Octaethylcorrphycene and its metal complexes. Radiolytic reduction studies

One-electron and multielectron reductions of 2,3,6,7,11,12,17,18-octaethylcorrphycene (H(2)OECn) and its sn(IV), Fe(III), Co(II), Ni(II), Cu(II), and Ag(II) complexes in 2-propanol (2-PrOH) solutions have been studied by radiolytic techniques. Formation and decay of unstable intermediates formed upon one-electron reduction have been followed by kinetic spectrophotometric pulse radiolysis. The absorption spectra of stable reduction products have been recorded following gamma-radiolysis, H(2)OECn is reduced to a transient pi-radical anion, (H(2)OECn)(.-), which decays by disproportionation to form a product with a chlorin-like spectral signature. Sn(IV)OECn is reduced io a stable pi-radical anion and subsequently to the dianion, which protonates to a species that, on the basis of its spectral characterization, Is considered to be a phlorin-anion-type product, Fe(III), Co(III), Co(II), and Ag(II) corrphycenes undergo radiolytic reduction at the metal center. The Fe(II) and Co(I) corrphycenes produced are stable, and upon farther reduction in neutral solutions they yield species with chlorin-like spectral signatures. When similar reductions are carried out in alkaline solutions, species with phlorin-anion-like characteristics are produced. Ag(I)OECn, due to its large ionic radius, undergoes demetalation. Cu(II)OECn is reduced al the ligand in neutral 2-PrOH, but in alkaline solutions it forms an unstable Cu(I)OECn complex, which disproportionates and demetalates. In contrast, reduction of Ni(II)OECn yields the pi-radical anion in acidic, neutral, and alkaline 2-PrOH solutions. These results suggest that the larger size of the corrphycene core, as compared with that of porphycenes, results in greater stability of complexes with metal ions of and larger radii. Ni(ll), Co(II), and Fe(II) corrphycenes also react rapidly with (CH3)-C-. radicals to form sigma-bonded CH3-M(III)OECn complexes, Whereas the CH3-Ni(III)OECn complex decays within <1 ms, the CH3-Fe(III)OECn complex proved stable in the absence of oxygen, and the corresponding CH3-Co(III)OECn species was found to be stable even in the presence of O-2.