Water-soluble Tb3+ and Eu3+ complexes based on task-specific ionic liquid ligands and their application in luminescent poly(vinyl alcohol) films

Article abstract of DOI:10.1039/c5dt02555a

Novel water-soluble lanthanide complexes (Ln(IMI-DPA)₃) have been synthesized using the task-specific ionic liquid consisting of a dipicolinic acid motif as the sensitizer of lanthanide luminescence. In Ln(IMI-DPA)₃, Ln³⁺ ions are in 9-fold coordination through six carboxylate oxygen atoms and three nitrogen atoms in pyridine units, and the water molecule is excluded from the coordination sphere of the lanthanides. It is found that Ln(IMI-DPA)₃ possess bright luminescence, long luminescence lifetime in aqueous solution, high thermal stability and good water solubility. Furthermore, these complexes can be incorporated into water-soluble poly(vinyl alcohol) (PVA) matrixes to obtain highly luminescent, transparent and flexible PVA composite films. The emission colors of the films can be tuned from red, orange, yellow, light green, green to white light by regulating the concentration of the various luminescent components.

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Water-Soluble Tb3+ and Eu3+ Complexes Based on Task-Specific
Ionic Liquid Ligand and Their Application in Luminescent
Poly(vinyl alcohol) Films
Received 00th January 20xx,
Qing-Feng Li,*a Dan Yue,a Gen-wu Ge,a Xiaodi Du,a Yanchuan Gong,a Zhenling Wang*a and Jianhua
Hao*b
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
Novel water-soluble lanthanide complexes (Ln(IMI-DPA)3) have been synthesized using the task-specific ionic liquid
consisting of a dipicolinic acid motif as the sensitizer of lanthanide luminescence. In Ln(IMI-DPA)3, Ln3+ ions are in 9-fold
coordination through six carboxylate oxygen atoms and three nitrogen atoms in pyridine units, and water molecular is
excluded from the coordination sphere of the lanthanides. It is found that Ln(IMI-DPA)3 possess bright luminescence, long
luminescence lifetime in aqueous solution, high thermal stability and good water solubility. Furthermore, these complexes
can be incorporated in water-soluble poly(vinyl alcohol) (PVA) matrixes to obtain the highly luminescent, transparent and
flexible PVA composite films. The emission colors of the films can be tuned from red, orange, yellow, light green, green to
white light by regulating the concentration of the various luminescence components.
solution still remains an open issue for developing this kind of
materials. The primary question needed to be addressed is the very
low luminescence efficiency of the lanthanide complexes since the
Introduction
Task-specific ionic liquids (TSILs), especially imidazolium cation-
based ionic liquids are commonly used as solvents, ion conductive
materials or organic ligands for metallic complexes which are widely
used in heterogeneous or homogeneous catalysis.1-4 One of the
most stunning features of TSILs is their easily tailable properties
through the chemical modification of both cations and anions.5
Considering the attractive feature of TSILs, specific functional
groups designed for selective complexation of lanthanide metal
ions have been covalently conjugated either to the cation or to the
anion of TSILs, aiming at improving thephysicochemical properties
and water-solubility of TSILs.6-9 Indeed, some well-designed TSILs
are used as the ionophilic ligands for the preparation of novel
luminescence complexes.10-12 For instance, Rodrigues and co-
workers reported two water-soluble lanthanide complexes with
aromatic carboxylic acid grafted ionic liquid as the ligand, which
could be acted as a fluorescence imaging probe for invasive
mammal cancer cells.13 Currently, the introduction of a hydrophilic
group such as imidazolium salts into lanthanide complexes seems to
be one of the effective ways to improve their water solubility.
However, the design and synthesis of water-soluble lanthanides
complexes with excellent luminescence properties in aqueous
luminescence is likely quenched by the solvent molecule such as
water molecule.
