Syntheses and characterizations of two zinc(II) metal-organic frameworks based on 1,4-naphthalenedicarboxylate and imidazole ligands

Article abstract of DOI:10.1002/zaac.201000315

Two new compounds, namely [Zn(1,4-ndc)(L1)] (1), and [Zn(1,4-ndc)(L2)] ·0.25H₂O (2) [L1 = 2-phenylimidazole, L2 = 1,1'-(1,4-butanediyl)bis(imidazole), and 1,4-ndc = 1,4-naphthalenedicarboxylate] were successfully synthesized under similar hydrothermal conditions. In compound 1, each 1,4-ndc anion links two neighboring Zn^II cations with its carboxylate groups to generate a 2D layer structure. The L1 ligands are attached on both sides of the layers. In compound 2, each carboxylate group of 1,4-ndc connects one Zn^II atom in monodentate mode to form a 1D zigzag chain. Further, the L2 ligands link the chains to generate an expanded diamond net. Four diamond networks interweave to form a 3D interpenetrating diamond framework in an unusual [2+2] mode. Furthermore, the title compounds exhibit good luminescent properties in the range from ultraviolet to visible light and may find potential applications as fluorescent materials. Copyright

Full text of DOI:10.1002/zaac.201000315

ARTICLE
DOI: 10.1002/zaac.201000315
Syntheses and Characterizations of two Zinc(II) Metal-organic Frameworks
based on 1,4-Naphthalenedicarboxylate and Imidazole Ligands
Jingyuan Wang*[a] and Hongpeng You*[a]
Keywords: Metal-organic frameworks; 2-Phenylimidazole; 1,1'-(1,4-Butanediyl)bis(imidazole); 1,4-Naphthalenedicarboxylate;
Luminescence; Zinc
Abstract. Two new compounds, namely [Zn(1,4-ndc)(L1)] (1), and pound 2, each carboxylate group of 1,4-ndc connects one ZnII atom in
[Zn(1,4-ndc)(L2)]·0.25H2O (2) [L1 = 2-phenylimidazole, L2 = 1,1'- monodentate mode to form a 1D zigzag chain. Further, the L2 ligands
(1,4-butanediyl)bis(imidazole), and 1,4-ndc = 1,4-naphthalenedicar- link the chains to generate an expanded diamond net. Four diamond
boxylate] were successfully synthesized under similar hydrothermal networks interweave to form a 3D interpenetrating diamond frame-
conditions. In compound 1, each 1,4-ndc anion links two neighboring work in an unusual [2+2] mode. Furthermore, the title compounds ex-
ZnII cations with its carboxylate groups to generate a 2D layer struc- hibit good luminescent properties in the range from ultraviolet to visi-
ture. The L1 ligands are attached on both sides of the layers. In com- ble light and may find potential applications as fluorescent materials.
sively employed in the construction of a rich variety of in-
triguing architectures. However, the imidazole-containing li-
The rational design and synthesis of metal-organic frame-
gands have not been well studied.[7]
1. Introduction
works (MOFs) have attracted considerable attention due to
Recent studies have demonstrated that mixed organic li-
their interesting topologies and potential applications in non-
gands, especially the mixed polycarboxylate and nitrogen-con-
linear optics, magnetism, molecular recognition, gas adsorp-
taining ones with more tunable factors, are good candidates for
tion, etc.[1] With the development of supramolecular chemistry
the construction of novel MOFs. Following such a mixed-li-
and crystal engineering of MOFs, it is possible to design and
gand strategy, we focused our attention in this study on the
construct novel MOFs with desired topologies and rationally
reactions of the ligand 1,4-naphthalenedicarboxylate (1,4-ndc)
predict the final structures of the product.[2] Generally, the di-
with different imidazole ligands and ZnII salts and made a sys-
versity in the framework structures greatly depends on the se-
tematic investigation on the impact of imidazole ligands on the
lection of the metal, the inorganic counterion, the solvent sys-
structures of the complexes. Herein, we report the syntheses,
tem, and sometimes the metal-to-ligand ratio.[3] In this regard,
crystal structures, and photoluminescent properties of two new
the selection of the ligand is an important factor that may be
ZnII MOFs with two different imidazole ligands, namely,
utilized in determining the framework topology, which has not
[Zn(1,4-ndc)(L1)] (1), and [Zn(1,4-ndc)(L2)]·0.25H2O (2)
been widely employed to date.[4] The changes in functional
[L1 = 2-phenylimidazole and L2 = 1,1'-(1,4-butanediyl)bis(im-
group, flexibility, length, and symmetry of the ligands can re-
idazole)]. Complexes 1 and 2 were characterized by IR spec-
sult in a remarkable class of materials with diverse architec-
troscopy and X-ray crystallography.
