The present invention relates to chelates resulting from the complexation of bifunctional do2pa derivatives ligands of formula (I), wherein the substituents R1, R1', R2, R2', R3, R3', L1, L1', L2 and L2' are defined as in the claims, with metallic cations, especially Pb(II) and Bi(III). The invention further relates to bifunctional do2pa derivatives ligands of formula (I). Another object of the invention is the use of chelates of the invention in nuclear medicine and the use of ligands of the invention in cations detection or epuration of effluents.