Lanthanides complexes containing one or more N, O-chelating
ligands usually exhibit sharp and intense emission lines, long
lifetimes and high quantum efficiency of luminescence under the
excitation of ultraviolet (UV) light, because of the effective
intramolecular energy transfer from the ligands to the lanthanide
ions14-21
. Some of the water-soluble lanthanide complexes
demonstrate potential applications in time-resolved fluoro-
immunoassay, fluorescence imaging, metal ion detection and
protein labelling.22-25 Among them, dipicolinic acid (DPA) has shown
to be an efficient N, O-chelating ligand for sensitizing the
luminescence of Tb3+ and Eu3+ ions.26-30 The ligands are capable of
forming stable [Ln(DPA)3]3- complexes with the lanthanides, in
which the coordination number of the central Ln3+ reaches its
coordination-saturated state.31,32 Therefore, the nonradiative
deactivation of lanthanides luminescence due to the coupled O-H
vibrations is greatly reduced because water molecule is excluded
from the coordination sphere of the lanthanides. Hence, it is
reasonable to envisage the combination of a DPA-functionalized
ionic liquid with lanthanide ions to afford new water-soluble
luminescence complexes. Herein, we report the synthesis of novel
water-soluble lanthanide complexes based on an ionophilic ligand
a The Key Laboratory of Rare Earth Functional Materials and Applications, Zhoukou
Normal University, Zhoukou 466001, P. R. China.
by functionalizing the imidazolium ionic liquid with
a DPA
E-mail: liqingf335@163.com, zlwang2007@hotmail.com; Fax/Tel:+86-394-8178518
b Department of Applied Physics, The Hong Kong Polytechnic University, HongKong,
P. R. China, Email: jh.hao@polyu.edu.hk
substituent. The introduction of imidazolium cations can improve
the water-solubility of the luminescence complexes as well as
intersolubility with the water-soluble and full-biodegradable
†Electronic Supplementary Information (ESI) available: 1H-NMR, 13C-NMR, UV-vis
absorption spectra, and CIE diagram. See DOI: 10.1039/x0xx00000x
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poly(vinyl alcohol) (PVA). Therefore, the transparent and flexible
phosphor films are readily obtained by casting the water-soluble
luminescence complexes with the aqueous solution of PVA.
Moreover, the obtained PVA films exhibit various emission colors
simply by changing the concentration of the various luminescence
components.
Results and discussion
Preparation
The synthesis procedure of IMI-DPA and corresponding lanthanide
complexes is illustrated in Scheme 1. 4-(hydroxylmethyl)pyridine-2,
6-dicarboxylate (compound 2), 4-(chloromethyl)pyridine-2, 6-
dicarboxylate (compound 3) were synthesized as described in the
literature.33 Compound 4 was obtained by a simple nucleophilic
substitution reaction of 4-(chloromethyl)pyridine-2, 6-dicarboxylate
with 1-methylimidazole in anhydrous acetonitrile, and then
hydrolyzed under acidic aqueous conditions to yield the target
compound (IMI-DPA) as a white powder. The designed organic
Fig. 1 The crystal structure of Eu(IMI-DPA)3
FT-IR spectrum
The FT-IR spectra of IMI-DPA, Tb(IMI-DPA)3 and Eu(IMI-DPA)3 are
displayed in Fig. 2. The absorption bands located at 1735, 1237,
3518 and 1431 cm-1 observed in Fig. 2a can be ascribed to
stretching vibrations of the C=O (1735 cm-1), C-O (1237 cm-1), O-H
(3518 cm-1) and bending vibrations of O-H (1431 cm-1),
respectively.11 The bands at 1602, 1555, 1431 cm-1 correspond to
the skeleton vibration of imidazole and pyridine ring, and the
unsaturated C-H stretching vibration modes appear at 3149, 3092
and 3072 cm-1.34,35 However, the absence of the absorption band at
1735 cm-1 ascribed to C=O of the free carboxylic acid suggests the
coordination of Ln3+ to oxygen atoms of IMI-DPA (Fig. 2b and 2c). In
fact, the asymmetric and symmetric stretching vibration of the
COO- group in Tb(IMI-DPA)3 or Eu(IMI-DPA)3 can be detected at
1640 and 1406 cm-1, respectively. This finding is consistent with
previous reports on Ln3+ coordinated to the carboxylate groups.11
1
ligand has been characterized by H-NMR, 13C-NMR (Fig. S1 and S2)
and mass spectrometry. The crystals of the lanthanide complexes
were obtained by the conventional solvent evaporation method.
