Luminescent soft material: Two new europium-based ionic liquids

Article abstract of DOI:10.1002/hlca.200900173

Two new Eu-based ionic liquid systems, [C₄mim][DTSA] : [Eu(DTSA)₃] and 2[C₄mim] [DTSA] : [Eu(DTSA)₃] were synthesized at 120° under inert conditions from 1-butyl-1- methylimidazolium ditoluenesulfonylamide ([C

Full text of DOI:10.1002/hlca.200900173

Helvetica Chimica Acta – Vol. 92 (2009)
2375
Luminescent Soft Material: Two New Europium-Based Ionic Liquids
by Sifu Tanga), Joanna Cybinskaa)b), and Anja-Verena Mudring*a)
a) Anorganische Chemie I – Festkçrperchemie und Materialien, Ruhr-Universitꢀt Bochum, D-44801,
Bochum (e-mail: anja.mudring@rub.de)
b) Faculty of Chemistry, University of Wrocław, Joliot-Curie 14, PL-50-383 Wrocław
Dedicated to Professor Dr. Jean-Claude Bꢀnzli on the occasion of his 65th birthday
Two new Eu-based ionic liquid systems, [C4mim][DTSA]:[Eu(DTSA)3] and 2[C4mim]
[DTSA]:[Eu(DTSA)3] were synthesized at 1208 under inert conditions from 1-butyl-1-methylimidazo-
lium ditoluenesulfonylamide ([C4mim][DTSA]). The identity and purity of the synthesized compounds
1
were confirmed by elemental analysis, IR, Raman, and H-NMR spectroscopy. As they solidify below
1008 as glasses they qualify as ionic liquids. Fluorescence measurements show that the materials exhibit a
strong red luminescence of high color purity. Therefore, they have the potential to be used for optical
applications such as in emission displays.
Introduction. – In the past few years, ionic liquids (ILs) have attracted considerable
attention due to their unique chemical and physical properties [1], such as low vapor
pressure, wide liquid range, large electrochemical window, and so on. ILs are seen as
ꢁmulti-purpose liquidsꢂ and have already found usage in almost every field of chemistry
(e.g. separation/extraction, catalysis, synthesis, electrochemistry) [2]. As commonly
accepted, ionic liquids are organic salts, composed of distinct cations and anions which
melt below 1008. When a metal ion is introduced into the complex anion of the ionic
liquid, a so-called metal-containing ionic liquid is obtained. Compared to ordinary
organic ionic liquids, metal-containing ionic liquids combine both the properties of
ionic liquids and those of the metal cation which can be magnetic, photo physical/
optical or catalytic properties [3]. Recently a row of investigations devoted to
lanthanide-containing ionic liquids have shown that solutions of lanthanide compounds
in ionic liquids are promising soft luminescent materials for use in photochemistry and
spectroscopy [4 – 8]. It is very well-known that especially lanthanide (Ln) b-diketonate
complex compounds exhibit very strong luminescence sensitized by efficient photon
absorption in the organic ligand. Such a process, called ꢁantenna effectꢂ, involves the
energy transfer of the absorbed photon to the triplet state of the ligand and subsequent
intramolecular transfer to the LnIII ion. As a consequence, enhancement in the LnIII
emission is observed. However, it is very important to notice that the efficiency of this
process depends strongly on the donor– acceptor properties of the ligands which
influence the energy of the charge transfer (CT) state, controlling the energy transfer
and efficiency of Ln emission [9 – 13].
Ln-Containing ionic liquids can be obtained by two methods. The first method is to
dissolve a Ln complex or oxide in an ionic liquid. A high quantum yield and an
ꢃ 2009 Verlag Helvetica Chimica Acta AG, Zꢄrich

