CПЕКТРОСКОПИЧЕСКОЕ ИССЛЕДОВАНИЕ ДИМЕРИЗАЦИИ 5,10,15,20-ТЕТРАКИС(6-N-МЕТИЛХИНОЛИНИЛ)-ПОРФИРИНА В ВОДНЫХ РАСТВОРАХ

Dimerization of 5,10,15,20-tetrakis(6-N-methylquinolinyl)-porphyrin in water solutions in the temperature range of 274—343 K was studied using absorption and fluorescence spectroscopy. The equilibrium dimerization constant K D was shown to vary in a wide range upon the temperature changes. The enthalpy ΔH ≠ and entropy ΔS ≠ of dimerization in solution with different ionic strength were measured and dimerization was found to be enthalpy driven process in all the cases. Large negative values of the dimerization enthalpy ΔH ≠ were proposed to be explained by the optimal overlapping of porphyrin macrocycles due to the minimization of the Coulomb repulsion of ionized peripheral substituents located at a large distance from the macrocycle.