Synthesis and luminescence properties of the Pr(III), Sm(III), Eu(III), Nd(III), and Yb(III) complexes with propane-1, 3-dione derivatives

Article abstract of DOI:10.1134/S1070328411030080

The luminescence method, mass spectrometry, and elemental analysis are used to reveal that under optimal conditions (pH 5-8) Ln³⁺ ions (Ln = Pr, Sm, Eu, Nd, and Yb) with 1-(2-hydroxy-4-meth- ylphenyl)-3-(5-methyl-1-phenyl- ¹H-1,2,3-triazol-4-yl)propane-1,3-dione form complexes with the mole ratio Ln : ligand = 2 : 3. According to the IR spectral data, Ln³⁺ ions coordinate three oxygen atoms of two carbonyl groups and one hydroxyl group. In the IR spectra of the complexes, an intense band at 628.7 cm ^-1 is assigned to the Ln-O bond vibrations. The X-ray diffraction patterns of the complexes contain no lines corresponding to the ligand. The luminescence intensity of the complexes in the visible spectral range changes in the series Eu(lll)

Full text of DOI:10.1134/S1070328411030080

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2011, Vol. 37, No. 4, pp. 309–315. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © S.B. Meshkova, Z.M. Topilova, V.S. Matiichuk, N.T. Pokhodylo, I.P. Kovalevskaya, I.M. Rakipov, P.G. Doga, 2011, published in Koordinatsionnaya
Khimiya, 2011, Vol. 37, No. 4, pp. 305–311.
Synthesis and Luminescence Properties of the Pr(III), Sm(III),
Eu(III), Nd(III), and Yb(III) Complexes with Propaneꢀ1,3ꢀdione
Derivatives
S. B. Meshkovaa, Z. M. Topilovaa, V. S. Matiichukb, N. T. Pokhodylob, I. P. Kovalevskayaa,
I. M. Rakipova, and P. G. Dogaa
a Bogatskii Physicochemical Institute, National Academy of Sciences of Ukraine, Chernomorskaya doroga 86, Odessa, Ukraine
b Franko National University, ul. Lomonosova 8, Lviv, Ukraine
eꢀmail: s_meshkova@ukr.net
Received June 17, 2010
Abstract—The luminescence method, mass spectrometry, and elemental analysis are used to reveal that
under optimal conditions (pH 5–8) Ln3+ ions (Ln = Pr, Sm, Eu, Nd, and Yb) with 1ꢀ(2ꢀhydroxyꢀ4ꢀmethꢀ
ylphenyl)ꢀ3ꢀ(5ꢀmethylꢀ1ꢀphenylꢀ1Hꢀ1,2,3ꢀtriazolꢀ4ꢀyl)propaneꢀ1,3ꢀdione form complexes with the mole
ratio Ln : ligand = 2 : 3. According to the IR spectral data, Ln3+ ions coordinate three oxygen atoms of two
carbonyl groups and one hydroxyl group. In the IR spectra of the complexes, an intense band at 628.7 cm–1
is assigned to the Ln–O bond vibrations. The Xꢀray diffraction patterns of the complexes contain no lines
corresponding to the ligand. The luminescence intensity of the complexes in the visible spectral range
changes in the series Eu(III) > Sm(III) > Pr(III), whereas in the IR region the order is Yb(III) > Nd(III). In
all cases, luminescence of the solid complexes is considerably more intense than that of their solutions.
DOI: 10.1134/S1070328411030080
INTRODUCTION
fꢀluminescence bands, which are rigidly charꢀ
strong sixꢀmembered rings including the central ion and the
efficient absorption by the ligand of the light energy, the
transfer of which to the Ln3+ ion allows one to observe lumiꢀ
nescence.
Narrow 4
acteristic of each Ln3+ ion, provide both radiation color
purity and rather high luminescence intensity of elements of
this series in complexes with many organic reagents [1].
