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【Chinatungsten Online News Net- Tungsten News】

Tungsten-183NMR spectroscopy of polyo xotungstates. The 183W nuclide is theonly NMR-active natural tungsten isotope with a spin of 1/2 and natural abundance of 14.3%. It gives rise to very narrow resonance lines. The NMR spectral envelope depends on the structure and symmetry of the anion. The 183W chemical shifts aresensitive to their surrounding environment, including central atom, electric charge and size of adjacent elements, counterions in solution and solvent. There placement of ligand atoms in an anion by the quadrupolar vanadium nucleus or by paramagnetic ions either in a ligand site or in the central site cause the resonance signals of the tungsten atoms djacent to the substituted atoms to shift dramatically and broaden or even disappear. The spectral envelope, relative intensity of the lines and homonuclear and heteronuclear coupling constants provide the basis to identify anionic structure. Tungsten-183NMR spectroscopy including2-DCOSYand2-D INADEQUATE spectroscopy are used to distinguish new synthetic species, to examine product purity, to differentiate isomers and to establish new structures in solution as well as to monitor the progress of reaction. Tungsten-183NMR spectroscopy has already become apowerful routine tool of structural characterization for polyoxotungstates in solution.