Syntheses and crystal structures of lanthanide complexes of new 15-membered macrocyclic ligands with three pendant acetato groups

Two new 15-membered functionalized macrocycles, dioxo-polyazacycloalkanes with three pendant acetato groups, have been synthesized by the condensation reaction of DTP A dianhydride (DTPA = diethylenetriaminepentaacetic acid) with 1,2-diaminopropane, (15-DTPA-1, 2-pn), or 1, 2-diaminocyclohexane, (15-DTPA-1,2-cy). Their lanthanide complexes [Ln(15-DTPA-1, 2-pn) (H₂O)]₂[Ln = Eu (1), Gd (2)] and [Ln(15-DTPA-1,2-cy)(H₂O)]₂[Ln = Eu (3), Gd (4)] were also prepared. Single crystal X-ray diffraction analyses of complexes 2 and 4 show that they have dimeric structures in solid state; each metal ion is nine-coordinated in a distorted tricapped-trigonal prism. In complex 4, the coexistence of two diastereoisomeric molecules in the crystal lattice was observed.