Kinetics of zinc ion incorporation in base into a centrally aprotic beta-octabrominated cationic water-soluble porphyrin and its monolithium complex

Abstract

The kinetics of zinc incorporation from pH 12 to 13 into the centrally aprotic BrP (4)2+ form of beta-octabromo-meso-tetrakis(N-methyl-4-pyridyl)porphyrin and its monolithium complex were studied at 25.0 °C, ionic strength (I) = 0.10. The reactions were first order in porphyrin and total zinc concentrations. For BrP (4)2+, the specific rate constant was 5.1 × 105 M -1 s -1 for Zn ( OH )2 aq , 9.9 × 104 M -1 s -1 for [Formula: see text] and [Formula: see text] was unreactive. The Li - BrP (4)3+ complex had a formation constant with BrP (4)2+ of 1.1 × 103 M -1 from both kinetic and equilibrium measurements. In solutions containing both BrP (4)2+ and Li - BrP (4)3+, zinc incorporation proceeded only through BrP (4)2+.