Evaluating a triaza-18-crown-6 picolinate chelator for [212/203Pb]Pb2+ and [212/213Bi]Bi3+ theranostics

H3tripa (H3macrotripa), a triaza-18-crown-6 macrocycle bearing three picolinate arms, enables quantitative radiolabeling of [203Pb]Pb2+ and [213Bi]Bi3+ and exhibits robust human serum stability. NMR spectroscopy, X-ray crystallography, density functional theory, and UV-potentiometry investigate its coordination geometry and thermodynamics with Bi3+ and Pb2+, highlighting H3tripa as a promising Pb/Bi theranostic chelator.