tures and functions. Among them, the rigid organic polycar-
boxylates are often employed as bridging ligands to afford a
variety of novel functional complexes due to their versatile
coordination modes.[5] On the other hand, nitrogen-donor li-
2. Experimental Section
gands have been intensely investigated for the construction of
novel MOFs, and the use of nitrogen-donor ligands is an ef-
All reagents and solvents for syntheses were purchased from commer-
fective method because they can satisfy and even mediate the
cial sources and used as received. Powder X-ray diffraction (XRD)
coordination needs of the metal atoms and consequently gener-
data were collected with a Siemens D5005 diffractometer with Cu-Kα
radiation (λ = 1.5418 Å). Inductively coupled plasma (ICP) analysis
ate more meaningful architectures.[6] So far, the rigid nitrogen-
donor ligands (4,4'-bipyridine, pyrazine, etc.) have been exten-
was performed with a Perkin–Elmer Optima 3300DV spectrometer.
Elemental analysis was conducted with a Perkin–Elmer 2400 elemental
analyzer. Thermogravimetric analyses (TGA) were carried out with a
NETZSCH STA 449C TGA/DTA analyzer in air with a heating rate
of 10 °C·min–1. IR spectra were recorded with a Bruker TENSOR 27
Fourier Transform Infrared Spectrometer using KBr pellet. Fluorescent
emission spectra for the solid samples were recorded with a Hitachi
F-4500 luminescence spectrometer.
* Dr. J. Wang
E-Mail: wangjingyuan1208@gmail.com
* Prof. Dr. H. You
E-Mail: hpyou@ciac.jl.cn
[a] State Key Laboratory of Rare Earth Resource Utilization
Changchun Institute of Applied Chemistry
Changchun 130022, P. R. China
Z. Anorg. Allg. Chem. 2011, 637, 415–420
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J. Wang, H. You
ARTICLE
CCDC-785008 and CCDC-785009 contain the supplementary crystal-
lographic data for 1 and 2. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cam-
bridge Crystallographic Data Centre CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK; Fax: +44-1223-336-033; or E-Mail:
deposit@ccdc.cam.ac.uk.
2.1. Syntheses of the Metal Complexes
2.1.1. Synthesis of [Zn(1,4-ndc)(L1)] (1)
A mixture of 1,4-ndc (0.216 g, 1 mmol), L1 (0.15 g, 1 mmol), ZnCl2
(0.136 g, 1 mmol), NaOH (0.08 g, 2.00 mmol), and H2O (12 mL) was
stirred for 1 h and afterwards sealed in a 25 mL Teflon-lined stainless
steel container. The container was heated at 140 °C for 3 days. After
slow cooling, colorless block crystals of 1 were yielded along with
some unidentified yellow powder. The crystalline samples of 1 were
picked for the analysis in ca. 52 % yield. The product was initially
characterized by elemental analyses and ICP and the data were as fol-
lows: found C 59.21; H 3.67; N 6.45; Zn 15.59 %; anal. calcd: C
3. Results and Discussion
3.1 Descriptions of Crystal Structures
3.1.1 Structure of [Zn(1,4-ndc)(L1)] (1)
59.52; H 3.33; N 6.61; O 15.10; Zn 15.43 %. IR (KBr): ν = 3744 (w),
˜
3112 (w), 2853(w), 1610 (m), 1562 (s), 1350 (m), 1224 (m), 1121 (m),
X-ray single crystal diffraction revealed that complex 1 has
a 2D layer structure. The asymmetric unit consists of one
zinc(II) ion, one 1,4-ndc ligand, and one unique L1 ligand. As
shown in Figure 1, the ZnII atom shows a distorted {ZnNO4}
square pyramidal arrangement, which is coordinated by one
nitrogen atom (N1) from one L1 ligand, and four carboxylate
oxygen atoms (O2A, O3A, and O4A) from three different 1,4-
ndc anions. The Zn–O and Zn–N distances range from 1.974
to 2.015 Å, which are similar to the reported values. Both car-
boxylate groups of 1,4-ndc ligand are deprotonated during the
reaction and the ligand adopts a bidentate bridging mode to
link two zinc ions. In this mode, each 1,4-ndc anion links two
neighboring ZnII cations with carboxylate groups to generate a
2D layer structure (Figure 2). The L1 ligands are attached on
both sides of the layers. From the topological view, if the dinu-
clear ZnII ions are considered as four-connected nodes, com-
pound 1 shows a 2D (4,4) topological network. Further, the
resulting (4,4) networks are packed in a parallel fashion (Fig-
ure 3). The adjacent layers are further connected through inter-
molecular N–H···O hydrogen bonds (N2–H2···O4 2.764(4) Å)
to extend the 2D layers in to a 3D supramolecular framework.
