Open-Framework Cadmium Succinates with Interpenetrating Frameworks Formed by Tetrahedral [ClCd4O24] and [BrCd4O24] Clusters R. Vaidhyanathan, Srinivasan Natarajan, and C. N. R. Rao*
CRYSTAL GROWTH & DESIGN 2003 VOL. 3, NO. 1 47-51
Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P. O., Bangalore 560 064, India Received July 24, 2002
ABSTRACT: By carrying out a metathetic reaction between sodium succinate and CdCl2 or CdBr2 in an n-butanolwater mixture, two novel open-framework cadmium succinates, [Na3Cd5(C4H4O4)6Cl], I, and [Na3Cd5(C4H4O4)6Br], II, have been isolated. Both of these compounds possess interpenetrating three-dimensional open-framework structures wherein tetrahedral Cl(Br)Cd4O24 clusters are connected by succinate linkages. The tetrahedral cluster itself is formed of four CdO6 octahedra surrounding a halogen atom. The three-dimensional cadmium succinate framework incorporates sodium ions. Four sodiums surround the second nearest neighbor halogen atom, forming a Na4Cl(Br) tetrahedron. Introduction The pursuit of open crystalline assemblies extending across a wide variety of organic and inorganic compositions is motivated by the interest in creating structures with cavities and channels of potential use in nanotechnology, shape and size selective catalysis, separations, and molecular recognition.1-5 One of the recent trends has been to design hybrid architectures employing inorganic secondary building units (SBUs) and linking them with suitable rigid organic ligands into threedimensional (3D) structures.4,5 Such frameworks are often stabilized by solvent molecules, organic amines, or metal ions. One of the interesting strategies employed to generate novel hybrid inorganic-organic frameworks has been to connect inorganic metal-ligand clusters via dicarboxylate ligands.4 In the context of hybrid materials, the new family of cadmium oxalates wherein the metal oxalate frameworks incorporate extended alkali halide structures of various dimensionalities is noteworthy.6,7 Some of the oxalates contain Cd6O18 clusters, which incorporate halide ions. These cadmium oxalates were obtained by carrying out metathetic reactions of alkali metal oxalates with cadmium halides under hydrothermal conditions. Such reactions yield other novel hybrid structures as well. In this paper, we describe two new interpenetrating 3D open-framework cadmium succinate structures, [Na3Cd5(C4H4O4)6Cl], I, and [Na3Cd5(C4H4O4)6Br], II, formed by Cl(Br)Cd4O24 clusters. Experimental Section Compounds I and II were prepared by the metathetic reaction between sodium succinate and CdCl2(Br2) under hydrothermal conditions. In a typical synthesis of I, 0.1053 g of Na2CO3 was dissolved in a mixture of 2 mL of n-butanol and 0.5 mL of water. To this, 0.1173 g of succinic acid was added under continuous stirring. The contents were stirred for 20 min, followed by the addition of 0.2 g of CdCl2‚H2O. To this mixture, 0.11 mL of glacial acetic acid was added and the * To whom correspondence should be addressed. E-mail: cnrrao@ jncasr.ac.in.
