Two series of luminescent flexible polycarboxylate lanthanide coordination complexes with double layer and rectangle metallomacrocycle structures

Article abstract of DOI:10.1021/cg400174r

Two series of eight polycarboxylate lanthanide coordination complexes, namely, [Ln(cpia)(H₂O)₂]·4H₂O {Ln = Ce (1), Nd (2), and Sm (3)} and [Ln(cpia)(H₂O)_n] ₂·2H₂O {Ln = Eu (4), G

Full text of DOI:10.1021/cg400174r

Article
pubs.acs.org/crystal
Two Series of Luminescent Flexible Polycarboxylate Lanthanide
Coordination Complexes with Double Layer and Rectangle
Metallomacrocycle Structures
Guang-Feng Hou, Hong-Xing Li, Wei-Zuo Li, Peng-Fei Yan,* Xiao-Hong Su, and Guang-Ming Li*
Key Laboratory of Functional Inorganic Material Chemistry (MOE), School of Chemistry and Materials Science, Heilongjiang
University, Harbin 150080, P. R. China
S
* Supporting Information
ABSTRACT: Two series of eight polycarboxylate lanthanide coordination
complexes, namely, [Ln(cpia)(H2O)2]·4H2O {Ln = Ce (1), Nd (2), and Sm (3)}
and [Ln(cpia)(H2O)n]2·2H2O {Ln = Eu (4), Gd (5), Tb (6), Er (7), and Lu (8), n =
5 in 4−7; n = 4 in 8} {H3cpia = N-[4-(carboxymethoxy)phenyl]iminodiacetic acid},
have been synthesized by self-assembly and characterized by IR, thermogravimetric
analysis, and X-ray crystallography. Complexes 1−3 are isomorphic featuring two-
dimensional double layer structures, while the isomorphic complexes 4−8 exhibit [2
+ 2] rectangle metallomacrocycle structures. Further, photoluminescence (PL)
spectra of complexes 2, 4, and 6 show the strong characteristic luminescence of
Eu(III), Tb(III), and Nd(III) ions, respectively, suggesting that cpia3− is able to
efficiently sensitize the luminescence of lanthanide ions.
hydrogen bond acceptors as well as donors to construct
supramolecular frameworks. The H3cpia ligand was first
reported in 2010,13 in which the H3cpia ligand reacted with a
transition metal to produce four complexes with three-
dimensional (3D) supramolecular networks. Herein, we report
the synthesis, structure, and photoluminesce of two series of
eight LMOCs, which represent the first example of H3cpia-
based LMOCs.
INTRODUCTION
■
The design and synthesis of metal−organic complexes (MOCs)
have attracted much attention due to their intrinsic
physicochemical properties, which promote applications in
the areas of luminescent materials, heterogeneous catalysis,
magnetism, and electrochemistry, as well as their intriguing
variety of architectures and topologies.1−4 In this area, one
important branch is the construction of lanthanide-based
metal−organic complexes (LMOCs) because of many
applications of such materials in biomedical and optical
technologies.5,6 It is well known that lanthanides ions have
affinity for hard donor atoms, and thus the ligands containing
oxygen atoms have been extensively used in the synthesis of
lanthanide complexes. Several classes of ligands such as
cryptands,7 β-diketone,8 and carboxylic acid9 have been utilized.
Among all types of ligands, polycarboxylate compounds with
plentiful coordination points and varied coordination molds10
represent a significant type of ligand for construction of new
LMOC materials.11 By designing the distances and angles
between the carboxyls, chemists could control and synthesize
multifariously novel structures.12
Accordingly, in the present work, we focus on synthesis of
novel LMOCs by using the semirigid ligand, namely, N-[4-
(carboxymethoxy)phenyl]iminodiacetic acid (H3cpia), consid-
ering three reasons: (a) H3cpia as a polycarboxylate compound
possesses multiple coordination sites and can provide various
coordination modes. (b) H3cpia has not only the characteristics
of flexibility and rigidity but also a long spacer, which will help
to form amazing entangled or interpenetrated architectures. (c)
The many O atoms and O−H groups of H3cpia can serve as
EXPERIMENTAL SECTION
■
Materials and Measurements. All commercially available
chemicals were reagent grade and used as received. LnCl3·6H2O
were synthesized by dissolving lanthanide oxide in a slight excess of
hydrochloric acid. Elemental analyses of C, H, N were performed on a
Perkin-Elmer 2400 elemental analyzer. The IR spectra were recorded
on a Perkin-Elmer Spectrum 100 FT-IR spectrometer equipped with a
DGTS detector (32 scans) by using KBr disks in the range of 4000 to
500 cm−1. Thermal analyses were conducted on a Perkin-Elmer STA
6000 with a heating rate of 10 °C·min−1 in a temperature range from
30 to 800 °C under air atmosphere. The luminescent spectra for the
powdered solid samples were recorded at room temperature on an
Edinburgh FLS 920 fluorescence spectrophotometer.
