Syntheses and Characterizations of Two 3D Cobalt− Organic

CRYSTAL GROWTH & DESIGN

Syntheses and Characterizations of Two 3D Cobalt-Organic Frameworks from 2D Honeycomb Building Blocks

2005 VOL. 5, NO. 5 1849-1855

Yu-Ling Wang,†,‡ Da-Qiang Yuan,† Wen-Hua Bi,† Xing Li,† Xiao-Ju Li,†,‡ Feng Li,†,‡ and Rong Cao*,† State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, People’s Republic of China, and Graduate School of the Chinese Academy of Sciences, Beijing 100039, People’s Republic of China Received March 28, 2005;

Revised Manuscript Received May 25, 2005

ABSTRACT: The hydrothermal reaction of Co(NO3)2‚6H2O, imidazole 4,5-dicarboxylic acid (H3IDC), and 4,4′bipydine (bipy) under different conditions affords two interesting metal-organic compounds, {[Co3(IDC)2(4,4′-bipy)(H2O)4]‚2H2O}n (1) and {[Co3(IDC)2(4,4′-bipy)3]‚6H2O‚DMF}n (2), both of which have been structurally characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. Temperature-dependent magnetic susceptibility for 1 and 2 were also studied. The “all-chair” two-dimensional honeycomb networks, structurally analogous to CFx, were linked by the bridging 4,4′-bipy ligand in compound 1 to give rise to a 2-fold interpenetrated 3D architecture. Compound 2 features a three-dimensional open framework with hexagonal channels, generated from two-dimensional graphene-like layers pillared by 4,4′-bipy. The simplest cyclic motif of the 2D networks in 1 and 2 is a 24-membered hexagonal ring consisting of six Co(II) cations and six IDC3- trianions. Introduction Recently, great efforts have been devoted to the rational design of new metal-organic frameworks (MOFs) in the field of crystal engineering with the driving force of intriguing architectures and potential applications as functional materials of the products.1,2 In general, structural motifs of these MOFs are closely related to the geometry around the metal centers and the number of coordination sites provided by the organic ligands.3 So, judicious combination of a metal “node” and a ligand “spacer” is important for the construction of novel MOFs. It is well-known that Co2+ cations are able to coordinate simultaneously in solution to both oxygencontaining and nitrogen-containing ligands. Imidazole 4,5-dicarboxylic acid (H3IDC) (Chart 1a) potentially has a rich coordination chemistry, which derives from both imidazole and carboxylate functionality. It can be partially or fully deprotonated to generate H2IDC-, HIDC2-, and IDC3- at different pH values, and this results in some interesting supramolecular architectures through the coordinative interactions and hydrogen bonds.4 In particular, the fully deprotonated anion, IDC3-, is planar and has well-defined metal binding sites and has been used as linear spacer ligand (Chart 1b) to successfully construct rigid molecular squares and metal-organic cubes.4b,4c It thus is a good candidate for developing molecular building blocks that may yield a new generation of MOFs with specific topologies. We notice that if the uncoordinated oxygen atoms of the two * Corresponding author. Mailing address: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, People’s Republic of China. Tel: +86-591-83796710. Fax: +86-59183796710. E-mail: [email protected]. † Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences. ‡ Graduate School, Chinese Academy of Sciences.

exo-carboxylic groups of IDC3- ligand (Chart 1b) further bite a metal atom, the IDC3- ligand will connect three metal atoms in a tri(bidentate) mode (Chart 1c). Considering the rigidity and coordination mode of the IDC3- ligand, it is possible to create a two-dimensional honeycomb-like or graphene-like structure by combining the ligand and suitable transition metals. Furthermore, this opens an opportunity to predictably generate a three-dimensional architecture by inserting a suitable exo-bidentate auxiliary ligand into adjacent 2D honeycomb layers. In this context, we choose 4,4′-bipyridine (bipy) as auxiliary ligand on the basis that it was experimentally proven to be a very useful N-containing auxiliary ligand with an extensive coordination polymer chemistry.5 When being introduced into the system of the H3IDC ligands with transition metal ions, it may lead to new structural evolution and fine-tune the structural motif of these metal-organic hybrid compounds.6 The experimental results proved our prediction. Two interesting three-dimensional metal-organic frameworks, {[Co3(IDC)2(4,4′-bipy)(H2O)4]‚2H2O}n (1) and {[Co3(IDC)2(4,4′-bipy)3]‚6H2O‚DMF}n (2), were obtained. Herein, we report their syntheses and characterizations. Experimental Section General Methods. All chemicals were obtained commercially and used without further purification. Elemental analyses were carried out on an Elementar Vario EL III analyzer. Infrared (IR) spectra were recorded with PerkinElmer Spectrum One as KBr pellets in the range 4000-400 cm-1. Thermogravimetric analyses were carried out with a NETZSCH STA 449C unit at a heating rate of 10 °C min-1 under nitrogen. Magnetic susceptibility was measured in the temperature range of 4-300 K at 1 T for 1 and 2-300 K at 0.5 T for 2 on a Quantum Design PPMS60000. X-ray powder diffraction measurements were recorded on a RIGAKU DMAX2500PC diffractometer using Cu KR radiation.

