H₂Me-do2pa: an attractive chelator with fast, stable and inert (nat)Bi³⁺ and ²¹³Bi³⁺ complexation for potential α-radioimmunotherapy applications.

The complexation properties of H₂Me-do2pa towards (nat)Bi(3+) reveal a rather fast formation of the [Bi(Me-do2pa)](+) complex, which is endowed with a very high thermodynamic stability (log K(BiL) = 34.2) and presents a single non-fluxional structure in solution. X-ray diffraction and solution NMR studies showed an octadentate binding of the ligand to the metal ion. The labelling of H₂Me-do2pa with (213)Bi was performed and the resulting complex was stable in vitro, sustaining its use as an attractive alternative to taken here as a reference.