Issue 9, 2001

Abstract

We report valence tautomerism in the spin-labeled complex, Co(nnbpy)(3,5-DTBSQ)2, where nnbpy is a bipyridine substituted nitronyl nitroxide radical, 4-methyl-4′-(4,4,5,5-tetramethyl-1-oxido-3-ylooxy-4,5-dihydro-3H-imidazol-2′-yl)-2,2′-bipyridine, and 3,5-DTBSQ is 3,5-di-tert-butylbenzosemiquinone. The temperature dependence of the magnetic susceptibility indicates a tautomeric conversion, Co3+(nnbpy)(3,5-DTBSQ˙)(3,5-DTBSQ2−) → Co2+(nnbpy)(3,5-DTBSQ˙)2, above 250 K with the thermodynamic parameters of ΔH = 34 kJ mol−1 and ΔS = 98 J K−1 mol−1. The ligand radical, nnbpy, behaves as a Curie spin over the whole temperature region. The EPR spectra in the temperature range 150–380 K consist of a single absorption at g = 2.004 that gradually fades away above 300 K with a characteristic increase in linewidth.

Graphical abstract: Inner- and outer-sphere magnetic moments in the cobalt–quinone valence tautomeric system

Article information

Article type
Paper
Submitted
08 Mar 2001
Accepted
29 Jun 2001
First published
02 Aug 2001

J. Mater. Chem., 2001,11, 2142-2145

Inner- and outer-sphere magnetic moments in the cobalt–quinone valence tautomeric system

A. Yamaguchi and K. Awaga, J. Mater. Chem., 2001, 11, 2142 DOI: 10.1039/B102214H

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