10.1021/cg0501128 CCC: $30.25 © 2005 American Chemical Society Published on Web 06/21/2005

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{[Co3(IDC)2(4,4′-bipy)(H2O)4]‚2H2O}n (1). A mixture of Co(NO3)2‚6H2O (38 mg, 0.13 mmol), 4,5-dicarboxyimidazole (20 mg, 0.13 mmol), 4,4′-bipy (20 mg, 0.13 mmol), and Et3N (0.036 mL, 0.26 mmol) in 15 mL of distilled water was sealed in a Teflon-lined stainless autoclave and heated at 160 °C for 4 days and then cooled to room temperature during 48 h. Red rhombus crystals (21 mg) were isolated in 66% yield and washed with distilled water. Anal. Calcd for C20H22N6O14Co3: C, 32.13; N, 11.24; H, 2.95. Found: C, 32.18; N, 11.20; H, 3.15. {[Co3(IDC)2(4,4′-bipy)3]‚6H2O‚DMF}n (2). A mixture of Co(NO3)2‚6H2O (38 mg, 0.13 mmol), 4,5-dicarboxyimidazole (20 mg, 0.13 mmol), 4,4′-bipy (20 mg, 0.13 mmol), and Et3N (0.072 mL, 0.52 mmol) in 15 mL of H2O-DMF mixture (3:1 by volume) was sealed in a Teflon-lined stainless autoclave and heated at 160 °C for 4 days and then cooled to room temperature during 48 h. Orange prism crystals (26 mg) were isolated in 51% yield and washed with distilled water. Anal. Calcd for C43H45N11O15Co3: C, 45.58; N, 13.60; H, 3.98. Found: C, 45.68; N, 13.28; H, 4.07. Crystallographic Analyses. X-ray diffraction data were collected on a Rigaku diffractometer with a Mercury CCD area detector (Mo KR; λ ) 0.710 73 Å) for 1 at 173(2) K and 2 at 293(2) K. Empirical absorption corrections were applied to the data using the CrystalClear program.7 The structures were solved by the direct method and refined by the full-matrix least-squares on F2 using the SHELXTL-97 program.8 All of the non-hydrogen atoms were refined anisotropically except for the disordered oxygen atoms of aqua and disordered atoms of DMF molecules. The H atoms bonded to C atoms were positioned geometrically and refined using a riding model [C-H ) 0.93 Å and Uiso(H) ) 1.2Ueq(C)]. The H atoms bonded to O atoms in 1 were located from Fourier difference maps and refined isotropically with the O-H distances fixed at 0.82 Å [Uiso(H) ) 1.5Ueq(O)]. The H atoms in the lattice water and DMF molecules in 2 were not located on the F-map and not taken into consideration. Crystallographic data and other pertinent information for 1 and 2 are summarized in Table 1. Selected bond lengths and bond angles are listed in Table 2. CCDC numbers are 272442 for 1 and 272441 for 2.

Results and Discussion Hydrothermal synthesis has been successful for the preparation of new materials.9 In a heated sealed solution above ambient temperature and pressure, the problems associated with ligand solubility were minimized, and the reactivity of reactants was enhanced in favor of efficient molecular building during the crystallization process.9 Compound 1 was obtained by hydrothermal reaction of Co(NO3)2‚6H2O, H3IDC, 4,4′-bipy, triethylamine, and H2O in a molar ratio of 1:1:1:2:5200 with medium yield, and slightly excessive or less triethylamine would cause a failure. Compound 2 was synthesized by hydrothermal reaction of Co(NO3)2‚ 6H2O, H3IDC, 4,4′-bipy, and triethylamine in H2ODMF (3:1) mixed solution with medium yield. The solvent mixtures above 50% DMF (by volume) cannot afford any products of 2. The results indicate that the forming of MOFs of 1 and 2 are considerably influenced by the nature of the solution. Both compounds are not

Table 1. Crystallographic Data for {[Co3(IDC)2(4,4′-bipy)(H2O)4]‚2H2O}n (1) and {[Co3(IDC)2(4,4′-bipy)3]‚6H2O‚DMF}n (2) empirical formula formula weight crystal system space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z Fcalc (mg/m3) µ (Mo KR) (mm-1) no. of data collected no. of unique data (all) no. of obsd data [F > 2(σF)] params R1,a wR2b (I > 2σ(I)) R1,a wR2b (all data) GOF

