Journal of Molecular Structure 1108 (2016) 516e520
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Two novel 2D lanthanide sulfate frameworks: Syntheses, structures,
and luminescence properties
Zhong-Yi Li, Chi Zhang, Fu-Li Zhang, Fu-Qiang Zhang, Xiang-Fei Zhang, Su-Zhi Li,
Guang-Xiu Cao, Bin Zhai*
College of Chemistry and Chemical Engineering, Shangqiu Normal University, Shangqiu, 476000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 October 2015
Received in revised form
17 December 2015
Accepted 19 December 2015
Available online 22 December 2015
Two novel lanthanidesulfate compounds, [Ln2(SO4)3(H2O)8] (Ln ¼ Tb (1) and Dy (2)), have been synthesized under hydrothermal reactions. X-ray crystal structure analyses reveal that 1 and 2 are
isomorphous and crystallize in monoclinic C2/c pace group, showing a layered structure. The layers bear
a rare quasi-honeycomb metal arrangement, which is fastened by m3 ¼ h1:h1:h1 and m2 ¼ h1:h1 sulfates. If
assigning the m3 ¼ h1:h1:h1 sulfate as a 3-connected node and the Ln3þ ion as a 4-connected node, the
network can be rationalized as a binodal (3,4)-connected V2O5 topology with a Sch€
afli symbol of
(42$63$8) (42$6). In addition, the infrared, thermogravimetric analysis and luminescent properties were
also studied. Complexes 1 and 2 exhibit outstanding thermal stability and characteristic terbium and
dysprosium luminescence.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
Lanthanide
Sulfate
2D framework
Luminescence
1. Introduction
In recent years, inorganic open-framework materials based
sulfate anion have attracted great interest because of not only their
fascinating structural diversities but also their various potential
applications such as cathode materials, magnetic properties and
luminescence properties [1e6]. As a simple tetrahedral oxo-anion,
the sulfate anion displays a variety of coordination modes and bears
excellent affinity to transition and rare-earth metal ions. Up to now,
a number of transition metal and rare earth sulfates have been
prepared and characterized [7e19]. Compared with transition
metals, rare-earth elements adopt more various coordination
numbers from 8 to 12 and flexible LneO bond lengths to give
lanthanide sulfates with new topologies [7e9,14]. In addition, the
lanthanide-based complexes usually exhibit interesting luminescence behavior and have important applications as fluorescent
probes in many emission-related fields, especially in biochemistry
[7,8]. Consequently, it is crucial to design novel lanthanide sulfates
with an intriguing variety of structures to explore their optical
properties and understand the formation mechanism [8,14].
To our knowledge, most of the lanthanide sulfate frameworks
were synthesized under the presence of the organic amines, which
* Corresponding author.
E-mail address: zhaibin_1978@163.com (B. Zhai).
http://dx.doi.org/10.1016/j.molstruc.2015.12.058
0022-2860/© 2015 Elsevier B.V. All rights reserved.
usually played a role of true templates, structural directing agents
or space fillers [8,20,21]. Herein, two two-dimensional (2D)
lanthanide sulfate frameworks, [Ln2(SO4)3(H2O)8] (Ln ¼ Tb (1) and
Dy (2)), were prepared by Ln(NO3)3 and amino tris(methylene
phosphonic acid) (ATMP) with a mole ratio of 6:1 under hydrothermal conditions. The pH value is about 1.5 adjusted by sulfuric
acid aqueous solution. Interestingly, the structures of the products
did not contain the ATMP ligand, while without it no products
could be given, indicating that ATMP may play an important role
over the synthesis procedure of 1 and 2.
2. Experimental
2.1. Materials and methods
All chemicals were obtained from commercial sources and used
without further purification. FT-IR spectra were recorded in the
range of 4000e400 cm1 on a JASCO FT/IR-430 spectrometer with
KBr pellets. X-ray Powder Diffraction (XRPD) measurements were
carried out on a Riguku D/Max-2400 X-ray Diffractometer using Cu
Ka (l ¼ 1.5418 Å) at room temperature. Thermogravimetric analyses were performed under a flow of nitrogen (40 mL/min) at a
ramp rate of 10 C/min, using a NETZSCH STA 449F3 instrument.