Synthesis of N-[4-(Carboxymethoxy)phenyl]iminodiacetic
Acid (H3cpia). The ligand H3cpia was synthesized using an modified
method described elsewhere.14 A solution of KOH (22.40 g, 0.4 mol)
in water (100 mL) was added dropwise to a solution of monochloro-
acetic acid (37.92 g, 0.4 mol) in water (100 mL). To the resulting
alkaline solution, 4-amino-phenol (10.93 g, 0.1 mol) was added, and
Received: January 29, 2013
Revised: July 4, 2013
Published: July 8, 2013
© 2013 American Chemical Society
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Figure 1. (a) Stick-ellipsoid representation of the asymmetric unit of complex 1 with thermal ellipsoids at 50% probability; lattice water molecules
were omitted for clarity. The inset shows the coordination geometry of the Ce(III) center; (b) the double layer structure of complex 1; (c) schematic
illustration of A−B type stacking framework. Symmetry codes: (I) 1 − x, 1 − y, 2 − z; (II) 1 + x, y, z; (III) 1 − x, 2 − y, 1 − z; (IV) x, −1 + y, 1 + z.
the mixture was refluxed for 10 h at about 80 °C. Then the reaction
mixture was cooled to room temperature, the pH value of the reaction
mixture was carefully adjusted to about 2.0 with concentrated
hydrochloric acid, and a pale brown precipitate appeared. The solid
was filtered off and washed using 50 mL of cold deionized water,
followed by vacuum drying to give H3cpia in 74% yield based on 4-
amino-phenol. H3cpia was characterized by 1H NMR (500 MHz,
DMSO): 3.93 (s, 4H), 4.51 (s, 2H), 6.35 (d, 2H), 6.76 (d, 2H), and
the H atoms of the carboxylate groups were not observed. Elemental
analysis calcd for C12H13O7N (283.2): C 50.89, H 4.63, N 39.54%;
found: C 50.75, H 4.55, N 39.65%. IR (KBr pellet, cm−1): 3394 (m),
2918 (w), 1740 (s), 1680 (s), 1510 (s), 1426 (m), 1359 (s), 1226 (m),
1132 (w), 1086 (m), 971 (w), 885 (w), 806 (m), 757 (m), 655 (w),
526 (w). UV−vis (MeOH, λmax): 264, 320 nm.
Synthesis of [Ce(cpia)(H2O)2]·4H2O (1). First, the Na3(cpia)
ligand was prepared by reacting H3cpia (28.35 g, 0.1 mol) with NaOH
(12.01 g, 0.3 mol) at a molar ratio of 1:3 in methanol solution. Three
milliliters of water as a buffer layer was slowly diffused into a 15 mm
×150 mm test tube, which was already added to a solution of
CeCl3·6(H2O) (0.12 g, 0.33 mmol) in H2O (5 mL) and then 5 mL of
Na3(cpca) aqueous solution (0.8 mmol/mL) was added to the above
mixture in the same way sequentially. Crystals suitable for X-ray
determination were obtained in 2 days (28.8% yield based on Ce).
Elemental analysis (%) calcd. for C12H22CeNO13 (528.4): C 27.28, H
4.20, N 2.65%; found: C 27.40, H 4.04, N 2.67%. IR (KBr pellet,
cm−1): 3303 (s), 2921 (w), 1569 (s), 1512 (s), 1459 (s), 1417 (s),
1346 (s), 1285 (m), 1245 (s), 1189 (m), 1132 (w), 1060 (m), 986
(w), 951 (m), 852 (w), 813 (m), 708 (m), 619 (w), 557 (w), 434 (w).
The synthesis of complexes 2−8 were the same as that for 1 except
that the Ce(Cl)3·6H2O was replaced by other LnCl3·6H2O.
Synthesis of [Nd(cpia)(H2O)2]·4H2O (2). Yield: 37.9% based on
Nd. Elemental analysis (%) calcd for C12H22NdNO13 (532.6): C
27.06, H 4.16, N 2.63; found: C 27.22, H 4.05, N 2.70. IR (KBr pellet,
cm−1): 3388 (s), 2909 (w), 1613 (s), 1577 (s), 1521 (s), 1463 (s),
1423 (s), 1345 (m), 1273 (m), 1239 (s), 1191 (m), 1136 (w), 1070
(m), 982 (m), 950 (m), 852 (w), 806 (m), 721 (m), 606 (w), 429
(w).
