Structures, luminescent and magnetic properties of a series of (3,6)-connected lanthanide-organic frameworks

Article abstract of DOI:10.1039/c3dt52305e

Through hydrothermal reactions with corresponding lanthanide nitrates and 4-(4-carboxyphenylsulfonyloxy)-3-metnoxybenzoic acid (H₂vspc), seven novel three-dimensional (3D) lanthanide-organic frameworks ([Ln(vspc)(Hvspc) (H₂O)]_n [Ln = Pr (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6) and Er (7)]) have been synthesized and structurally characterized. All of them are isostructural and crystallize in the monoclinic crystal system, P2 ₁/c space group. Their structures feature a (3,6)-connected topological network, in which Ln³⁺ were connected by carboxylate groups to give a 1D lanthanide chain, and the adjacent chains are further spanned by vspc^2- and Hvspc^- anions to form a 3D framework. The luminescent properties and lifetimes of 2 (Eu^III), 4 (Tb^III), and 5 (Dy^III) have been studied, and the corresponding luminescent lifetimes are 0.53, 0.99 and 0.014 ms, respectively. The magnetic investigations reveal that compound 3 displays weak antiferromagnet interaction, 4 and 5 exhibit ferromagnetic coupling, and compound 5 exhibits slow magnetic relaxation behavior. The Royal Society of Chemistry.

Full text of DOI:10.1039/c3dt52305e

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Structures, luminescent and magnetic properties
of a series of (3,6)-connected lanthanide–organic
frameworks†
Cite this: Dalton Trans., 2014, 43,
1814
Yin-Ling Hou,a,b Rui-Rui Cheng,a,b Gang Xiong,a,b Jian-Zhong Cuib and Bin Zhao*a
Through hydrothermal reactions with corresponding lanthanide nitrates and 4-(4-carboxyphenylsulfonyl-
oxy)-3-metnoxybenzoic acid (H2vspc), seven novel three-dimensional (3D) lanthanide–organic frame-
works ([Ln(vspc)(Hvspc)(H2O)]n [Ln = Pr (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6) and Er (7)]) have been
synthesized and structurally characterized. All of them are isostructural and crystallize in the monoclinic
crystal system, P21/c space group. Their structures feature a (3,6)-connected topological network, in
which Ln3+ were connected by carboxylate groups to give a 1D lanthanide chain, and the adjacent chains
are further spanned by vspc2− and Hvspc− anions to form a 3D framework. The luminescent properties
and lifetimes of 2 (EuIII), 4 (TbIII), and 5 (DyIII) have been studied, and the corresponding luminescent life-
times are 0.53, 0.99 and 0.014 ms, respectively. The magnetic investigations reveal that compound 3 dis-
plays weak antiferromagnet interaction, 4 and 5 exhibit ferromagnetic coupling, and compound 5 exhibits
slow magnetic relaxation behavior.
