The asymmetric macrocyclic compartmental ligand H2L, derived from the [1+1] condensation of 3,3'-(3-oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde) with 1,5-diamine-3-azamethylpentane, forms the complexes [LnNa(L)(Cl)(2)(CH3OH)] (Ln = La-Nd, Sm-Lu) where the lanthanide(iii) ion resides in the N3O2 Schiff base coordination site and the sodium ion is located in the 0302 crown-like cavity, The new heterodinuclear complexes [LnCa(L)(Cl)2(CH3OH)(H2O)]Cl (Ln = Tb, Dy, Tm, Yb) were prepared and characterised by single-crystal X-ray diffraction, IR, H-1 and C-13 NMR spectroscopy and their homogeneity and stoichiometry (Ln:Ca:Cl = 1:1:3 molar ratio) were ascertained by SEM-EDS analysis. The single-crystal X-ray structure of [YbCa(L)(Cl-2)(EtOH)(H2O)]-Cl-2H(2)O has been determined. The complex is monoclinic, space group P2(1)/c, with a = 10.033(2), b = 11.702(2), c = 27.796(6) angstrom and beta = 105.51(3)degrees. The ytterbium ion is seven-coordinate within the N3O2 site and is in a pentagonal bipyramidal environment and bonded, in the axial positions, to two chloride ions. The calcium ion is seven-coordinate within the O3O2 site and is bonded to the ethyl alcohol oxygen and to one water molecule. The significant contact between the calcium ion and the chloride ions increases the coordination number of the metal ion to eight in a square antiprismatic environment. The selectivity of the etheric site towards alkali and alkaline-earth metal ions has been quantitatively assessed by evaluating, with Na-23 NMR spectroscopy, the transmetallation reaction involving the coordinated Na+ ion in the complexes [LnNa(L)(Cl)(2) (CH3OH)] (Ln = Tb, Dy, Tin and Yb) and Li+, K+ and Call. The affinity constants follow the general order K-Ca >> K-Li >= K-K. Quantitative kinetic analyses were performed on the complex [TmNa(L)(Cl)(2)(CH3OH)] using variable temperature Na-23 NMR spectroscopy in CD3OD. It was ascertained that the exchange rate Na-bound/Na-free is independent of the presence of increasing amounts of water in the methanolic solution
Selectivity of asymmetric macrocyclic compartmental lanthanide(III) complexes towards alkali and alkaline-earth metal ions
BARGE, Alessandro;
2005-01-01
Abstract
The asymmetric macrocyclic compartmental ligand H2L, derived from the [1+1] condensation of 3,3'-(3-oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde) with 1,5-diamine-3-azamethylpentane, forms the complexes [LnNa(L)(Cl)(2)(CH3OH)] (Ln = La-Nd, Sm-Lu) where the lanthanide(iii) ion resides in the N3O2 Schiff base coordination site and the sodium ion is located in the 0302 crown-like cavity, The new heterodinuclear complexes [LnCa(L)(Cl)2(CH3OH)(H2O)]Cl (Ln = Tb, Dy, Tm, Yb) were prepared and characterised by single-crystal X-ray diffraction, IR, H-1 and C-13 NMR spectroscopy and their homogeneity and stoichiometry (Ln:Ca:Cl = 1:1:3 molar ratio) were ascertained by SEM-EDS analysis. The single-crystal X-ray structure of [YbCa(L)(Cl-2)(EtOH)(H2O)]-Cl-2H(2)O has been determined. The complex is monoclinic, space group P2(1)/c, with a = 10.033(2), b = 11.702(2), c = 27.796(6) angstrom and beta = 105.51(3)degrees. The ytterbium ion is seven-coordinate within the N3O2 site and is in a pentagonal bipyramidal environment and bonded, in the axial positions, to two chloride ions. The calcium ion is seven-coordinate within the O3O2 site and is bonded to the ethyl alcohol oxygen and to one water molecule. The significant contact between the calcium ion and the chloride ions increases the coordination number of the metal ion to eight in a square antiprismatic environment. The selectivity of the etheric site towards alkali and alkaline-earth metal ions has been quantitatively assessed by evaluating, with Na-23 NMR spectroscopy, the transmetallation reaction involving the coordinated Na+ ion in the complexes [LnNa(L)(Cl)(2) (CH3OH)] (Ln = Tb, Dy, Tin and Yb) and Li+, K+ and Call. The affinity constants follow the general order K-Ca >> K-Li >= K-K. Quantitative kinetic analyses were performed on the complex [TmNa(L)(Cl)(2)(CH3OH)] using variable temperature Na-23 NMR spectroscopy in CD3OD. It was ascertained that the exchange rate Na-bound/Na-free is independent of the presence of increasing amounts of water in the methanolic solution
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