Solvent and Temperature Dependence of Spin Echo Dephasing for Chromium(V) and Vanadyl Complexes in Glassy Solution

doi:10.1006/jmre.1998.1610

Journal of Magnetic Resonance

Volume 136, Issue 1, January 1999, Pages 63-68

https://doi.org/10.1006/jmre.1998.1610 Get rights and content

Abstract

The solvent and temperature dependence of the rate constant for spin echo dephasing, 1/T_m, for 0.2 to 1.2 mM glassy solutions of chromyl bis(1-hydroxy-cyclohexanecarboxylic acid), CrO(HCA)⁻₂; aquo vanadyl ion, VO²⁺(aq), and vanadyl bis(trifluoroacetylacetonate), VO(tfac)₂were examined. At low temperatures where 1/T₁⪡ 1/T_m, 1/T_min 1:1 H₂O:glycerol is dominated by solvent protons. At low temperature 1/T_mincreases in the order 1:1 H₂O:glycerol or 9:1 CF₃CH₂OH:ethyleneglycol (no methyl groups) < 9:1i-PrOH:MeOH (hindered methyl groups) < 9:1n-PrOH:MeOH (less hindered methyl groups). This solvent dependence of 1/T_mis similar to that observed for nitroxyl radicals, which indicates that the effect of solvent methyl groups on spin-echo dephasing at low temperature is quite general. At higher temperatures the echo dephasing is dominated by spin–lattice relaxation and is concentration dependent. As the glass softens, echo dephasing is dominated by the onset of molecular tumbling.

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Regular ArticleSolvent and Temperature Dependence of Spin Echo Dephasing for Chromium(V) and Vanadyl Complexes in Glassy Solution☆

Abstract

J. Magn. Reson.

Chem. Phys. Lett.

J. Magn. Reson. A

Phys. Rev.

Time Domain Electron Spin Resonance

Sov. Phys. JETP

J. Chem. Phys.

Appl. Magn. Reson.

Isr. J. Chem.

Regular Article
Solvent and Temperature Dependence of Spin Echo Dephasing for Chromium(V) and Vanadyl Complexes in Glassy Solution☆