Lanthanide(iii) complexes of monophosphinate/monophosphonate DOTA-analogues: effects of the substituents on the formation rate and radiolabelling yield.

Hdota and its analogues are routinely used for complexation of lanthanide radioisotopes in nuclear medicine. Many of the radioisotopes have short half-lives and, thus, the complexation rate plays an important role. Notwithstanding that, the relationship between ligand structures and complexation rates is not well understood.

DOTA analogues with a phosphinate-iminodiacetate pendant arm: modification of the complex formation rate with a strongly chelating pendant.

The new ligand Hdo3aP combines the macrocyclic DOTA-like cavity and the open-chain iminodiacetate group connected through a coordinating phosphinate spacer. Its acid-base and coordination properties in solution were studied by potentiometry. Thermodynamic coordination characteristics of both chelating units are similar to those reported for Hdota and iminodiacetic acid themselves, respectively, so, macrocyclic and iminodiacetate units behave independently.

Methylene-bis[(aminomethyl)phosphinic acids]: synthesis, acid-base and coordination properties.

Three symmetrical methylene-bis[(aminomethyl)phosphinic acids] bearing different substituents on the central carbon atom, (NH(2)CH(2))PO(2)H-C(R(1))(R(2))-PO(2)H(CH(2)NH(2)) where R(1) = OH, R(2) = Me (H(2)L(1)), R(1) = OH, R(2) = Ph (H(2)L(2)) and R(1),R(2) = H (H(2)L(3)), were synthesized. Acid-base and complexing properties of the ligands were studied in solution as well as in the solid state. The ligands show unusually high basicity of the nitrogen atoms (log K(1) = 9.