833 (m), 783 (w) cm–1.
2.1.2 Synthesis of [Zn(1,4-ndc)(L2)]·0.25H2O (2)
Complex 2 was obtained by a similar procedure to that used for prepa-
ration of 1 except for using L2 (0.185 g, 1 mmol) instead of L1 as
starting material. Colorless block crystals of 2 were manually isolated
and washed with water several times in 39 % yield. Elemental analyses
and ICP data were as follows: found: C 55.21; H 4.54; N 11.60; Zn
13.97 %; anal. calcd: C 55.71; H 4.36; N 11.82; O 14.34; Zn 13.78 %.
IR (KBr): ν = 3742 (w), 3103 (w), 2930 (w), 1650 (s), 1614 (m), 1363
˜
(m), 1318 (m), 1223 (m), 822 (w), 791 (m) cm–1.
2.2. X-ray Crystallography
Single-crystal X-ray diffraction data for compounds 1 and 2 were re-
corded with a Bruker Apex CCD diffractometer with graphite-mono-
chromated Mo-Kα radiation (λ = 0.71073 Å) at 293 K. Absorption cor-
rections were applied using multi-scan technique. All the structures
were solved by Direct Methods with SHELXS-97[8] and refined by
full-matrix least-squares techniques using SHELXL-97[9] within
WINGX. Non-hydrogen atoms were refined with anisotropic tempera-
ture parameters. The disordered carboxylate oxygen atoms (O4 and
O4') in compound 2 were refined using oxygen atoms split over two
sites, with a total occupancy of 1. The hydrogen atoms attached to 3.1.2 Structure of [Zn(1,4-ndc)(L2)]·0.25H2O (2)
carbons were generated geometrically; the aqua hydrogen atoms of 2
were not located from difference Fourier maps.
To study the influence of the arrangement and flexibility of
imidazole ligands in the formation of the final structures, the
ligand L2 was selected to react with 1,4-ndc under similar syn-
thetic conditions, and a structurally different complex [Zn(1,4-
ndc)(L2)]·0.25H2O (2) was obtained. X-ray single crystal dif-
fraction revealed that complex 2 shows an unusual 3D fourfold
interpenetrating diamond structure. The asymmetric unit con-
sists of one zinc ion, one 1,4-ndc ligand and two half L2 li-
gands. As illustrated in Figure 4, each central ZnII atom is co-
ordinated by two oxygen atoms (Zn–O 2.199(3)–2.211(3) Å)
of two different 1,4-ndc anions and two nitrogen atoms (Zn–
N 2.198(4)–2.231(4) Å) of two different L2 ligands to furnish
a disordered tetrahedral arrangement.
Notably, the coordination mode of 1,4-ndc in 2 is entirely
different from that in 1. Each carboxylate group connects one
ZnII atom in monodentate mode to form a 1D zigzag chain.
Further, the L2 ligands link the chains to generate an expanded
diamond net. Figure 5a,b shows a single cage delimited by
four cyclohexane-like windows in chair conformations. Water
molecules are found in the adamantane cages of the network.