Synthesis of [Sm(cpia)(H2O)2]·4H2O (3). Yield: 42.2% based on
Sm. Elemental analysis (%) calcd for C12H22SmNO13 (538.7): C
26.76, H 4.11, N 2.60; found: C 26.92, H 3.99, N 2.66. IR (KBr pellet,
cm−1): 3404 (m), 2908 (w), 1623 (m), 1573 (s), 1522 (m), 1463 (m),
1428 (s), 1330 (w), 1273 (w), 1241 (s), 1189 (w), 1137 (w), 1070
(m), 983 (w), 951 (w), 852 (w), 805 (w), 724 (w), 695 (w), 604 (w).
Synthesis of [Eu(cpia)(H2O)5]2·2H2O (4). Yield: 39.0% based on
Eu. Elemental analysis (%) calcd. for C24H44Eu2N2O26 (1080.5): C
26.67, H 4.10, N 2.59; found: C 26.74, H 3.98, N 2.63. IR (KBr pellet,
cm−1): 3425 (s), 2898 (w), 1643 (s), 1592 (s), 1544 (s), 1455 (s),
1434 (s), 1346 (m), 1232 (m), 1170 (m), 1070 (m), 977 (w), 930
(w), 850 (w), 809 (w), 701 (m), 679 (w), 525 (w).
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Synthesis of [Gd(cpia)(H2O)5]2·2H2O (5). Yield: 46.5% based on
Gd. Elemental analysis (%) calcd. for C24H44Gd2N2O26 (1091.1): C
26.42, H 4.06, N 2.57; found: C 26.55, H 3.92, N 2.64. IR (KBr pellet,
cm−1): 3438 (s), 2902 (w), 1639 (s), 1589 (s), 1510 (s), 1453 (m),
1432 (m), 1409 (m), 1347 (w), 1233 (w), 1192 (w) 1072 (w), 977
(w), 928 (w), 813 (w), 680 (w), 570 (w), 528 (w).
Synthesis of [Tb(cpia)(H2O)5]2·2H2O (6). Yield: 37.8% based on
Tb. Elemental analysis (%) calcd. for C24H44Tb2N2O26 (1094.5): C
26.34, H 4.05, N 2.56; found: C 26.51, H 3.94, N 2.60. IR (KBr pellet,
cm−1): 3426 (s), 2900 (w), 1639 (s), 1511 (s), 1450 (m), 1431 (s),
1409 (s), 1345 (m), 1232 (w), 1075 (m), 980 (w), 930 (w), 847 (w),
810 (m), 724 (w), 692 (w), 569 (w), 531 (w).
Synthesis of [Er(cpia)(H2O)5]2·2H2O (7). Yield: 43.7% based on
Er. Elemental analysis (%) calcd. for C24H44Er2N2O26 (1111.1): C
25.94, H 3.99, N 2.52; found: C 26.02, H 3.85, N 2.57. IR (KBr pellet,
cm−1): 3436 (m), 2888 (w), 1680 (m), 1646 (s), 1551 (m), 1517 (m),
1456 (m), 1436 (s), 1334 (w), 1283 (w), 1261 (w), 1176 (wm), 1131
(w), 1078 (m), 981 (w), 935 (w), 851 (w), 809 (w), 714 (m), 636
(w), 697 (w), 525 (w).
Synthesis of [Lu(cpia)(H2O)4]2·2H2O (8). Yield: 41.2% based on
Lu. Elemental analysis (%) calcd. for C24H40Lu2N2O24 (1090.5): C
26.43, H 3.70, N 2.57; found: C 26.59, H 3.64, N 2.63. IR (KBr pellet,
cm−1): 3638 (m), 3301 (m), 2380 (w), 1597 (s), 1510 (m), 1441 (m),
1397 (m), 1345 (m), 1232 (m), 1189 (w), 1154 (w), 1067 (w), 928
(w), 815 (w), 684 (w), 519 (w).
triclinic system with P1 space group. The asymmetric unit of 1
̅
has one Ce(III) cation, one cpia3− anion, two coordinated
water molecules, and four lattice water molecules (Figure 1a).