There is a recent tendency to synthesize reagents with many
cycles (photoantennas) and branched structures, providing
the possibility of coordinating two and more Ln3+ ions,
being luminescence emitters [2–6]. Thus increased lumiꢀ
nescence quantum yield favors the enlargement of potentiꢀ
alities of using Ln complexes in biology and medicine as bioꢀ
probes (biomarkers) and contrast agents and for the conꢀ
struction of new materials for UV and IR lasers, active light
guides, etc. [7–9]. The Ln (Sm, Eu, Nd, and Yb) comꢀ
The purpose of the present work is to study the forꢀ
mation conditions, compositions, and spectral lumiꢀ
nescence properties of the Pr(III), Sm(III), Eu(III),
Nd(III), and Yb(III) complexes with 1ꢀ(2ꢀhydroxyꢀ4ꢀ
methylphenyl)ꢀ3ꢀ(5ꢀmethylꢀ1ꢀphenylꢀ1Hꢀ1,2,3ꢀtriꢀ
azolꢀ4ꢀyl)propaneꢀ1,3ꢀdione ( ).
L
EXPERIMENTAL
pounds with
formed are characterized by high stability constants (log
14–18) and luminescence intensity [10]. The
β
ꢀdiketones are best studied. Tris(chelates)
The ligand was synthesized by the acylation of
1ꢀ(2ꢀhydroxyꢀ5ꢀmethylphenyl)ethanone with 1ꢀpheꢀ
β
=
β
ꢀdiketone nylꢀ5ꢀmethylꢀ1Нꢀ1,2,3ꢀtriazoleꢀ4ꢀcarboxylic acid
fragment in the structures of the synthesized organic comꢀ chloride followLed by the Baker–Vankataraman rearꢀ
pounds with two or several cycles favors the formation of rangement of the ester formed
Me
O
OH
Me
O
O
O
HO
(L)
O
N
N
Me
N
N
Me
N
N
N
Cl
N
O
+
N
KOH
N
N
Me
Me
O
Me
Me
309

310
MESHKOVA et al.
The compound synthesized was identified and its reference sample. Elemental analysis for N was carried
purity was checked by elemental analysis, NMR specꢀ out by the Dumas method [12]. Lanthanides were
troscopy, and chromatography combined with mass analyzed complexonometrically using arsenazo I as an
1
detection. The H NMR spectra were recorded on a indicator.
Mercury 400 instrument with the working frequency
400 MHz using DMSOꢀd6 (deuterated dimethyl sulꢀ
foxide) as a solvent. Chemical shifts are presented relꢀ
atively to the signal from tetramethylsilane. Mass
spectra were obtained on an Agilent 1100 LC/MD
chromatograph coupled with a mass spectrometer
The IR spectra of the ligand and complexes
were recorded on a FTIRꢀ8400S Shimadzu spectromꢀ
eter (KBr pellets). Mass spectra were measured on a
VGꢀ7070 mass spectrometer (VG ANALYTICAL,
Great Britain). Desorption ionization was carried out
using a beam of argon atoms with an energy of 8 keV.
3ꢀNitrobenzyl alcohol served as a matrix.
1
using chemical ionization. H NMR for ligand L
(
δ
, ppm): 2.32 (s, 3H, CH3), 2.64 (s, 3H, CH3), 4.82
(br.s, 1H, CH2), 6.88 (d, = 8.37 Hz, 1H, HArꢀ4), 7.20
(dd, = 8.35 Hz, 1.68, 1H, HArꢀ5). 7.60–7.67 (m, 5H,
HPh), 7.71 (s, 1H, HArꢀ3). 10.71 (br.s, 1H, OH), 11.26
Xꢀray diffraction studies were carried out by the
J
powder method on a DRON diffractometer (Cu
K
α
J
radiation, nickel filter). Interplanar spacings were
determined using the published tables [13].
The UV spectra of the ligand and complexes were
recorded on a Lambdaꢀ9 UV/VIS/NIR spectrophoꢀ
(br.s, 1H, OH). Mass spectrum (
m/z
): 336 [M + H]+.
tometer (PerkinElmer) using a quartz cell with
1 cm.
l =
For C19H17N3O3
anal. calcd., %:
Found, %:
C, 68.05;
C, 68.19;
H, 5.11;
H, 5.03;
N, 12.53.
N, 12.75.
