Kinetics of the metallation of coproporphyrin-I in water with cadmium(II) and manganese(II)

✍ Scribed by Vito Bartocci; Rita Giovannetti; Enrico Carsetti

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 133 KB
• Volume: 02
• Category: Article
• ISSN: 1088-4246
• DOI: 10.1002/(sici)1099-1409(199803/04)2:2<139::aid-jpp58>3.0.co;2-f

✦ Synopsis

The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I ( CPI ) with cadmium(II) was studied spectrophotometrically and its kinetic and equilibrium constants were determined. The influence of temperature on the reaction rate was also studied. At different ratios of [ CPI ]/[ Cd(II) ] two types of complex were formed: CdII ( CPI ) and ( CdII )~2~( CPI ); an investigation of the solution properties and the mechanism of aggregation of ( CdII )~2~( CPI ) at different pH were performed. It is verified that cadmium(II) accelerates the reaction of the incorporation of manganese(II) into CPI by the substitution of cadmium(II) with manganese(II) in the CdII ( CPI ) complex; the kinetics and mechanism of this substitution reaction at alkaline pH were studied. A sensitive kinetic method for the determination of cadmium(II) at ppb levels has been established; the molar absorptivity and the Sandell's sensitivity (for A = 0.001) of the recommended procedure at 458 nm and 300 s after the start of the reaction are (6.175 ± 0.026) × 10^5^ 1 mol^−1^ cm^−1^ and (1.820 ± 0.008) × 10^−4^ μg cm^−2^ respectively.