2376
Helvetica Chimica Acta – Vol. 92 (2009)
enhanced photostability of such Ln-containing ionic liquids – or better Ln-doped ionic
liquids – was observed, for example, when doping an europium b-diketonate complex
into a imidazolium ionic liquid [5] or by dissolving europium oxide and an organic
ligand into a task-specific ionic liquid bearing a carboxylic group [6]. The merit of this
method is its easy feasibility. However, the structure of the optically active component,
especially the local environment of the LnIII ion, is most of the times unknown and
makes a strategic improvement of the material difficult. In contrast, by reacting a Ln
salt with an ionic liquid which shares the same counter anion as the used ionic liquid
leads to the formation of a compound or solution where the LnIII ion is solely
coordinated by the common anion. The target compound can be tuned by reacting the
salt with the ionic liquid at different molar ratios or selecting different cations and
anions. In our previous work, we synthesized via this method three dysprosium-based
ionic liquids [C6mim]5ꢀx[Dy(SCN)8ꢀx(H2O)x] (x ¼ 0 – 2, C6mim ¼ 1-hexyl-3-methyl-
imidazolium) from [C6mim]SCN, KSCN, and Dy(ClO4)3 · 6 H2O. These ILs show high
response to external magnetic fields and have excellent photophysical properties [7].
Three Eu-containing ionic liquids with the compositions [R]x[Eu(Tf2N)3þx] (Tf2N ¼
bis(trifluoromethanesulfonyl)amide; x ¼ 1 for R ¼ 1-propyl-3-methylimidazolium
(C3mim) and 1-butyl-3-methylimidazolium (C4mim); x ¼ 2 for R ¼ 1-butyl-3-methyl-
pyrrolidinium (C4mpyr) were also obtained without the using of neutral co-ligands [8].
They show excellent photophysical properties such as long lifetimes of luminescence at
high EuIII concentration, small linewidth, and high color purity. To improve the
photophysical properties, we continued our work by replacing the CF3 groups of the
Tf2N anion with toluene groups in the ligand (DTSA ¼ ditoluenesulfonylamide) in the
hope that the toluene group can serve as a better light – absorbing chromophore
(antenna).
Results and Discussion. – Materials with compositions similar to the Eu-Tf2N
compounds which we investigated previously [8], were studied. [C4mim]-
[DTSA]:[Eu(DTSA)3] and 2[C4mim][DTSA]:[Eu(DTSA)3] were synthesized at
1208 under inert conditions from 1-butyl-3-methylimidazolium ditoluenesulfonylamide
([C4mim][DTSA]) and europium ditoluenesulfonylamide (Eu[DTSA]3).
Thermal Properties. DSC (differential scanning calorimetry) shows that all
materials qualify as ionic liquids as they solidify below 1008 (Fig. 1). The DSC traces
show a thermal behavior which is commonly encountered for ionic liquids:
Crystallization is strongly inhibited and the compounds solidify rather as a glass. This
also makes the determination of a reliable phase diagram impossible, and we cannot
judge whether [C4mim][DTSA]:[Eu(DTSA)3] and 2[C4mim]2[DTSA]:[Eu(DTSA)3]
are true compounds or have rather to be viewed as a solution of [Eu(DTSA)3] in
[C4mim][DTSA].

Helvetica Chimica Acta – Vol. 92 (2009)
2377
Fig. 1. Thermogram of [C4mim][DTSA] (a), [C4mim][DTSA]:[Eu(DTSA)3] (b), and 2[C4mim]-
[DTSA]:[Eu(DTSA)3] (c)
Structural Characterization. Unfortunately neither by employing homogeneous or
heterogeneous crystallization techniques we were able to obtain crystalline materials in
the system [C4mim][DTSA]/[Eu(DTSA)3]. In consequence, the materials were
characterized by vibrational spectroscopy. Fig. 2 shows a comparison of the infrared
(IR) spectra of the materials, Fig. 3 the respective Raman spectra.
The IR and Raman spectra provide good evidence that the metal ion is coordinated
by the DTSA anion. For the ꢁfreeꢂ DTSAꢀ in the ionic liquid [C4mim][DTSA], the
ns(SNS) band is found at 768 cmꢀ1. Under complexation, the ns(SNS) band of the anion
shifts in [C4mim][DTSA]:[Eu(DTSA)3] and 2[C4mim][DTSA]:[Eu(DTSA)3] to 774
and 772 cmꢀ1, respectively (see Fig. 3). The ns(SO2) which should be directly influenced
by coordination of the sulfonyl O-atom to a metal center is observed for the ionic liquid
[C4mim][DTSA] at 1150 cmꢀ1. In [C4mim][DTSA]:[Eu(DTSA)3] and 2[C4mim]-
[DTSA]:[Eu(DTSA)3] this spectral region is broadened due to the overlap of SꢀO
modes involving the coordinating and non-coordination sulfonyl O-atoms. The peaks
are located at 1152 and 1162 cmꢀ1, respectively, indicating a weakening of the SꢀO
bond upon coordination. A similar observation was made for alkaline earth-Tf2N
complexes [9] and for the above mentioned Eu(III)-Tf2N ionic liquids [8]. It is highly
likely that the first coordination shell around EuIII in [C4mim][DTSA]:[Eu(DTSA)3]
and 2[C4mim][DTSA]:[Eu(DTSA)3] is similar to the one in [C4mim][Eu(Tf2N)4]
where nine O-atoms form an irregular coordination polyhedron around EuIII, which
can be best described as a strongly distorted monocapped square anti-prism.