Scheme 1 Synthesis procedure for IMI-DPA and corresponding
lanthanide complexes
Single-crystal X-ray diffraction
Single-crystal X-ray diffraction analysis reveals that Eu(IMI-DPA)3
and Tb(IMI-DPA)3 are isostructural, crystallizing in the triclinic space
group P/-1. As for Eu(IMI-DPA)3, and the Eu3+ ions is nine-
coordinated with three nitrogen atoms of pyridine units and six
oxygen atoms of carboxyl groups from three different IMI-DPA
ligands (Fig. 1). The coordination sphere of Eu3+ is saturated by
three IMI-DPA ligands, leaving no coordination site for water or
other solvent molecules, and this kind of complex usually exhibits
excellent luminescence properties and long luminescent lifetime in
aqueous solution.
Fig. 2 FT-IR spectra of IMI-DPA (a), Eu(IMI-DPA)3 (b) and Tb(IMI-
DPA)3 (c)
Thermal analysis
In order to investigate the thermal stability of the obtained
lanthanide complexes, the thermogravimetric analysis (TGA) of
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the π→π* electronic transition of the complexes (Fig. 4a and c),
respectively. This indicates that these two kinds of different
lanthanide complexes can be excited by the UV light with the same
wavelength and exhibit different color emissions caused by the
different central lanthanide ions. As expected, under the excitation
with the same wavelength (290 nm), the Tb(IMI-DPA)3 solution
gives the characteristic emission of Tb3+ with the peaks centered at
492, 543, 582, 622 nm, corresponding to the transitions from the
5D4 level to 7FJ (J=6, 5, 4, 3) levels of Tb3+, respectively, of which the
5D4→7F5 emission is the most prominent one (Fig. 4b).13,38-40 While,
the Eu(IMI-DPA)3 solution reveals the characteristic Eu3+ emission
peaks centered at 592, 615, 649 and 695 nm, corresponding to the
5D0→7FJ (J=1, 2, 3, 4) transitions, respectively.30,41-44 Among these
transitions, the 5D0→7F2 transition shows the strongest emission,
resulting in the red luminescence. No broad emission band from the
organic ligand in both Tb(IMI-DPA)3 and Eu(IMI-DPA)3 complexes
can be observed in the region, which demonstrates that the energy
transfer occurs from the ligand to the central Ln3+ (Ln =Tb or Eu).45
Tb(IMI-DPA)3 and Eu(IMI-DPA)3 is carried out in N2 atmosphere
from 30 to 900 oC at a heating rate of 10 oC min-1 (Fig. 3). The
weight loss observed for both samples is occured at three
temperature regimes. The first weight loss at temperature lower
than 120 oC is mostly attributed to the loss of small amount of
physically adsorbed water molecules. While the relatively large
weight loss occurs quickly at about 340 oC in the temperature range
of 340-800 oC (approximately 65 % for Tb(IMI-DPA)3 and 63.7% for
Eu(IMI-DPA)3), which can be ascribed to the thermal decomposition
of organic components. At temperatures higher than 800 oC, the
weight loss is not obvious. The results of TGA show that the
prepared complexes exhibit high thermal stability, which makes
them promising for application in optical device.
Fig. 3 TGA curves of Eu(IMI-DPA)3 (a) and Tb(IMI-DPA)3 (b)
Optical properties
The optical properties of Tb(IMI-DPA)3 and Eu(IMI-DPA)3 solution
were investigated by UV-vis absorption and photoluminescence (PL)
spectra. The UV-vis absorption spectrum of IMI-DPA exhibits a
broad band with maxima at 273 nm (ε= 8.2×103 L· moL-1 · cm-1) (Fig.
