MIXED-VALENT STATES IN THE REDOX CHEMISTRY OF DOUBLE-DECKER-SANDWICH AND TRIPLE-DECKER-SANDWICH FREE-BASE AND COPPER PORPHYRINS

Double- and triple-decker-sandwich free base and copper porphyrins, wh ere tetraphenylporphyrin rings are linked together by two urea bridges , have been studied by cyclic voltammetry and UV-vis spectroelectroche mistry. Mixed-valent states appear in all cases, even with dimers and trimers containing twice or thrice the same porphyrin. The separations between the standard potentials in the H-2-H-2, CU-Cu, H-2-Cu dimers as well as in the H-2-H-2-H-2, Cu-Cu-Cu, H-2-Cu-H-2 trimers are interp reted in terms of Coulombic repulsion and interaction with the counter cations.