As shown in Figure 6, the hexagonal channels of
Detailed crystallographic data and structure refinement parameters for
1 and 2 are summarized in Table 1, and selected bond length and bond
angle data are summarized in Table 2.
Table 1. Crystal data and structure refinements for compounds 1 and 2.
1
2
Formula
Molecular weight
Crystal system
Space group
a /Å
C21H14N2O4Zn C22H20.5N4O4.25Zn
423.71
474.29
Orthorhombic
Pbca
Monoclinic
C2/c
16.6595(6)
12.7896(5)
17.4093(6)
17.779(4)
18.305(4)
15.540(4)
123.389(4)
4222.9(18)
8
b /Å
c /Å
β /°
V /Å3
3709.4(2)
8
1.055
0.0385
0.0615
Z
GOF
1.042
R1 [I > 2σ(I)]a)
0.0549
0.1598
wR2 (all data)b)
a) R1 = Σ||Fo|–|Fc||/Σ|Fo|. b) wR2 = |Σw(|Fo|2–|Fc|2)|/Σ|w(Fo ) |
2 2 1/2.
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Zinc(II) MOFs with 1,4-Naphthalenedicarboxylate and Imidazole Ligands
Table 2. Selected bond lengths /Å and bond angles /° for compounds 1 and 2.
1
2
O(1)–Zn(1)
1.991(2)
2.032(2)
2.093(2)
2.196(2)
1.998(2)
2.032(2)
2.093(2)
2.196(2)
101.44(11)
102.85(9)
95.58(10)
128.63(9)
124.32(11)
95.25(9)
90.62(9)
101.95(10)
155.34(8)
60.51(8)
N(1)–Zn(1)
2.002(4)
2.011(4)
1.981(4)
1.917(5)
1.917(5)
110.7(3)
103.3(3)
122.2(2)
122.4(2)
96.23(19)
103.35(17)
O(2)–Zn(1)#2
N(3)–Zn(1)
O(3)–Zn(1)#1
O(1)–Zn(1)
O(4)–Zn(1)#1
O(3)–Zn(1)#3
Zn(1)–N(1)
Zn(1)–O(3)#4
Zn(1)–O(2)#2
O(3)#4–Zn(1)–O(1)
O(3)#4–Zn(1)–N(1)
O(1)–Zn(1)–N(1)
O(3)#4–Zn(1)–N(3)
O(1)–Zn(1)–N(3)
N(1)–Zn(1)–N(3)
Zn(1)–O(3)#3
Zn(1)–O(4)#3
O(1)–Zn(1)–N(1)
O(1)–Zn(1)–O(2)#2
N(1)–Zn(1)–O(2)#2
O(1)–Zn(1)–O(3)#3
N(1)–Zn(1)–O(3)#3
O(2)#2–Zn(1)–O(3)#3
O(1)–Zn(1)–O(4)#3
N(1)–Zn(1)–O(4)#3
O(2)#2–Zn(1)–O(4)#3
O(3)#3–Zn(1)–O(4)#3
Symmetry transformations used to generate equivalent atoms for 1: #1 x, –y–1/2, z–1/2; #2 –x+1, –y, –z; #3 x, –y–1/2, z+1/2. Symmetry trans-
formations used to generate equivalent atoms for 2: #1 –x+1/2, –y–1/2, –z; #2 –x+1/2, –y–1/2, –z+1; #3 x+1/2, –y+1/2, z+1/2; #4 x–1/2, –y+1/2,
z–1/2.
Figure 1. Coordination environment of the ZnII ion in compound 1.
Figure 3. The stacking mode of two layers of 1.
Figure 2. View of a single layer of 1.
Figure 4. Coordination environment of the ZnII ion in compound 2.
Z. Anorg. Allg. Chem. 2011, 415–420
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J. Wang, H. You
ARTICLE
Figure 5. (a) Single adamantanoid cage in compound 2. (b) Schematic representation of single adamantanoid cage in compound 2.