Solid state luminescence properties were carried out using a F4600 FL Spectrophotometer.
Z.-Y. Li et al. / Journal of Molecular Structure 1108 (2016) 516e520
2.2. Syntheses
517
Table 2
Selected bond lengths (Å) and angles ( ) for 1.
2.2.1. Syntheses of 1 and 2
The following is the general progress for the preparation of 1
and 2. 600 mL Ln(NO3)3 (1 M, 0.6 mmol) (Ln ¼ Tb and Dy) aqueous
solution and 100 mL amino tris(methylene phosphonic acid) (1 M
0.1 mmol) aqueous solution were added into a 15 mL vial with 2 mL
deionized water. 1 M sulfuric acid aqueous solution was added
dropwisely to adjust the pH value of the resulting solution to about
1.5 under stirring. The vial was sealed and heated at 90 C in an
oven for 24 h, then cooled to room temperature. Colourless block
crystals of the products were obtained. [Tb2(SO4)3(H2O)8] (1): Yield,
36% based on Tb. [Dy2(SO4)3(H2O)8] (2): Yield, 32% based on Dy.
2.2.2. X-ray structure determinations
The intensity data were measured at 298(2) K on a Bruker
SMART APEX II CCD area detector system with graphitemonochromated Mo-Ka (l ¼ 0.71073 Å) radiation. Data reduction
and unit cell refinement were performed with Smart-CCD software
[22]. The structures were solved by direct methods using SHELXS97 and were refined by full-matrix least squares methods using
SHELXL-97 [23]. For 1 and 2, all non-hydrogen atoms were refined
anisotropically. Hydrogen atoms on the coordinated water molecules were initially found on Fourier difference maps and then
restrained by using the DFIX instruction. A summary of the
important crystal and structure refinement data of 1 and 2 were
given in Table 1. Selected bond lengths and angles for 1 were listed
in Table 2.
3. Result and discussion
3.1. Crystal structures
Single-crystal X-ray diffraction analyses reveal that 1 and 2 are
isostructural and crystallize in the monoclinic C2/c pace group.
Therefore, we take 1 as a representative to describe their structures
in detail. Compound 1 features a (3,4)-connected 2D network
3þ
which is formed by 3-connected SO2
4 anion and 4-connected Tb
ion (Fig. 1). The asymmetric unit contains 12.5 non-hydrogen
atoms, which all are owned by the inorganic framework,
including one terbium atom, four oxygen atoms from four terminal
water molecules and one point five sulfate groups. As shown in
Fig. 1a, each Tb3þ ion is eight-coordinated and have a distorted
square antiprismatic {O8} donor set, completed by four terminal
Formula
Tb2H16O20S3
Mr.
750.15
Cryst. system
Monoclinic
Space group
C2/c
a/Å
13.5255(11)
b/Å
6.7222(6)
c/Å
18.2758(15)
a/
90
b/
102.129(2)
g/
90
3
V (Å )/Z
1624.6(2)/4
3
dcalcd., g/cm
3.067
F(000)
1416.0
a
R1, (I > 2s (I))
0.0229(1355)
b
wR2(all data)
0.0626(1402)
Max/mean shift in final cycle
0.002/0.000
P
P
a
R1 ¼ (jjFojjFcjj)/ jFoj.
P
P
b
wR2 ¼ f w½ðF2o F2c Þ= w½ðF2o Þ2 g0:5 .
