Modulation of magnetic properties at room temperature: Coordination-Induced Valence Tautomerism (CIVT)in a cobalt dioxolene complex

Witt, A., Heinemann, F. W., Sproules, S. and Khusniyarov, M. M. (2014) Modulation of magnetic properties at room temperature: Coordination-Induced Valence Tautomerism (CIVT)in a cobalt dioxolene complex. Chemistry: A European Journal, 20(35), pp. 11149-11162. (doi:10.1002/chem.201402129)

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Publisher's URL: http://dx.doi.org/10.1002/chem.201402129

Abstract

The valence tautomeric six-coordinate complex [Co(tbdiox)2(4-papy)2] 1 (tbdiox = redox-active 3,5-di-tert-buty-o-dioxolene; 4-papy = 4 phenylazopyridine) has been synthesized and its electronic structure examined. While in the solid state 1 shows a regular thermally driven valence tautomerism, it partially dissociates in solution to form the five-coordinate species [Co(tbdiox)2(4-papy)] 2 and free 4-papy. Species 1 and 2 reveal different electronic structures – low-spin (ls) CoIII and high-spin (hs) CoII, respectively – in solution at room temperature and therefore different magnetic properties. Since 1 and 2 are in equilibrium that is 4-papy dependent, the magnetic moment of the solution species can be tuned by the ligand content. Thus the concept of Coordination-Induced Valence Tautomerism (CIVT) has been introduced. The electronic structures of 1 and 2, and their CIVT have been elucidated by X-ray crystallography, electrochemistry, titration experiments and all variable-temperature SQUID susceptometry, NMR, EPR and electronic absorption spectroscopy. The experimental findings are strongly supported by broken-symmetry DFT calculations. Insight into magnetic exchange interactions within different types of valence tautomeric cobalt complexes is explored computationally.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Sproules, Dr Stephen
Authors: Witt, A., Heinemann, F. W., Sproules, S., and Khusniyarov, M. M.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Chemistry: A European Journal
Journal Abbr.:Chem. Eur J.
Publisher:Wiley
ISSN:0947-6539
ISSN (Online):1521-3765

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