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Luminescence of Eu 3+ and Tb 3+ Complexes of Two Macrobicyclic Ligands Derived from a Tetralactam Ring and a Chromophoric Antenna
Author(s) -
Galaup Chantal,
Azéma Joëlle,
Tisnès Pierre,
Picard Claude,
Ramos Patricia,
Juanes Olga,
Brunet Ernesto,
RodríguezUbis Juan Carlos
Publication year - 2002
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(200206)85:6<1613::aid-hlca1613>3.0.co;2-k
Subject(s) - chemistry , luminescence , chromophore , photochemistry , quantum yield , pyridine , ligand (biochemistry) , phosphorescence , ring (chemistry) , bipyridine , metal , triplet state , singlet state , metal ions in aqueous solution , fluorescence , excited state , molecule , crystallography , medicinal chemistry , crystal structure , atomic physics , organic chemistry , physics , optoelectronics , biochemistry , receptor , quantum mechanics
Two macrobicyclic ligands derived from an 18‐membered tetralactam ring and 2,2′‐bipyridine or 2,6‐bis(pyrazol‐1‐yl)pyridine moieties, 1 and 2 , respectively, form stable complexes with Gd III , Eu III , and Tb III ions in aqueous solution. The ligand‐based luminescence is retained in the Gd III cryptates, whereas this radiative deactivation is quenched in the Eu III and Tb III cryptates by ligand‐to‐metal energy transfer, resulting in the usual metal‐centered emission spectra. Singlet‐ and triplet‐state energies, emission‐decay lifetimes, and luminescence yields were measured. [Tb⊂ 1 ] 3+ cryptate shows a long luminescence lifetime ( τ =1.12 ms) and a very high metal luminescence quantum yield ( Φ =0.25) in comparison with those reported in the literature for Tb 3+ complexes sensitized by a bipyridine chromophore. By comparison to [Ln⊂ 1 ] 3+ , [Ln⊂ 2 ] 3+ presents markedly lower luminescence properties, due to worse interaction between the 2,6‐bis(pyrazol‐1‐yl)pyridine unit and the metal ion. Moreover, the luminescent metal and the triplet ligand energy levels of [Eu⊂ 2 ] 3+ do not match. The effects of H 2 O molecules coordinated to the metal centre and of thermally activated decay processes on nonradiative deactivation to the ground‐state are also reported.