2378
Helvetica Chimica Acta – Vol. 92 (2009)
Fig. 2. IR Spectra of, from top to bottom, [C4mim][DTSA], Eu[DTSA]3, [C4mim][DTSA]:[Eu(DT-
SA)3], and 2[C4mim][DTSA]:[Eu(DTSA)3]
Fig. 3. a) Comparison of the Raman spectra of [C4mim][DTSA] (black) and [C4mim]-
[DTSA]:[Eu(DTSA)3] (grey) and b) [C4mim][DTSA] (black) and 2[C4mim][DTSA]:[Eu(DTSA)3]
(grey)
Photophysical Properties. The excitation (lex ¼ 393 nm and lex ¼ 290 nm) and
emission (lem ¼ 615 nm) spectra of Eu[DTSA]3, [C4mim][DTSA]:[Eu(DTSA)3], and
2[C4mim][DTSA]:[Eu(DTSA)3] were recorded at three different temperatures,
namely 77, 298 and 353 K (Figs. 4 – 6). The results show that the respective spectra
are quite similar and all show the characteristic EuIII f – f-transitions.
For the reason that the excitation and emission of [C4mim][DTSA]:[Eu(DTSA)3]
and 2[C4mim][DTSA]:[Eu(DTSA)3] show no significant deviations, we will discuss
and compare only the data obtained for Eu[DTSA]3 and [C4mim][DTSA]:[Eu(DTSA)3].
The excitation spectrum of the samples recorded at liquid N2 temperature, under

Helvetica Chimica Acta – Vol. 92 (2009)
2379
Fig. 4. a) Excitation and b) emission spectra of Eu[DTSA]3, [C4mim][DTSA]:[Eu(DTSA)3], and
2[C4mim][DTSA]:[Eu(DTSA)3], recorded at 77 K
5
7
emission of the D0 ! F2 transition at lem ¼ 611 nm, show a broad band between 250
and 320 nm attributed to p – p* transitions of the DTSA ligand. The narrow, much
more intense lines in the spectrum correspond to discrete f – f transitions at 360.5, 365
5
5
5
5
5
(7F0 ! D4), 372, 375 (7F0/1 ! GJ), 379, 383 (7F0/1 ! L7, GJ), 392.5, 395 (7F0 ! L6),
414.5 (7F0 ! D3), 463 (7F0 ! D2), 524 (7F0 ! D1), and 534 nm (7F1 ! D1). The
presence of a broad band in the UV region proves that the DTSA ligand transfers the
absorbed photons to Eu(III). The maximum of this broad band is found at
comparatively high energies (ca. 290 nm). Ligand singlet states can serve as a donating
state in the sensitization of, for example, EuIII and SmIII ions, however usually excited
states of luminescent LnIII ions are populated by a fast intramolecular energy transfer
process from a triplet state of the ligand. The ligand triplet state is populated from the
singlet state by intersystem crossing [10][14].
5
5
5
5
At low temperature (77 K), the intensity of the ligand band compared to the
narrow EuIII transitions is not very high, which suggests a low efficiency in the energy
transfer process. For [C4mim][DTSA]:[Eu(DTSA)3], the intensity of this broad band
drastically decreases with rising the temperature to 353 K, only narrow lines attributed
to EuIII f – f transitions can be observed. The decrease of the efficiency of energy
transfer with decreasing temperature is probably due to the fact that the CT state is

2380
Helvetica Chimica Acta – Vol. 92 (2009)
Fig. 5. a) Excitation and b) emission spectra of Eu[DTSA]3, [C4mim][DTSA]:[Eu(DTSA)3], and
2[C4mim][DTSA]:[Eu(DTSA)3] recorded at 298 K.
involved in the de-activation process. Such an effect was already noted for several EuIII
complexes [14][15].
Analysis of low-temperature excitation spectra indicates that some of these lines
may be accompanied by a number of satellites of vibronic or ion pair origin. Sharp lines
in the excitation spectra recorded at room temperature are associated with transition
from the ground-state (7F0) and also from the first excited state (7F1) of the EuIII ion to
7
different 5DJ states, according to the thermal population of F1,2 levels of the EuIII ion.
5
This assumption is backed by the higher intensity of the 7F1 ! D1 transition at elevated
temperature (353 K).
The luminescence spectra recorded at the three different temperatures (77, 298, and
5
353 K) under excitation into the band corresponding to the 7F0 ! L6 transition of the
EuIII ion (lex ¼ 393 nm) all show a strong red light emission. The spectra consist of sharp
5
7
7
lines attributed to D0 ! FJ (J ¼ 0 – 4) transitions of EuIII (578.5 (5D0 ! F0), 591
(5D0 ! F1), 611, 613.5, 616.5 (5D0 ! F2), 653 (5D0 ! F3) and 690, 698 nm (5D0 ! F4).
7
7
7
7
The spectra are dominated by a band with a maximum around 611 nm which belongs to
5
7
the hypersensitive transition D0 ! F2 in agreement with a low point symmetry for
Eu(III). Although the emission occurs mainly from the 5D0 level, it is important to note
5
that also transitions from the higher energy D1 level can be observed in the spectral
range from 520 to 570 nm. Neither Eu(DTSA)3 nor [C4mim][DTSA]:[Eu(DTSA)3]