The Ce(III) cation is nine-coordinated in a tricapped triangular
prism geometry defined by seven O atoms from six carboxyl
groups of five cpia3− anions and two O atoms from two
coordinated water molecules. The bond distances around the
Ce1 center are in range of 2.431(2)−2.627(3) Å. The cpia3−
anions serve as a hexadentate ligand coordinating with five
Ce(III) cations involving all of three carboxylate groups in
binding mode of μ5 - η1: η1: η1: η1: η2: η1. The three carboxylate
groups exhibit different coordination modes: (a) the carbox-
ylate group from hydroxyacetic acid group shows bridging
coordination mode, which link two Ce(III) cations to form a
dinuclear {Ce2} moiety with a Ce···Ce distance of 4.127(1) Å;
(b) one carboxylate group of the iminodiacetic acid group
exhibits chelating and bridging mode coordinating with one
dinuclear {Ce2} moiety; (c) the other one shows the bridging
mode linking two dinuclear {Ce2} moieties (Scheme 1).
Scheme 1. Coordination Modes of cpia3− Anions in
Complexes 1−8
X-ray Crystallography. Single-crystal X-ray diffraction data for
complexes 1−8 were collected on a Rigaku R-AXIS RAPID imaging
plate diffractometer with graphite-monochromated Mo Kα (λ =
0.71073 Å) at 291 K. Empirical absorption corrections based on
equivalent reflections were applied. The structures of 1−8 were solved
by direct methods and refined by full-matrix least-squares methods on
F2 using the SHELXS-97 crystallographic software package.15 One of
the lattice water molecules was free-refined isotropically and was
disordered over two positions with an occupancy of 0.34 and 0.66 in 1,
0.38 and 0.62 in 2, 0.37 and 0.63 in 3, and their H atoms were not
added. The crystal parameters, data collection, and refinement results
for 1−8 are summarized in Table 1. Selected bond lengths are listed in
Table S1 (see the Supporting Information).
Through these coordinated interactions, a double chain is
built up by cpia3− anions linking the Ce(III) cations with the
distance between two {Ce2} moieties of 12.086(6) Å along the
RESULTS AND DISCUSSION
■
Synthesis. The crystals of complexes 1−8 were synthesized
by using solution diffusion reactions rather than the hydro-
thermal reactions, which is normally applied in the reactions of
organic acids and metal ions. In the preparation of complexes
1−8, a 3 mL water solution was used as a buffer layer to reduce
the output of powder. Such a process improves the yield and
purity of the crystal products. Furthermore, the influence of the
counteranions was investigated by employing the lanthanide
nitrates instead of lanthanide chlorides. However, the same
products were obtained with slight difference in the yields.
Notably, the reaction temperature affects the structure of
complexes 1−3. When the reaction temperature was above 25
°C, complexes 1−3 were isolated. When the reaction
temperature was below 25 °C, complexes 1−3 were not
isolated. However, complexes 4−8 were able to be isolated
easily by mixing the Na3(cpia) ligand and lanthanide salts in
H2O. In fact, the yields for complexes 1−8 are based on the
crystalline products. The overall yields including the powder
product for complexes 4−8 are quite high. However, the yields
for complexes 1−3 were low because some unknown
byproduct remained. Complexes 1−8 were heated at 80 °C
under a vacuum for 2 h to obtain the dehydrated products,
namely, complexes 1′−8′.
[0 1 1] direction. Furthermore, the adjacent double chains are
̅
connected by a third coordinated mode to form a two-
dimensional (2D) double layer structure with the lattice water
molecules filling in the cavities with a dimension of 5.575(1) ×
12.608(5) Å and stabilizing by the hydrogen bonds (Figure 1b).
Adjacent networks are in an A−B type offset fashion and linked
by O−H···O hydrogen bonds between coordinated and lattice
water molecules into a 3D supramolecular framework (Figure
1c, hydrogen bond distances and angles; see Table S2).
Crystal Structure of Complexes 4−8. Complexes 4−8
crystallize in the monoclinic system with C2/c space group and
are also isomorphic. In a typical structure of 4−8, the
asymmetric unit of complex 4 consists of one Eu(III) cation,
one cpca3− ligand, five coordinated water molecules, and one
lattice water molecule (Figure 2a). The Eu(III) cation is eight-
coordinated in a distorted square antiprismatic geometry
defined by two O atoms from two carboxylate groups of one
cpia3− anion, one O atom from another cpia3− anion, and five O
atoms from five coordinated water molecules. The bond
distances of Eu−O range from 2.257(2) to 2.453(3) Å. The
three carboxylate groups of the cpia3− anion in complex 4 are
monodentate coordinations (μ2 - η1: η0: η1: η0: η1: η0) with
adjacent Eu(III) cations (Scheme 1) to construct a [2 + 2]
rectangle metallomacrocycle. Each [2 + 2] metallomacrocycle is
surrounded by eight other metallomacrocycles (Figure 2b).
