title: Metal ion effects in isotopic hydrogen exchange in biologically important heterocycles.
abstract: The binding of metal ions to heteroatomic centers of biomolecules has been utilized as a probe of metal ion effects in living systems. This article focuses on the effect of N-coordination by transition metals, especially Pt(II), Co(III), Cr(III), on isotopic C(2)-H or C(8)-H exchange of imidazoles, thiazoles, and purines. The usual reactivity trend, protonated >> metalated >> neutral substrate, is excepted for Cr(III)/1-methylimidazole, where Cr(III) activates stronger than H(+). An interplay of factors is considered, including metal-to-ligand back-bonding, electronic structure of metal ions, and differences in crystal field stabilization energy.
authors.affiliation: Department of Chemistry, Queen's University, Kingston, Canada K7L 3N6.
authors.forename: E
authors.initials: E
authors.lastname: Buncel
authors.forename: O
authors.initials: O
authors.lastname: Clement
authors.forename: I
authors.initials: I
authors.lastname: Onyido
mesh_terms: D002412:Cations; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007554:Isotopes; D007700:Kinetics; D008670:Metals / Q000737:chemistry*
chemical_list: D002412:Cations; D006571:Heterocyclic Compounds; D007554:Isotopes; D008670:Metals; D006859:Hydrogen