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Issue 3, 2003
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Iron and cobalt complexes of 5,5′-di(methylene-N-aminoacidyl)-2,2′-bipyridyl ligands: ligand design for diastereoselectivity and anion binding

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Abstract

The syntheses and coordination chemistry of 5,5′-di(methylene-N-aminoacidyl)-2,2′-bipyridyl ligands, where the amino acid is valine (1) or alanine (2), are presented. Complexes [M(1)3]n+, where M = Co(II), Co(III) and Fe(II), form diastereoselectively when the amine group of the amino acid arm is protonated. At higher pH the diastereoselectivity drops significantly. The solid state structure of [CoIII(1H2)3]Cl2(ClO4)7 was determined by X-ray crystallography. Two chloride ions were found to be encapsulated by the amino acid arms of the complex via electrostatic attractions and hydrogen bonding to the protonated amine groups, as seen previously for the Fe(II) complex. No anion binding was detected in aqueous solution, but complexes [FeII(1H2)2(1H)]7+ and [CoIII(1H2)3]9+ bind chloride ions in CD3OD with binding constants of 60(4) and 24(2) M−1 respectively, as determined by 1H NMR spectroscopy. 1H NMR spectroscopy suggests considerable conformational change of the ligand sidearms upon chloride binding. Complexes [FeII(2)3]2+ and [CoII(2)3]2+ are formed with d.e.'s of 33 and 56% respectively.

Graphical abstract: Iron and cobalt complexes of 5,5′-di(methylene-N-aminoacidyl)-2,2′-bipyridyl ligands: ligand design for diastereoselectivity and anion binding

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Publication details

The article was received on 13 Sep 2002, accepted on 28 Nov 2002 and first published on 10 Jan 2003


Article type: Paper
DOI: 10.1039/B208934C
Citation: Dalton Trans., 2003, 435-440
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    Iron and cobalt complexes of 5,5′-di(methylene-N-aminoacidyl)-2,2′-bipyridyl ligands: ligand design for diastereoselectivity and anion binding

    S. G. Telfer, G. Bernardinelli and A. F. Williams, Dalton Trans., 2003, 435
    DOI: 10.1039/B208934C

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