Received 22nd August 2013,
Accepted 15th October 2013
DOI: 10.1039/c3dt52305e
www.rsc.org/dalton
electrons shielded by outer electrons, lanthanide compounds
usually possess extremely narrow peaks and long luminescent
Introduction
The constructions of metal–organic frameworks have attracted lifetimes,16,17 which is exploited for luminescent probes and
much attention not merely because of their tunable synthesis laser materials.10 (3) Lanthanide compounds generally have
and fascinating structures,1 but also for their potential applica- unique magnetic properties due to strong unquenched orbital
bility in gas adsorption and separation,2 catalytic,3 molecule angular momentum of most of Ln3+ 8c–g
which is supported by
,
and ion sensors,4 optic,5 electronic,6 and magnetic systems.7 the fact that the single molecule magnetic (SMM) behavior is
Compared with the metal–organic frameworks based on tran- frequently observed in the lanthanide-based compounds.8b,c
sition metal ions, lanthanide–organic frameworks possess dis- (4) Ln3+ ions would be the one of the most competitive candi-
tinct superiority for the following reasons: (1) because of the dates for constructing multifunctional compounds due to
high coordination numbers and flexible coordination geome- their excellent luminescence, unique magnetic properties,
tries of Ln3+, it is easy to construct high connected lanthanide porous properties including adsorption/exchanges and toxic
compounds with interesting topological structures
- for substance separations etc. According to above four points, the
example, the high 9-connected compound of [(2-i-PrC6H4- lanthanide ions as metal centers were frequently selected to
ORb)6·(diox)4.5] reported by Morris and co-workers,8a and the fabricate multifunctional metal–organic frameworks.3a,8e,9a
unique (3,12)-connected topology discovered by our group.8b
It is well known that lanthanide ions are easily coordinated
(2) Originating from f–f transitions of their particular 4f to oxygen atoms, and various organic carboxylate ligands have
been usually employed to build lanthanide–organic frame-
works, such as mono-, di- and poly-carboxylic acids.9,11 In this
work, we used a dicarboxylic acid ligand with sulfonate
group, 4-(4-carboxyphenylsulfonyloxy)-3-metnoxybenzoic acid
(H2vspc) (Scheme 1), to construct 3D lanthanide–organic
frameworks based on the following considerations: (1) there
are two carboxylate groups that may be completely or partially
deprotonated, yielding a variety of coordination modes and
higher dimensional compounds with interesting structures; (2)
the sulfonate group and methoxyl group may show additional
steric hindrance due to their important geometric asymmetry;
aDepartment of Chemistry, Key Laboratory of Advanced Energy Material Chemistry,
MOE, TKL of Metal and Molecule Based Material Chemistry, and Synergetic
Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University,
Tianjin 300071, China. E-mail: zhaobin@nankai.edu.cn
bDepartment of Chemistry, Tianjin University, Tianjin, 300072, China
†Electronic supplementary information (ESI) available: Table of bond lengths
and angles, TG curves, the emission spectrum of free H2vspc ligand, lumines-
cent decay curves of 2, 4 and 5, and other magnetic data. X-ray crystallographic
files in cif format for compounds 1–7. CCDC 956810 (1), 956811 (2), 956812 (3),
956813 (4), 956814 (5), 956815 (6) and 956816 (7). For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c3dt52305e
1814 | Dalton Trans., 2014, 43, 1814–1820
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bond lengths and angles for 1–7 were listed in Table S1 and S2
(ESI†), respectively.
Synthesis
[Ln(vspc)(Hvspc)(H2O)]n [ Ln = Pr (1), Eu (2), Gd (3), Tb (4),
Dy (5), Ho (6) and Er (7)]. 0.05 mmol H2vspc (0.0176 g),
0.1 mmol Ln(NO3)3·6H2O [Ln = Pr (0.0435 g), Eu (0.0446 g), Gd
(0.0451 g), Tb (0.0453 g), Dy (0.0457 g), Ho (0.0459 g) and Er
(0.0461 g)], 0.25 mmol NH4SCN (0.0190 g), and 8 mL H2O were
added to a 25 mL Telfon-lined stainless steel container and
heated to 130 °C for 72 h under autogenous pressure, then
cooled to room temperature in 72 h. Needle crystals were
obtained and the yields are ca. 23% (1), 38% (2), 55% (3), 53%
(4), 50% (5), 42% (6), and 35% (7) based on H2vspc. Elemental
analysis of C30H23O17S2Pr (1): calcd: C 41.87, H 2.69; found: C
41.68, H 2.82%; C30H23O17S2Eu (2): calcd: C 41.34, H 2.66;
found: C 41.49, H 2.48%; C30H23O17S2Gd (3): calcd: C 41.09, H
2.64; found: C 41.25, H 2.67%; C30H23O17S2Tb (4): calcd: C
41.01, H 2.64; found: C 41.32, H 2.50%; C30H23O17S2Dy (5):
Scheme 1 The structure of H2vspc.
