TY - JOUR
T1 - Spectroscopy and non-radiative processes in Gd3+, Eu3+ and Tb3+ tropolonates
AU - Santos, B. S.
AU - de Mello Donegá, C.
AU - de Sá, G. F.
AU - de Oliveira, L. F. C.
AU - Santos, P. S.
PY - 1998/11/1
Y1 - 1998/11/1
N2 - Complexes of Eu3+, Gd3+, and Tb3+ with
tropolone (tropolone=2-hydroxy-2,4,6-cycloheptatrien-1-one) were
synthesized and characterized by C and H elemental analysis, infrared
vibrational spectroscopy, X-ray powder diffraction analysis and Raman
vibrational spectroscopy. The results show that the complexes are
isostructural and have the formula [Ln(trop)3], where
Ln=Eu3+, Gd3+ or Tb3+ and
trop=tropolone. The characteristic luminescence of the Eu3+
and Tb3+ ions was not observed either upon ligand excitation
(300-380nm) or upon direct f-f excitation, not even at 4.2 K. In order
to understand this phenomenon the spectroscopic properties of the
Gd(trop)3 complex (absorption spectra at 298 K, excitation
and emission spectra from 4.2 to 298 K and decay time measurements from
20 to 298 K) were investigated. The emission spectra show three distinct
bands, which are ascribed to ligand electronic states: a singlet state,
S1 (π-π*), at 24 270 cm-1, and two
triplet states, T1 and T2, at
15 630cm-1 and 16 610cm-1,
respectively. Both triplet states are situated below the emitting states
of the Eu3+ and Tb3+ ions
(5Do and 5D4, respectively),
thus suppressing the luminescence from these states by back-transfer.
AB - Complexes of Eu3+, Gd3+, and Tb3+ with
tropolone (tropolone=2-hydroxy-2,4,6-cycloheptatrien-1-one) were
synthesized and characterized by C and H elemental analysis, infrared
vibrational spectroscopy, X-ray powder diffraction analysis and Raman
vibrational spectroscopy. The results show that the complexes are
isostructural and have the formula [Ln(trop)3], where
Ln=Eu3+, Gd3+ or Tb3+ and
trop=tropolone. The characteristic luminescence of the Eu3+
and Tb3+ ions was not observed either upon ligand excitation
(300-380nm) or upon direct f-f excitation, not even at 4.2 K. In order
to understand this phenomenon the spectroscopic properties of the
Gd(trop)3 complex (absorption spectra at 298 K, excitation
and emission spectra from 4.2 to 298 K and decay time measurements from
20 to 298 K) were investigated. The emission spectra show three distinct
bands, which are ascribed to ligand electronic states: a singlet state,
S1 (π-π*), at 24 270 cm-1, and two
triplet states, T1 and T2, at
15 630cm-1 and 16 610cm-1,
respectively. Both triplet states are situated below the emitting states
of the Eu3+ and Tb3+ ions
(5Do and 5D4, respectively),
thus suppressing the luminescence from these states by back-transfer.
U2 - 10.1016/S1386-1425(98)00143-7
DO - 10.1016/S1386-1425(98)00143-7
M3 - Article
SN - 1386-1425
VL - 54
SP - 2237
EP - 2245
JO - Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
JF - Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
IS - 13
ER -