Helvetica Chimica Acta – Vol. 92 (2009)
2381
Fig. 6. a) Excitation and b) emission spectra of [C4mim][DTSA]:[Eu(DTSA)3], and 2[C4mim]-
[DTSA]:[Eu(DTSA)3] recorded at 353 K.
are sensitive to changes in the energy of excitation. The emission spectra recorded
under excitation into UVand directly into the EuIII levels are the same in sense that, the
shapes of the band as well as their relative intensities are not changing. The bands
5
7
assigned to the D0 ! FJ (J ¼ 0 – 4) transitions are relatively broad and unsplitted.
Lowering of the temperature does not lead to substantial band narrowing. The 5D0 !
5
7
7F0 transition is unsplitted, however, relatively broad. The half width of the D0 ! F0
band is about 25 cmꢀ1. This could be due to a high flexibility in the local EuIII
surrounding. The decay rates can be fitted as monoexpontential curves, and all data
collected in the Table were obtained in this way. For all samples, the decay times are
strongly temperature dependent. At 298 K for Eu(DTSA)3 the shortest decay time was
obtained. This could confirm the assumption that the multiphonon relaxation processes
for EuIII in the IL are reduced because of better shielding. The relative intensities
5
7
7
between the D0 ! F2/5D0 ! F1 transitions can be used to determine the symmetry
and strength of the ligand field around EuIII. A variation of the ligand field strength
5
7
leads to a change of the intensity of the electric dipole (ED) D0 ! F2 transition, in
5
7
contrast to the intensity of the magnetic dipole (MD) D0 ! F1. The latter is hardly
affected by the ligand field. In the systems under investigation the ratio is strongly
temperature dependent. For Eu(DTSA)3 at r.t. and 77 K, it is 9.7 and 7.6, respectively.
For the [C4mim][DTSA]:[Eu(DTSA)3] the asymmetry parameter vary with temper-
ature between 11.2 (77 K), 11.7 (298 K), and 12 (353 K). The large ratio of the
fluorescence intensities is typical for EuIII in a low site symmetry without an inversion

