Complexation of oxoanions and cationic metals by the biscatecholate siderophore azotochelin |
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Authors: | Jean-Philippe Bellenger Françoise Arnaud-Neu Zouhair Asfari Satish C B Myneni Edward I Stiefel Anne M L Kraepiel |
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Institution: | (1) UMR 7517 (CNRS-ULP), EOST, 1 Rue Blessig, 67084 Strasbourg Cedex, France;(2) Department of Geosciences, Guyot Hall, Princeton University, Princeton, NJ 08544, USA;(3) UMR 7512 (CNRS-ULP), ECPM, 25 Rue Becquerel, 67087 Strasbourg Cedex 02, France;(4) Chemistry Department, 101 Hoyt Laboratory, Princeton University, Princeton, NJ 08544, USA;(5) Chemistry Department, PEI, Guyot Hall, Princeton University, Princeton, NJ 08544, USA |
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Abstract: | Azotochelin is a biscatecholate siderophore produced by the nitrogen-fixing soil bacterium Azotobacter vinelandii. The complexation properties of azotochelin with a series of oxoanions Mo(VI), W(VI) and V(V)] and divalent cations Cu(II),
Zn(II), Co(II) and Mn(II)] were investigated by potentiometry, UV–vis and X-ray spectroscopy. Azotochelin forms a strong 1:1
complex with molybdate (log K = 7.6 ± 0.4) and with tungstate and vanadate; the stability of the complexes increases in the order Mo < V < W (log K
appMo = 7.3 ± 0.4; log K
appV = 8.8 ± 0.4 and log K
appW = 9.0 ± 0.4 at pH 6.6). The Mo atom in the 1:1 Mo–azotochelin complex is bound to two oxo groups in a cis position and to the two catecholate groups of azotochelin, resulting in a slightly distorted octahedral configuration. Below
pH 5, azotochelin appears to form polynuclear complexes with Mo in addition to the 1:1 complex. Azotochelin also forms strong
complexes with divalent metals. Of the metals studied, Cu(II) binds most strongly to azotochelin , followed by Zn(II) , Mn(II) and Co(II) . Since very few organic ligands are known to bind strongly to oxoanions (and particularly molybdate) at circumneutral pH,
the unusual properties of azotochelin may be used for the separation and concentration of oxoanions in the laboratory and
in the field. In addition, azotochelin may prove useful for the investigation of the biogeochemistry of Mo, W and V in aquatic
and terrestrial systems.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. |
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Keywords: | Molybdenum Vanadium Tungsten N N-di(2 l-lysine" target="_blank">3-dihydroxybenzoyl)-l-lysine l-LysineCAM" target="_blank">l-LysineCAM |
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