Jean-Claude Bunzli - Stability, structure and dynamics of cationic lanthanide(III) complexes of N,N '-bis(propylamide)ethylenediamine-N, N '-diacetic acid

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      Platas-Iglesias,C., Corsi,D.M., Vander Elst,L., Muller,R.N.,   Imbert,D., Bunzli,J.C.G., Toth,E., Maschmeyer,T., Peters,J.A.   Dalton Transactions 2003 (4) 727-737

      Abstract: The cationic [Ln(EDTA-PA(2))](+)   complexes (EDTA-PA(2) = EDTA-bispropylamide) have been   characterised by a multinuclear NMR study. Y-89 and C-13 NMR data   indicate the formation of 1 : 1 and 1 : 2 (Ln : ligand) complexes   in aqueous solution. The stability constants of these complexes,   as determined by potentiometric measurements, are log K-GdL =   10.3 and log K-GdL2 = 14.3. C-13 Relaxation times of the Nd3+   complex show hexadentate binding of the organic ligand via the   two amines, the two carboxylates and the two amide oxygen atoms.   The complexes are present in solution as a mixture of three   isomers: two trans forms and a cis one. Luminescence measurements   demonstrate that both Eu3+ and Tb3+ complexes are   nona-coordinated at low concentrations (similar to10(-3) M).   Three water molecules then complete the coordination sphere. At   higher concentrations, the complexes exist in solution as a   mixture of nona- and octa-coordinated species, the relative   concentration of the latter increases with increasing   concentration as a consequence of intermolecular interactions   operating in aqueous solutions. Data sets obtained from   variable-temperature O-17 NMR at 7.05 T and variable-temperature   H-1 nuclear magnetic relaxation dispersion (NMRD) on the Gd3+   complex were fitted simultaneously to give insight into the   parameters governing the water H-1 relaxivity. Fast rotation   limits the relaxivity at 10-40 MHz

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