Synthesis of water soluble DTPA complexes with pendant uracil moieties capable of forming complementary hydrogen bonds

Abstract

Two new DTPA (diethylenetriaminepentaacetic acid) functionalised bis(amides) with pendant uracil moieties have been synthesised from the condensation reaction between DTPA bis(anhydride) and 5-aminouracil or 5,6-diaminouracil. These ligands are representative of an increasing number of ligands capable of forming triple hydrogen bonds with complementary organic bases. However, these ligands are unusual since they form water soluble complexes with a variety of metal ions. In this paper, the syntheses of the two DTPA-uracil ligands, seven metal complexes and the crystal structure of the bismuth complex of DTPA bis(4,5-diamino-6-hydroxy-2-mercaptopyrimidine) L¹ are reported. The most important feature of this solid state structure is that the two arms on which the uracil moieties are situated have a high degree of rotational freedom and this allows these groups to form multiple hydrogen bonds involving both uracil moieties on one side of the molecule.