Modulating the Photophysical Properties of Azamacrocyclic Europium Complexes with Charge-Transfer Antenna Chromophores
Two europium complexes with bis(bipyridine) azamacrocyclic ligands featuring pendant arms with or without pi-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.
Keywords: Luminescent Lanthanide Complexes ; Time-Resolved Fret ; Cross-Sections ; Energy-Transfer ; 2-Photon-Sensitized Luminescence ; 2-Photon-Excited Luminescence ; Efficient Sensitization ; Optical-Properties ; Tb(Iii) Complexes ; Terbium Complexes
Record created on 2012-01-17, modified on 2016-08-09