25.9 Å × 20.6 Å are expanded from the diamond net (corre-
It should be noted that the N-donor ligand plays an important
sponding to the longest intracage Zn···Zn distances) (Figure 6). function in the formation of the final structure. In compounds
Because of the large windows in the diamond network the in- 1 and 2, the structural differences are primarily affected by the
terweaving results are not surprising. Four diamond networks introduction of the N-donor ligands. L1 is a rigid monodentate
interweave to form a 3D interpenetrating diamond framework imidazole ligand with a phenyl group, whereas L2 is a flexible
in an unusual [2+2] mode, as shown in Figure 7a,b. This inter- bidentate imidazole ligand. The additional imidazole groups in
penetration mode differs from the normal mode and can be the backbone may significantly increase the dimensions of
described as two sets of normal 2- and twofold nets, that is, their structures, leading to structural differences in their com-
an unusual [2+2] mode of interpenetration.
plexes. In compound 1, the L1 ligands are attached on both
sides of the layers formed by the 1,4-ndc anions and ZnII cati-
ons. Nevertheless, when a flexible L2 ligand was used under
the same reaction condition, the structurally different com-
pound 2 was obtained. In 2, the L2 ligands link the 1D zigzag
Zn-1,4-ndc chains to form a 3D diamond-like structure.
3.2. PXRD Patterns of Compounds 1 and 2
The simulated and experimental PXRD patterns of com-
pounds 1 and 2 are shown in Figure 8. The experimental
PXRD patterns are in good agreement with the simulated ones
except for the relative intensity variation because of preferred
orientations of the crystals. For compounds 1 and 2, the final
products include crystal samples of 1 and 2 and a small amount
of powder impurities, respectively. Attempts to prepare mono-
phase materials failed. However, the yields of compounds 1
and 2 were improved when hydrothermal syntheses were used.
Figure 6. Schematic representation of the diamond net of 2.
3.3. Thermal Stability Analysis
To characterize compounds 1 and 2 in more detail, TGA
studies were carried out in nitrogen from 35 to 800 °C (Fig-
ure 9). The TG curve of compound 1 exhibits one weight loss
stage in the temperature range 290–517 °C. The weight loss of
79.10 % can be assigned to the decomposition of 2-phenylim-
idazole and 1,4-naphthalenedicarboxylate ligands (weight loss
calcd. 80.80 %). The TG curve of compound 2 exhibits two
weight loss stages in the temperature range 320–650 °C. The
total weight loss of 2 is 81.42 %, it can be assigned to the
decomposition of 1,1'-(1,4-butanediyl)bis(imidazole) and 1,4-
naphthalenedicarboxylate ligands (weight loss calcd. 81.90 %).
Figure 7. (a) Four interpenetrating diamondoid cages in compound 2.
(b) Schematic representation of the four interpenetrating diamondoid
cages in compound 2.
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Zinc(II) MOFs with 1,4-Naphthalenedicarboxylate and Imidazole Ligands
Figure 8. Experimental and simulated XRD patterns for 1 (a) and 2 (b).
gands show contribution to the fluorescence of compounds 1
and 2 simultaneously. The difference in their emissions is prob-
ably due to the differences in organic ligands and coordination
environment around the metal ions, because the photolumines-
cence behavior is closely associated with the metal ions and
the organic ligands coordinated around them. These observa-
tions suggest that these compounds could be anticipated as po-
tential fluorescent materials.
4. Conclusions
Two new zinc-organic compounds were successfully crystal-
lized through the variation of the N-donor ligands. In com-
pound 1, 1,4-ndc anions link ZnII cations to generate a 2D
layer structure. The 2-phenylimidazole ligands are attached on
both sides of the layers. In compound 2, each carboxylate
group of 1,4-ndc connects one ZnII atom in monodentate mode
to form a 1D zigzag chain. Further, the 1,1'-(1,4-butane-
diyl)bis(imidazole) ligands link the chains to generate an ex-
panded diamond net. Four diamond networks interweave to
Figure 9. Thermogravimetric analysis curves for compounds 1 and 2.
