Formation of manganese(II) porphyrin derivatives from manganese(III) derivatives by ionizing radiation

Exposure of manganese(III) porphyrin solutions to 60Co γ-rays at 77 K gave the manganese(II) derivatives, with g(perpendicular)(apparent) approximately = 6, A(55Mn) approximately = 77 G and /D/ >= 0.3 cm-1. The spectra are very similar to those for Mnsup(II) derivatives prepared chemically. Weak features in the g = 2 region for these complexes were obscured by features from a symmetrical Mnsup(II) derivative of unknown origin. These features grew in intensity on melting and re-freezing. These results suggest that low-temperature irradiation coupled with e.s.r. spectroscopy may be a suitable technique for detecting Mnsup(III) derivatives in biological systems. (author)