Modulating the photophysical properties of azamacrocyclic europium complexes with charge-transfer antenna chromophores |
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Authors: | Bourdolle Adrien Allali Mustapha Mulatier Jean-Christophe Le Guennic Boris Zwier Jurriaan M Baldeck Patrice L Bünzli Jean-Claude G Andraud Chantal Lamarque Laurent Maury Olivier |
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Institution: | Cisbio Bioassays, Parc Marcel Boiteux, BP 84175, 30204 Bagnols-sur-Ce?ze Cedex, France. |
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Abstract: | Two europium complexes with bis(bipyridine) azamacrocyclic ligands featuring pendant arms with or without π-conjugated donor groups are synthesized and fully characterized by theoretical calculations and NMR spectroscopy. Their photophysical properties, including two-photon absorption, are investigated in water and in various organic solvents. The nonfunctionalized ligand gives highly water-stable europium complexes featuring bright luminescence properties but poor two-photon absorption cross sections. On the other hand, the europium complex with an extended conjugated antenna ligand presents a two-photon absorption cross section of 45 GM at 720 nm but is poorly luminescent in water. A detailed solvent-dependent photophysical study indicates that this luminescence quenching is not due to the direct coordination of O-H vibrators to the metal center but to the increase of nonradiative processes in a protic solvent induced by an internal isomerization equilibrium. |
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