2382
Helvetica Chimica Acta – Vol. 92 (2009)
center [16]. In the previously reported [C4mim][Eu(Tf2N)4], these values were equal
to 8.36 and 3.49 for solid (crystalline) and liquid, respectively, which suggests larger Eu-
ligand interaction in the solid compounds than in the liquids [8]. In the materials
investigated here, the asymmetry parameter is higher and increasing with the
temperature, indicating a stronger coupling between the anion and EuIII, which can
be expected at higher temperature [17].
Table. Experimental Lifetime, Calculated Radiative and Nonradiative Decay Rates, and Quantum
Efficiency (q) of the 5D0 State for Eu[DTSA]3 at 77 K and Room Temperature for [C4mim]-
[DTSA]:[Eu(DTSA)3] at 77 K, Room Temperature, and 353 K, as well as for 2[C4mim]-
[DTSA]:[Eu(DTSA)3] at 77 K, Room Temperature, and 353 K
Compounds
Temp. [K]
t [ms]
kr
knr
q [%]
Eu[DTSA]3
Eu[DTSA]3
77
298
77
298
353
77
1.67
1.24
1.88
1.608
1.20
1.84
1.615
1.13
0.35
0.44
0.39
0.44
0.42
0.39
0.43
0.40
0.248
0.366
0.142
0.182
0.413
0.153
0.189
0.485
58.5
54.6
73.3
70.8
50.4
71.8
69.5
45.2
[C4mim][DTSA]:[Eu(DTSA)3]
[C4mim][DTSA]:[Eu(DTSA)3]
[C4mim][DTSA]:[Eu(DTSA)3]
2[C4mim][DTSA]:[Eu(DTSA)3]
2[C4mim][DTSA]:[Eu(DTSA)3]
2[C4mim][DTSA]:[Eu(DTSA)3]
298
353
To characterize the luminescence of Eu(DTSA)3, [C4mim][DTSA]:[Eu(DTSA)3],
and 2[C4mim][DTSA]:[Eu(DTSA)3] with respect to its emission color under
excitation 366 nm at 77, 293, and 353 K, the CIE (x,y) coordinates were calculated
7
(Fig. 7). As it could be seen from the excitation spectra recorded at 5D ! F2 transition,
the imidazolium states are involved into energy transfer to Eu(III). However, it is very
well known, that UV light induces transitions in the imidazolium ring and as
consequence one can observe a broad emission band in the 400 – 600 nm spectral range
[17]. Using the line 366 nm we were able to simultaneously excite the imidazolium ring
and the EuIII ions. In consequence, we observed a change of color of emission
depending on the number of imidazolium groups present in the material. As it could be
expected, a pure red color was obtained for the Eu(DTSA)3. For the other materials,
the color was shifted to blue due to contributions of imidazolium emission. It is also
important to notice, that only for Eu(DTSA)3 the color is almost temperature
independent.
To check if the quantum yield depends on the first coordination shell of Eu3þ and
5
temperature, we tried to estimate the D0 quantum efficiency (q) from the emission
5
spectrum and lifetime of the D0 state by assuming that only nonradiative (knr) and
radiative (kr) processes are involved in the depopulation of the 5D0 state [18]. The q can
be defined as:
q ¼ kr/(kr þ knr)
(1)
7
The influence of the 5D0 ! F5,6 transitions on the depopulation of the 5D0 state can
be ignored because of their relatively weak intensities with respect to those of the
5
7
remaining D0 ! F0–4 transitions [19]. The radiative contribution therefore can be

Helvetica Chimica Acta – Vol. 92 (2009)
2383
Fig. 7. CIE Color coordinates for Eu[DTSA]3, [C4mim][DTSA]:[Eu(DTSA)3], and 2[C4mim]-
[DTSA]:[Eu(DTSA)3] at 77, 298, and 353 K
7
calculated from the relative intensities of the 5D0 ! F0–4 transitions and can be
expressed as:
4
X
ꢀhw0!1
S0!1
S0ꢀJ
ꢀhw0!1
kr ¼ A0!1
(2)
J¼0
where A0!1 is the Einstein coefficient of spontaneous emission between the 5D0 and 7F1
Stark levels, usually considered to be equal to 50 sꢀ1. The ꢀhw0!J and S0!J are the energy
5
7
and the integrated intensity of the D0 ! FJ transitions, respectively. Appropriate
analyses of the emission spectra of [C4mim][DTSA]:[Eu(DTSA)3] yielded the
quantum efficiencies to be 0.733 (77 K), 0.708 (298 K), and 0.504 (353 K) (for
2[C4mim][DTSA]:[Eu(DTSA)3] these numbers were 77 K: 0.718, 298 K: 0.695, 353 K:
0.452) (see Table). It is obvious that the compounds have the highest quantum
efficiency at 77 K and the lowest at 353 K. The lower value (50.4%) at higher
temperature is caused by the higher nonradiative transition probability (knr), but when
compared with those of some europium bistriflimide complexes Eu[N(SO2C3F7)3]
(5%) or Eu[N(SO2C3F7)3][L]8 (L ¼ DPSO, diphenyl sulfoxide, 32%; L ¼ TPPO,
triphenylphosphine oxide, 5.6%; L ¼ phen, phenanthroline, 5.1%) (0.05 mol/l MeCN
solution) [20], this number is still very high, especially when the high EuIII
concentration is considered.
Conclusions. – In summary, two Eu-based ionic liquids have been synthesized. The
identity and purity of the synthesized compounds were confirmed by elemental
analysis, IR, Raman and 1H-NMR spectroscopy. Their thermal behaviour was
investigated by DSC. Both compounds, [C4mim][DTSA]:[Eu(DTSA)3] and
2[C4mim][DTSA]:[Eu(DTSA)3], qualify as ionic liquids as they solidify well below

