MULTINUCLEAR NMR-STUDY OF THE INTERACTIONS BETWEEN THE LA(III) COMPLEX OF DTPA-BIS(GLUCAMIDE) AND ZN(II) OR BORATE

The interaction between ZnCl2 and La(DTPA) (DTPA = diethylenetriamine- N,N,N',N '',N ''-penta-acetate), La(DTPA-PA(2)) (DTPA-PA(2) = DTPA-bis (propylamide)) or La(DTPA-GlucA(2)) (DTPA-GlucA(2) = DTPA-bis(glucamid e)) has been studied using C-13 and La-139 NMR. Extensive transmetalla tion occurs, which is assisted by interaction between the ionic specie s formed. It is shown that these interactions involve mainly the DTPA backbone of the ligands. The sugar side-chains of La(DTPA-GlucA(2)) ha ve no significant affinity for the metal ions. With the aid of B-11 NM R it is demonstrated that berate does interact with the polyhydroxy si de-chains. The stoichiometries of the various berate ester species der ived from DTPA-GlucA(2) and its Ln(III) complexes are investigated by recording the corresponding Job plots. A major species has a berate mo iety linking the two glucitol side-chains under the formation of a mac rocyclic compound. The stability constants of the occurring berate est er species as determined by B-11 NMR are reported. (C) 1998 Elsevier S cience S.A.