(3) compounds based on H2vspc ligands have never been
reported, as far as our information goes. Here, seven novel 3D
lanthanide compounds, [Ln(vspc)(Hvspc)(H2O)]n [ Ln = Pr (1),
Eu (2), Gd (3), Tb (4), Dy (5), Ho (6) and Er (7)], were syn-
thesized and characterized. All of them are isostructural and
belong to the monoclinic crystal system, P21/c space group.
The luminescent properties and lifetimes of 2 (EuIII), 4 (TbIII)
and 5 (DyIII) have been thoroughly studied. The magnetic
investigations reveal that compound 5 displays slow magnetic
relaxation behavior.
calcd:
C
40.85,
H
2.63; found:
C
40.64,
H
2.81%;
Experimental section
C30H23O17S2Ho (6): calcd: C 40.73, H 2.62; found: C 40.55, H
2.79%; C30H23O17S2Er (7): calcd: C 40.63, H 2.61; found: C
40.36, H 2.84%; IR spectra (KBr, cm−1): compound 1: 3479
(br), 1697 (s), 1618 (s), 1552 (m), 1399 (vs), 1270 (w), 1192 (m),
1165 (m), 1110 (m), 1090 (m), 1034 (w), 870 (m), 776 (m), 713
(w), 613 (w), 543 (w); compound 2: 3515 (br), 1698 (s), 1600 (s),
1552 (m), 1419 (vs), 1278 (w), 1200 (m), 1157 (m), 1112 (m),
1087 (m), 1029 (w), 871 (m), 783 (m), 713 (w), 615 (w), 548 (w);
compound 3: 3484 (br), 1691 (s), 1615 (s), 1542 (m), 1410 (vs),
1268 (w), 1195 (m), 1155 (m), 1114 (m), 1092 (m), 1031 (w), 873
(m), 780 (m), 716 (w), 609 (w), 538 (w); compound 4: 3500 (br),
1695 (s), 1614 (s), 1549 (m), 1408 (vs), 1275 (w), 1189 (m), 1158
(m), 1109 (m), 1085 (m), 1031 (w), 869 (m), 774 (m), 710 (w),
616 (w), 540 (w); compound 5: 3469 (br), 1688 (s), 1609 (s),
1546 (m), 1389 (vs), 1265 (w), 1200 (m), 1163 (m), 1115 (m),
1093 (m), 1030 (w), 865 (m), 768 (m), 709 (w), 608 (w), 535 (w);
compound 6: 3499 (br), 1687 (s), 1621 (s), 1545 (m), 1394 (vs),
1268 (w), 1193 (m), 1160 (m), 1109 (m), 1085 (m), 1027 (w), 863
(m), 770 (m), 717 (w), 619 (w), 537 (w); compound 7: 3484 (br),
1693 (s), 1619 (s), 1557 (m), 1406 (vs), 1275 (w), 1194 (m), 1159
(m), 1114 (m), 1091 (m), 1030 (w), 877 (m), 766 (m), 709 (w),
617 (w), 533 (w).
Materials and methods
All chemicals were commercially available, and used without
further purification. The used water is distilled. Powder X-ray
diffraction patterns were obtained on a D/Max-2500 X-ray
diffractometer using Cu Kα radiation. The Fourier transform
infrared (FT-IR) spectra were recorded with a Bruker Tensor 27
spectrophotometer on KBr disks. The elemental analyses (C, H
and N) were measured by a Perkin-Elmer elemental analyzer.
Thermogravimetric analyses were determined on a Netzsch TG
209 TG-DTA analyzer from room temperature to 800 °C under
nitrogen atmosphere with heating rate of 10 °C min−1. The
emission spectra in the visible region were conducted on a
Cary Eclipse fluorescence spectrophotometer, and the lumi-
nescent lifetimes were taken on an Edinburgh Analytical
Instrument F900. Variable-temperature magnetic suscepti-
bilities
were
performed
on
a
Quantum
Design
MPMS-XL7 magnetometer, and the alternating current (ac)
magnetic measurements were performed on a PPMS-9 ACMS
magnetometer. Diamagnetic corrections were made with
Pascal’s constants for all the constituent atoms.