2.307(4)
2.331(4)
2.368(3)
2.444(4)
79.92(14)
70.70(13)
79.71(15)
144.11(12)
79.43(13)
99.79(13)
147.83(13)
75.92(12)
134.15(13)
140.74(13)
79.20(13)
74.59(12)
76.27(13)
68.47(12)
Tb1eO5
Tb1eO9
Tb1eO2
Tb1eO10
O1eTb1eO7
O1eTb1eO9
O7eTb1eO9
O5eTb1eO4
O9eTb1eO4
O5eTb1eO2
O9eTb1eO2
O1eTb1eO8
O7eTb1eO8
O4eTb1eO8
O1eTb1eO10
O7eTb1eO10
O4eTb1eO10
O8eTb1eO10
2.321(3)
2.366(4)
2.430(3)
2.484(3)
88.23(15)
146.85(13)
109.14(16)
125.67(13)
68.55(12)
141.25(12)
80.61(15)
70.19(12)
74.34(15)
74.03(12)
73.26(12)
142.97(13)
133.13(12)
125.26(12)
water molecules and four oxygen atoms from four sulfate anions.
The TbeO and SeO bond lengths are in the range of 2.307(4)e
2.484(3) and 1.458(4)e1.472(4) Å, respectively, which are similar to
those reported for other lanthanide compounds based on sulfate
anion [7,8,19].
The sulfates in 1 adopt two coordination modes: m3 ¼ h1:h1:h1
and m2 ¼ h1:h1 (Scheme 1). The m3 ¼ h1:h1:h1 one bridges three Tb3þ
ions to give a Tb3 triangle with the average Tb$$$Tb distance of 5.78
(2) Å. Each of the Tb3 triangles is fastened only by one m3 ¼ h1:h1:h1
sulfate in the center and the neighboring Tb3 ones share one edge
to result in a ladderlike chain (Fig. 1b). Every m2 ¼ h1:h1 sulfate links
two Tb3þ ions from two neighboring ladderlike chains. The Tb$$$Tb
distance is 6.12 (1) Å. The adjacent ladderlike chains are further
linked together by the m2 ¼ h1:h1 sulfates to form a 2D layer
structure (Fig. 1c).
To get better insight of this 2D framework, topology analysis has
been programmed by using TOPOS software [24]. As shown in
Fig. 2, the framework can be rationalized as a binodal (3,4)-connected V2O5 topology by assigning the m3 ¼ h1:h1:h1 sulfate as a 3connected node and the Tb3þ ion as a 4-connected node with a
€fli symbol of (42$63$8)(42$6).
Scha
When the lanthanide connectivity alone is considered in the
structure, a quasi-honeycomb arrangement is observed (Fig. 3). To
our knowledge, the formation of such network in lanthanide containing compounds is rarely reported.
3.2. Infrared spectroscopy
Table 1
Crystal data and structure refinement for 1 and 2.
1
Tb1eO1
Tb1eO7
Tb1eO4
Tb1eO8
O1eTb1eO5
O5eTb1eO7
O5eTb1eO9
O1eTb1eO4
O7eTb1eO4
O1eTb1eO2
O7eTb1eO2
O4eTb1eO2
O5eTb1eO8
O9eTb1eO8
O2eTb1eO8
O5eTb1eO10
O9eTb1eO10
O2eTb1eO10
2
Dy2H16O20S3
757.31
Monoclinic
C2/c
13.4951(15)
6.7070(8)
18.240(2)
90
102.050(3)
90
1614.5(3)/4
3.116
1424.0
0.0125(1384)
0.0342(1404)
0.001/0.000
Complexes 1 and 2 have similar FT-IR spectra showing only
slight shifts in some band positions (Fig. S1). The strong and broad
absorption bands in the range of 3000e3500 cm1 in 1 and 2 are
attributed to the characteristic peaks of OH vibration. The band at
around 1640 cm1 is due to the bending modes of water molecules
coordinated to metal ions. The strong band at about 1145 cm1 and
middle band at 610 cm1 correspond to the vibration modes of the
SeO groups ions. These assignments are consistent with those reported previously [6,8,25].
