ChemInform Abstract: A UV STUDY OF THE MAGNESIUM HAEMATOPORPHYRIN COMPLEX

The interaction between magnesium and haematoporphyrin has been studied spectrophotometricaly as a function of concentration, pH and temperature and the existence of a strong 1 : 1 complex has been established. The Benesi-Hildebrand equation was used to determine Kc’s at various wavelengths and temperatures, at pH’s of 7.4, 8.2, and 9.0. The enthalpy of complex formation is seen to change from +9.78 kcal/mol to −9.50 kcal/mol as the pH changes from 8.2 to 9.0. This change may be a reflection of the change in the various ligands which coordinate to the magnesium ion in addition to the porphyrin ring.