A SOLUTION STUDY OF THE INTERACTION OF SUPERSTRUCTURED IRON(III) PORPHYRINS WITH CATECHOL

The interaction of two series of superstructured iron(III) porphyrins with catechol as an axial ligand have been studied in order to mimic the substrate binding in catechol dioxygenase. The formation equilibrium of hydrogenocatecholate complexes of two iron(III) "basket-handle" porphyrins, a-BHP(C-12)(2)Fe(III) and e-BHP(C-12)(2)Fe(III), have been investigated in a dimethytsulfoxide (dmso)-water (80 : 20, v/v) solution. A combined spectrophotometric and potentiometric study allowed us to determine the stability constant for the complex Fe-III(a-BHP(C-12)(2))-Hcat : log beta = 8.6 (0.1 M KNO3, 25 degrees C). The deprotonation of the hydrogenocatecholate complex in a basic medium and its reactivity with dioxygen have been studied.