3.3. Thermal properties
The thermal stabilities of 1 and 2 were examined by thermogravimetric (TG) analysis in a nitrogen atmosphere from 25 to
1000 C. As shown in Fig. 4, the TG curves of 1 and 2 are similar and
three mass steps are observed. In the first step, the weight loss of 1
and 2 in the range of 25e230 C are 19.24% and 19.08%, respectively,
518
Z.-Y. Li et al. / Journal of Molecular Structure 1108 (2016) 516e520
Fig. 1. (a) Coordination environment of Tb3þ ion in 1. Symmetry codes: A, 0.5x, 0.5y, 1z; B, x, 1þy, z; C, 1x, y, 1.5z; (b) The one-dimensional ladderlike chain in 1 viewed
along a axis; (c) View of the 2D lanthanide sulfate layer in the ab plane.
Scheme 1. The coordination modes of SO2
4 anion.
Z.-Y. Li et al. / Journal of Molecular Structure 1108 (2016) 516e520
3þ
Fig. 2. Schematic representation of (3,4)-connected net. Yellow, SO2
ion
4 ; pink, Tb
(For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.).
519
Fig. 5. The solid-state photoluminescence spectrum of 1 at room temperature, excited
at 370 nm.
and 900 C, indicating that they are thermal stable even up to
900 C. It is higher than other reported lanthanide sulfate polymers,
whose structures usually have collapsed after 500 C [18e20]. After
900 C, the materials shows a striking weight loss, indicating
complete decomposition of the polymers.
3.4. Luminescence properties
Fig. 3. The quasi-honeycomb layer of the lanthanide connectivity in 1.
The solid-state luminescent spectra of 1 and 2 were investigated
at room temperature. As shown in Fig. 5, compound 1 shows green
luminescence and four narrow emission bands centered at 491,
544, 583 and 621 nm, which are attributed to 5D4/7FJ (J ¼ 6, 5, 4, 3)
transitions of Tb3þ ion, respectively. Comparatively, compound 1
shows a very sharp and strong emission band, 5D4/7F5, which is in
great agreement with the reported Tb3þ compounds previously
[8,13]. As shown in Fig. 6, the emission peaks of compound 2 at 480
and 574 nm are assigned to the 4F9/2/6HJ (J ¼ 15/2, 13/2) transitions of the Dy3þ ion, respectively, and the spectrum is dominated
by the 4F9/2 / 6H15/2 transition at 480 nm, which gives a blue
luminescence output for the solid sample. The luminescence in the
green and blue light regions suggests that 1 and 2 may be excellent
candidates for green or blue fluorescent materials, respectively.
Fig. 4. TG curves of 1 and 2. Temperature variation from 25 to 1000 C at a heating rate
of 10 C min1 in a N2 atmosphere.
which could be ascribed to the loss of four coordinated water
molecules for each formula unit (calculated 19.21% for 1 and 19.03%
for 2). Then, the weights of 1 and 2 keep constant between 230 C
Fig. 6. The solid-state photoluminescence spectrum of 2 at room temperature, excited
at 365 nm.
520
Z.-Y. Li et al. / Journal of Molecular Structure 1108 (2016) 516e520
4. Conclusion
In summary, We have successfully obtained two novel 2D
lanthanide sulfate frameworks [Ln2(SO4)3(H2O)8] (Ln ¼ Tb and Dy)
by means of a hydrothermal method. These compounds have a
quasi-honeycomb metal arrangement and display excellent thermal stability. The metal arrangement is fastened by m3 ¼ h1:h1:h1
and m2 ¼ h1:h1 sulfates. Moreover, these two compounds displays
characteristic terbium and dysprosium luminescence at room
temperature, respectively.
Acknowledgments
This work was supported by the National Natural Science
Foundation of China (NSFC) (grant numbers 21401126, 21371114,
21471095, 21201116, 21271125, 21571123 and 21501117), Natural
Science Research Program of Education Department of Henan
province (2010A150018), Scientific and Technological Projects of
Science and Technology Department of Henan province
(122102210255), Key Teacher Project of Shangqiu Normal University (2012GGJS15).
Appendix A. Supplementary data
IR spectra and PXRD patterns. CCDC 1430690 (1) and 1430689
(2) contain the supplementary crystallographic data for this paper.
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/.
Appendix B. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.molstruc.2015.12.058.
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