1,4,7-Triazacyclononane-Based Bifunctional Picolinate Ligands for Efficient Copper Complexation

Amaury Guillou, Luís M.P. Lima, Mélissa Roger, David Esteban-Gómez, Rita Delgado, Carlos Platas-Iglesias, Véronique Patinec, Raphaël Tripier

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18 Citations (Scopus)


Three 1,4,7-triazacyclononane-based (tacn-based) ligands containing picolyl and picolinate pendant arms (no3py, no2pa1py, and no3pa) were synthesized, and their copper(II) complexation properties were studied to evaluate their potentials as chelators for copper radioisotopes. The thermodynamic stability constants of the complexes were determined by potentiometric titrations. These studies evidenced the formation of mononuclear species for no3py and mono- and dinuclear species for no2pa1py and no3pa. The pCu values decreased as the number of carboxypicolyl arms increased. The [Cu(no3py)]2+ complex presented a very high stability constant (log KCuL = 27.4) and a very high selectivity towards Zn2+ ions (log KZnL = 17.25). Vis/NIR (NIR = near-infrared) absorption and electron paramagnetic resonance (EPR) spectroscopy indicated that the three complexes present distorted octahedral geometries with two paramagnetic species, which were identified as the Δ(δδδ) and Λ(δδδ) isomers [and their corresponding enantiomeric forms Λ(λλλ) and Δ(λλλ)] by DFT calculations. The electrochemical properties were investigated by cyclic voltammetry, which revealed quasireversible behavior for the [Cu(no3py)]2+ complex but irreversible Cu2+/Cu+ systems for [Cu(no2pa1py)] and [Cu(no3pa)].

Original languageEnglish
Pages (from-to)2435-2443
Number of pages9
JournalEuropean Journal of Inorganic Chemistry
Issue number18
Publication statusPublished - 1 Jan 2017


  • Copper
  • Imaging agents
  • Macrocyclic ligands
  • N ligands
  • Potentiometry


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