S3), which is ascribed to the typical absorpꢀon of the π→π*
transition of aromatic ring. In addition, the absorption spectra of
Tb(IMI-DPA)3 and Eu(IMI-DPA)3 revealed two peaks at 273
(ε=1.68×104 L· moL-1 · cm-1 for Tb(IMI-DPA)3 and ε= 1.48×104
L· moL-1 · cm-1 for Eu(IMI-DPA)3) and 281 nm, attributable to the
π→π* transition of the complexes (Fig. S3). Usually, for lanthanide
complexes with three β-diketone derivatives as the ligands, the
molar absorption coefficient (ε) value of the complexes are about
Fig. 4 PL excitation and emission spectra of Tb(IMI-DPA)3 (a, b) and
Eu(IMI-DPA)3 (c, d) in aqueous solution, and the insets of Fig. 4b and
d are photos of Tb(IMI-DPA)3 (green) and Eu(IMI-DPA)3 (red)
solution excited by UV light (254 nm)
The lifetime values of the excited state 5D4 (Tb3+) in Tb(IMI-
DPA)3 solution and 5D0 (Eu3+) in Eu(IMI-DPA)3 solution can be
determined by the luminescent decay curves. As shown in Fig. 5,
both the luminescence decay curves are well fitted into a single-
three times higher than that of the ligand.36,37 However, For exponential function of I = I0 exp (−t/τ), where I0 is the initial
lanthanide complexes with three dipicolinic acid derivatives as the
ligands, the ε value of the complexes are only a little higher or
lower than that of the ligand.38 As for Ln(IMI-DPA)3, the ε value of
the complexes are less than two times than that of IMI-DPA. It
seems that the relative ε value of complex is dependent on the
structure of the ligand or complex. The PL excitation and emission
spectra of Tb(IMI-DPA)3 and Eu(IMI-DPA)3 in aqueous solution are
shown in Fig. 4. It is evident that the Tb(IMI-DPA)3 and Eu(IMI-DPA)3
solution show bright green and red characteristic emissions under
UV light (254 nm) excitation (insets of Fig. 4b and d). The excitation
spectra of Tb(IMI-DPA)3 and Eu(IMI-DPA)3 solution monitored at
intensity at t = 0, τ is the 1/e lifetime of the lanthanide ions. The
result implies the presence of single luminescence center.
According to the fitting results, the lifetime values of Tb(IMI-DPA)3
and Eu(IMI-DPA)3 are determined to be 1.73 and 1.56 ms,
respectively. The quantum efficiencies of the Tb(IMI-DPA)3 and
Eu(IMI-DPA)3 are about 21.6% and 49.0%, respectively. The optical
data like molar absorptivity (ε), excitation wavelength (λex),
emission wavelength (λem), lifetime (τ) and luminescence quantum
efficiency (η) of our samples and [Ln(DPA)3]3- (Ln = Tb or Eu) are
listed in Table 1. It appears that the quantum efficiency of Eu(IMI-
543 nm for Tb3+ and 615 nm for Eu3+ possess a similar excitation DPA)3 is higher than that in [Eu(DPA)3]3-, while as for Tb(IMI-DPA)3,
the quantum efficiency is lower than that in [Tb(DPA)3]3-, and other
band with a maximum at about 290 nm which can be assigned to
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optical data for our samples are very similar to that obtained in wavelength UV light, hence these complexes might be formed
[Ln(DPA)3]3- (Ln = Tb or Eu).
homogeneously mutual solubility with some hydrophilic or water-
soluble substances to obtain the luminescent materials with
different states such as liquid, film and powders. Moreover, the
luminescent color of these homogeneous composites only could be
adjusted through changing the relative component of Tb(IMI-DPA)3
and Eu(IMI-DPA)3 complexes. It is well known that Poly(vinyl
alcohol) (PVA) is a water-soluble, nontoxic and full-biodegradable
organic polymer. This material has excellent film-forming ability,
high tensile strength and bending flexibility, which make it an
attractive material for a wide range of applications.47 It has been
confirmed in this work that the obtained water-soluble lanthanide
complexes can be readily well-dispersed into PVA aqueous solution
to form a transparent film, and the representative PVA and Eu(IMI-
DPA)3 film is shown in Fig. 6 (2)f, clearly showing the transparent
and flexible characteristic.