2384
Helvetica Chimica Acta – Vol. 92 (2009)
1008, 2[C4mim][DTSA]:[Eu(DTSA)3] even below room temperature. However, no
crystallization could be observed – only glass formation. [C4mim][DTSA]:[Eu(DT-
SA)3] and 2[C4mim][DTSA]:[Eu(DTSA)3] exhibit a bright red luminescence of high
color purity. Therefore, they have the potential to be used in optical applications such as
in emission displays. Further work will be undertaken to the synthesis of luminescent
ionic liquids by the replacement of CꢀH bonds by electron-withdrawing CꢀF bonds in
the chelating parts of the ligands to tune the LMCT states as well as minimize the non-
radiative decay pathways.
Support by the DFG priority program SPP 1191 ꢁIonic Liquidsꢂ and the Fonds der Chemischen
Industrie through a Dozentenstipendium for A.V.M. is gratefully acknowledged.
Experimental Part
Instrumentation. IR Spectra: Bruker Alpha-P FT-IR spectrometer in the range of 4000 – 400 cmꢀ1
.
Raman Spectra: from the bulk solids recorded at 150 mW on a Bruker IFS-FRA-106/s; for the
measurement, the respective samples were sealed under Ar atmosphere in glass capillaries; the data were
recorded at r.t. 1H-NMR Spectra: Bruker Advance DPX-250 instrument. Elemental analyses: Vario EL
III elemental analyzer. Phase transition temperatures: differential scanning calorimeter (NETZSCH
DSC 240 F1); measurements were carried out at a heating rate of 58/min and an Ar flow rate of 20 ml/
min; the reference sample was an empty Al container; the measurements with ca. 10 mg of
[C4mim][DTSA]:[Eu(DTSA)3] and 2[C4mim][DTSA]:[Eu(DTSA)3] were performed under Ar in
cold-sealed aluminium containers. Immediately before the measurement the Al lid was pierced to allow
for the thermal expansion of Ar. Solid state excitation and emission spectra were recorded using a
Fluorolog 3 (Jobin Yvon GmbH, Mꢄnchen, Germany) with a Xe lamp as the excitation source and a
photomultiplier tube for detection; bulk samples were sealed in silica cells (1 cm). Electronic transitions
were assigned according to the energy level diagrams of trivalent rare earth ions [21].
Synthesis of [C4mim][DTSA]. Equal molar amounts of 1-butyl-3-methyl-1H-imidazol-1-ium
chloride ([C4mim]Cl) and sodium bis[4-methylphenyl)sulfonyl]azanide (Na[DTSA]) were dissolved
in dry acetone, the soln. was stirred for 24 h at 808. Then, the white precipitate was filtered off and the
solvent was removed by using a rotary evaporator. The obtained viscous liquid was dried for 48 h at 608.
IR: 3147.3w, 3105.9w, 3067.3w, 2960.1m, 2930.1w, 287w, 1598.9w, 1568.9m, 1496.0w, 1457.4m, 1270.3s,
1150.3s, 1128.9s, 1077.4vs, 1047.4s, 1013.1s, 811.7m, 757.4m, 707.4m, 666.0s, 550.3vs. Raman: 95.1, 272.5,
359.3, 637.0, 768.2, 806.7, 1022.7, 1057.4, 1096.0, 1115.3, 1150.0, 1180.9, 1211.7, 1261.9, 1304.3, 1339.0,
1381.4, 1418.1, 1447.0, 1495.2, 1576.2, 1599.4, 2577.1, 2735.2, 2872.2, 2922.3, 2960.9, 3026.5, 3063.1.
1H-NMR (CDCl3, 250 MHz, 258): 0.91 (t, J ¼ 14.5, MeꢀCH2); 1.30 (sext., J ¼ 37.3, MeꢀCH2); 1.79 – 1.85
(m, MeꢀCH2ꢀCH2); 2.29 (s, 2 MeꢀPh); 4.03 (s, MeN); 4.27 (t, J ¼ 14.8, CH2ꢀN); 6.98 (d, J ¼ 9.3, 4
arom. H ortho to CMe); 7.25 (s, CH¼CH); 7.35 (s, CH¼CH); 7.51 (d, J ¼ 8.0, 4 arom. H ortho to CꢀS);
9.66 (s, HꢀC(2) of imidazol). Anal. calc. for [C4mim][DTSA] (C22H29N3O4S2, 463.61): C 56.99, H 6.30, N
9.06, S 13.83; found: C 57.05, H 6.22, N 9.05, S 13.88.
Eu[DTSA]3. The title compound was obtained by dissolving a slight excess of europium oxide in aq.
soln. of 4-methyl-N-[(4-methylphenyl)sulfonyl]benzenesulfonamide, filtration of traces of non-reacted
starting materials, and removal of the solvent. The obtained white solid was dried at 1008 for 48 h in
vacuum. IR: 1597.9w, 1494.7w, 1449.3w, 1401.6w, 1380.3w, 1260.4 (sh, m), 1224.7m, 1186.1w, 1115.7s,
1077.1vs, 1012.9s, 808.6s, 767.1m, 701.4m, 657.1s, 552.9vs, 521.4s. Anal. calc. for Eu(DTSA)3 (C42H42-
EuN3O12S6, 1125.1644): C 44.83, H 3.76, N 3.73, S 17.10; found: C 44.68, H 3.45, N 3.69, S 17.11.
Syntheses of [C4mim][DTSA]:[Eu(DTSA)3] and 2[C4mim][DTSA]:[Eu(DTSA)3]. In a small
Schlenk tube, equal molar amounts of [C4mim][DTSA] and Eu[DTSA]3 (for 2[C4mim]-
[DTSA]:[Eu(DTSA)3] the molar ratio was 2 :1) were mixed and stirred at 1208 for 2 h. Then the
homogenous soln. was cooled to r.t. slowly.
Data of [C4mim][DTSA]:[Eu(DTSA)3]. IR: 3148.0vw, 3092.7vw, 3065.3vw, 2957.1vw, 2922.6vw,
2868.1vw, 1598.1w, 1568.7vw, 1495.0w, 1450.4w, 1400.7w, 1258.6s, 1116.0s, 1076.0vs, 1013.1s, 808.9s, 766.0s,

