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The cation exchange rates in cryptates may be obtained most conveniently from variable temperature 1SC nmr spectra of 1/1 cryptateligand mixtures (forthcoming report). Double probe 13C, 23Na nmr studies may provide detailed information on the electric effects produced by ligand structure, binding sites, ion pairing, and me-dium15 as well as on molecular tumbling. Complexes of other metal cations may also be investigated (lithium and cesium for instance).30 (30) The use of nitrogen-14 as the quadrupolar nucleus allows similar studies to be performed on nitrogen-containing substances of chemical or biological interest.24•25 (31) ERA No. 265 from CNRS.

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