Table 1 The optical data including molar absorptivity (ε), excitation
wavelength (λex), emission wavelength (λem), lifetime (τ) and
luminescence quantum efficiency (η) of the Ln(IMI-DPA)3 (Ln = Tb,
Eu) and previously reported [Ln(DPA)3]3-.
The luminescence lifetime of Ln3+ is greatly affected by the
vibration of the solvent molecules which are known to be
deactivators of the vibrationally excited states of the Ln3+ ions.46
However, as for our complexes, the coordination sphere of Ln3+ is
saturated by the ligands, leaving no coordination site for water
molecules, resulting in long luminescence lifetimes of Ln3+ in
aqueous solution. The chromaticity diagram (CIE) indicates that the
emission of the complexes lie in green and red region with the
chromaticity coordinates (x = 0.36, y = 0.59) for Tb(IMI-DPA)3 and (x
= 0.66, y = 0.33) for Eu(IMI-DPA)3, respectively (Fig. S4). Moreover,
the chromaticity coordinate of the Eu(IMI-DPA)3 is very close to the
edge of the CIE diagram, showing the high color purity of this
sample.
Fig. 6 (1) Chromaticity diagram (CIE) of the luminescent films under
290 nm UV illumination (a) PVA-Eu, (b) PVA-Eu1Tb1, (c) PVA-Eu1Tb3,
(d) PVA-Eu1Tb5, (e) PVA-Tb; (2) Photos of the corresponding
luminescence films on glass substrate under 254 nm (a-e) UV
illumination, and (f) photo of PVA-Eu film under daylight
Fig. 5 Luminescence decay curves of Tb(IMI-DPA)3 (a) and Eu(IMI-
DPA)3 (b) in aqueous solution
The transparent, flexible and luminescence PVA films
embedded with Eu(IMI-DPA)3 or Tb(IMI-DPA)3, denoted as PVA-Eu
or PVA-Tb were prepared simply by dropping the PVA solution of
Eu(IMI-DPA)3 or Tb(IMI-DPA)3 onto a glass substrate, followed by
drying at 50 oC. The same procedure afforded the mixed systems
As mentioned above, Tb(IMI-DPA)3 and Eu(IMI-DPA)3
complexes have well water-soluble, prominent luminescent
properties and multi-color emission under the excitation of a single
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described above, with Eu/Tb molar ratios of 1:1, 1:3 and 1:5, organic salt, usually used to regulate the white light emission of the
yielding PVA-Eu1Tb1, PVA-Eu1Tb3, PVA-Eu1Tb5 films, respectively. luminescence materials.55 In principle, the obtained prominent
The metal compositions of the designed films were confirmed by luminescence Eu(IMI-DPA)3 (red) and Tb(IMI-DPA)3 (green)
energy dispersive X-ray (EDX) analysis and found to be matching complexes can be mixed with Na-BTC (blue), thus white-light
with that of the nominal one in each sample (Table 2 and Fig. S6).48
emission might be realized only through altering the relatively ratio
of Eu(IMI-DPA)3, Tb(IMI-DPA)3 and Na-BTC. To prove the hypothesis,
Eu(IMI-DPA)3, Tb(IMI-DPA)3 and Na-BTC were dispersed into PVA
solution with a molar ratio of 1:1:77 (The metal compositions of the
designed films was also confirmed by energy dispersive X-ray (EDX)
analysis (Table 2 and Fig. S6)), and a novel luminescence PVA-Na-
BTC-Eu1Tb1 film was made. Upon the excitation of UV light at 305
nm, PVA-Na-BTC-Eu1Tb1 shows a broad emission band in the blue
region from Na-BTC, the green emission lines from Tb(IMI-DPA)3
complex and red emission lines from Eu(IMI-DPA)3 complex, as
shown in Fig. 7. Incorporation of blue emission component in the
presence of Eu3+ and Tb3+ result in white emission (Fig. 7 inset) with
CIE co-ordinates of (0.31, 0.31) (Fig. S7), which is close to the co-
ordinate of standard white light (0.33, 0.33).
