LIGAND-EXCHANGE REACTION OF ZN(II)-ACETYLACETONATE COMPLEX WITH 10,15,20-TETRAPHENYL-21H,23H-PORPHINETETRASULFONIC ACID

Ligand exchange reaction of Zn(II)-acetylacetonate complex (Zn-acac(2) ) with 10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (H2TPPS ) has been investigated spectrophotometrically and radiometrically. Th e exchange reaction was observed by spectral change from H2TPPS to Zn- TPPS or activity of Zn-65(acac)(2) extracted into tile chloroform phas e. The 2nd order rate constants (kappa(2)) for the exchange reaction a t 70 degrees C and at pH 7.8 were found to be 32.8+/-2.3 and 31.2+/-3. 2 M(-1). s(-1) from the spectrometric and radiotracer experiments, res pectively. For the direct complexation of Zn(II) with H2TPPS, a simila r 2nd order rate constant (k=32.4+/-4.7 M(-1). s(-1)) was obtained as that in the ligand exchange reaction. The aclivation energies (E) for the exchange and the formation of Zn-TPPS were found to be 69.3+/-0.2 and 69.4+/-0.2 kJ . mol(-1), respectively, in the temperature range fr om 40 to 70 degrees C.