contents were stirred to attain homogeneity. The final mixture of the composition CdCl2‚H2O:Na2CO3:H6C4O4:1.93CH3COOH: 22n-C4H9OH:28 H2O was sealed in a PTFE-lined stainless steel autoclave and heated at 150 °C for 72 h. The resulting product, a crop of crystals with truncated octahedral shape, was filtered, washed, and dried under ambient conditions. The yield was about 40%. Compound II was obtained in 15% yield by a similar procedure using CdBr2‚4H2O in place of CdCl2‚ H2O. The role of acetic acid in the syntheses of I and II is still not clear, but in its absence, we could not obtain these compounds. Elemental microanalysis showed Anal. calcd for I: C, 21.1%; H, 1.8%. Found: C, 21.8%; H, 1.8%. Anal. calcd for II: C, 20.5%; H, 1.7%. Found: C, 20.1%; H, 1.8. Initial characterizations of I and II were carried out using powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), and IR spectroscopy. The powder XRD patterns indicated that the products were new materials and were entirely consistent with the structures determined using the singlecrystal XRD. The simulated and the experimental powder XRD patterns for I are presented in Figure 1. A least-squares fit (Cu KR) of the XRD patterns, using the hkl indices generated from the single-crystal structure, gave the following lattice parameters: a ) 11.842 (2) Å, b ) 11.842 (2) Å, c ) 11.842 (2) Å, R ) β ) γ ) 90.000° for I; a ) 11.819 (5) Å, b ) 11.819 (5) Å, c ) 11.819 (5) Å, R ) β ) γ ) 90.000° for II. IR spectra (KBr pellet) showed characteristic features of the dicarboxylate units.8 The various bands observed were νas(CO2-) at 1559(s) cm-1 (I) and 1545(s) cm-1 (II); νs(CO2-) at 1439(s) cm-1 (I) and 1423(s) cm-1 (II); νs(CO) + ν(CC) at 1323(w) cm-1 (I) and 1324(w) cm-1 (II); νs(CO) + δ(O-CdO) at 1253(w) cm-1 (I) and 1252(w) cm-1 (II); νas(CH2) at 2974(m) cm-1 (I) and 2938(m) cm-1 (II); and νs(CH2) at 2930(m) cm-1 (I) and 2849(m) cm-1 (II). Bands due to metal-oxygen and metal-halogen vibrations are also found in the 280-700 cm-1 region. TGA was carried out under a flow of nitrogen (50 mL min-1) from 25 to 700 °C (heating rate ) 5 °C min-1). Both I and II showed two distinct mass losses. For I, the mass loss in the range of 380-500 °C (53.3%) occurs due to the loss of the succinate unit (calcd 51.1%). For II, the mass loss in the range of 350-500 °C (51.8%) is due to the loss of succinate units (calcd 49.5%). A broad tail in the 500-600 °C range is observed in both cases due to the loss of the halogen. The powder XRD pattern of the calcined samples of I and II was crystalline and corresponded to Na2CdO2 (JCPDS: 36-1199). Single-Crystal Structure Determination. A suitable single crystal of each compound was carefully selected under a polarizing microscope and glued at the tip of a thin glass fiber with cyano-acrylate (super glue) adhesive. Single-crystal
10.1021/cg0200309 CCC: $25.00 © 2003 American Chemical Society Published on Web 11/01/2002
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Figure 1. Powder XRD patterns of I: (a) simulated and (b) experimental. Table 1. Crystal Data and Structure Refinement Parameters for I and II empirical formula crystal system space group crystal size (mm3) a (Å) volume (Å3) Z formula mass Fcalcd (g cm-3) λ (Mo KR) (Å) µ (mm-1) total data collected observed data (I > 2σ(I)) refinement method R indexes [I > 2σ(I)] R (all data) goodness of fit (Sobs) no. of variables
I
II
[Na3Cd5(C4H4O4)6(Cl)] cubic I23 (no. 197) 0.08 × 0.0.08 × 0.08 11.8931 (10) 1682.23 (2) 12 1363.09 2.691 0.71073 3.329 3570 408 full-matrix least-squares on |F2| R1 ) 0.0180, wR2 ) 0.0448 R1 ) 0.0205, wR2 ) 0.0467 1.230 45
[Na3Cd5(C4H4O4)6(Br)] cubic I23 (no. 197) 0.11 × 0.11 × 0.11 11.8526 (10) 1665.10 (2) 12 1407.64 2.807 0.71073 4.482 3598 415 full-matrix least-squares on |F2| R1 ) 0.0543, wR2 ) 0.1391 R1 ) 0.0543, wR2 ) 0.1391 1.186 45
a R ) ||F | - |F ||/|F |. b wR ) {[w(F 2 - F 2)2]/[w(F 2)2]}1/2. w ) 1/[σ2(F )2 + (aP)2 + bP], P ) [max(F 2,0) + 2(F )2]/3, where a ) 0.0000 1 0 c 0 2 0 c 0 0 0 c and b ) 0.2411 for I and a ) 0.0450 and b ) 71.7116 for II.
structure determination by XRD was performed on a Siemens Smart-CCD diffractometer equipped with a normal focus, 2.4 kW sealed tube X-ray source (Mo KR radiation, λ ) 0.71073 Å) operating at 50 kV and 40 mA. A hemisphere of intensity data was collected at room temperature in 1321 frames with ω scans (width of 0.30° and exposure time of 20 s per frame) in the θ range of 2.42-23.30°. Pertinent experimental details for the structure determinations are presented in Table 1. The structure was solved and refined by using the SHELXTLPLUS9 suite of programs. An absorption correction based on symmetry equivalent reflections was applied using the SADABS program.10 The hydrogen positions were fixed using geometric locations and were held in the riding mode and were refined. The last cycles of refinement included atomic positions for all of the atoms and anisotropic thermal parameters for all of the atoms. Full-matrix least-squares structure refinement against |F2| was carried out using the SHELXTL-PLUS package of programs. Details of the crystal data and final refinements are given in Table 1. The selected bond distances and angles for compounds I and II are presented in Table 2.
