Rodríguez-Rodríguez, AuroraRegueiro-Figueroa, MartínEsteban-Gómez, DavidRodríguez-Blas, TeresaPatinec, VéroniqueTripier, RaphaëlTircsó, GyulaCarniato, FabioBotta, MauroPlatas-Iglesias, Carlos2017-03-312017-01-23Rodríguez-Rodríguez, A., Regueiro-Figueroa, M., Esteban-Gómez, D., Rodríguez-Blas, T., Patinec, V., Tripier, R., Tircsó, G., Carniato, F., Botta, M., Platas-Iglesias, C. (2017), Definition of the Labile Capping Bond Effect in Lanthanide Complexes. Chem. Eur. J., 23: 1110-1117. https://doi.org/10.1002/chem.2016043900947-65391521-3765http://hdl.handle.net/2183/18354[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.engThis is the peer reviewed version of the following article: Rodríguez-Rodríguez, A., Regueiro-Figueroa, M., Esteban-Gómez, D., Rodríguez-Blas, T., Patinec, V., Tripier, R., Tircsó, G., Carniato, F., Botta, M., Platas-Iglesias, C. (2017), Definition of the Labile Capping Bond Effect in Lanthanide Complexes. Chem. Eur. J., 23: 1110-1117, which has been published in final form at https://doi.org/10.1002/chem.201604390. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Density functional calculationsGadoliniumMagnetic resonance imagingNMR spectroscopyWater exchangejournal articleopen access