X-ray diffraction studies
Suitable single crystals of 1–7 were mounted on an Oxford
diffractometer SuperNova TM with a graphite-monochromatic
MoKα radiation (λ = 0.71073 Å) using the ω-scan technique. All
Results and discussion
Description of structures
the structures were solved by direct methods and refined Single crystal X-ray diffraction analyses reveal that compounds
by full-matrix least-squares techniques based on F2 using the 1–7 are isostructural and crystallize in the monoclinic crystal
SHELXS-97 and SHELXL-97 programs.12 All the non-hydrogen system, P21/c space group. Thus, compound 5 as a representa-
atoms were refined with anisotropic parameters while H atoms tive example is selected to describe the crystal structures in
were placed in calculated positions and refined using a riding details. In compound 5, the asymmetric unit consists of one
model. ISOR and SIMU instructions in SHELXL were imposed independent Dy3+, one full deprotonated vspc2− anion, one
on some carbon atoms and oxygen atoms to get reasonable half deprotonated Hvspc− anion, and one coordinated H2O
displacement parameters in compounds 2–7. Detailed crystal- molecule (Fig. 1). The eight-coordinated Dy3+ is surrounded by
lographic data for 1–7 were summarized in Table 1. Selected two monodentate O atoms (O3 and O4A) from two different
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Table 1 Crystallographic data for compounds 1–7
Compound
1 (Pr)
2 (Eu)
3 (Gd)
4 (Tb)
5 (Dy)
6 (Ho)
7 (Er)
Formula
Fw
T (K)
C
30H23O17S2Pr
C30H23O17S2Eu C30H23O17S2Gd C30H23O17S2Tb C30H23O17S2Dy C30H23O17S2Ho C30H23O17S2Er
860.51
124(2)
871.56
876.85
124(2)
878.52
124(2)
882.10
124(2)
884.53
124(2)
886.86
124(2)
124(2)
Crystal system Monoclinic
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Space group
P21/c
a (Å)
b (Å)
c (Å)
α (°)
23.4546(7)
14.1658(6)
9.8960(4)
90
23.428(2)
14.0753(13)
9.8845(8)
90
23.4006(7)
14.1988(5)
9.9356(4)
90
23.3952(15)
14.0348(11)
9.8470(6)
90
23.3391(5)
14.0385(4)
9.8581(3)
90
23.327(2)
14.0248(11)
9.8469(6)
90
23.318(2)
14.0046(15)
9.8371(10)
90
β (°)
95.692(3)
90
3271.8(2)
4
1.747
1.696
94.907(8)
90
3247.5(5)
4
1.783
2.140
94.468(3)
90
3291.2(2)
4
1.770
2.221
94.930(6)
90
3221.3(4)
4
1.811
2.406
94.703(2)
90
3219.09(14)
4
1.820
2.532
94.653(7)
90
3210.9(4)
4
1.830
2.675
94.552(9)
90
3202.3(5)
4
1.840
2.832
γ (°)
V (Å3)
Z
Dcalcd (Mg m−3
)
μ (mm−1
F (000)
)
1720
1736
1740
1744
1748
1752
1756
θ range (°)
Limiting
indices
2.95/25.01
−20 ≤ h ≤ 27,
−16 ≤ k ≤ 15,
−10 ≤ l ≤ 11
13 564/5756
2.89/25.01
−27 ≤ h ≤ 27,
−16 ≤ k ≤ 14,
−11 ≤ l ≤ 11
13 629/5719
2.51/25.01
−27 ≤ h ≤ 23,
−16 ≤ k ≤ 16,
−11 ≤ l ≤ 11
13 237/5785
2.53/25.01
−27 ≤ h ≤ 27,
−15 ≤ k ≤ 16,
−11 ≤ l ≤ 11
12 160/5681
2.90/25.01
−20 ≤ h ≤ 27,
−16 ≤ k ≤ 15,
−10 ≤ l ≤ 11
12 334/5676
3.03/25.01
−27 ≤ h ≤ 23,
−16 ≤ k ≤ 15,
−11 ≤ l ≤ 10
12 179/5655
2.91/25.01
−27 ≤ h ≤ 25,
−16 ≤ k ≤ 16,
−11 ≤ l ≤ 11
13 502/5646
Reflections
collected/
unique
[R(int) = 0.0481] [R(int) = 0.0816] [R(int) = 0.0362] [R(int) = 0.0413] [R(int) = 0.0476] [R(int) = 0.1060] [R(int) = 0.1087]
Completeness 99.8%
99.8%
99.9%
99.9%
99.9%
99.8%
99.9%
to θ = 25.01
GOF on F2
1.055
0.0496, 0.1046
1.061
0.0595, 0.1142
1.056
0.0431, 0.0963
1.036
0.0466, 0.1038
1.033
0.0485, 0.1043
1.017
0.0745, 0.1098
1.045
0.0691, 0.1021
R1a/wR2
b
(I > 2σ(I))
R1/wR2 (all
data)
0.0710, 0.1169
0.1042, 0.1342
0.0586, 0.1061
0.0660, 0.1157
0.0698, 0.1174
0.1452, 0.1420
0.1459, 0.1391
Largest diff.