The excitation and luminescence spectra of the
ligand and complexes were recorded on a Fluorolog
FL 3ꢀ22 spectrofluorimeter (HORIBA JobinꢀYvon
Inc., France) with a 450W ozoneless Xe lamp. For
measurements in the IR spectral range, the spectrofluꢀ
orimeter was equipped with an InGaAs photoresisꢀ
tance (DSSꢀIGAO20L, ElectroꢀOptical Systems,
Inc.) cooled with liquid nitrogen. In addition, lumiꢀ
nescence spectra were also recorded on an SDLꢀ1 difꢀ
fraction spectrometer (LOMO, St. Petersburg) with a
DRShꢀ250 mercury lamp, and the emission of the
most intense line of the lamp at 365 nm was picked out
with the UFSꢀ2 light filter. The energy of the triplet
level of the ligand (ET1, cm–1) was determined by the
phosphorescence spectrum of the Gd(III) complex at
77 K. The luminescence quantum yield of the comꢀ
plexes was determined by comparing with references,
namely, tris(2,2'ꢀbipyridine)ruthenium(II) chloride
(Ru(Bipy)3Cl2) and zinc mesoꢀtetraphenylporphyriꢀ
nate (ZnTPP).
A 0.01 M solution of the ligand in acetonitrile preꢀ
pared by an exact weighed sample of the ligand was
used. Aqueous 0.1 M solutions of praseodymium,
neodymium, samarium, europium, and ytterbium
perchlorates were prepared from the corresponding
oxides (Ln2O3, 99.98%) by the dissolution of the oxides
in perchloric acid with removal of its excess by evapoꢀ
ration to the wet salts. The dry residue was dissolved in
bidistilled water, and the solution was brought to a
necessary volume in a volumetric flask. An exact conꢀ
centration of Ln(III) was determined by titration with
a solution of Trilon B in the presence of the indicator
arsenazo I. Solutions with a lower concentration were
obtained by the dilution of the starting solutions.
Other reactants used were reagent or analytical
grade. Organic solvents of grades lower than analytical
grade were purified by distillation [11].
Solutions of the complexes were prepared by mixꢀ
ing of an aqueous solution of Ln(ClO4)3 with an acetoꢀ
nitrile solution of the ligand in the presence of the
buffer with a necessary pH value. Acetate–ammonia
buffer solutions were used. The pH values were meaꢀ
sured using an OP 211/1 pH meter (Hungary) with an
ESLꢀ43ꢀ07 glass electrode and a silver chloride referꢀ
ence electrode.
The luminescence of the lanthanide complexes
with the ligand as a suspension of precipitates in soluꢀ
tions [1] was detected for Pr3+ (in the range from 580
to 630 nm), Sm3+ (550–670 nm), Eu3+ (570–660 nm),
Nd3+ (850–1100 nm), and Yb3+ (920–1100 nm). A
quartz cell (l = 1 cm) was used for solutions of the
complexes, and a cell with a hole 7 mm in diameter
was used for solid samples.
The solid complexes were obtained by the dropwise
addition of an acetonitrile solution (
Ln(III) perchlorate to an acetonitrile solution (
1 ×
10–1 M) of
RESULTS AND DISCUSSION
1 ×
10–2 M)
of the ligand in the mole ratio Ln : L = 2 : 3 followed
by vigorous stirring. After stirring for 1 h, the solution
was left in air at room temperature until the solvent was
completely removed. The precipitate that formed was
It was found by the luminescence method from the
radiation intensity maximum that the complex formaꢀ
tion of Ln3+ ions with the ligand occurred in the
pH region from 4 to 8, thereat pH 5–6 is optimal for
Pr3+, pH 6–7 is optimal for Sm3+ and Eu3+, and pH 6–
dried at 70 С (1 h) and stored in a desiccator.
°
8 is optimal for Nd3+ and Yb3+
.
