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Final Activity Report Summary - METSALT (Metal Salt Complexation for Environmental Clean-up and Hydrometallurgy)

A series of heteroditopic ionophores for use as extractants for metal salts species were synthesised. A range of thioether polychelates were used as metal binding sites and these were incorporated with amide, amine, urea, thiourea and sulphonamide moieties as anion binding functions. The complexation with Ni(II), Pd(II) and Pt(II) was systematically studied through microanalysis, NMR titration, UV-Vis titration and, where appropriate, by single crystal X-ray diffraction. A further series of extractants based on thioether-pyridyl ionophores as metal binding site were designed and synthesised, and these have been found to be good building blocks for the binding of a range of metal cations. These ionophores were also functionalised with anion binding sites via the incorporation of amide, urea, thiourea, and sulphonamide groups. The complexation of these ditopic ligands were systematically researched using mass spectrometry, microanalysis, NMR titration, UV-Vis titration and single crystal X-ray diffraction. The solid-state and solution properties of the complexes demonstrate that these types of ditopic ligand could potentially be extractants for the environmental clean-up and hydrometallurgy via complexation of metal cation and concomitant anion. Thus, the Fellowship has delivered the proof-of-principle sought within the original proposal for the design of new heterotopic ionophores for metal salt binding. A key highlight was the isolation and unambiguous characterisation of a nickel sulphate complex in which Ni(II) is bound specifically to the thioether-pyridyl group with the sulphate hydrogen-bonded to the urea moieties.

The synthetic skills of the Fellow and his knowledge of the project and related field have improved enormously over the past two years, especially in the field of modification of pyridine and thioether containing molecules. A range of scientific research skills and training relating to the project have been undertaken including chromatography, distillation, multi-nuclear NMR spectroscopy, mass spectrometry, UV-Vis spectrometry and X-ray single crystal diffraction.

The multi-property materials prepared above are being studied currently for applications in the binding and extraction of metal salts, and their specific and detailed abilities to extract (aqueous to organic phase) and transport (aqueous to organic to aqueous phase) metal salts selectively are being established. The Nottingham group works very closely with Tasker (University of Edinburgh), Lindoy (University of Sydney, Australia), and Gloe (University of Dresden) on the development of functional nanoreceptors for metal cation and / or anion extraction, and we are currently seeking to functionalise our receptors in order to improve their solubilities in non-polar solvents.

Reported by

University Park
United Kingdom
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