ESR measurement of translational diffusion constants

Fawthrop, Susan A.; Gillies, Donald C.; Sutcliffe, L. H.; Symms, Mark R.

doi:10.1002/mrc.1260331317

Cited by 4 publications

(5 citation statements)

References 21 publications

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“…ESR Experiments. The translational diffusion constant for TMIO (it was not necessary to use the isotopically-labeled version, NTMIOD, of the radical) in triglyme was measured using the ESR capillary method. , A 10 cm long thin-walled capillary of internal diameter 1.3 mm was filled to a depth of 7 cm with air-saturated triglyme. To the top of the liquid column was introduced 5 μL of a millimolar solution of TMIO in triglyme.…”

Section: Methodsmentioning

confidence: 99%

“…NMR tube that was pushed through the cavity with the calibrated screw. The data were processed using the corrected-zero method as described in ref (note that in this reference there are three errors (i) the slopes referred to after eqs 8 and 15 should be (4 Dt ) -1 , (ii) eq 16 should read a = (4 ln 2)/ , (iii) W b in Figure should be W b /2).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Translational Diffusion Constants and Intermolecular Relaxation in Paramagnetic Solutions with Hyperfine Coupling on the Electronic Site

et al. 1998

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We investigate the NMR relaxation of solvent nuclei in non viscous paramagnetic solutions, in the case where the electronic spin of the paramagnetic species is submitted to an internal hyperfine field H hyp . General expressions of the intermolecular longitudinal relaxation rates 1/T 1 are provided, and three distinct regimes corresponding to an applied external field lower, larger and much larger than H hyp appear, with three distinct linear laws for the relaxation rate 1/T 1 vs ν I 1/2 , where ν I is the nuclear resonance frequency. From each of these laws and mainly the third one, it is possible to derive the relative diffusion constant of the paramagnetic and solvent molecules without any model assumption for solutions with a rather high radical concentration of 10 -1 mol L -1 . This is illustrated for a triglyme solution with new stable 15 NTMIOD free radicals at various concentrations. For this solution, T 1 measurements were performed at ν I ) 244 MHz, then at low and intermediate frequencies by the field cycling technique and finally in the Earth's magnetic field. From these results and from measurements of the solvent molecule diffusion constant by the pulsed magnetic field gradient technique, a determination of the diffusion constant of the free radicals is obtained which is compared with that obtained from a direct ESR measurement at low concentration. These data are used for the interpretation of the frequency and temperature dependence of the relaxation rates in this solution.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Translational Diffusion Constants and Intermolecular Relaxation in Paramagnetic Solutions with Hyperfine Coupling on the Electronic Site

et al. 1998

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“…15 The ease of synthesis of 2 H and 15 N labelled derivatives 11 of the isoindoline aminoxyls provides access to probes with specifically tailored spectroscopic characteristics, widening the scope of their application, as has been demonstrated by the development of a simple EPR technique for the measurement of translational diffusion constants using the tetrakis(trideuteriomethyl) analogue (TMIOD) of TMIO in conjunction with the deuterated 5-sulfonate derivative (NaTMIODS). [16][17][18] While the suitability of isoindoline aminoxyls for use as spin probes has been adequately demonstrated, their full potential has been somewhat limited by a lack of structural variation, especially with regards to water solubility. To this end, we have synthesised a range of new substituted isoindoline aminoxyls, including halogenated 19 and carboxy species (CTMIO, 6) 20 suitable for further derivatisation.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, single crystal X-ray structure and W-band (95 GHz) EPR spectroscopy of a new anionic isoindoline aminoxyl: synthesis and characterisation of some derivatives

Bottle

Gillies

Hughes

et al. 2000

J. Chem. Soc., Perkin Trans. 2

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Here we describe the improved synthesis and full characterisation, including W-band EPR analysis and X-ray crystallography, of an anionic isoindoline aminoxyl, 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl 6 (CTMIO), which is more water soluble than the parent 1,1,3,3-tetramethylisoindolin-2-yloxyl 1 (TMIO). We also report the synthesis and characterisation of three novel CTMIO derivatives: the n-hexyl ester 9, anhydride 10, and N-hydroxysuccinimide ester 11.Selective AlCl 3 -catalysed bromination of 2-benzyl-1,1,3,3-tetramethylisoindoline 2 produces the aminoxyl precursor, 5-bromo-1,1,3,3-tetramethylisoindoline 3 in high yield. Lithiation and subsequent carboxylation of this species generates 5-carboxy-1,1,3,3-tetramethylisoindoline 5, which undergoes tungstate-H 2 O 2 oxidation to give the target aminoxyl, CTMIO 6. The analogous synthesis of 5-formyl-1,1,3,3-tetramethylisoindolin-2-yloxyl 8 is also described.W-band (95 GHz) EPR studies of toluene solutions of CTMIO, both liquid and frozen, indicate that aggregates are formed: the liquid state was used to measure the equilibrium dimer formation constant (30 ± 40 M Ϫ1 at 298 K); the solid state was used to estimate the distance (19.3 Å) between the two aminoxyl groups in the dimer. A single crystal X-ray examination reveals that there is short-range intermolecular hydrogen bonding between aminoxyl and carboxylic groups, and that the aminoxyl groups are separated by 10.2 Å. However, it is concluded from the EPR spectral evidence that, in toluene solution, the dimers are formed by hydrogen bonding between pairs of carboxylic groups. Using the molecular dimensions determined by X-ray analysis, the distance between the aminoxyl groups in the dimer in frozen solution was estimated to be 17 Å.

