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1.
Inorg Chem ; 56(5): 2742-2749, 2017 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-28211688

RESUMO

In this Article, we report the self-assembly of lanthanide complexes formed with two new tripodal ligands, L2 and L3, where binding strands are connected to a rigid triptycene anchor. The pyridine moieties are functionalized with methoxy and PEG groups to enhance ligand solubility and to evaluate the effect of these substituents on lanthanide coordination. These ligands were successfully synthesized and characterized, and their coordination properties were examined along the lanthanide series through speciation studies with NMR and ESI-MS. Well-defined tetranuclear complexes are formed with both ligands, but their stabilities with heavier lanthanides are considerably reduced, especially for complexes with L3. This is attributed to a destabilizing effect of pending PEG arms in combination with increased steric hindrance between binding strands upon complexation with smaller cations. The sensitization of lanthanide luminescence in tetranuclear complexes occurs despite one water molecule being coordinated to a metal ion.

2.
Chemistry ; 21(18): 6695-9, 2015 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-25765709

RESUMO

Herein, we report on the rational design, preparation and characterization of a novel homo-octanuclear helicate, which results from a spatial extension of the central tetranuclear platform. The 3D supramolecular assembly is obtained by complexing europium(III) with a new hexatopic tripodal ligand. The isolated octanuclear helicate is fully characterized by different methods clearly evidencing the structure predicted with molecular modelling. The ligand preorganization plays a crucial role in a successful self-assembly process and induces the formation of a well-defined triple-stranded helical structure. This prototypal octanuclear edifice accommodating functional lanthanides within a 3D scaffold offers attractive perspectives for further applications.

3.
Dalton Trans ; 41(16): 4817-23, 2012 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-22392102

RESUMO

This contribution investigates Ln(III) complexes formed with a small ditopic ligand, L1, and their structural, thermodynamic and photophysical properties. The spectrophotometric and NMR titrations evidence the triangular assemblies [Ln(3)(L1-H)(3)](6+) at stoichiometric conditions and their properties are discussed in relation to L2-containing analogues. In addition, the dinuclear species, [Ln(2)(L1-H)](5+), is observed with an excess of metal.

4.
Chem Commun (Camb) ; 48(9): 1281-3, 2012 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-22179299

RESUMO

A new tripodal ligand has been designed by connecting pyridine-based coordination units to a rigid triptycene moiety. Its reaction with europium(III) provides three-dimensional tetranuclear edifices, whose structural and photophysical characteristics as well as host-guest interactions are discussed in this contribution.

5.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 7): m968-9, 2011 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-21836945

RESUMO

In the title compound, [Tb(C(7)H(4)NO(4))(3)]·2.75H(2)O, the Tb(3+) atom is coordinated by three tridentate 6-carb-oxy-pyridine-2-carboxyl-ate ligands and lies on a crystallographic threefold rotation axis. The coordination polyhedron around Tb(III) adopts a distorted tricapped trigonal-prismatic geometry. Disordered water mol-ecules with partial occupancy are also present in the crystal, one of which is associated with each of the carboxyl-ate O atoms of the complex unit.

6.
J Am Chem Soc ; 133(28): 10764-7, 2011 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-21688784

RESUMO

The self-assembly of the first pentanuclear helicate was predicted on the structural basis obtained for linear and tetranuclear parent supramolecular compounds. Accordingly, the designed ternary supramolecular system requires appropriate polytopic organic receptors, which were successfully synthesized. Indeed, the formation of pentanuclear complexes was experimentally evidenced with NMR and ESMS spectra that perfectly reflect the expected pattern. The structural features in the europium pentanuclear complex are highlighted with semiempirical molecular modeling. The present work validates the combinatorial approach leading to the thermodynamically driven formation of tower-like pentanuclear edifices.

7.
Dalton Trans ; 40(16): 4284-90, 2011 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-21394331

RESUMO

The self-assembly of a carbonylpyridine-based heptadentate ligand with Ln(III) results in the formation of triangular trinuclear europium complexes, which exhibit interesting luminescent properties in the solid state and in solution. With a view to developing multimodal responsive systems, we report here the preparation and characterisation of analogous complexes with Gd(III). The X-ray crystal structure of Gd(3)L2(3) indeed reveals the isostructurality with the Eu(III) complexes. A combination of (1)H NMRD and variable temperature studies yields the parameters elucidating the exchange of coordinated water and relaxivity properties. Conveniently, the competitive spectrophotometric titrations with EDTA and NTA are used to determine the thermodynamic stability constants of the europium complexes in aqueous media. In addition, the exchange reaction with EDTA is monitored with NMR and fluorimetry. The interactions of the Eu(III) trinuclear complex with some potentially interfering ligands are qualitatively investigated by means of luminescence titrations.


Assuntos
Elementos da Série dos Lantanídeos/química , Ácidos Carboxílicos/química , Cristalografia por Raios X , Ácido Edético/química , Espectroscopia de Ressonância Magnética , Magnetismo , Modelos Moleculares , Conformação Molecular , Termodinâmica
8.
Chemistry ; 15(14): 3355-8, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19235190

RESUMO

Triangular luminescent box: Self-assembly of a new multidentate receptor with europium cations results in the formation of trinuclear discrete complexes. X-ray crystallography shows that nine-coordinate cations are linked by ligands to provide a triangular complex in the solid state and in solution. Despite the coordinated solvent molecules, this topologically unusual complex exhibits remarkable luminescent properties.


Assuntos
Európio/química , Substâncias Luminescentes/química , Compostos Organometálicos/química , Cátions/química , Cristalografia por Raios X , Substâncias Luminescentes/efeitos da radiação
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