peak/hole
1.501/−0.659
1.147/−0.846
1.229/−0.642
1.914/−0.780
1.986/−0.873
1.302/−1.032
1.757/−1.184
(e Å−3
)
a R1 = ∑||Fo| − |Fc||/∑|Fo|. b wR2 = {∑[w(Fo2 − Fc2)2]/∑[w(Fo2)2]}1/2
.
Fig. 1 The coordinated environments of Dy3+ in compound 5, all
hydrogen atoms were deleted for clarity. A = −x, −0.5 + y, 2.5 − z.
Scheme 2 Coordination modes of vspc2− anion (a), and Hvspc−
anion (b).
vspc2− anions, three monodentate O atoms (O1, O11, and
O16A) coming from three different Hvspc− anions, two
chelated O atoms (O9A and O10A) from one vspc2− anion, and
one O atom (O2) from one coordinated H2O molecule, forming
a distorted dodecahedron (Fig. 1). The Dy–O bond distances
range from 2.255(5) to 2.538(4) Å, and the O–Dy–O angles are
in the region of 52.61(14)–154.33(17)°, which fall into the
Dy-based compounds range values reported previously.9a,11
In compound 5, vspc2− and Hvspc− anions adopt different
coordination modes, as shown in Scheme 2. The two
carboxylate groups of vspc2− anion bridge two Dy3+ and
chelate one Dy3+, respectively. For Hvspc− anion, one carboxy-
late group bridges two Dy3+, and the other without deprotona-
tion links one Dy3+, in which the C–OH and C–ODy bond length
is 1.311 and 1.225 Å, respectively. The C–O bonds with signifi-
cant difference suggest the H atoms located in the carboxylic
groups were not removed, which was frequently observed in
previous reports.9b,c
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Fig. 2 (a) The 1D chain viewed along the c axis, (b) 2D plane, and (c) 3D
framework in 5. All hydrogen atoms were omitted for clarity.
Fig. 4 The PXRD patterns of experimentation for 1–7 and simulation
of 5.
PXRD patterns of 1–7 are in accord with the corresponding
simulated one obtained from the single-crystal data of com-
pound 5, indicating the purity of the solid samples.
The thermogravimetric analyses of 1–7 were measured
under N2 atmosphere by the heating rate of 10 °C min−1, as
shown in Fig. S1 (ESI†). The TG curves of 1–7 were similar
since they are isomorphic. From room temperature to about
160 °C, no weight loss occurs, suggesting that there are no
guest molecules in the 3D frameworks, which is also proved by
single-crystal data. Between 160 °C and 240 °C, the weight loss
are 1.88%, 1.84%, 1.46%, 1.55%, 1.84%, 2.23% and 2.90%,
corresponding to the theoretical value of removal one co-
ordinated water molecule for 1–7 (1, 2.09%; 2, 2.07%; 3,
2.06%; 4, 2.05%; 5, 2.04%; 6, 2.04%; 7, 2.03%), respectively.
