980
Y. Sun et al. / Spectrochimica Acta Part A 64 (2006) 977–980
that is believed to result from difference of triplet state (2) in
[15].
4. Conclusions
Results of this work represent a novel ligand design based on
diketonate lanthanide complexes with interesting in luminescent
properties. NMR spectroscopy and element analysis had been
used to fully confirm the preparation of new Eu(III) complexes.
The complexes has long luminescent lifetime and high lumines-
cent quantum yields even in the case of the presence of H2O.
These results indicate that the energy transfer process is efficient
in Eu(III) complex with H2O, resulting from high absorption
efficiency and not resulting from change of singlet and triplet
energy level, which is confirmed by luminescent (luminescence
and phosphorescence) spectra and UV–vis absorption spectra
of ligand and its Eu(III) complex. So it can well overcome the
problem that strongly luminescence quenching was observed
in previous Eu(III) complexes with water for its O H oscil-
lators. In our systems, the magnitude of the lifetime and the
luminescent efficiency of the Eu(III) complexes are higher and
longer comparing with previous Eu(III) complex with crystal
water molecules, which indicate that such results are attributed
to delicate balance between highly energy transfer efficiency and
quenching effect from O H oscillators of water.
Fig. 6. Excitation and luminescent spectra of (A) Eu(TAP)3·2H2O and (B)
Eu(TAP)3·Phen complex in DMSO.
confirming the suitability of the ligand as sensitizer for that lan-
thanide of Eu(III).
Although the excitation spectra (Fig. 6) of Eu(III) complex
was inconsistent to absorption spectra (Fig. 3), they all show a
maximum band at around 350 nm, confirming that energy trans-
fer takes place from the ligand to Eu(III) ion. Light excitation
*
(ca. 350 nm) into the ligand – state of Eu(III) complex in
DMSO is followed by the strong red luminescence and charac-
5
teristic of the D0–7FJ (J = 0–4) luminescent bands of Eu(III).
Acknowledgements
Eu(III) complexes showed similar luminescent and excitation
spectra, suggesting that the 4f state of Eu(III) and excited state
of TAP was independent on the second ligand.
This work was supported by the National Natural Science
Foundation of China (No. 50025309, and No. 90201016). The
authors gratefully acknowledge thanks to Zhao Hui for making
important suggestions.
In Fig. 7, we show the energy level diagrams of ligand and
Eu(III) excited states. For the compounds with water and Phen,
the triplet state (2) is same at 20,121 cm−1 that is agreement
with the result in luminescent spectra at 77 K. However, the
maximal absorption sate of compounds with water and Phen
is different, corresponding to the level (4) and (3) as shown in
Fig. 7, respectively. It is clear that Eu(TPA)3·2H2O complex has
higher absorption coefficients, comparing with Eu(TAP)3·Phen
at excitation bands around 350 nm. So high luminescent quan-
tum yields and long luminescent lifetime from Eu(TPA)3·2H2O
complex can be obtained, which is different from previous work
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