Results and Discussion The asymmetric units of I and II contain eight independent nonhydrogen atoms. There are two crystallographically distinct cadmium atoms along with one
sodium atom and one halogen atom. The structure of these compounds is built up of tetrahedral clusters of the composition (XCd4O24, XdCl, Br) with Cd(1)-Cl and Cd(1)-Br distances of 2.674(6) and 2.686(2) Å, respectively, and an average Cd(1)-X-Cd(1) angle of 109.5° (Figure 2). The tetrahedral cluster is constituted by four Cd atoms, each coordinated to six succinate oxygens, with the CdO6 octahedra surrounding a central halogen atom (see inset of Figure 2). The central Cl atom in I resides in a special position with 1/12th occupancy. The CdO6 octahedra are distorted with Cd(1)-O distances in the range of 2.286(1)-2.530(4) Å [avg ) 2.408 Å] and an average O-Cd(1)-O angle of 83.1°. The tetrahedral (XCd4O24) cluster gets cross-linked by the succinate units into three-dimensions with intersecting channels as shown in Figure 2 (distance between the centers of the adjacent tetrahedral clusters is ∼11.813 Å). The 3D architecture is comparable to the R-polonium structure, if we consider the tetrahedral cluster, (XCd(1)4O24), as the six-connecting node and the succinate, [C(2)C(1)O(1)O(2)], arising from each cluster as the arm connecting the adjacent clusters. This 3D lattice, undesirably, is
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Table 2. Selected Bond Distances and Bond Angles for I and IIa Compound I moiety
distance (Å)
moiety
distance (Å)
Cd(1)-O(1) Cd(1)-O(1) #1 Cd(1)-O(1) #2 Cd(1)-O(2) #1 Cd(1)-O(2) Cd(1)-O(2) #2 Cd(1)-Cl(1) #3 Cd(2)-O(1) #5 Cd(2)-O(1) #6 Cd(2)-O(1) #7 Cd(2)-O(2) #8 Cd(2)-O(2) #9
2.286(3) 2.286(3) 2.286(3) 2.530(4) 2.530(4) 2.530(4) 2.6743(6) 2.371(4) 2.371(4) 2.371(4) 2.450(4) 2.450(4)
Cd(2)-O(2) #10 Na(1)-O(1) #5 Na(1)-O(1) #6 Na(1)-O(1) #7 Na(1)-O(2) #8 Na(1)-O(2) #9 Na(1)-O(2) #10 C(2)-C(2) #14 C(2)-C(1) O(2)-C(1) O(1)-C(1)
2.450(4) 2.371(4) 2.371(4) 2.371(4) 2.450(4) 2.450(4) 2.450(4) 1.505(10) 1.523(7) 1.257(7) 1.272(5)
moiety
angle (°)
moiety
angle (°)
O(1)-Cd(1)-O(1) #1 O(1)-Cd(1)-O(1) #2 O(1) #1-Cd(1)-O(1) #2 O(1)-Cd(1)-O(2) #1 O(1) #1-Cd(1)-O(2) #1 O(1) #2-Cd(1)-O(2) #1 O(1)-Cd(1)-O(2) O(1) #1-Cd(1)-O(2) O(1) #2-Cd(1)-O(2) O(2) #1-Cd(1)-O(2) O(1)-Cd(1)-O(2) #2 O(1) #1-Cd(1)-O(2) #2 O(1) #2-Cd(1)-O(2) #2 O(2) #1-Cd(1)-O(2) #2 O(2)-Cd(1)-O(2) #2 O(1)-Cd(1)-C(1) #1 O(1) #1-Cd(1)-C(1) #1 O(1) #2-Cd(1)-C(1) #1 O(2) #1-Cd(1)-C(1) #1
