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  4. Enantiopure, supramolecular helices containing three-dimensional tetranuclear lanthanide(III) arrays: Synthesis, structure, properties, and solvent-driven Trinuclear/Tetranuclear interconversion
 
research article

Enantiopure, supramolecular helices containing three-dimensional tetranuclear lanthanide(III) arrays: Synthesis, structure, properties, and solvent-driven Trinuclear/Tetranuclear interconversion

Lama, Marco
•
Mamula, Olimpia
•
Kottas, Gregg S.
Show more
2008
Inorganic Chemistry

The enantiomerically pure pinene-bipyridine-based receptor, (-) or (+) L-, diastereoselectively self-assembles in dry acetonitrile in the presence of Ln(III) ions (Ln = La, Pr, Nd, Sm, Eu, Gd, and Tb) to give a C-3-symmetrical, pyramidal architecture with the general formula Ln(4)(L)(9)(mu(3)-OH)(2)) (abbreviated as tetra-Ln(4)L(9)). Three metal centers shape the base: an equilateral triangle surrounded by two sets of helically wrapping ligands with opposite configurations. This part of the structure is very similar to the species Ln(3)(L-6(mu(3)-OH)(H2O)(3)(2)) (recently reported by us and abbreviated as tris-LnL(2)) formed by the ligand and the Ln(III) ions when the reactions are performed in methanol. The tetranuclear structure is completed by a capping, helical unit LnL(3) whose chirality is also predetermined by the chirality of the ligand. A complete characterization of these isostructural, chiral compounds was performed in solid state (X-ray, IR) and in solution (ES-MS, NMR, CD, UV-vis and emission spectroscopies). The sign and the intensity of the CD bands in the region of the pi pi* transitions of the bipyridine (absolute Delta epsilon values at 327 nm are about 280 M-1.cm(-1)) are highly influenced by the helicity of the capping fragment LnL(3). The photophysical properties (lifetime, quantum yield) of the visible (Eu and Tb complexes) and NIR (Nd complex) emitters indicate a good energy transfer between the ligands and the metal centers. The two related superstructures tetra-Ln(4)L(9) and tris-LnL(2) can be interconverted in acetonitrile, the switching process depending on the amount of water present in the solvent, the size of the Ln(III) ion, and the concentration. The weak chiral recognition capabilities of the self-assembly leading to the formation of tetra-Ln(4)L(9) either by direct synthesis from a racemic mixture of the ligand and Ln(III) ions or by the conversion of a tris-Ln(+/-)-L racemate were likewise demonstrated.

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Type
research article
DOI
10.1021/ic7021006
Web of Science ID

WOS:000259093700016

Author(s)
Lama, Marco
Mamula, Olimpia
Kottas, Gregg S.
De Cola, Luisa
Stoeckli-Evans, Helen
Shova, Sergiu
Date Issued

2008

Published in
Inorganic Chemistry
Volume

47

Start page

8000

End page

8015

Subjects

Dynamic Combinatorial Chemistry

•

Coordination-Compounds

•

Complexes

•

Ligands

•

Equilibrium

•

Luminescence

•

Architectures

•

Libraries

•

Chirality

•

Behavior

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SB  
Available on Infoscience
November 30, 2010
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/61036
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