Table 2 Molar ratios of Eu/Tb for designed films by EDX analysis, a
Relative mass percentage, b measured by EDX
Weight % a
Luminescent
materials
Stoichiometric
Ratio (Eu/Tb)
Eu/Tb molar
ratios b
Eu
Tb
PVAꢀEu1Tb1
PVAꢀEu1Tb3
PVAꢀEu1Tb5
1:1
1:3
1:5
47.0
24.8
16.3
53.0
75.2
83.7
1:1.07
1:2.90
1:4.91 \
PVAꢀNaꢀ
BTCꢀEu1Tb1
1:1
46.4
53.6
1:1.10
The emission colors of the films can be tuned from red to
green by doping the required amounts of luminophor as displayed
in CIE (1) and luminescence photos (2) in Fig. 6a to e. The emission
spectra of the films are shown in Fig. S5. We observe the sharp
characteristic emission peaks of the Eu3+ ions at 592, 615, 649 and
695 nm and Tb3+ ions at 492, 543, 582 and 622 nm, respectively.
Moreover, the intensity ratio of the red to green emission
decreases obviously with increasing the Tb3+ concentrations, and
the emission colors of the films thus varied from red, orange,
yellow, light green to green correspondingly. However, according to
the equation (1) as follow:49,50
Conclusions
A new type of water-soluble luminescence complexes of terbium
and europium has been prepared with DPA-functionalized ionic
liquid (IMI-DPA) as the ligand. The complexes display
intenseluminescence, long luminescence lifetime and high
luminescence quantum efficiency in aqueous solution irradiated
with the same wavelength. The resulting water-soluble and
prominent luminescence lanthanide complexes as well as sodium
1,2,4,5-benzenetetracarboxylate can be used as building blocks for
fabricating luminescence PVA composite films, where various
emission colors ranging from red, orange, yellow, light green, green
to white light can be tuned by modulating the concentration of the
various luminescence components. Such tunable phosphor films are
promising in the use of optical systems, sustainable energy devices
and biological applications.56,57
η = 1- τ1/τ0
(1)
where τ1 and τ0 are the excited state lifetimes of the donor in the
presence and absence of the acceptor, the energy transfer from
Tb3+ to Eu3+ is not obviously observed in the films at room
temperature.
Experimental section
Materials
1-Methylimidazole (99%, Energy chemical), Terbium (III) chloride
hexahydrate (99.99%, Energy chemical), Europium (III) chloride
hexahydrate (99.99%, Energy chemical) were used without further
purification.
3-((2,6-bis(methoxycarbonyl)pyridin-4-yl)methyl)-1-
methylimidazolium chloride (4)
4-(chloromethyl)pyridine-2, 6-dicarboxylate (3.65g, 0.015mol) was
dissolved in anhydrous acetonitrile (40mL) and then 1-
methylimidazole (2.46g, 0.03mol) was added to the above mixture
under an atmosphere of argon. The mixture was stirred at 80 oC for
about 16 h, and then cooled down to room temperature. The
resulting white suspension was filtered, washed with acetonitrile
and dried under vacuum at 40 oC for 8 h (3.74g, 76.3%). 1H-NMR
(400MHz, D2O) δ ppm: 8.90 (1H, s), 8.07 (2H, s), 7.47 (2H, d), 5.57
(2H, s), 3.85 (9H, s). 13C-NMR(100MHz, D2O) δ ppm: 165.3, 148.0,
Fig. 7 The emission spectrum of the luminescence PVA-Na-BTC-
Eu1Tb1 film upon excitation at 305 nm, and the inset of Fig. 7 is the
photo of PVA-Na-BTC-Eu1Tb1 film excited by UV light (305 nm)
White-light emitting materials have attracted considerable
interest over the past years due to their practical applications in
full-color flat panel display and general lighting.51-54 Sodium 1,2,4,5-
benzenetetracarboxylate (Na-BTC), as a kind of blue light emitting
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147.1, 137.1, 127.1, 124.5, 122.7, 53.5, 50.9, 36.2. ESI-MS: M/Z high-energy micro-second flash lamp as the excitation sources. The
calcd for C14H16N3O4+ : 290.2945, M+: found: 290.1143.
quantum efficiencies were determined using an integrating sphere
whose inner face was coated with BenFlect from FLS920P
Edinburgh spectrofluorometer. The quantum yield described by R.
