The dioxygen adducts of several manganese(II) porphyrins. Electron paramagnetic resonance studies Academic Article uri icon

abstract

  • The reversible dioxygen adduct of manganese porphyrin (Mn(Por)) is five coordinate and of intermediate spin state (S=3/2) unlike the adducts of cobalt, iron, and chromium porphyrins. We have prepared a series of Mn(Por)(02) complexes, where Por = para-substituted tetraphenylporphyrin ([T(p-X)PP]; X = F, H,η-BuO) or octaethylporphyrin (OEP), and have examined their magnetic properties. The EPR parameters of the four complexes are qualitatively similar, but do differ within narrow limits: -D~2-3.2 cm-1; E/D~-1/3)-A(55Mn)~52-54ËŸ10-4 cm-1; -B(55Mn)~86-88 ËŸ l0-4 cm-1. We have also remeasured the effects of 17O substitution, and at low temperature (~10 K) find that it is possible to obtain the value of the small l70 hfs constant: a(l7O)~2.3ËŸ10-4 cm-1. Solely on the basis of the magnetic resonance parameters obtained, it is possible to rule out most possible combinations of an odd-electron configuration and Mn-C2 binding geometry. These results and qualitative bonding considerations support the original description in terms of a Mnlv-022- valency formalism with a symmetric, edge-on dioxygen. © 1978, American Chemical Society. All rights reserved.

published proceedings

  • Journal of the American Chemical Society

author list (cited authors)

  • Hoffman, B. M., Szymanski, T., Brown, T. G., & Basolo, F

citation count

  • 48

complete list of authors

  • Hoffman, Brian M||Szymanski, Thomas||Brown, Theodore G||Basolo, Fred

publication date

  • November 1978