Kinetic Study of the Reactions of Porphyrin with Co(II), Ni(II) and Zn(II) Compounds in Supercritical Carbon Dioxide

Abstract

The transition metal ions incorporation reactions into 5, 10, 15, 20-tetrakis (pentafluorophenyl) porphyrin(H2tpfpp) to form the metal porphyrin complexes M(tpfpp) (M=Co, Ni, Zn) have been kinetically investigated using diaquabis(1, 1, 1, 5, 5, 5-hexafluoropentane-2, 4-dionato) metal compounds [M(hfac)2(H2O)2] in supercritical carbon dioxide (scCO2) medium in a spectrophotometric cell. The reactions are first order with respect to H2tpfpp under the conditions where [M(hfac)2(H2O)2] is in large excess relative to H2tpfpp. The saturation dependence of the conditional first-order rate constants as a function of the mole fraction of the excess metal compounds [M(hfac)2(H2O)2] is observed for the reaction systems [Co(hfac)2(H2O)2+H2tpfpp] and [Ni(hfac)2(H2O)2+H2tpfpp], and the linear dependence is observed for the reaction system [Zn(hfac)2(H2O)2+H2tpfpp]. The mechanisms are discussed and the thermodynamic and kinetic parameters for the reactions are obtained.