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Issue 24, 2014
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Tetraphosphonated thiophene ligand: mixing the soft and the hard

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The synthesis of ligand LTH8, based on a thiophene framework containing two bis(aminomethyldiphosphonate) functions in the ortho position to the central sulfur atom, is described, together with the characterization of the intermediate compounds. The physico-chemical properties of the ligand were first studied by means of potentiometry and UV-Vis absorption spectrophotometric titrations to determine its pK values. Six successive equilibrium constants were determined in aqueous solutions. The same means were then used to quantify the interactions of the ligand with Ni(II), Cu(II) and Zn(II). Following the conventional Irving–Williams trend, LT was shown to have the highest affinity towards Cu(II) (log K(CuLT) = 16.11(3)), while Zn(II) and Ni(II) showed similar values (log K(MLT) = 10.81(8) and 10.9(1), respectively), revealing a large selectivity of LT toward Cu(II). Based on a combination of UV-Vis absorption spectroscopy and EPR measurements as a function of pH, along with DFT calculations, the coordination behavior of the hard phosphonate, medium amino and soft thiophene entities are questioned regarding their coordination to the Cu atom.

Graphical abstract: Tetraphosphonated thiophene ligand: mixing the soft and the hard

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The article was received on 12 Feb 2014, accepted on 14 Apr 2014 and first published on 15 Apr 2014

Article type: Paper
DOI: 10.1039/C4DT00451E
Author version available: Download Author version (PDF)
Citation: Dalton Trans., 2014,43, 9070-9080
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    Tetraphosphonated thiophene ligand: mixing the soft and the hard

    J. Brandel, A. Lecointre, J. Kollek, S. Michel, V. Hubscher-Bruder, I. Déchamps-Olivier, C. Platas-Iglesias and L. J. Charbonnière, Dalton Trans., 2014, 43, 9070
    DOI: 10.1039/C4DT00451E

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