Furthermore, these metallomacrocycles and lattice molecules
Crystal Structure of Complexes 1−3. Single-crystal X-ray
diffraction analysis shows that complexes 1−3 are isomorphic.
In a typical structure of 1−3, complex 1 crystallizes in the
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Figure 3. Coordination geometry changes of the lanthanide centers in
complexes 1−8.
caused by the partial collapse of the framework. However, the
diffraction peaks of the complexes 4′−8′ exhibit an additional
peak near 7.7° in contrast to those for complexes 1−8, which
may indicate the change of the molecules packing. The TGA
measurements of complexes 1−8 were carried out in
atmosphere in the temperature range 30−800 °C (Figure
S3). Complexes 1−3 exhibit similar two weight-loss processes.
The first weight loss of 11.82% for 1, 14.05% for 2, and 12.28%
for 3, respectively, correspond to the loss of four lattice water
molecules per formula unit (calcd: 13.62% for 1, 13.52% for 2,
and 13.37% for 3) in the temperature range of 30−115 °C. The
frameworks of complexes 1−3 collapse near 295 °C arising
from the decomposition of the cpia3− anions and coordinated
water molecules. The observed final mass residue of 32.04%,
31.48% and 33.95%, respectively, likely are ascribed to
generation of corresponding Ln2O3 (calcd: 31.06% for 1,
31.59% for 2 and 32.38% for 3). The TGA curves for
complexes 4−8 also show similar two weight loss processes.
The first weight loss of 19.29% for 4, 19.61% for 5, 19.74% for
6, 18.94% for 7, and 16.51% for 8, respectively, was observed in
the range of 80−180 °C, which corresponds to the loss of 12
lattice water molecules (10 lattice water molecules for 8) per
formula unit (calcd: 19.99% for 4, 19.79% for 5, 19.74% for 6,
19.44% for 7, and 15.59% for 8). Furthermore, the second
weight loss occurred in the temperature range of 310−700 °C,
which corresponds to the loss of two cpia3− anions per formula
unit. The observed final mass residue of 33.47%, 34.24%,
34.20%, 34.27%, and 37.55%, respectively, could be ascribed to
the residue of corresponding Ln2O3 (calcd: 32.57% for 4,
33.22% for 5, 33.43% for 6, 34.44% for 7, and 37.55% for 8).
Luminescent Properties. The UV−vis spectrum of the
H3cpia is recorded in MeOH solution (Figure S4). The typical
absorption at 264 nm is attributed to the π−π* transition of the
aromatic rings. The peak at 320 nm is attributed to n−π*
transition belonging to the tertiary amine group. The
photoluminescence (PL) spectra of free H3cpia, 4 and 6, and
the dehydrated complexes 4′ and 6′ were obtained in solid state
at room temperature. Upon excitation at the characteristic
absorbance band of the ligand H3cpia (λmax = 375 nm, Figure
S5), solid samples of complexes 4 and 6 show the characterized
visible luminescence of Eu(III) and Tb(III) ions at room
temperature. As expected, complex 4 exhibits four characteristic
emission bands of Eu(III) ion at 592, 614, 648, and 698 nm,
respectively, which are attributed to the transition of 5D0 → 7FJ
(J: 1 to 4) (Figure 4a). The strongest peak at 614 nm from the
Figure 2. (a) Stick-ellipsoid representation of the asymmetric unit of
complex 4 with thermal ellipsoids at 50% probability. The inset shows
the coordination geometry of the Eu(III) center; (b) schematic
illustration of 3D stacking framework. Symmetry codes: (I) −x, 1 − y,
−z.
are linked together through O−H···O hydrogen bonds to form
a 3D supramolecular framework with the adjacent layers
consisting of the [2 + 2] metallomacrocycles with different
orientations (Figure 2c, Table S2).
However, in complex 8, the Lu(III) cation is seven-
coordinated in a distorted monocapped triangular prism
geometry due to the lanthanide contraction causing only four
water molecules coordination with the Lu(III) cation (Figure
S1, Supporting Information). According to the order of the
lanthanide contraction, the bond distances of Ln−O and
Ln···Ln decrease linearly in 1−3 and 4−8, respectively. The
coordination numbers for the lanthanide ions are also declined
from 9 to 7 in complexes 1−8 (Figure 3). Notably, the
structural differences between the complexes 1−3 and 4−8
should be caused by the combined effect of the lanthanide
contraction and the thermodynamics effect.
