Rigidified Derivative of the Non-macrocyclic Ligand H₄OCTAPA for Stable Lanthanide(III) Complexation
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Rigidified Derivative of the Non-macrocyclic Ligand H₄OCTAPA for Stable Lanthanide(III) ComplexationAutor(es)
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2022-03-11Cita bibliográfica
Lucio-Martínez, F.; Garda, Z.; Váradi, B.; Kálmán, F. K.; Esteban-Gómez, D.; Tóth, É.; Tircsó, G.; Platas-Iglesias, C. Rigidified Derivative of the Non-Macrocyclic Ligand H₄OCTAPA for Stable Lanthanide(III) Complexation. Inorg. Chem. 2022, 61 (12), 5157–5171. https://doi.org/10.1021/acs.inorgchem.2c00501.
Resumo
[Abstract] The stability constants of lanthanide complexes with the potentially octadentate ligand CHXOCTAPA4–, which contains a rigid 1,2-diaminocyclohexane scaffold functionalized with two acetate and two picolinate pendant arms, reveal the formation of stable complexes [log KLaL = 17.82(1) and log KYbL = 19.65(1)]. Luminescence studies on the Eu3+ and Tb3+ analogues evidenced rather high emission quantum yields of 3.4 and 11%, respectively. The emission lifetimes recorded in H2O and D2O solutions indicate the presence of a water molecule coordinated to the metal ion. 1H nuclear magnetic relaxation dispersion profiles and 17O NMR chemical shift and relaxation measurements point to a rather low water exchange rate of the coordinated water molecule (kex298 = 1.58 × 106 s–1) and relatively high relaxivities of 5.6 and 4.5 mM–1 s–1 at 20 MHz and 25 and 37 °C, respectively. Density functional theory calculations and analysis of the paramagnetic shifts induced by Yb3+ indicate that the complexes adopt an unprecedented cis geometry with the two picolinate groups situated on the same side of the coordination sphere. Dissociation kinetics experiments were conducted by investigating the exchange reactions of LuL occurring with Cu2+. The results confirmed the beneficial effect of the rigid cyclohexyl group on the inertness of the Lu3+ complex. Complex dissociation occurs following proton- and metal-assisted pathways. The latter is relatively efficient at neutral pH, thanks to the formation of a heterodinuclear hydroxo complex.
Palabras chave
Ions
Ligands
Metals
Molecular structure
Stability
Ligands
Metals
Molecular structure
Stability
Descrición
Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG
Versión do editor
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Atribución 4.0 Internacional
ISSN
0020-1669
1520-510X
1520-510X