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“…Isoindolines 5 and 8 were identified by NMR and GC-MS but not characterised further, as they were not major synthetic targets. (22), 239/237 (7), 158 (21), 142 (23), 115 (16).…”

Section: 56-tribromo-1133-tetramethylisoindoline (6)mentioning

confidence: 99%

“…This has led to the development of a simple EPR technique for the measurement of translational diffusion constants using the tetrakis(trideuteriomethyl) analogue 11 of 1 in conjunction with a deuterated 5-sulphonyl derivative. [22][23][24] Further work has involved the synthesis of various isotopically labelled 5-(n-alkyl) isoindoline nitroxides which show promise as spin-probes of lipid systems. [11][12] While the potential of isoindoline nitroxides in imaging techniques and as spin probes/labels, as well as their usefulness in diffusion and EPR studies has been demonstrated, structural variation in the available nitroxides remains limited.…”

mentioning

confidence: 99%

Brominated isoindolines: precursors to functionalised nitroxides

Micallef¹,

Bott²,

Bottle³

et al. 1999

J. Chem. Soc., Perkin Trans. 2

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A new, convenient method for the preparation of functionalised precursors to stable tetraalkylisoindoline nitroxides (aminoxyls) is presented. Simple treatment of 2-benzyl-1,1,3,3-tetramethylisoindoline 2 with Br 2 in CCl 4 gives rapid oxidative debenzylation, generating benzaldehyde and an unusual bromamine, 2-bromo-1,1,3,3-tetramethylisoindoline 4, in high yield. Treatment of the bromamine 4 with FeSO 4 / H 2 SO 4 results in bromination of the aromatic ring in varying yield, while rapid treatment with peroxide / tungstate causes debromination, generating 1,1,3,3-tetramethylisoindoline 3. Bromination of the isoindoline aromatic ring is more readily afforded by treatment of 2-benzyl-1,1,3,3-tetramethylisoindoline 2 with Br 2 and AlCl 3 in CCl 4 , producing 2,5-dibromo-1,1,3,3-tetramethylisoindoline 7 and/or 2,5,6-tribromo-1,1,3,3-tetramethylisoindoline 6 in varying yields depending upon the exact reaction conditions. Rapid treatment with peroxide / tungstate generates the corresponding bromine substituted isoindolines, 5-bromo-1,1,3,3-tetramethylisoindoline 5 and 5,6-dibromo-1,1,3,3-tetramethylisoindoline 8. Prolonged peroxide / tungstate treatment oxidises the substituted bromamines to the corresponding nitroxides, 5-bromo-1,1,3,3-tetramethylisoindolin-2-yloxyl 9 and 5,6-dibromo-1,1,3,3-tetramethylisoindolin-2-yloxyl 10. SQUID magnetic susceptibility measurements of crystalline 10 reveal strong antiferromagnetic interradical spin coupling. The crystal structures of 10, 2-bromo-1,1,3,3-tetramethylisoindoline 4 and the hydrobromide dihydrate salt of 1,1,3,3-tetramethylisoindoline 3 (3a) have also been determined, with 10 displaying an interesting molecular packing arrangement.2

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ESR measurement of translational diffusion constants

Cited by 4 publications

References 21 publications

Translational Diffusion Constants and Intermolecular Relaxation in Paramagnetic Solutions with Hyperfine Coupling on the Electronic Site

Translational Diffusion Constants and Intermolecular Relaxation in Paramagnetic Solutions with Hyperfine Coupling on the Electronic Site

Synthesis, single crystal X-ray structure and W-band (95 GHz) EPR spectroscopy of a new anionic isoindoline aminoxyl: synthesis and characterisation of some derivatives

Brominated isoindolines: precursors to functionalised nitroxides

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