PXRD and Thermalgravimetric Analysis. The PXRD
patterns for complexes 1−8 and complexes 1′−8′ are presented
in Figure S2. The diffraction peaks of both calculated and
experimental patterns match well, indicating the phase purities
of complexes 1−8. The diffraction peaks of the complexes 1′−
3′ show an absence of the peaks around 10°, which may be
5D0
→
7F2 transition results in red emission. Complex 6
exhibits four characteristic emission bands of Tb(III) ion at
5
490, 544, 586, and 620 nm, attributed to the transition of D4
7
→ FJ (J: 6 to 3) (Figure 4b). The strongest peak at 544 nm
5
7
from the D4 → F5 transition results in green light emission.
Notably, the PL spectra for complexes Sm(III) (3) and Er(III)
(7) and their dehydrated species 3′ and 7′ were also obtained;
however, the characterized peaks for both Er(III) and Sm(III)
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Figure 4. Solid-state emission spectra of complexes 4, 4′, 6, and 6′.
ions were not observed, which should be caused by the poor
sensitization efficiency of the ligand for the Er(III) and Sm(III)
ions.
0−0 transition is the band at 404 nm (24 752 cm−1). Since the
6
lowest excited state, P7/2, of the Gd(III) ion is too high to
accept energy from the ligand, the data obtained from the
phosphorescence spectrum actually reveal the triplet energy
level of cpia3− anion in lanthanide complexes.19 According to
Dexter’s theory,20 the suitability of the energy gap between the
resonance level of the Ln(III) ion and the triplet state of the
ligand is a critical factor for efficient energy transfer. If the
energy gap is too large, the energy transfer rate constant
decreases due to the diminution in the overlap between the
donor and the acceptor. On the contrary, if the energy gap is
too small, the energy back-transfer can occur from the Ln(III)
ion to the resonance level of the triplet state of the ligand.
Latva’s empirical rule states that an optimal ligand-to-metal
energy transfer process needs ΔE (3ππ*−5DJ) = 2500−4000
cm−1 for Eu(III) and 2500−4500 cm−1 for Tb(III) ions.21 The
triplet levels of the cpia3− anion (24 752 cm−1) are obviously
The room-temperature luminescent decay profiles (Figure
S6) of complexes 4 and 6 are found to be single-exponential
functions, thus implying the presence of only one emissive
Eu(III) or Tb(III) center, respectively. The lifetimes of 101.9
and 197.1 μs were determined by monitoring the emission
5
7
decay curves within the D0 → F2 transition at 614 nm for 4,
5
7
and D4 → F5 transition at 544 nm for 6. Noticeably, the
intensity of the emissions for the dehydrated complexes 4′ and
6′ both show significant enhancements. And the lifetimes
increase up to 283.3 μs for complex 4′ and 621.3 μs for
complex 6′.
NIR Luminescence. The NIR luminescent spectrum of the
solid state complex 2 was investigated at room temperature. For
complex 2, upon excitation at 323 nm (Figure 5), the broad
5
5
higher than the D0 and D4 levels of Eu(III) (17 500 cm−1)
and Tb(III) (20 400 cm−1), and their energy gaps ΔE
(3ππ*−5D0/5D4) are 7252 and 4352 cm−1, respectively (Figure
6). It supports the observation of stronger emission of the
Tb(III) ion in complex 6 than that of Eu(III) ion in complex 4.
Figure 5. Solid-state NIR emission spectrum of complex 2.
emission band with triple peaks in the range of 900−990 nm is
observed and assigned to 4F3/2 → 4I9/2 transition. The strongest
4
emission band occurring at 1056 nm is assigned to F3/2
→
4I11/2 transition; moreover, the emission band at 1344 nm is
4
assigned to F3/2
→
4I13/2 transition, which offers the
opportunity to develop new laser and optical amplified
materials.16−18
Energy Transfer. To demonstrate the energy transfer
process, the phosphorescence spectrum of complex 5 was
measured at 77 K in a mixed solution of methanol/DMF (4:1
V/V) with a concentration of 1 × 10−4 mol·L−1. On the basis of
the phosphorescence spectrum of complex 5 (Figure S7), the
Figure 6. Simplified energy diagram showing the lowest lanthanide
excited and the estimated states triplet state of the sensitizer cipa3−
anion in the [Gd2(cpia)2] complex.
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(5) (a) Bunzli, J. C. G.; Piguet, C. Chem. Sov. Rev. 2005, 34, 1048.
̈
CONCLUSION
■
(b) Bunzli, J. C. G. Chem. Rev. 2010, 110, 2729. (c) Eliseeva, S. V.;
̈
Two series of eight polycarboxylate lanthanide coordination
complexes, constructed by cpia3− anions and lanthanides
featuring a unique 2D double layer and [2 + 2] rectangle
metallomacrocycle structures, have been isolated, which
represent the first examples of LMOCs based on H3cpia.