After about 320 °C, the weight loss is sharp, indicating the
decomposition of organic ligands and the collapse of the
frameworks.
Luminescent properties
Fig. 3 The bi-nodal (3,6)-connected topological structure of 5.
The luminescence properties of the solid H2vspc ligand and
compounds 2, 4 and 5 were investigated at room temperature.
Under the exciting wavelength of 320 nm, the H2vspc ligand
gives a maximum emitting peak at 362 nm (Fig. S2†), which is
ascribed to the transition of π* → π.16a The emission spectra of
2, 4 and 5 are shown in Fig. 5, and they display the character-
istic emissions of Eu3+, Tb3+ and Dy3+ with the excitation of
285, 280 and 280 nm, respectively. For 2, there are five emis-
sion peaks, 544, 592, 617, 654 and 699 nm, which are attribu-
Two Dy3+ are spanned by two carboxyl groups to form a 1D
chain along the c axis (Fig. 2(a)), and the Dy3+–Dy3+ distance is
4.931 Å. The adjacent 1D chains are connected by ligands to
generate a 2D plane (Fig. 2(b)), which further linked by ligands
to give a 3D framework (Fig. 2(c)).
Topologically, both vspc2− and Hvspc− anions are regarded
as 3-connected nodes, and the Dy3+ is considered as a 6-con-
nected node. Thus the structure of 5 can be simplified as (3,6)-
connected 3D framework, as shown in Fig. 3, giving the
Schläfli symbol is (42·6)2(44·62·87·102), and the topological type
is flu-3.
5
7
5
7
5
7
5
ted to the transitions of D1 → F1, D0 → F1, D0 → F2, D0
→ F3 and 5D0 → F4, respectively.8e,9a According to the tran-
sition rules of Eu3+, when it is in the centre of inversion, the
transitions mainly are magnetic dipole transitions (5D0 → 7F1),
emitting the orange light; on the contrary, the electric dipole
7
7
Powder X-ray diffraction (PXRD) and thermogravimetric
analyses (TGA)
transitions (5D0
→
7F2) are the major, emitting the red light.
5
7
5
Comparing the transitions of D0 → F1 (592 nm) and D0 →
The purity of crystalline powders of 1–7 was confirmed by 7F2 (617 nm) of 2, the intensity ratio is about 1 : 5, suggesting
PXRD, and the results are shown in Fig. 4. The experimental that Eu3+ is in the low-symmetry and the centre of inversion
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Fig. 6 The variable temperature magnetic susceptibilities of 3–6.
Fig. 5 The luminescent spectra of compounds 2, 4 and 5.
the temperature is decreased, the χMT value of 3 almost keeps
constant until to 50 K, and then slightly decreases below 50 K
to reach 7.61 cm3 K mol−1 at 2 K, indicating antiferromagnetic
interactions operate between adjacent Gd3+.
does not exist, which is in agreement with the results of the
structural analyses.8e,9a,13 For 4, the four characteristic emis-
sion peaks of Tb3+ are 490, 546, 585 and 622 nm, belonging to
As described in the part of the crystal structures, Gd3+ ions
were connected by carboxyl groups into a 1D chain structure in
compound 3, and the Gd3+–Gd3+ distance is 4.969 Å, much
shorter than the distance between adjacent 1D chains (longer
than 13 Å). So, the magnetic interaction between 1D chains
can be neglected, simplifying a 1D chain model. And the 1D
chain model eqn (1) deduced by Fisher20 could be used to
quantitatively analyze the interaction between adjacent Gd3+
with a large spin value of S = 7/2.
