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Definition of the Labile Capping Bond Effect in Lanthanide Complexes

Abstract : Two macrocyclic ligands containing a cyclen unit, a methyl group, a picolinate arm, and two acetate pendant arms attached to two nitrogen atoms of the macrocycle either in trans (1,7-H3Medo2 ampa = 2,2′-(7-((6-carboxypyridin-2-yl)methyl)-10-methyl-1,4,7,10-tetraazacyclododecane-1,4-diyl)diacetic acid) or in cis (1,4-H3Medo2 ampa) positions are reported. These ligands provide eight-coordination to the Ln3+ ions, leaving a coordination position available for a water molecule that occupies a capping position in the twisted square antiprismatic polyhedron (1,4-H3Medo2 ampa) or one of the positions of the square antiprism (1,7-H3Medo2 ampa). The charge neutral [Gd(1,7-Medo2 ampa)] complex presents an unprecedentedly low water-exchange rate (kex298=8.8×103 s−1), whereas water exchange in [Gd(1,4-Medo2 ampa)] is three orders of magnitude faster (kex298=6.6×106 s−1). These results showcase the labile capping bond phenomenon: A ligand occupying a capping position is hindered by the environment and thus is intrinsically labile.
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https://hal.univ-brest.fr/hal-01539203
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Submitted on : Wednesday, June 14, 2017 - 3:52:02 PM
Last modification on : Wednesday, October 30, 2019 - 3:54:02 PM

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Aurora Rodriguez-Rodriguez, Martin Regueiro-Figueroa, David Esteban-Gomez, Teresa Rodriguez-Blas, Véronique Patinec, et al.. Definition of the Labile Capping Bond Effect in Lanthanide Complexes. Chemistry - A European Journal, Wiley-VCH Verlag, 2017, 23 (5), pp.1110 - 1117. ⟨10.1002/chem.201604390⟩. ⟨hal-01539203⟩

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