The thermodynamic properties were studied for the axial coordination reaction（1）of 2,9,16,23-tetracarboxyphthalocynineiron（Ⅲ）with imidazole in dimethylsulfoxide（DMSO）[Fe（Ⅲ）Pc（COOH）4OH]+nL=[Fe（Ⅲ）Pc（COOH）4Ln]++OH （1）The equilibrium constant（K） and coordination number of reaction（1） were measured by spectrophotometry.The standard molar enthalpy(△rH○—m)and standard entropy(△rS○—m)of the reaction（1）were calculated.
