PREPARATION OF HYDROXY-3,5,7-TRIOXANONANE-2,4,6,8-TETRACARBOXYLIC ACID AND ITS COMPLEXATION WITH LANTHANIDE(III) CATIONS, AS STUDIED BY MULTINUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY

hydroxy-3,5,7-trioxanonane-2,4,6,8-tetracarboxylic acid (H4TT) has bee n prepared via a catalytic oxidation of D-trehalose with molecular oxy gen and via a two-step oxidation with periodate and chlorite. The lant hanide complexes have 1:1 and 1:2 metal-ligand stoichiometries. Ln(III )-induced effects on chemical shifts, relaxation rates, and vicinal pr oton-proton coupling constants yielded information on the geometries o f these complexes. The complexes with Ln(TT) stoichiometry have 2 wate r molecules in the first coordination sphere of Ln(III), and the remai ning 6-7 positions are occupied by carboxylate, ether, and -CH2OH oxyg ens of the two oxidized sugar units of TT. The -CH2OH oxygens are coor dinated for about 85% of the time. The Ln(TT)(2) complexes have one TT ligand that is bound in a hexadentate fashion via the two terminal ox ydiacetate units (each in a tridentate fashion), whereas the second TT ligand has only one oxydiacetate unit coordinated. The exchange betwe en bound and free oxydiacetate moieties in Ln(TT)(2) is rapid on the N MR time scale. in about 20% of the TT ligands of this complex one of t he coordinated carboxylate groups is substituted by a -CH2OH group.