124
K.-W. Lei et al. / Spectrochimica Acta Part A 66 (2007) 118–125
Table 5
gap between the two levels. As we know luminescence intensity
Fluorescence data for the complexes
of solid Ln (Ln = Eu, Tb) nitrate is poor (Fig. 4b), we consider
that efficiency of energy transfer from NO3 to Ln in [Ln(NO3)5]
is very poor, which results in incomplete energy transfer in the
whole nitrate complex molecule though that from L to Ln is
efficient. The [Ln(NO3)5] group is negatively effective to the
fluorescence intensity of the nitrate complexes.
Complexes
λex (nm)
λem (nm)
RFI
34
Assignment
[EuLa]·[Eu(NO3)5]·(NO3)
399
398
319
595
617
5D0 → F1
7
7
121
5D0 → F2
[EuLa]·(ClO4)3
594
616
285
865
5D0 → F1
7
5D0 → F2
7
[TbLa]·[Tb(NO3)5]·(NO3)
493
546
586
1179
2252
189
5D4 → F6
7
4. Conclusion
7
5D4 → F5
5D4 → F4
7
According to the data and discussion above, the amide-based
multipodal ligand could form complexes with lanthanide ions
and exhibit a caverned conformation. The complexes exhib-
ited characteristic fluorescence of europium and terbium ion,
respectively. It has been showed that the nature of the anion
has a great effect upon the composition of the complexes. The
difference in the composition of the complexes results in the dif-
ference in the emission properties of them. The luminescence
intensity of Ln(III) perchlorate complex is stronger than that of
nitrate complex. Based on those results, a series of new amide-
based multipodal derivatives could be designed and synthe-
sized to optimize the luminescent properties of these lanthanide
ions.
[TbLa]·(ClO4)3
309
492
546
585
4807
7998
822
5D4 → F6
7
7
5D4 → F5
7
5D4 → F4
[EuLb]·[Eu(NO3)5]·(NO3)
[EuLb]·(ClO4)3
399
397
321
595
618
35
131
5D0 → F1
7
5D0 → F2
7
7
594
617
105
298
5D0 → F1
7
5D0 → F2
[TbLb]·[Tb(NO3)5]·(NO3)
492
547
586
413
848
82
5D4 → F6
7
7
5D4 → F5
7
5D4 → F4
[TbLb]·(ClO4)3
306
399
492
546
586
1385
2574
310
5D4 → F6
7
7
5D4 → F5
7
5D4 → F4
[EuLc]·[Eu(NO3)5]·(NO3)
[EuLc]·(ClO4)3
595
618
26
102
5D0 → F1
7
7
5D0 → F2
Supplementary material
7
397
320
593
618
302
352
5D0 → F1
7
5D0 → F2
Crystallographic data for the structure analysis have been
deposited with the Cambridge Crystallographic Data Center,
CCDC No. 285256. Copies of this information may be obtained
free of charge from the Director, CCDC, 12 Union Road,
1223 336408; fax: +44 1223 336033).
[TbLc]·[Tb(NO3)5]·(NO3)
491
546
586
854
1506
171
5D4 → F6
7
7
5D4 → F5
7
5D4 → F4
[TbLc]·(ClO4)3
354
492
546
586
433
1041
81
5D4 → F6
7
7
5D4 → F5
7
5D4 → F4
RFI is relative fluorescence intensity.
Acknowledgements
We are grateful to the NSFC (Grants 20371022, 20431010
and 20021001), the Specialized Research Fund for the Doctoral
Program of Higher Education (200307300015), and the Key
Project of the Ministry of Education of China (Grant 01170)
for financial support.
5
7
546 nm from D4 → F5 electronic dipole is used to measure
the fluorescence intensities of Tb complexes. We can notice
solid luminescence intensity of each Eu perchlorate complex
is stronger than that of Eu nitrate complex with the same lig-
and, the case is the same with the Tb complexs (Fig. 4). This is
due to the conformation effect [16]. It has been showed that the
nature of the anion has a great effect upon the composition of the
complexes. The difference in the composition of the complexes
results in the difference in the emission properties of them. In
the studied examples, the luminescence intensity of Ln(III) per-
chlorate complex is stronger than that of nitrate complex. We
know that the complexes conform to [LnL]·[Ln(NO3)5]·(NO3)
(nitrate complexes) and [LnL]·(ClO4)3 (perchlorate complexes).
In every complex, a ligand chelates a Ln ion with nine O atom−s,
but the counter-anions are different: [Ln(NO3)5]2− and NO3
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