Carrier-facilitated bulk liquid membrane transport of iron(iii) hydroxamate complexes utilizing a labile recognition agent and amine recognition in the second coordination sphere

Journal Article (Journal Article)

Carrier-facilitated bulk liquid membrane transport from an aqueous source phase through a chloroform membrane phase to an aqueous receiving phase was studied for various Fe(iii) hydroxamate complexes (siderophore mimics) using second coordination sphere recognition. Iron transport systems were designed using a strategy whereby a tetradentate siderophore mimic sequesters iron(iii), leaving two labile aquated coordination sites for ternary complex formation. This aquated complex reacts with a bi-functional host/guest molecule capable of acting as a host for the iron complex via ternary complex formation, while simultaneously serving as a guest for a membrane-bound host (carrier). The bi-functional molecules utilized contain a hydroxamate host for Fe(iii) binding and a protonated primary amine that can be “recognized” by a liquid membrane-bound hydrophobic ionophore, which carries the hydrophilic Fe(iii)-complex across the hydrophobic membrane to an aqueous receiving phase. Four protonated amine hydroxamic acids were investigated as bi-functional host/guest molecules: β-alanine hydroxamic acid (H L ) , l-glutamic acid γ-monohydroxamic acid (H L ) , glycine hydroxamic acid (H L ) , and l-lysine hydroxamic acid (H L ) . These four bidentate ligands were each coordinated to Fe(iii) along with the tetradentate N, N′-dihydroxy-N, N′-dimethyldecanediamide (H L ) to form ternary complexes [Fe(L )(H L ) ; x = 1 or 2; y = ala, glu, gly, or lys; z = 0, +1, or +2] that were transported through a chloroform bulk liquid membrane by the lipophilic host carrier cis-dicyclohexano-18-crown-6 (DC18C6). No carrier-dependent flux was observed for Fe(L )(HL ), probably due to intramolecular H-bonding. Flux values for the transport of Fe(L )(H L ) (x = 1 or 2; y = ala, gly, or lys; z = +1 or +2) facilitated by the membrane carrier (DC18C6) were highest when y = gly and lowest when y = ala. Equilibrium constants pertaining to two-phase distribution or ion pairing, second coordination sphere host–guest formation, and overall extraction were determined and used to rationalize variations in flux values. © 2003 The Royal Society of Chemistry. 2 3 2 3 2 x x ala + glu + gly + lys 2+ 8 8 y z 8 glu 8 y z

Full Text

Duke Authors

Cited Authors

  • Wirgau, JI; Crumbliss, AL

Published Date

  • September 25, 2003

Published In

Volume / Issue

  • 3 / 19

Start / End Page

  • 3680 - 3685

International Standard Serial Number (ISSN)

  • 1477-9226

Digital Object Identifier (DOI)

  • 10.1039/b306810b

Citation Source

  • Scopus