METAL COMPLEXES WITH TETRAPYRROLE LIGANDS - 73 - OXIDATION AND REDUCTION OF CERIUM(IV) SANDWICH COMPLEXES WITH PORPHYRIN LIGANDS LINKED BY ALIPHATIC DIETHER BRIDGES OF VARIABLE CHAIN-LENGTH

Starting from roxyphenyl)-10,15,20-tris(4-methylphenyl)porphyrin (2a), the new bis(porphyrinyloxy)alkanes 4a and 4d were synthesized by ethe r formation with the alpha,omega-dibromoalkanes Br(CH2)(n)Br (n = 8, 1 1; 3a, 3d). 4a was obtained by a two-step reaction with the oxy)phenyl ]-10,ls,20-tris(4-methylphenyl)porphyrin (2b) as an intermediate. The diporphyrins 4a and 4d were metalated with cerium(III) acetylacetonate to yield the new (porphyrin)cerium sandwich complexes la and Id which were characterized by UV/Vis, IR, H-1-NMR, C-13-NMR spectroscopy and cyclic voltammetry. The mono-and dications and the cerium(III) bisporp hyrinate anions of 1a-d were produced by electrochemical oxidation and reduction, respectively, and were examined by UV/Vis/NIR spectroscopy . The length of the lateral chains does not have a specific effect on the first and second oxidation potentials of the porphyrin rings and t he reduction potentials of the cerium ions in the bisporphyrinate syst ems, and on the energy of the NIR bands of the monocations.