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Synthesis and characterization of beta-trifluoromethyl-meso-tetraphenylporphyrins

TitleSynthesis and characterization of beta-trifluoromethyl-meso-tetraphenylporphyrins
Publication TypeJournal Article
Year of Publication2003
AuthorsTerazono, Y, Dolphin, D
JournalJournal of Organic Chemistry
Volume68
Pagination1892-1900
Date PublishedMar
Type of ArticleArticle
ISBN Number0022-3263
KeywordsBROMINATED-PYRROLE TETRAPHENYLPORPHYRIN, COMPLEXES, EFFICIENT CATALYSTS, ELECTROCHEMISTRY, ELECTRON-DEFICIENT PORPHYRINS, HYDROXYLATION, METALLOPORPHYRINS, REDOX POTENTIALS, SUBSTITUENTS, X VARIES
Abstract

beta-Trifluoromethyl-meso-tetraphenylporphyrins were synthesized to investigate the electronic and steric effects of the trifluoromethyl groups on the macrocycle. Preparation of these novel porphyrins was carried out by copper-assisted trifluoromethylation of beta-tetrabromo-meso-tetraphenylporphyrin metal complexes and in situ generated CF3Cu. For comparison, the beta-methyl analogues were also prepared. Analysis of beta-trifluoromethylporphyrins by UV-vis, NMR, and cyclic voltammetry (CV) showed that the electron-withdrawing effects of the trifluoromethyl groups on the antipodal pyrroles required the macrocycle to take a fixed 18pi-electron pathway. UV-vis, CV, and molecular modeling studies suggest that the novel porphyrins are distorted following introduction of trifluoromethyl groups onto the pyrrolic beta-position of meso-tetraphenylporphyrin. The pK(a) difference of beta-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin from that of DBU in CH2Cl2, obtained by spectrophotometric titration, affirms that it is one of the most electron-deficient porphyrins so far prepared.

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