Isolation of complexes 1−8 unambiguously demonstrates that
the lanthanum contraction dominates the structures of these
complexes. PL spectra reveal that cpia3− anions are able to
sensitize the luminescence of Nd(III), Eu(III), and Tb(III) ions
in complexes 2, 4, and 6, respectively. The study on the energy
transfer between the resonance level of the Ln(III) ion and the
triplet state of the ligand suggests that the match of the energy
gap for complex 6 is better than that for complex 4, resulting in
the strong green luminescence for complex 6. Further, both
luminescent intensity and lifetimes for the dehydrated
complexes 4′ and 6′ are significantly enhanced in contrast to
those for complexes 4 and 6. This approach offers the
opportunity to develop potential laser and optical amplified
materials.
Bunzli, J. C. G. Chem. Sov. Rev. 2010, 39, 189. (d) Sabbatini, N.;
̈
Guardogi, M.; Lehn, J. M. Coord. Chem. Rev. 1993, 123, 201. (e) Kido,
J.; Okamoto, Y. Chem. Rev. 2002, 102, 2357.
(6) (a) Archer, R. D.; Chen, H. Y.; Thompson, L. C. Inorg. Chem.
1998, 37, 2089. (b) Xu, J.; Cheng, J. W.; Su, W. P.; Hong, M. C. Cryst.
Growth Des. 2011, 11, 2294. (c) Yan, X. H.; Li, Y. F.; Wang, Q.;
Huang, X. G.; Zhang, Y.; Gao, C. J.; Liu, W. S.; Tang, Y.; Zhang, H. R.;
Shao, Y. L. Cryst. Growth Des. 2011, 11, 4205. (d) Zhao, Y.; Jiao, C. Q.;
Sun, Z. G.; Zhu, Y. Y.; Chen, K.; Wang, C. L.; Li, C.; Zheng, M. J.;
Tian, H.; Sun, S. H.; Chu, W. Cryst. Growth Des. 2012, 12, 3191.
(7) Galaup, C.; Picard, C.; Cathala, B.; Cazaux, L.; Tisnes, P. Helv.
Chim. Acta 1999, 82, 543.
(8) (a) Holz, R. C.; Thompson, L. C. Inorg. Chem. 1993, 32, 5251.
(b) Li, J. Y.; Li, H. F.; Yan, P. F.; Chen, P.; Hou, G. F.; Li, G. M. Inorg.
Chem. 2012, 51, 5050. (c) Li, H. F.; Yan, P. F.; Chen, P.; Wang, Y.; Xu,
H.; Li, G. M. Dalton Trans. 2011, 41, 900.
(9) (a) Cao, R.; Sun, D. F.; Liang, Y. C.; Hong, M. C.; Tatsumi, K.;
Shi, Q. Inorg. Chem. 2002, 126, 2087. (b) Zhang, H. B.; Li, N.; Tian, C.
B.; Liu, T. F.; Du, F. L.; Lin, P.; Li, Z. H.; Du, S. W. Cryst. Growth Des.
2012, 12, 670. (c) Feng, R.; Jiang, F. L.; Wu, M. Y.; Chen, L.; Yan, C.
F.; Hong, M. C. Cryst. Growth Des. 2010, 10, 2306. (d) Shi, P. F.;
Chen, Z.; Xiong, G.; Shen, B.; Sun, J. Z.; Cheng, P.; Zhao, B. Cryst.
Growth Des. 2012, 12, 5203.
(10) (a) Ghosh, S. K.; Bureekaew, S.; Kitagawa, S. Angew. Chem., Int.
Ed. 2008, 47, 3403. (b) Zou, R. O.; Sakurai, H.; Xu, Q. Angew. Chem.,
Int. Ed. 2006, 45, 2542.
ASSOCIATED CONTENT
* Supporting Information
■
S
Tables S1−S2 and Figures S1−S6. This material is available free
of charge via the Internet at http://pubs.acs.org. Crystallog-
raphy data have been deposited to the Cambridge Crystallog-
raphy Data Centre with deposition numbers CCDC nos.
909631−909634, 921245, 909635, 909636, and 919816 for
complexes 1−8.
(11) (a) Zhang, A. J.; Wang, Y. W.; Dou, W.; Dong, M.; Zhang, Y. L.;
Tang, Y.; Liu, W. S; Peng, Y. Dalton Trans. 2011, 40, 2844. (b) Zou, Y.
H.; Wei, Q.; Guo, Z. L.; Chen, S. P.; Gao, S. L. Inorg. Chim. Acta 2011,
375, 181. (c) Li, Y. X.; Yan, P. F.; Hou, G. F.; Li, H. F.; Chen, P.; Li, G.