119.41(2) 119.41(2) 119.41(2) 94.92(13) 54.16(12) 131.28(12) 54.16(12) 131.28(12) 94.92(13) 77.38(14) 131.28(12) 94.92(13) 54.16(12) 77.38(14) 77.38(14) 107.6(2) 27.18(13) 131.71(14) 27.06(14)
O(2)-Cd(1)-C(1) #1 O(1) #1-Cd(1)-C(1) O(1) #2-Cd(1)-C(1) O(2) #1-Cd(1)-C(1) O(2)-Cd(1)-C(1) O(2) #2-Cd(1)-C(1) Cl(1) #3-Cd(1)-C(1) #1 Cl(1) #3-Cd(1)-C(1) #2 C(1) #1-Cd(1)-C(1) #2 Cl(1) #3-Cd(1)-C(1) C(1) #1-Cd(1)-C(1) C(1) #2-Cd(1)-C(1) Cd(1) #11-Cl(1)-Cd(1) #5 Cd(1) #11-Cl(1)-Cd(1) #12 Cd(1) #5-Cl(1)-Cd(1) #12 Cd(1) #11-Cl(1)-Cd(1) #13 Cd(1) #5-Cl(1)-Cd(1) #13 Cd(1) #12-Cl(1)-Cd(1) #13
104.14(13) 131.71(14) 107.6(2) 87.10(13) 27.06(14) 104.14(13) 109.61(11) 109.61(11) 109.33(11) 109.61(11) 109.33(11) 109.33(11) 109.5 109.5 109.5 109.5 109.5 109.5
Compound II moiety
distance (Å)
moiety
distance (Å)
Cd(1)-O(1) Cd(1)-O(1) #1 Cd(1)-O(1) #2 Cd(1)-O(2) Cd(1)-O(2) #1 Cd(1)-O(2) #2 Cd(1)-Br(1)
2.259(10) 2.259(10) 2.259(10) 2.504(11) 2.504(11) 2.504(11) 2.686(2)
Na(1)-O(2) Na(1)-O(2) #1 Na(1)-O(2) #2 Na(1)-O(1) #3 Na(1)-O(1) #4 Na(1)-O(1) #5
2.446(13) 2.446(13) 2.446(13) 2.377(11) 2.377(11) 2.377(11)
moiety
angle (°)
moiety
angle (°)
O(1)-Cd(1)-Br(1) O(1) #1-Cd(1)-Br(1) O(1) #2-Cd(1)-Br(1) O(2)-Cd(1)-Br(1) O(2) #1-Cd(1)-Br(1) O(2) #2-Cd(1)-Br(1) Br(1)-Cd(1)-C(1) #1 Br(1)-Cd(1)-C(1)
85.6(3) 85.6(3) 85.6(3) 133.4(3) 133.4(3) 133.4(3) 109.3(3) 109.3(3)
Br(1)-Cd(1)-C(1) #2 Cd(1)-Br(1)-Cd(1) #6 Cd(1)-Br(1)-Cd(1) #7 Cd(1) #6-Br(1)-Cd(1) #7 Cd(1)-Br(1)-Cd(1) #8 Cd(1) #6-Br(1)-Cd(1) #8 Cd(1) #7-Br(1)-Cd(1) #8
109.3(3) 109.5 109.5 109.5 109.5 109.5 109.5
a Symmetry transformations used to generate equivalent atoms in I: #1, -z + 1, -x + 1, y; #2, -y + 1, z, -x + 1; #3, x - 1, y, z; #4, x - 1/2, - y + 3/2, - z + 3/2; #5, -x + 1, -y + 2, z; #6, z, -x + 1, -y + 2; #7, -y + 2, z, -x + 1; #8, -y + 3/2, -z + 3/2, x + 1/2; #9, x + 1/2, -y + 3/2, -z + 3/2; #10, -z + 3/2, x + 1/2, -y + 3/2; #11, x + 1, -y + 2, -z + 2; #12, -x + 1, y, -z + 2; #13, x + 1, y, z; #14, x, -y + 2, -z + 1. Symmetry transformations used to generate equivalent atoms in II: #1, -y + 1, z, -x + 1; #2, -z + 1, -x + 1, y; #3, z + 1/2, -x + 3/2, -y + 1/2; #4, y + 1/2, -z + 1/2, -x + 3/2; #5, x - 1/2, -y + 1/2, -z + 1/2; #6, -x + 2, y, -z; #7, -x + 2, -y, z; #8, x, -y, -z; #9, x + 1/2, -y + 1/2, -z + 1/2; #10, -x + 2, y, -z + 1.
