Examination of lutetium(III)-DOTA and copper(II)-NOTA solution structures using EXAFS

Targeted radionuclide therapy generally relies on the chelation of select short-lived isotopes such as 177Lu and 67Cu. The majority of Lu(III) and Cu(II) chelate structural information is derived from solid state diffraction data. Herein, the complexes Lu(DOTA)−, Cu(NOTA)− were examined in solution using EXAFS for the first time. Both ligands were fully deprotonated and coordinated to the metal with four and three carboxylic sites for Lu(DOTA)− and Cu(NOTA)−, respectively. Near-neighbor correlations from nitrogen atoms on the macrocyclic cages were also visible in the spectra in addition to the adjacent carbon backbones. Coordination numbers, bond distances, and Debye-Waller factors are reported and discussed alongside differences with known crystal structures.