SPECTROSCOPIC STUDIES ON THE REACTIONS OF SUPEROXIDE ION WITH THE COPPER(II) POLYVALENT PORPHYRIN COMPLEX, TETRAKIS(3,5-DI-TERT-BUTYL-4-HYDROXYPHENYL)PORPHYRINATOCOPPER(II)

The reactions of the polyvalent porphyrin tetrakis(3,5-di-tert-butyl-4-hydroxy-phenyl)porphyrinatocopper(II) [Cu(II)T(t)BHPP, 2] with superoxide ion (O2-) were investigated by use of UV-vis and ESR spectrometers. From the visible spectral changes observed by the successive addition of O2- to Cu(II)T(t)BHPP, it was shown that the absorption due to the Soret band which is typical of the porphyrin skeleton completely disappeared. Further, from the ESR spectrum observed after the O2- solutions were mixed with those of Cu(II)T(t)BHPP, it was shown that the superhyperfine structure due to pyrrole nitrogens in Cu(II)T(t)BHPP disappeared at room temperature and that the ESR signal due to O2- also completely disappeared at 77 K. From these results, it is concluded that the reaction product between Cu(II)T(t)BHPP and O2- may be the copper(II)-quinone complex (4) which is formed by the oxidation of the porphyrin moiety of Cu(II)T(t)BHPP with O2-.