interpenetrated by an identical but independent lattice (Figure 3). Such an interpenetration is found in R-polonium-related structures.11 The interpenetration reduces the size of the channel, occupied by Na and Cd(2) atoms. The Cd(2) and Na(1) occupy the same site, with 1/4th and 1/12th occupancies, respectively. The Cd(2) is sixcoordinated with respect to oxygen atoms forming an octahedron, with Cd(2)-O distances in the range of 2.371(4)-2.450(4) [avg ) 2.411 Å]. The structure of II is identical to that of I with the expected variations in
the geometric parameters (Table 2). The various distances and angles associated with the succinate units are as expected. The selected bond distances and bond angles observed in I and II are listed in Table 2. We can consider the (XCd4O24) clusters to be the SBUs in I and II. This arrangement is reminiscent of the Zn4O(BDC)3‚(DMF)8(C6H5Cl), (BDC ) 1,4-benzene dicarboxylate), MOF-5, where the capped Zn4O clusters are linked via benzene dicarboxylate units.4 Another structure related to that of I and II is Rb3Zn4O(PO4)3‚
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Figure 2. Cubelike architecture of I formed by connectivity between the (ClCd4O24) clusters and the succinate linkers (distance between the centers of the adjacent clusters is 11.831 Å). Inset shows the (Cl(Cd(Suc)3)4) cluster with Cl atom in the center. In II, the Cl is replaced by Br. Figure 4. (a) Three-connected 10-gon net (10,3) formed by linking of the cadmium nodes by the succinate linkers. (b) The 3D structure with intersecting channels formed by the (10,3) cadmium succinate net.
Figure 3. Interpenetration of lattices in I, comparable to that in R-polonium-related networks. Similar interpenetration is present in II as well.
3.5H2O, described by Harrison et al.12 The XCd4 (XdCl, Br) clusters are comparable to the OZn4 clusters observed in the zinc phosphate. Although these structures are related, certain differences between them are to be noted. The primary building unit in MOF-5 is the ZnO4 tetrahedron. The tetrahedra form supertetrahedra based on OZn4 clusters, and these units are linked by the benzene dicarboxylate units. In the present case, the primary building unit is the CdO6 octahedron, which forms the SBU of (XCd4O24) clusters, which get linked by the linear succinate units.
The cadmium succinate framework, in I and II, can be visualized based on three-connected nets (10,3) (Figure 4a). The 10-gon nets form a 3D architecture with a cubic symmetry possessing intersecting channels (Figure 4b), closely related to the (10,3)-net in the mineral eglestonite, [(Hg2)3O2H]Cl3.11,13,14 The similarity arises from the presence of pyramidal CdO6 nodes in the cadmium succinates. Thus, the cadmium succinate net gives rise to a tetrahedral site occupied by the halide atom, which interacts with the four nearest Cd neighbors forming (X(Cd(Suc)3)4) type tetrahedral clusters. The cubic net is a three-connected analogue of the diamond net. Other compounds exhibiting a similar three-connected net (10,3) topology with cubic symmetry include SrSi2, H2O2, and B2O3.13,14 The environment of the Na+ ions with respect to the second nearest neighbors, namely, the Cl-/Br- ions, presents an interesting structural feature. The Na+ ions in I and II are arranged in such a way that they form a XNa4 tetrahedron (X ) Cl, Br). The tetrahedra occupy the corners of a cube (Figure 5) and are interpenetrated by another identical but independent cube, similar to that in diamond-related structures. The Na-Cl distance in I is 4.242 Å as compared to 2.820 Å in normal NaCl. The Na-Br distance in II is 4.223 Å as compared to 2.990 Å in normal NaBr.
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framework cadmium succinates containing tetrahedral XCd4O24 (XdCl or Br) clusters, linked by the succinate units. The structures of these hybrid compounds are comparable to those of the dicarboxylate-linked hybrid structures.4,5 The tetrahedral cluster acts as the SBU and gives rise to a 3D cubic structure. This can be visualized from Scheme 1 presented here. According to this scheme, the primary building unit in the structures under discussion would be the CdO6 octahedron, while the SBU would be the motif (D), with MdCl, Br and the TBU would be the motif 5. Acknowledgment. We thank Prof. George M Sheldrick, for his suggestions in the crystal structure solutions of the compounds presented here. Supporting Information Available: Includes tables containing atomic coordinates of compounds I and II and CIFs of compounds I and II. This material is available free of charge via the Internet at http://pubs.acs.org. Figure 5. Structure of I, showing the primitive cubic arrangement formed by the Na4Cl tetrahedral motif.
