Frías Martínez, Juan CarlosSoriano, JoséBlasco, SalvadorGarcía-España, EnriqueRodríguez Rodríguez, AuroraEsteban Gómez, DavidCarniato, FabioBotta, MauroPlatas Iglesias, CarlosAlbelda, M. TeresaUCH. Departamento de Ciencias Biomédicas2024-01-122024-01-122020-05-07Frías, J.C., Soriano, J., Blasco, S., García-España, E., Rodríguez-Rodríguez, A., Esteban-Gómez, D., Carniato, F., Botta, M., Platas-Iglesias, C. & Albelda, M.T. (2020). Macrocyclic pyclen-based Gd3+ complex with high relaxivity and pH response. Inorganic Chemistry, vol. 59, i. 10 (07 may.), pp. 7306–7317. DOI: https://doi.org/10.1021/acs.inorgchem.0c006900020-16691520-510X (Electrónico)http://hdl.handle.net/10637/14862Este es el post-print del siguiente artículo: Frías, J.C., Soriano, J., Blasco, S., García-España, E., Rodríguez-Rodríguez, A., Esteban-Gómez, D., Carniato, F., Botta, M., Platas-Iglesias, C. & Albelda, M.T. (2020). Macrocyclic pyclen-based Gd3+ complex with high relaxivity and pH response. Inorganic Chemistry, vol. 59, i. 10 (07 may.), pp. 7306–7317, que se ha publicado de forma definitiva en: https://doi.org/10.1021/acs.inorgchem.0c00690We report the synthesis and characterization of the macrocyclic ligand 2,2′-((2-(3,9-bis(carboxymethyl)-3,6,9-triaza-1(2,6)-pyridinacyclodecaphane-6-yl)ethyl)azanediyl)diacetic acid (H4L) and several of its complexes with lanthanide ions. The structure of the free ligand was determined using X-ray diffraction measurements. Two N atoms of the pyclen moiety in the trans position are protonated in the solid state, together with the exocyclic N atom and one of the carboxylate groups of the ligand. The relaxivity of the Gd3+ complex was found to increase from 6.7 mM–1 s–1 at pH 8.6 to 8.5 mM–1 s–1 below pH ≈ 6.0. Luminescence lifetime measurements recorded from H2O and D2O solutions of the Eu3+ complex evidence the presence of a single complex species in solution at low pH (∼5.0) that contains two inner-sphere water molecules. DFT calculations suggest that the coordination environment of the Ln3+ ion is fulfilled by the four N atoms of the pyclen unit, two oxygen atoms of the macrocyclic acetate groups, and an oxygen atom of an exocyclic carboxylate group. The two inner-sphere water molecules complete coordination number nine around the metal ion. At high pH (∼9.3), the lifetime of the excited 5D0 level of Eu3+ displays a biexponential behavior that can be attributed to the presence of two species in solution with hydration numbers of q = 0 and q = 1. The 1H NMR and DOSY spectra recorded from solutions of the Eu3+ and Y3+ complexes reveal a structural change triggered by pH and the formation of small aggregates at high pH values.enopen accessChemistryQuímicaQuímica inorgánicaInorganic chemistryArtículohttps://doi.org/10.1021/acs.inorgchem.0c00690https://creativecommons.org/licenses/by-nc-nd/4.0/deed.es