The luminescence spectra and decay rate consts. of the [M.cntnd.2.2.1]3+ cryptates (M = Eu3+ or Tb3+) are strongly affected by addn. to the soln. of F- anions. Two distinct species, corresponding to the 1:1, [M.cntnd.2.2.1]3+-F-, and 1:2, [M.cntnd.2.2.1]3+-2F-, stoichiometries are formed. The F- ions replace H2O in the holes of the cryptate structure, preventing or limiting the radiationless decay of the emitting excited state that occurs via coupling with the O-H oscillators. In the case of M = Eu3+ the coordination of F- to the metal ion shifts the ligand-to-metal charge-transfer bands of the cryptate to higher energies, thereby preventing radiationless decay via low-lying charge-transfer levels. As a consequence, the luminescence quantum yield in D2O soln. at 300 K for f-f excitation increases from 0.03 to ∼1 in passing from [Eu.cntnd.2.2.1]3+ to [Eu.cntnd.2.2.1]3+-2F-. The reported results confirm that luminescence studies are a powerful method to elucidate the structure and compn. of the coordination sphere of lanthanide ions in soln. and show that it is possible to tune the photophys. properties of lanthanide complexes by appropriate perturbations. [on SciFinder(R)]

Influence of fluoride ions on the absorption and luminescence properties of the [Eu.cntnd.2.2.1]3+ and [Tb.cntnd.2.2.1]3+ cryptates

PERATHONER, Siglinda;
1987-01-01

Abstract

The luminescence spectra and decay rate consts. of the [M.cntnd.2.2.1]3+ cryptates (M = Eu3+ or Tb3+) are strongly affected by addn. to the soln. of F- anions. Two distinct species, corresponding to the 1:1, [M.cntnd.2.2.1]3+-F-, and 1:2, [M.cntnd.2.2.1]3+-2F-, stoichiometries are formed. The F- ions replace H2O in the holes of the cryptate structure, preventing or limiting the radiationless decay of the emitting excited state that occurs via coupling with the O-H oscillators. In the case of M = Eu3+ the coordination of F- to the metal ion shifts the ligand-to-metal charge-transfer bands of the cryptate to higher energies, thereby preventing radiationless decay via low-lying charge-transfer levels. As a consequence, the luminescence quantum yield in D2O soln. at 300 K for f-f excitation increases from 0.03 to ∼1 in passing from [Eu.cntnd.2.2.1]3+ to [Eu.cntnd.2.2.1]3+-2F-. The reported results confirm that luminescence studies are a powerful method to elucidate the structure and compn. of the coordination sphere of lanthanide ions in soln. and show that it is possible to tune the photophys. properties of lanthanide complexes by appropriate perturbations. [on SciFinder(R)]
1987
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/1907355
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