No 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, ti-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 ~V3; -/t(55Mn) ~52-54 X 10-4 cm-1; -5(55Mn) ~86-88 X 10-4 cm-1. We have also remeasured the effects of 170 substitution, and at low temperature (~10 K) find that it is possible to obtain the value of the small l70 hfs constant: (|70) ~2.3 X 10_4cm_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-02 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.

No abstract

No abstract

No abstract