H. Friend 58 can be represented in the equation below:
3-((2,6-dicarboxypyridin-4-yl)methyl)-1-methylimidazolium
chloride (IMI-DPA)
A mixture of the compound 4 (3.26g, 0.01mol) and hydrochloric
acid (6mol/L, 35mL) was refluxed under stirring for about 24 h, and
then cooled down to room temperature. The solvent was removed
under reduced pressure, and the slurry residue was recrystallizated
with ethanol to give 3-((2, 6-dicarboxypyridin-4-yl)methyl)-1-
methylimidazolium chloride as white solid (2.71g, 90.9%). 1H-NMR
(400MHz, D2O) δ ppm: 8.88 (1H, s), 7.96 (2H, s), 7.46 (2H, d), 5.59
(2H, s), 3.86 (3H, s). 13C-NMR(100MHz, D2O) δ ppm: 166.6, 148.8,
148.6, 137.3, 126.1, 124.6, 122.9, 51.0, 36.0. ESI-MS: M/Z calcd for
Where η is the quantum yield, Lemission is the luminescence emission
spectrum of the sample, collected using the sphere, Esolvent is the
spectrum of the light used for excitation with only the solvent in the
sphere, collected using the sphere, Esample is the spectrum of the
light used to excite the sample, collected using the sphere.
+
C12H12N3O4 : 262.2414, M+: found: 262.0816. Anal. Calcd for IMI-
Acknowledgements
DPA : C, 48.41; H, 4.06; N, 14.12; found C, 47.78; H, 4.51; N, 13.57.
This work is financially supported by the National Natural Science
Foundation of China (no. 21401218, 21171179), the Excellent Youth
Foundation of He'nan Scientific Committee (no. 134100510018),
the Innovation Scientists and Technicians Troop Construction
Projects of Henan Province (2013259), the Henan Province Key
Discipline of Applied Chemistry (201218692) and Program for
Innovative Research Team (in Science and Technology) in University
of Henan Province (no. 14IRTSTHN009).
Preparation of lanthanide complexes
IMI-DPA (0.597g, 2mmol) and LnCl3·6H2O (Ln= Tb or Eu, 0.66mmol)
were dissolved in 30mL distilled water, and the pH value of the
o
mixture was adjusted to 7.0. After evaporating the solvent at 50 C
for about 12h, the mixture was slowly cooled to room temperature,
and the colorless bulk-like crystals, denoted as Tb(IMI-DPA)3 or
Eu(IMI-DPA)3 were obtained in 65% yield based on IMI-DPA. Anal.
calcd for Eu(IMI-DPA)3 : C, 46.36; H, 3.24; N, 13.52; found C, 46.81;
H, 3.13; N, 13.06, Anal. calcd for Tb(IMI-DPA)3 : C, 46.06; H, 3.22; N,
13.42; found C, 46.28; H, 3.41; N, 13.58.
Notes and references
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6 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C5DT02555A
Water-Soluble Tb3+ and Eu3+ Complexes Based on Task-Specific
Ionic Liquid Ligand and Their Application in Luminescent
Poly(vinyl alcohol) Films
Qing-Feng Li,*a Dan Yue,a Gen-wu Ge,a Xiaodi Du,a Yanchuan Gong,a Zhenling
Wang*a and Jianhua Hao*b
Synthesis of water-soluble Tb3+ and Eu3+ complexes based on TSILs ligand and their
application in luminescent poly(vinyl alcohol) films
TOC Figure