3.4. Photoluminescent Properties
The photoluminescent properties of compounds 1 and 2 were form a 3D interpenetrating diamond framework in an unusual
investigated at room temperature. As shown in Figure 10, the [2+2] mode. The results suggest that the structural diversifica-
title compounds show interesting photoluminescence. The tion of MOFs may result from the different coordination modes
emission spectrum of compound 1 shows a broad signal at of organic ligands and the coordination arrangement of metal
385 nm when an excited at 353 nm. When excited at 272 nm, ions. Our current studies on ligand effect are helpful in achiev-
compound 2 exhibits a main signal at about 324 nm. The emis- ing further insights into the rational design and construction of
sion bands of compounds 1 and 2 are assigned to ligand-to- diverse MOFs through the intelligent selection of the ligands
metal-charge-transfer (LMCT). Both N-donor and O-donor li- under corresponding conditions. Moreover, the title com-
Figure 10. Excitation and emission spectra of compounds 1 (a) and 2 (b) at room temperature.
Z. Anorg. Allg. Chem. 2011, 415–420
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J. Wang, H. You
ARTICLE
Carlucci, G. Ciani, D. M. Proserpio, CrystEngComm 2003, 5, 269.
[3] a) S. R. Batten, K. S. Murray, Coord. Chem. Rev. 2003, 246, 103;
b) M. L. Tong, X. M. Chen, S. R. Batten, J. Am. Chem. Soc. 2003,
125, 16170.
pounds possess good luminescent properties and may find po-
tential applications in the fields of lighting, displays, or bio-
medicine.
[4] a) C.-D. Wu, W. Lin, Angew. Chem. Int. Ed. 2007, 46, 1075;
b) B. F. Abrahams, S. R. Batten, M. J. Grannas, H. Hamit, B. F.
Hoskins, R. Robson, Angew. Chem. Int. Ed. 1999, 38, 1475;
c) S. R. Batten, B. F. Hoskins, R. Robson, Angew. Chem. Int. Ed.
Engl. 1997, 36, 636.
[5] a) P. Jensen, D. J. Price, S. R. Batten, B. Moubaraki, K. S. Murray,
Chem. Eur. J. 2000, 6, 3186; b) J. M. Taylor, A. H. Mahmoud-
khani, G. K. H. Shimizu, Angew. Chem. Int. Ed. 2007, 46, 795;
c) M. Dan, C. N. R. Rao, Angew. Chem. Int. Ed. 2006, 45, 281.
[6] a) S. Q. Liu, T. Kuroda-Sowa, H. Konaka, Y. Suenaga, M. Maek-
awa, T. Mizutani, G. L. Ning, M. Munakata, Inorg. Chem. 2005,
44, 1031; b) X. M. Chen, G. F. Liu, Chem. Eur. J. 2002, 8, 4811.
[7] J.-F. Ma, J. Yang, G.-L. Zheng, L. Li, J.-F. Liu, Inorg. Chem. 2003,
42, 7531.
Acknowledgement
This work was supported by the National Natural Science Foundation
of China (Grant No. 20771098) and the Fund for Creative Research
Groups (Grant No. 20921002).
References
[1] a) O. M. Yaghi, M. O’Keeffe, N. W. Ockwig, H. K. Chae, M. Ed-
daoudi, J. Kim, Nature 2003, 423, 705; b) S. R. Batten, R. Robson,
Angew. Chem. Int. Ed. 1998, 37, 1460; c) L. Carlucci, G. Ciani,
D. M. Proserpio, Coord. Chem. Rev. 2003, 246, 247; d) C. N. R.
Rao, S. Natarajan, R. Vaidhyanathan, Angew. Chem. Int. Ed. 2004,
43, 1466.
[2] a) S. A. Bourne, J. Lu, B. Moulton, M. J. Zaworotko, Chem. Com-
mun. 2001, 861; b) N. W. Ockwig, O. Delgado-Friederichs, M.
O’Keeffe, O. M. Yaghi, Acc. Chem. Res. 2005, 38, 176; c) S. Kita-
gawa, R. Kitaura, S. I. Noro, Angew. Chem. Int. Ed. 2004, 43,
2334; d) O. R. Evans, W. Lin, Acc. Chem. Res. 2002, 35, 511; e) L.
[8] G. M. Sheldrick, SHELXS-97, Program for X-ray Crystal Structure
Solution, University of Göttingen, Göttingen, Germany, 1997.
[9] G. M. Sheldrick, SHELXL-97, Program for X-ray Crystal Structure
Refinement, University of Göttingen, Göttingen, Germany, 1997.
Received: August 12, 2010
Published Online: November 25, 2010
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Z. Anorg. Allg. Chem. 2011, 415–420