NONIONIC LN(III) CHELATES AS MRT CONTRAST AGENTS - SYNTHESIS, CHARACTERIZATION AND H-1-NMR RELAXOMETRIC INVESTIGATIONS OF BIS(BENZYLAMIDE) DIETHYLENETRIAMINEPENTAACETIC ACID LU(III) AND GD(III) COMPLEXES

The syntheses of the ligand bis(benzylamide)diethylenetriaminepentaace tic acid (BBA-DTPA) and its Gd(lII) and Lu(III) complexes are reported . The solid state structure of Lu(III)BBA-DTPA was determined in a sin gle crystal X-ray diffraction study. The lutetium ion adopts a nine-co ordinate geometry, which is best described as a distorted tricapped pr ism. Eight coordination sites are occupied by the ligand (three nitrog en atoms, two carboxamide oxygens and three carboxylate oxygens) and t he ninth site is occupied by the oxygen atom of a water molecule. The VT C-13 NMR spectra of Lu(III)BBA-DTPA are consistent with the presenc e of three isomers in solution. Water proton relaxation rates have sho wn that Gd(III) BBA-DTPA displays an analogous behaviour to that obser ved for other Gd(III) complexes of related bisamide derivatives of DTP A. The solubility of Gd(III)BBA-DTPA has been markedly improved by the presence of an excess of hydroxypropyl-beta-cyclodextrin The thermody namic stability of the inclusion complex has been evaluated by measuri ng the proton relaxation enhancement upon addition of beta-cyclodextri n.