexyl) sodium sulphosuccinate (Aerosol OT), with allyl alcohol (CH2=CH-CH2-OH, AA) as the probe. Resonances due to both muoniated radicals, CMuH2-C*H-CH2-OH and C*H2-CHMu-CH2-OH, were observed with the former being the dominant species. All resonances displayed solvent dependence, with those in the microemulsion observed as a single resonance located at intermediate magnetic fields to those present in either of the pure solvents. Observation of a single resonance is strong evidence for interfacial transfer being in the fast exchange limit. Monte-Carlo calculations of the M=0 ALC resonances are consistent with the experimental data, indicating exchange rates greater than 10 9 s -1 , placing the rate of interfacial transfer at the diffusion limit.

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“…Electron self-exchange experimental studies were performed in a pure solvents providing useful information for the theory of electron transfer and understanding the solvent effects. 14 Application of the electron self-exchange reactions of the paramagnetic probes to assess chemical microenvironment in complex biological systems seems to be hardly possible.…”

mentioning

confidence: 99%

“…An exception is electron self-exchange reactions which denote the one-electron transfer between the partners of a redox couple (e.g., NR and its oxoammonium cation) which results in no net chemical reaction. Electron self-exchange experimental studies were performed in a pure solvents providing useful information for the theory of electron transfer and understanding the solvent effects . Application of the electron self-exchange reactions of the paramagnetic probes to assess chemical microenvironment in complex biological systems seems to be hardly possible.…”

mentioning

confidence: 99%

Exchange Phenomena in the Electron Paramagnetic Resonance Spectra of the Nitroxyl and Trityl Radicals: Multifunctional Spectroscopy and Imaging of Local Chemical Microenvironment

et al. 2017

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This Feature overviews the basic principles of using stable organic radicals involved in reversible exchange processes as functional paramagnetic probes. We demonstrate that these probes in combination with electron paramagnetic resonance (EPR)-based spectroscopy and imaging techniques provide analytical tools for quantitative mapping of critical parameters of local chemical microenvironment. The Feature is written to be understandable to people who are laymen to the EPR field in anticipation of future progress and broad application of these tools in biological systems, especially in vivo, over the next years.

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ESR Spectroscopy of Nitroxides: Kinetics and Dynamics of Exchange Reactins

Cited by 3 publications

References 114 publications

2,5-Di-tert-butyl-2,5-diethylpyrrolidine-1-oxyls: Where Is a Reasonable Limit of Sterical Loading for Higher Resistance to Reduction?

2,5-Di-tert-butyl-2,5-diethylpyrrolidine-1-oxyls: Where Is a Reasonable Limit of Sterical Loading for Higher Resistance to Reduction?

Rate of Molecular Transfer of Allyl Alcohol across an AOT Surfactant Layer Using Muon Spin Spectroscopy

Exchange Phenomena in the Electron Paramagnetic Resonance Spectra of the Nitroxyl and Trityl Radicals: Multifunctional Spectroscopy and Imaging of Local Chemical Microenvironment

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