5
7
transitions of D4 → FJ (J = 6, 5, 4, 3), respectively, which are
often observed in Tb-based compounds.8e,9a,13a In the case of
5, only two characteristic emissions of Dy3+ are obtained in the
4
visible region, which are ascribed to the transitions of F9/2
→
6H15/2 for 482 nm and 4F9/2 → 6H13/2 for 573 nm.8e,9a,13c
The luminescence lifetimes of compounds 2, 4 and 5 were
gauged under the excitation of 285 nm for 3, 280 nm for 4 and
5 at room temperature, and the plots of the luminescence
decay of them are shown in Fig. S3†. For 2, 4 and 5, the decay
5
5
4
curves of excited states of D0 for Eu3+, D4 for Tb3+ and F9/2
for Dy3+, monitored at 617, 546 and 573 nm, respectively, fit
well with the monoexponential function: I = A + Bexp(−t/τ),14
where A and B are the fitting parameters, and τ is the lumines-
cent lifetime, yielding the lifetimes are 0.53, 0.99 and 0.014 ms
for 2, 4 and 5, respectively. The mono-exponential behavior of
the luminescence decay curves for 2, 4 and 5 indicates one
emission center exists in these compounds,15 which can be
clearly explained by the crystal structures, in which there is
only one crystallographic independent Ln3+ ion.
Ng2β2 1 þ u
χchain
¼
SðS þ 1Þ
ð1Þ
3kT 1 ꢀ u
u ¼ cothðJcSðS þ 1Þ=kTÞ ꢀ kT=JcSðS þ 1Þ
In eqn (1), N is Avogadro’s number, β is the Bohr magne-
tron, k is the Boltzmann constant, and Jc is the exchange coup-
ling parameter between adjacent spins. The best fitting of the
susceptibility data for 3 gives g = 1.992, Jc = −0.02 cm−1
,
and the agreement factor R = ∑[(χMT)obsd − (χMT)calcd)]2/
2
∑[(χMT)obsd
]
= 2.29 × 10−5. The negative and small Jc value
The luminescence lifetimes of 2 and 4 are moderate com-
pared to some previous studies,9a,16 and both of them are in
the millisecond order. For 5, the luminescence lifetime
is much shorter than those of the previous reports,9a,17 and is
only slightly longer than a few reported.18 That is because the
coordinated water molecule can shorten the luminescence
lifetime.18b,19
indicates that very weak antiferromagnetic coupling exists
between adjacent Gd3+, consistent with the previous
reports.21,22 The negative value of θ = −0.69 K (Fig. S4†)
obtained from the Curie–Weiss fitting further proved the exist-
ence of antiferromagnetic interaction in compound 3.
For 4–6, the χMT values of 11.61, 14.05 and 13.83 cm3
K
mol−1 at room temperature, are consistent with the corres-
ponding expected values of uncoupled Tb3+ (S = 3, L = 3, F6,
7
Magnetic properties
6
g = 3/2, χMT = 11.82 cm3 K mol−1), Dy3+ (S = 5/2, L = 5, H15/2
,
Variable temperature magnetic susceptibilities of compounds g = 4/3, χMT = 14.17 cm3 K mol−1) and Ho3+ (S = 2, L = 6, g =
3–6 were investigated at the magnetic field of 1000 Oe in the 5/4, χMT = 14.07 cm3 K mol−1), respectively. Upon cooling, the
temperature range of 2–300 K. The curves of χMT versus T are χMT values of 4 and 5 keep unchanged, and for 6, it gradually
depicted in Fig. 6. For 3, the room temperature χMT value of declines. Then the χMT values undergo a more sudden
7.82 cm3 K mol−1 is close to the theoretical value of 7.88 cm3 K reduction at temperatures below 50 K, reaching values of 6.61,
8
mol−1 for noninteracting Gd3+ (S = 7/2, L = 0, S7/2, g = 2). As 11.34 and 10.82 cm3 K mol−1 for 4–6, respectively. The
1818 | Dalton Trans., 2014, 43, 1814–1820
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Paper
Acknowledgements
This work was supported by the 973 Program (2012CB821702
and 2011CB935902), and NSFC (91122004 and 21271137).
Notes and references
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In summary, seven lanthanide coordination polymers have
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Tb3+ and Dy3+, respectively, and their corresponding lumines-
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≈
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