Electrochemical, Spectroscopic and Acid-base Properties of Pyridylporphyrins in Nonaqueous Media
This thesis describes the electrochemical, spectroscopic and acid-base properties of pyridylporphyrins, tetramethylpyridyl porphyrins and corroles in nonaqueous media. Several corroles are also examined. Free-base and metal derivatives (CoII, NiII, CuII and ZnII) of pyridylporphyrins possessing one, two or four pyridyl meso-substituents were examined before, during and after the addition of protons to solution in the form of trifluoroacetic acid (TFA). The free-base (metal-free) pyridylporphyrins undergo an initial protonation on the pyridyl substituents and this is followed by protonation of the central nitrogen atoms in a second step. The pyridylporphyrins with metal centers are only protonated at the meso-pyridyl groups. Both sites of protonation are associated with specific changes in the electrochemical and spectroscopic properties of the compounds. The utilized solvent was shown to have an effect on the protonation constants, which varied from 102 to 104, depending upon the specific compound. The tetrapositively-charged free-base tetra-N-methylpyridylporphyrins possess four Cl-, Br-, I- or PhSO3- counteranions and the electrochemistry of these compounds was examined in DMF or DMSO, containing 0.1 M tetra-n-butylammonium hexafluorophosphate (TBAPF6) or tetra-n-butylammonium iodide (TBAI). These measurements were made in order to study the interaction of the counteranion, the solvent and the supporting electrolyte on the reductions. Finally, the electrochemical properties of iron ferrocenylcorroles with NO, C6H5 or Cl- axial ligands were examined in PhCN containing 0.05 M tetrakis-fluorophenylborate (TFAB).