Jp. Gisselbrecht et al., Electrochemical properties of 'figure-eight'-cyclooctapyrroles (octaphyrins) and their metal complexes, J ELEC CHEM, 469(2), 1999, pp. 170-175
In this paper the first electrochemical results obtained on 'figure-eight'-
cyclooctapyrrolic macrocycles (octaphyrins) 1 to 3, and on some of their mo
no- and bi-nuclear transition metal complexes, i.e. compounds 5-8 and 9-16,
respectively, are reported. All these species undergo five distinct redox
steps. The two reductions and the first two oxidations are reversible one-e
lectron transfers. The third oxidation is a global two electron reaction ex
cept in the Co(IT) complexes. In the latter, this step corresponds to the C
o(II) --> Co(III) oxidation. The free base octaphyrins display electrochemi
cal gaps (E-ox1 - E-red1) from 1.43 to 0.85 V, lower than any previously ob
served gap in porphyrins and porphycenes, and-at further variance with thes
e tetrapyrrolic molecules - this gap changes with the coordinated metal. An
other special feature of binuclear metallo-octaphyrins is an intense and sh
arp absorption band exhibited at 700 nm and beyond in their two electron re
duced form. (C) 1999 Elsevier Science S.A. All rights reserved.