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- Title
Modulation of Magnetic Properties at Room Temperature: Coordination-Induced Valence Tautomerism in a Cobalt Dioxolene Complex.
- Authors
Witt, Alexander; Heinemann, Frank W.; Sproules, Stephen; Khusniyarov, Marat M.
- Abstract
The valence-tautomeric six-coordinate complex [Co(tbdiox)2(4-papy)2] ( 1; tbdiox=redox-active 3,5-di- tert-butyl- o-dioxolene, 4-papy=4-phenylazopyridine) was synthesized and its electronic structure examined. Whereas 1 shows regular thermally driven valence tautomerism in the solid state, 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 exhibit 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 an equilibrium that is 4-papy-dependent, the magnetic moment of the solution species can be tuned by means of the ligand content. Thus, the concept of coordination-induced valence tautomerism (CIVT) has been introduced. The electronic structures of 1 and 2 as well as their CIVT were 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. The magnetic exchange interactions in different types of valence-tautomeric cobalt complexes were explored computationally.
- Subjects
COBALT compounds; TRANSITION metal compounds; THERMAL properties; PROPERTIES of matter; TAUTOMERISM
- Publication
Chemistry - A European Journal, 2014, Vol 20, Issue 35, p11149
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201402129