A Highly Oxidized Cobalt Porphyrin Dimer: Spin Coupling and Stabilization of the Four-Electron Oxidation Product
Soumyajit Dey, Debangsu Sil, and Sankar Prasad Rath*
[*] S. Dey, D. Sil, Prof. Dr. S. P. Rath
Department of Chemistry, Indian Institute of Technology Kanpur Kanpur-208016 (India)
Department of Chemistry, Indian Institute of Technology Kanpur Kanpur-208016 (India)
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
DOI: 10.1002/anie.201509430
http://onlinelibrary.wiley.com/doi/10.1002/anie.201509430/abstract
DOI: 10.1002/anie.201509430
http://onlinelibrary.wiley.com/doi/10.1002/anie.201509430/abstract
Abstract
A highly oxidized cobalt porphyrin dimer is reported. Each
cobalt(II) ion and porphyrin ring underwent 1e oxidation with iodine as
the oxidant to give a 4e-oxidized cobalt(III) porphyrin π-cation radical
dimer. The bridging ethylene group allows for substantial conjugation
of the porphyrin macrocycles, thus leading to a strong antiferromagnetic
coupling between the π-cation radicals and to stabilization of the
singlet state. X-ray crystallography clearly showed that the complex may
be considered as a real supramolecule rather than two cobalt(III)
porphyrin π-cation radicals that interact through space.
Four to be sure: The oxidation of a cobalt(II) porphyrin
dimer with iodine readily produced a cobalt(III) porphyrin π-cation
radical dimer (see scheme). Extensive π conjugation through the ethylene
bridge led to several unusual spectral and geometrical features of this
four-electron oxidized complex and stabilized the singlet state by
enabling strong antiferromagnetic coupling between the π-cation
radicals.
コメント