EFFECT OF ELECTROLYTE CONCENTRATION ON AXIAL ANION LIGATION IN MANGANESE(III) MESO-TETRAPHENYLPORPHYRIN CHLORIDES

The ionic strength dependence of axial ligation in manganese(III) 5,10,15,20-tetraarylporphyrin chlorides has been investigated and found to be much more important than has hitherto been recognized. In this study tetrahydrofuran solutions of the metalloporphrin, 0.0-0.5 M in the electrolyte tetrabutylammonium tetrafluoroborate, were examined by electronic absorption and resonance Raman spectroscopies as well as ultramicroelectrode voltammetry. The metalloprphyrin complexes were found to be significantly dissociated even at moderate electrolyte concentrations. In all cases, anion dissociation was promoted as concentration of electrolyte was increased. The fully dissociated analogues were independently generated by reaction of the manganese(III) porphyrin with AgBF4. Tentative assignments for the low-wavenumber region of the resonance Raman spectra of the studied complexes are made and solution structures inferred.