M. J. Organomet. Chem. 2013, 723, 176.
(12) (a) Thomas, D.; Christian, S.; Nathalie, A.; Jerome, M.; Gerard,
F. J. Am. Chem. Soc. 2005, 127, 12788. (b) Zhao, Y. H.; Xu, H. B.;
Shao, K. Z.; Xing, Y.; Su, Z. M.; Ma, J. F. Cryst. Growth Des. 2007, 7,
513.
(13) Liu, C. B.; Wen, H. L.; Gong, Y. N.; Liu, X. M.; Tan, S. S. Z.
Anorg. Allg. Chem. 2011, 637, 122.
(14) (a) Tan, S. S.; Wen, H. L.; Liu, C. B.; Peng, X. P. Z. Kristallogr.
NCS. 2007, 222, 137. (b) Kaupp, G.; Naimi-Jamal, M. R.; Schmeyers,
J. Tetrahedron 2003, 59, 3753.
(15) Sheldrick, G. M. Acta Crystallogr. A 2008, 64, 112.
(16) Klink, S. I.; Alink, P. O.; Grave, L.; Peters, F. G. A.; Hofstraat, J.
W.; Geurts, F.; Van Veggel, F. C. J. M. J. Chem. Soc., Perkin Trans.
2001, 63, 363.
(17) Lai, W. P. W.; Wong, W. T. New J. Chem. 2000, 24, 943.
(18) Feng, J.; Yu, J. B.; Song, S. Y.; Sun, L. N.; Fan, W. Q.; Guo, X.
M.; Dang, S.; Zhang, H. J. Dalton Trans. 2009, 240.
(19) Wang, Y. W.; Zhang, Y. L.; Dou, W.; Zhang, A. J.; Qin, W. W.;
Liu, W. S. Dalton Trans. 2010, 9013.
(20) Dexter, D. L. J. Chem. Phys. 1953, 21, 836.
(21) Latva, M.; Takalo, H.; Mukkala, V. M.; Matachescu, C.;
Rodriguez-Ubis, J. C.; Kankare, J. J. Lumin. 1997, 75, 149.
AUTHOR INFORMATION
Corresponding Author
*(G.M.L.) Tel.: +86 451 86608458; fax: +86 451 86673647; e-
mail: gmli_2000@163.com. (P.-F.Y) e-mail: yanpf@vip.sina.
com.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work is financially supported by the National Natural
Science Foundation of China (Nos. 21072049, 21072050,
21272061), Heilongjiang Province (No. 2010td03), and
Heilongjiang University (2010hdtd-08 and 2010hdtd-11).
REFERENCES
■
(1) (a) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.;
O’Keeffe, M.; Yaghi, O. M. Senience 2002, 295, 469. (b) Matsuda, R.;
Kitaura, R.; Kitagawa, S.; Kubota, Y.; Belosludov, R. V.; Kobayashi, T.
C.; Sakamoto, H.; Chiba, T.; Takata, M.; Kawazoe, Y.; Mita, Y. Nature
2005, 436, 238. (c) Ma, L. O.; Jin, A.; Xie, Z. G.; Lin, W. B. Angew.
Chem., Int. Ed. 2009, 48, 9905.
(2) (a) Li, J. R.; Kuppler, R. J.; Zhou, H. C. Chem. Soc. Rev. 2009, 38,
́
1477. (b) Corma, A.; García, H.; Llabres i Xamena, F. X. Chem. Rev.
2010, 110, 4606. (c) O’Keeffe, M.; Peskov, M. A.; Ramsden, S. J.;
Yaghi, O. M. Acc. Chem. Res. 2008, 41, 1782.
(3) (a) Hou, G. F.; Bi, L. H.; Li, B.; Wu, L. X. Inorg. Chem. 2010, 49,
6474. (b) Hou, G. F.; Bi, L. H.; Li, B.; Wang, B.; Wu, L. X.
CrystEngComm 2011, 13, 3526. (c) Hou, G. F.; Wang, X. D.; Yu, Y. H.;
Gao, J. S.; Wen, B.; Yan, P. F. CrystEngComm 2013, 15, 249.
(4) (a) Liu, Y.; Eubank, J. F.; Cairns, A. J.; Eckert, J.; Kravtsov, V. C.;
Luebke, R.; Eddaoudi, M. Angew. Chem., Int. Ed. 2007, 119, 3342.
(b) Kitagawa, S.; Matsuda, R. Coord. Chem. Rev. 2007, 251, 2490.
(c) Mulfort, K. L.; Hupp, J. T. J. Am. Chem. Soc. 2007, 129, 9604.
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