Helvetica Chimica Acta – Vol. 92 (2009)
2385
702.7m, 689.9m, 655.6vs, 559.1vs, 522.0 (sh, s). Raman: 89.3, 241.7, 303.4, 357.4, 428.8, 450.0, 563.8, 603.1,
662.1, 704.5, 772.0, 814.5, 1022.7, 1057.4, 1097.9, 1119.2, 1161.6, 1184.7, 1213.7, 1277.3, 1306.2, 1339.0,
1381.4, 1450.9, 1495.2, 1599.4, 2737.2, 2874.1, 2922.3, 2959.0, 2982.1, 3067.0. Anal. calc. for [C4mim][-
DTSA]:[Eu(DTSA)3] (C64H71EuN6O16S8, 1588.7863): C 48.38, H 4.50, N 5.29, S 16.15; found: C 48.40, H
4.66, N 5.55, S 15.85.
Data of 2 [C4mim][DTSA]:[Eu(DTSA)3]. IR: 3148.1vw, 3109.6vw, 3068.1vw, 2956.7vw, 2923.9vw,
2872.4vw, 1597.9m, 1569.3w, 1494.4w, 1451.6w, 1400.1w, 1380.1w, 1259.0s, 1126.1s, 1076.1vs, 1013.3s, 810.4s,
764.7s, 703.3m, 659.0s, 550.6vs. Raman: 93.2, 239.8, 276.4, 301.5, 357.4, 426.8, 448.0, 492.4, 558.0, 635.1,
658.2, 704.5, 774.0, 814.5, 1022.7, 1096.0, 1151.9, 1182.8, 1211.7, 1271.5, 1285.0, 1302.4, 1339.0, 1381.4,
1416.2, 1450.9, 1495.2, 1599.4, 2735.2, 2874.1, 2924.2, 2959.0, 3067.0. Anal. calc. for 2 [C4mim]-
[DTSA]:[Eu(DTSA)3] (C86H100EuN9O20S10, 2052.4083): C 50.33, H 4.91, N 6.14, S 15.62; found: C 49.82,
H 5.05, N 6.21, S 15.05.
REFERENCES
[1] N. V. Plechkova, K. R. Seddon, Chem. Soc. Rev. 2008, 37, 123.
[2] P. Wasserscheid, T. Welton, ꢁIonic Liquids in Synthesisꢂ, Wiley-VCH, Weinheim, 2003; J. L.
Anderson, J. Ding, T. Welton, D. W. Armstrong, J. Am. Chem. Soc. 2002, 124, 14247; V. Znamenskiy,
M. N. Kobrak, J. Phys. Chem. B 2004, 108, 1072; S. V. Dzyuba, R. A. Bartsch, Tetrahedron Lett. 2002,
43, 4657; S. N. V. K. Aki, J. F. Brennecke, A. Samanta, Chem. Commun. 2001, 413; A. J. Carmichael,
K. R. Seddon, J. Phys. Org. Chem. 2000, 13, 591.
[3] P. Nockemann, B. Thijs, N. Postelmans, K. Van Hecke, L. Van Meervelt, K. Binnemans, J. Am. Chem.
Soc. 2006, 128, 13658.
[4] a) K. Driesen, P. Nockemann, K. Binnemans, Chem. Phys. Lett. 2004, 395, 306; b) E. Guillet, D.
Imbert, R. Scopelliti, J.-C. G. Bꢄnzli, Chem. Mater. 2004, 16, 4063; c) A. Babai, A.-V. Mudring,
Chem. Mater. 2005, 17, 6230; d) S. Arenz, A. Babai, K. Binnemans, K. Driesen, R. Giernoth, A.-V.
Mudring, P. Nockemann, Chem. Phys. Lett. 2005, 402, 75.
[5] P. Nockemann, E. Beurer, K. Driesen, R. Van Deun, K. Van Hecke, L. Van Meervelt, K. Binnemans,
Chem. Commun. 2005, 4354.
[6] H. Li, H. Shao, Y. Wang, D. Qin, B. Liu, W. Zhang, W. Yan, Chem. Commun. 2008, 5209.