Elemental analyses for C and H were carried out by
the Helcher method [12]. Control combustion was
The mole ratio of the components in the complexes
carried out using NꢀmethylꢀDꢀglucamine (Fluka) as a determined by independent methods is Ln : L = 2 : 3.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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2011

SYNTHESIS AND LUMINESCENCE PROPERTIES
311
Table 1. Spectral luminescence characteristics of the complexes Ln2L3 (aqueous solutions + 1% acetonitrile (cPr, Sm, Nd, Yb = 1 × 10–5,
c
Eu = 1 × 10–6, and cL = 1 × 10–4 mol/l)
ε ×
mol–1 l cm–1
10–3,
**
Complex
λ
max, nm
λ
exc, nm
Σ
I
,
arb. units*
ϕ
×
103
Pr2L3
382.7
378.7
377.5
377.7
377.4
9.4
8.3
9.0
8.2
9.6
361
360
366
365
365
197.7
777.0
196.8
92.3
2.19
4.62
Sm2L3
Eu2L3
Nd2L3
Yb2L3
10.79
0.08
99.4
0.11
* ΣI is the integral luminescence intensity.
** ϕ = 0.042 for (Ru(Bipy) Cl ) and 0.0315 for ZnTPP.
3
2
This was confirmed by the data of mass spectrometry shifting in the spectrum of the complex and is accomꢀ
of the complexes ( , found/calculated for Sm, Eu, panied by the appearance of an intense band at
and Yb: 1305/1301, 1307/1304, and 1347/1346, 628.7 cm–1 due to Eu–O bond vibrations. A molecule
m/z
respectively) and by elemental analysis data.
of the europium complex includes water of crystallizaꢀ
tion, which is indicated by the band with a maximum
at 3360 cm–1. Similar lowꢀintensity bands were also
observed for the Pr(III), Sm(III), Nd(III), and
Yb(III) complexes. Thus, in the Ln(III) complexes
the ligand is bound to the central ion by three oxygen
atoms through the tridentate cyclic mode.
For C57H47N9O10Sm2 (Sm2L3 · H2O)
anal. calcd., %: C, 52.63; H, 3.49; N, 9.69; Sm, 23.12.
Found, %:
C, 52.44; H, 3.57; N, 9.72; Sm, 23.01.
The structure of the Ln(III) complex with the
ligand was established from the elemental analysis and
IR and mass spectral data using the HyperChem proꢀ
gram (Fig. 1).
For C57H47N9O10Eu2 (Eu2L3 · H2O)
anal. calcd., %: C, 52.50; H, 3.49; N, 9.67; Eu, 23.31.
Found, %:
C, 53.02; H, 3.38; N, 9.59; Eu, 23.25.
The luminescence characteristics of the lanthanide
complexes Ln2L3 are presented in Table 1. The absorpꢀ
tion band maxima of the complexes, their molar coefꢀ
ficients, and the luminescence excitation wavelengths
differ insignificantly, but the values of luminescence
and quantum yield differ substantially. As it should be
expected, the Ln2L3 complex is characterized by the
For C57H47N9O10Yb2 (Yb2L3 · H2O)
anal. calcd., %: C, 50.85; H, 3.38; N, 9.37; Yb, 25.71.
Found, %:
C, 50.63; H, 3.31; N, 9.28; Yb, 25.61.
(Hereinafter, molecules of water of crystallization
in all complexes are omitted for clarity.)
highest luminescence quantum yield (
changing in the series Eu > Sm > Pr > Yb > Nd,
ϕ
). The order of
ϕ
The Xꢀray diffraction data for the Eu2L3 complex
which is mainly determined by their spectroscopic
characteristics, is also observed for the complexes with
other organic reagents.
confirm that the compound is pure and a ligand
1
admixture is absent.
The dentate and coordination modes of Ln3+ ions
The luminescence spectra of the Sm(III) and
Eu(III) complexes (visible spectral region, spectromꢀ
eter gaps 0.1–0.2) and the Nd(III) and Yb(III) comꢀ
plexes (IR region, gaps 0.5–1.0) are shown in Fig. 2.
