Lanthanide(III) Complexes with a Reinforced Cyclam Ligand Show Unprecedented Kinetic Inertness

Rodríguez-Rodríguez, Aurora and Esteban-Gómez, David and Tripier, Raphaël and Tircsó, Gyula and Garda, Zoltán and Tóth, Imre and Blas, Andrés de and Rodríguez-Blas, Teresa and Platas-Iglesias, Carlos (2014) Lanthanide(III) Complexes with a Reinforced Cyclam Ligand Show Unprecedented Kinetic Inertness. Journal of American Chemical Society, 136 (52). pp. 17954-17957.

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Abstract

Lanthanide(III) complexes of a cross-bridged cyclam derivative containing two picolinate pendant arms are kinetically inert in very harsh conditions such as 2 M HCl, with no dissociation being observed for at least 5 months. Importantly, the [Ln(dota)] complexes, which are recognized to be extremely inert, dissociate under these conditions with lifetimes in the range ca. 1 minute to 12 hours depending upon the Ln3+ ion. X-ray diffraction studies reveal octadentate binding of the ligand to the metal ion in the [Eu(cb-tedpa)]+ complex, while 1H and 13C NMR experiments in D2O point to the presence of a single diastereoisomer in solution with a very rigid structure. The structure of the complexes in the solid state is retained in solution, as demonstrated by the analysis of the Yb3+-induced paramagnetic shifts.

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