[7] B. Mallick, B. Balke, C. Felser, A.-V. Mudring, Angew. Chem. 2008, 120, 7747; B. Mallick, B. Balke,
C. Felser, A.-V. Mudring, Angew. Chem., Int. Ed. 2008, 47, 7635.
[8] S. Tang, A. Babai, A.-V. Mudring, Angew. Chem. 2008, 120, 7743; S. Tang, A. Babai, A.-V. Mudring,
Angew. Chem., Int. Ed. 2008, 47, 7631.
[9] A. Babai, A.-V. Mudring, Inorg. Chem. 2006, 45, 3249.
[10] J.-C. G. Bꢄnzli, ꢁLuminescent Lanthanide Probes as Diagnostic and Therapeutic Toolsꢂ, in ꢁMetal
Complexes in Tumor Diagnosis and as Anticancer Agentsꢂ, Eds. A. Sigel, H. Sigel, Dekker, New
York, 2004, Vol. 42, Chapter 2, pp. 39 – 75.
´
´
[11] G. F. de Sa, O. L. Malta, C. de Mello Donega, A. M. Simas, R. L. Longo, P. A. Santa-Cruz, E. F. da
Silva Jr., Coord. Chem. Rev. 2000, 196, 165.
[12] P. Gawryszewska, J. Sokolnicki, J. Legendziewicz, Coord. Chem. Rev. 2005, 249, 2489.
[13] J.-C. G. Bꢄnzli, S. Comby, A.-S. Chauvin, C. D. B. Vandevyver, J. Rare Earths 2007, 25, 257.
[14] F. R. Goncalves e Silva, O. L. Malta, C. Reinhard, H. U. Gꢄdel, C. Piguet, J. E. Moser, J.-C. G.
Bꢄnzli, J. Phys. Chem. A 2002, 106, 1670.
[15] P. Gawryszewska, O. L. Malta, R. L. Longo, F. R. Goncalves e Silva, S. Alves Jr., K. Mierzwicki, Z.
Latajka, M. Pietraszkiewicz, J. Legendziewicz, ChemPhysChem 2004, 5, 1577.
´
[16] L. S. Fu, R. A. Sa Ferreira, N. J. O. Silva, A. J. Fernandes, P. Ribeiro-Claro, I. S. GonÅalves, V.
De Zea Bermudez, L. D. Carlos, J. Mater. Chem. 2005, 15, 3117; K. Binnemans, P. Lenaerts, K.
Driesen, Christiane Gçrller-Walrand, J. Mater. Chem. 2004, 14, 191.
[17] A. Getsis, A.-V. Mudring, Cryst. Res. Technol. 2008, 43, 1187.
[18] V. Tsaryuk, V. Zolin, J. Legendziewicz, J. Lumin. 2003, 102 – 103, 744; L. D. Carlos, Y. Messaddeq,
´
H. F. Brito, R. A. Sa Ferreira, V. de Zea Bermudez, S. J. L. Ribeiro, Adv. Mater. 2000, 12, 594; R. A.

2386
Helvetica Chimica Acta – Vol. 92 (2009)
´
Sa Ferreira, L. D. Carlos, R. R. GonÅalves, S. J. L. Ribeiro, V. de Zea Bermudez, Chem. Mater. 2001,
13, 2991.
´
[19] M. Fernandes, V. de Zea Bermudez, R. A. Sa Ferreira, L. D. Carlos, A. Charas, J. Morgado, M. M.
Silva, M. J. Smith, Chem. Mater. 2007, 19, 3892.
[20] S. Yanagida, K. Sogabe, Y. Hasegawa, Euro. Pat., EP 1318143, 2003.
[21] G. H. Dieke, ꢁSpectra and energy levels of rare earth ions in crystalsꢂ, Interscience Publishers, New
York, 1968.
Received May 8, 2009