The splitting of the bands corresponding to hypersenꢀ
sitive transitions, which is observed in the luminesꢀ
cence spectra of Eu3+ (two maxima at 590 and 594 nm;
in the complexes were determined by the IR spectral
data. IR for L (
(C=C), 1284
ring); IR for Eu2L3 (
1485 (C=C), 1284
phenyl ring), 628 (Eu–O). A comparative analysis of
ν
, cm–1): 1624, 1593, 1554
ν
(CO), 1497
(C–H of phenyl
, cm–1): 1621, 1566, 1520
(CO),
(C6H5–OH), 1146 νbenc(C–H of
ν
ν(C6H5–OH), 1170
δ
ν
ν
ν
ν
ν
transition 5D0
and 626 nm; transition 5D0
trum of Nd(III) (two pronounced maxima at 879 and
7F1 and three maxima at 612, 618,
the IR spectra of the ligand and Eu(III) complex in the
region of characteristic vibrational frequencies of
functional groups forming the coordination node with
the central ion indicates the coordination of the lanꢀ
thanide ion with all CO groups, whose vibrational freꢀ
quencies decrease in the complex, whereas the intenꢀ
7F2) and in the specꢀ
4
902 nm; transition F3/2
4I9/2), indicates the low
symmetry of the coordination polyhedron [1].
It should be mentioned that the determined value
sities of the bands corresponding to
decrease threefold. The intensity of the band correꢀ
ν
(СО) vibrations
of the triplet level energy of the ligand (ET1
=
18180 cm–1) is considerably lower than the energy of
radiating levels of dysprosium (20963 cm–1) and terꢀ
bium (20500 cm–1). Therefore, the intramolecular
sponding to
ν(C6H4–OH) decreases sharply without
1
The Xꢀray diffraction data are available from the authors.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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312
MESHKOVA et al.
C
C
C
C
C
C
C
C
C
C
C
C
N
N
N
C
C
C
C
C
N
N
C
N
C
C
O
O
C
C
C
C
C
O
C
C
C
C
Eu
C
C
C
C
C
C
O
C
O
C
O
O
Eu
C
O
C
C
C
C
C
C
C
O
C
C
C
N
C
N
C
C
N
C
C
C
C
C
+
Fig. 1. Molecular structure of the Eu L complex optimized by the MM method (HyperChem).
2
3
energy transfer from the excited ligand to Dy and Tb In particular, the introduction of the second ligand or
cannot occur in principle as for other Ln3+, which
exhibit characteristic luminescence upon the transiꢀ
tion to the ground state.
In the most part of cases, ions Ln3+ coordinate from
one to several water molecules along with the main
ligand. The highꢀfrequency vibrations of these moleꢀ
an organic solvent favors the displacement of the water
molecules from the internal coordination sphere of the
complex [1, 14]. According to the IR spectra and the
results of analyses, the europium complex includes the
water molecule and, hence, the introduction of the
second ligand (Table 2) increases the luminescence
cules (OH oscillators) strongly quench luminescence. intensity. For example, in the presence of bathoꢀ
Table 2. Increase in the luminescence intensity of the Pr(III), Sm(III), Eu(III), Nd(III), and Yb(III) complexes with 1ꢀ(2ꢀhyꢀ
droxyꢀ4ꢀmethylphenyl)ꢀ3ꢀ(5ꢀmethylꢀ1ꢀphenylꢀ1Hꢀ1,2,3ꢀtriazolꢀ4ꢀyl)propaneꢀ1,3ꢀdione (L) upon the introduction of the
second ligand (L')* (cPr, Sm, Nd, Yb = 2 × 10–5, cEu = 1 × 10–6, and cL,L' = 2 × 10–4 mol/l)
I
(Ln2L3L')/I(Ln2L3)
Complex
α
,α
'ꢀBipy
Phen
Batophen
ТPPО
ТОPО
DAPM
GMP
Pr2L3
1.3
1.4
2.8
1.5
1.0
1.1
1.3
1.4
1.5
1.1
1.9
6.1
8.3
2.2
1.7
2.6
4.1
4.6
2.0
1.1
2.7
5.1
5.5
2.2
1.0
1.7
3.2
2.1
2.7
0.9
1.4
0.9
1.0
1.6
1.0
Sm2L3
Eu2L3
Nd2L3
Yb2L3
* L' is α,α'ꢀbipyridine (Bipy), 1,10ꢀphenanthroline (Phen), 4,7ꢀdiphenylꢀ1,10ꢀphenanthroline (Batophen), triphenylphosphine oxide
(TPPO), trioctylphosphine oxide (TOPO), diantipyrylpropylmethane (DAPM), and hexamethapol (GMP).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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2011

SYNTHESIS AND LUMINESCENCE PROPERTIES
313
612
(
5D0
7F2
)
1
2
3
4
λ
, nm
Fig. 2. Luminescence spectra of the complexes (1) Sm L , (2) Eu L , (3) Nd L , and (4) Yb L .
