Lanthanide complexes metal luminescence intensity

Metal ion complexes can form an imprint site that exhibits both a spectral signature and can be expected to survive incorporation into a pol)oner. A solution analogue of the imprint site can be prepared and the utility for use in imprinting may be established. For a d-block complex, adduction may be characterized by obtaining absorbance, or in some cases, luminescence spectra. The spectral changes that accompany adduct formation are either changes in band position or intensity. Lanthanide-based transduction complexes are usually based on luminescence intensity. If, as in the case of a lanthanide-based reporter, luminescence varies with the degree of analyte inclusion, a luminescence titration will reveal stoichiometry. 

Mameri et al. developed acyclic ligand 51 containing bipyridine carboxylic moieties, which gave high stabihty and hydrophihcity of the lanthanide complex [131]. This formed luminescent 1 1 complexes with Eu " and Tb cations, where two water molecules located in the first coordination sphere of the lanthanide centers. The efficient ligand-to-metal energy transfer was ensured by the bipyridine photoantenna. Upon addition of ATP anion, the Eu luminescence intensity decreased to 20% of its initial value. Since the luminescence lifetime increased from 0.28 to 0.58 and 0.65 ms with the addition of 10 and 20 equivalents of ATP anion, the two boimd water molecules were replaced by the external ATP anion. In contrast, ADP, AMP, and NOs an-... 

Sabbatini et al. 1993). An efficient antenna is expected to lead to metal luminescence much more intense than that obtained upon metal excitation since lanthanide ions are characterized by very low molar absorption coefficients. These complexes can be considered light-conversion molecular devices because they are able to transform light absorbed by the ligand into light emitted by the ions via an intramolecular energy transfer (Balzani and Scandola 1991). 

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