title: Iron chelation by polyamidoamine dendrimers: a second-order kinetic model for metal-amine complexation.
abstract: This study presents a kinetic model of the chelation of iron ions by generation 4 hydroxyl-terminated polyamidoamine (PAMAM) with ethylenediamine core (G4-OH). The coordination processes of iron ions from ferric chloride, FeCl(3), and ferrous bromide, FeBr(2), to G4-OH dendrimers were analyzed using ultraviolet-visible (UV-vis) spectroscopy, proton nuclear magnetic resonance ((1)H NMR) spectroscopy, and liquid chromatography-mass spectrometry (LC-MS). In the visible region, a charge-transfer was observed when the dendrimer was added to a ferric chloride solution. This phenomenon is a ligand-to-metal charge-transfer (LMCT) between the free electron group of the dendrimer's internal amines and the dehalogenated iron ion that takes 2 h to complete at room temperature. Analysis of potential rate laws and diffusion effects led to a second-order kinetic model for this reaction. By measuring the rate coefficients as a function of temperature (22-37 °C), an apparent activation energy of 41.5 kJ/mol was obtained using the Arrhenius method. The results of this study will fuel research of PAMAM dendrimers for environmental, pharmaceutical, and materials applications.
authors: Department of Chemical and Biomedical Engineering, University of South Florida, 4202 East Fowler Avenue, ENB 118, Tampa, Florida 33620, USA.
authors: Michael R
authors: MR
authors: Mankbadi
authors: Mohamed A
authors: MA
authors: Barakat
authors: Mohamed H
authors: MH
authors: Ramadan
authors: H Lee
authors: HL
authors: Woodcock
authors: John N
authors: JN
authors: Kuhn
mesh_terms: D000588:Amines / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D050091:Dendrimers / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D007700:Kinetics; D009757:Nylons / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000588:Amines; D002614:Chelating Agents; D002712:Chlorides; D056831:Coordination Complexes; D050091:Dendrimers; D005290:Ferric Compounds; D005296:Ferrous Compounds; D009757:Nylons; C520550:PAMAM-G4; C024555:ferric chloride