2
3
2
3
2
3
2 3
phenanthroline, the luminescence intensity increases centration of 30 vol %. Probably, the weak enhanceꢀ
by 8.3 times. In the case of complexes of other lanꢀ ment of the luminescence in the presence of DMSO is
due to its high donor ability competing with that of the
ligand.
thanides, the introduction of the second ligands either
exerts no effect or enhances their luminescence to a
smaller extent. Organic solvents affect the luminesꢀ
cence of the Ln2L3 complexes in different way,
depending on the concentration (Fig. 3). In the presꢀ
ence of ethanol (40 vol %), the luminescence of Yb2L3
increases by 4.5 times, and its luminescence is
enhanced to a smaller extent by dioxane (3.5 times),
Photostability is an important characteristic of the
Ln(III) complexes, which determines the possibility
of using these complexes as luminescent probes. The
plots presented in Fig. 4 show the change in the lumiꢀ
nescence intensity of the synthesized complexes upon
continuous UV irradiation ( = 365 nm) for 30 min.
λ
acetonitrile (3 times), and DMSO (2 times) at a conꢀ The Nd2L3 complex is characterized by the highest
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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2011

314
MESHKOVA et al.
Ilum., arb. units
250
200
150
100
50
1
2
3
4
0
10
20
30
40
50
, vol %
с
Fig. 3. Effect of organic solvents on the luminescence intensity of the complex Yb L : (
1
) ethanol, (
2) acetonitrile, (3) DMSO,
2
3
ꢀ5
ꢀ4
and (
4
) dioxane (
c
= 1
×
10 and
c
= 1
×
10 mol/l).
Yb
L
Ilum., arb. units
200
180
160
140
120
100
80
1
2
3
60
40
4
20
5
0
5
10
15
20
25
30
τ
, min
Fig. 4. Plots of the luminescence intensity of the solid complexes (1) Yb L , (2) Nd L , (3) Pr L , (4) Eu L , and (5) Sm L vs.
2 3 2 3 2 3 2 3 2 3
time of continuous UV irradiation.
photostability. During the first 5 min of irradiation, the
Thus, the synthesis of reagents containing βꢀdikeꢀ
luminescence intensity of Pr2L3 decreases by 15% and tone fragments provides the formation of stable sixꢀ
that of Eu2L3 and Sm2L3 decreases by 50% and then membered rings, and the presence of aryl substituents
remains unchanged. The luminescence of Yb2L3 (photoantennas) results in the intense absorption of
decreases continuously, and an approximately 50% the exciting radiation. On the one hand, the ligands
decrease occurs within the first 20 min of irradiation.
synthesized are branched and shield the central ion
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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2011

SYNTHESIS AND LUMINESCENCE PROPERTIES
315
6. Zhang, H.ꢀJ., Li, G., Yan, L., et al., J. Lumin., 2007,
from water molecules entering into the internal coorꢀ
dination sphere. On the other hand, they prevent the
formation of trisꢀchelate. Three ligand molecules
coordinate two lanthanide ions (luminescence emitꢀ
ters) instead of one ion, which increases the luminesꢀ
cence quantum yield.
vol. 127, p. 316.
7. Zolin, V.F. and Koreneva, L.G., Redkozemel’nyi zond v
khimii i biologii (Lanthanide Probe in Chemistry and
Biology), Moscow: Nauka, 1980.
8. Kido, J. and Okamoto, Y., Chem. Rev., 2002, vol. 102,
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Koord. Khim., 2006, vol. 32, no. 12, p. 894 [Russ. J.
Coord. Chem. (Engl. Transl.), vol. 32, no. 12, p. 858].
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