Scheme 1. General Scheme Illustrating the Building Up of Complex 3D Architectures from Simpler Primary and SBUsa
a A-F are SBUs (SBUs, with MdCl, Br, O, S, Se, etc.) formed by the cubelike primary building unit, which could be a tetrahedron, octahedron, or pentagonal bipyramid. Graphics 1-5 are tertiary building units (TBU). In I and II, 5 is the TBU.
Earlier studies have shown that metathetic reactions between CdCl2 and (MCOO)2 (MdK, Rb) result in noninterpenetrating 3D cadmium oxalate frameworks incorporating a 3D MCl structure with an expanded Fm3m lattice.6,7 In the present case, however, a similar reaction between CdX2 (XdCl, Br) and sodium succinate results in an interpenetrating cadmium succinate framework incorporating Na4X units, which adopt a cubic arrangement. Conclusions The metathetic reaction between CdCl2‚H2O or CdBr2‚ 4H2O and sodium succinate yields unusual 3D open-
References (1) (a) Cheetham, A. K.; Fe´rey, G.; Loiseau, T. Angew. Chem., Int. Ed. 1999, 38, 3269. (b) Lehn, J.-M. Supramolecular Chemistry: Concepts and Perspectives; VCH: New York, 1995. (2) (a) Dalton Discussion No. 3, Inorganic Crystal Engineering. J. Chem. Soc., Dalton Trans. 2000, 21. (b) Thomas, J. M. Angew. Chem., Int. Ed. 1999, 38, 3588. (c) Thomas, J. M. Chem. Eur. J. 1997, 3, 1557. (3) (a) Millange, F.; Serre, C.; Fe´rey, G. Chem. Commun. 2002, 822. (b) Forster, P. M.; Cheetham, A. K. Angew. Chem., Int. Ed. 2002, 41, 457. (c) Serre, C.; Millange, F.; Marrot, J.; Fe´rey, G. Chem. Mater. 2002, 14, 2409 and references therein. (d) Riou, D. D.; Fe´rey, G. J. Mater. Chem. 1998, 8, 2733. (4) Li, H.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Nature 1999, 402, 276. (5) (a) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319 and references therein. (b) Moulton, B.; Zaworotko, M. J. Advances in Supramolecular Chemistry; JAI Press Inc.: London, 2000; Vol. 7, p 235 and references therein. (c) Rosi, N. L.; Eddaoudi, M.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Angew. Chem., Int. Ed. 2002, 41, 284. (d) Livage, C.; Egger, C.; Fe´rey, G. Chem. Mater. 2001, 13, 410 and references therein. (6) Vaidhyanathan, R.; Neeraj, S.; Prasad, P. A.; Natarajan, S.; Rao, C. N. R. Angew. Chem., Int. Ed. 2000, 39, 3470. (7) Vaidhyanathan, R.; Natarajan, S.; Rao, C. N. R. Chem. Mater. 2001, 13, 3524. (8) (a) Infrared and Raman Spectra of Inorganic and Coordination Compounds, 5th ed.; Nakamoto, K., Ed.; John Wiley: New York, 1997. (b) Spectrometric Identification of Organic Compounds, 6th ed.; Silverstein, R. M., Webster, F. X., Eds.; John Wiley and Sons, Inc.: New York, 1997. (c) Livage, C.; Egger, C.; Ferey, G. Chem. Mater. 2001, 13, 410 and references therein. (9) Sheldrick, M. SHELXTL-PLUS Program for Crystal Structure Solution and Refinement; University of Go¨ttingen: Go¨ttingen, Germany. (10) Sheldrick, G. M., SADABS Siemens Area Detector Absorption Correction Programm; University of Go¨ttingen: Go¨ttingen, Germany. (11) (a) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. Engl. 1998, 37, 1460 and references therein. (b) Batten, S. R. Cryst. Eng. Commun. 2001, 18, 1. (12) Harrison, W. T. A.; Broach, R. W.; Bedard, R. A.; Gier, T. E.; Bu, X.; Stucky, G. D. Chem. Mater. 1996, 8, 691. (13) (a) Mereiter, K.; Zemman, J.; Hewat, W. Am. Miner. 1992, 77, 839. (b) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Oxford University Press: Oxford, 1983. (14) Wells, A. F. Three-Dimensional Nets and Polyhedra; WileyInterscience: New York, 1997.
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