Complexation of Ln 3+ Ions with Cyclam Dipicolinates: A Small Bridge that Makes Huge Differences in Structure, Equilibrium, and Kinetic Properties

Aurora Rodriguez-Rodriguez 1, 2 Martin Regueiro-Figueroa 1 David Esteban-Gomez 1 Raphaël Tripier 2 Gyula Tircso 3 Ferenc Krisztian Kalman 3 Attila Csaba Benyei 4 Imre Toth 3 Andres De Blas 1 Teresa Rodriguez-Blas 1 Carlos Platas-Iglesias 1
1 Departamento de Química Fundamental
2 CEMCA - Chimie, Electrochimie Moléculaires et Chimie Analytique
3 Faculty of Science and Technology, University of Debrecen
4 Department of Pharmaceutical Chemistry
Abstract : The coordination properties toward the lanthanide ions of two macrocyclic ligands based on a cyclam platform containing picolinate pendant arms have been investigated. The synthesis of the ligands was achieved by using the well-known bis-aminal chemistry. One of the cyclam derivatives (cb-tedpa2–) is reinforced with a cross-bridge unit, which results in exceptionally inert [Ln(cb-tedpa)]+ complexes. The X-ray structures of the [La(cb-tedpa)Cl], [Gd(cb-tedpa)]+, and [Lu(Me2tedpa)]+ complexes indicate octadentate binding of the ligands to the metal ions. The analysis of the Yb3+-induced shifts in [Yb(Me2tedpa)]+ indicates that this complex presents a solution structure very similar to that observed in the solid state for the Lu3+ analogue. The X-ray structures of [La(H2Me2tedpa)2]3+ and [Yb(H2Me2tedpa)2]3+ complexes confirm the exocyclic coordination of the metal ions, which gives rise to coordination polymers with the metal coordination environment being fulfilled by oxygen atoms of the picolinate groups and water molecules. The X-ray structure of [Gd(Hcb-tedpa)2]+ also indicates exocyclic coordination that in this case results in a discrete structure with an eight-coordinated metal ion. The nonreinforced complexes [Ln(Me2tedpa)]+ were prepared and isolated as chloride salts in nonaqueous media. However, these complexes were found to undergo dissociation in aqueous solution, except in the case of the complexes with the smallest Ln3+ ions (Ln3+ = Yb3+ and Lu3+). A DFT investigation shows that the increased stability of the [Ln(Me2tedpa)]+ complexes in solution across the lanthanide series is the result of an increased binding energy of the ligand due to the increased charge density of the Ln3+ ion.
Type de document :
Article dans une revue
Inorganic Chemistry, American Chemical Society, 2016, 55 (5), pp.2227 - 2239. 〈http://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.5b02627?journalCode=inocaj〉. 〈10.1021/acs.inorgchem.5b02627〉
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http://hal.univ-brest.fr/hal-01539579
Contributeur : Nicolas Renard <>
Soumis le : jeudi 15 juin 2017 - 10:09:02
Dernière modification le : jeudi 22 février 2018 - 14:22:03

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Aurora Rodriguez-Rodriguez, Martin Regueiro-Figueroa, David Esteban-Gomez, Raphaël Tripier, Gyula Tircso, et al.. Complexation of Ln 3+ Ions with Cyclam Dipicolinates: A Small Bridge that Makes Huge Differences in Structure, Equilibrium, and Kinetic Properties. Inorganic Chemistry, American Chemical Society, 2016, 55 (5), pp.2227 - 2239. 〈http://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.5b02627?journalCode=inocaj〉. 〈10.1021/acs.inorgchem.5b02627〉. 〈hal-01539579〉

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