Protonation equilibria of (octakis(3-trifluoromethylphenyl)-, (3-trifluoromethylphenoxy)-, and (3,5-di-tert-butylphenoxy)phthalocyaninato) manganese(III) acetate

Abstract

Acid-base reactions of (octakis(3-trifluoromethylphenyl)phtalocyaninato) manganese(III) acetate (AcO)MnPc(3-CF3Ph)8, (octakis(3-trifluoromethylphenoxy)phtalocyaninato) manganese(III) acetate (AcO)MnPc(3-CF3PhO)8 and (octakis(3,5-di-tert-butylphenoxy) phtalocyaninato) manganese(III) acetate (AcO)MnPc(3,5-di-tBuPhO)8 are studied spectrophotometrically in a trifluoroacetic acid-dichloromethane system by molar ratios method. Protonation of complexes is found to include two reversible stepwise reactions that are bi- and trimolecular. The thermodynamic stability constants of the acid forms and their dependence on the chemical structure of the molecules is determined using data on Hammett’s acidity functions H0 for a mixed solvent. Substituents 3-CF3Ph, 3-CF3PhO, and 3,5-di-tBuPhO display positive electronic effects with respect to the macrocycle and reaction centers that are enhanced when the second and third proton bond in one stage.