1

2

C20H22N6O14Co3 747.23 monoclinic P21/n 8.1051(7) 17.6812(14) 8.5047(7) 90 90.072(7) 90 1218.79(17) 2 2.036 2.108 9367

C43 H45 N11O15Co3 1132.69 triclinic P1 h 11.4932(2) 11.6132(1) 11.8182(1) 65.275(8) 81.174(12) 72.752(10) 1367.58(3) 1 1.375 0.969 10 640

2789 (R(int) ) 0.0484) 2305

6171 (R(int) ) 0.0252) 4870

215 0.0547, 0.1016

310 0.0759, 0.2146

0.0705, 0.1092

0.0943, 0.2295

1.058

1.097

R ) ∑||Fo| - |Fc||/∑|Fo|. ) - Fc2)2/∑w(Fo2)2]1/2. w ) 1/[σ2(Fo2) + (0.0321P)2 + 4.9833P], where P ) (Fo2 + 2Fc2)/3 for 1. w ) 1/[σ2(Fo2) + (0.1066P)2 + 5.8818P], where P ) (Fo2 + 2Fc2)/3 for 2. a

b

wR(F2)

[∑w(Fo2

soluble in water and organic solvents such as methanol, ethanol, acetone, dichloromethane, toluene, DMSO, DMF, and chloroform. The assembly of a honeycomb-like structure is challenging since the hexagon represents the most common pattern in nature and is familiar from benzene to the honeycomb of the bee.10 Honeycomb-like networks have been previously obtained from the assembly of rigid symmetrical three-connecting ligands such as 1,3,5-tricyanobenzene, 1,3,5-benzenetricarboxlic acid, and 1,3,5tris(1-imidazolyl) benzene with transition metals.10b,11 It is uncommon to generate honeycomb-like networks using the IDC3- ligand with relatively low symmetry. Especially, in compound 1, the “all-chair” two-dimensional honeycomb network that is structurally analogous to CFx is rare. In previous literature, Rosseinsky reported a three-dimensional metal-organic framework, Ni3(btc)2(µ-4AP)2(4AP)4‚6C4H9OH‚2H2O11b (btc ) 1,3,5benzenetricarboxylate; AP ) 4-aminopyridine), containing such a corrugated honeycomb network. They reasoned that the different geometric requirements of the two ends of the linker AP enforce the CFx geometry onto the sheets. However, in our experiment, we used 4,4′bipy as auxiliary ligands, the two ends of which have the same geometry, to create a three-dimensional MOF

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Table 2. Selected Bond Distances (Å) and Angles (deg) for {[Co3(IDC)2(4,4′-bipy)(H2O)4]‚2H2O}n (1) and {[Co3((IDC)2(4,4′-bipy)3]‚6H2O‚(DMF)}n (2)a Co1-O1 Co1-O6 Co1-N3 Co2-O2 Co2-O5 O1-Co1-O6 N3-Co1-O3 O3-Co1-N2A#1 O2-Co2-O5 O2-Co2-N1

Compound 1 2.066(3) Co1-O3 2.129(3) Co1-O4A#1 2.130(3) Co1-N2A#1 2.067(3) Co2-N1 2.152(3) 173.84(12) O1-Co1-O3 92.03(12) N3-Co1-O4A#1 94.22(12) N2A#1-Co1-O4A#1 89.55(13) N1-Co2-O5 79.38(11) O5-Co2-O5B#2

Co1-O1 Co1-N3 Co2-N1 Co3-N2 Co3-N5 N3-Co1-N3A#3 O1-Co1-N3 O1-Co1-O3A#3 N1-Co2-O4 N1-Co2-N4 N2C#5-Co3-O2 N2-Co3-O2

Compound 2 2.075(3) Co1-O3 2.166(4) Co2-O4 2.049(4) Co2-N4 2.058(4) Co3-O2 2.195(4) 180 O3-Co1-N3 87.14(16) O1-Co1-O3 87.60(15) N4-Co2-N4B#4 79.07(15) N1-Co2-O4B#4 89.44(16) N5-Co3-N5C#5 100.61(14) O4-Co2-N4 79.39(14) N5-Co3-O2

2.061(3) 2.152(3) 2.067(3) 2.069(3) 93.60(11) 95.91(11) 77.63(11) 93.08(13) 180 2.066(3) 2.125(4) 2.219(4) 2.107(4) 89.75(15) 92.40(15) 180 100.93(15) 180 85.79(16) 87.48(16)

Figure 2. A single corrugated sheet composed of Co2+ and IDC3-, which is structurally analogous to the layers in CFx. The 4,4′-bipy and water molecules have been omitted. (Co1, light blue; Co2, blue; C, gray; O, red).

a Symmetry transformations used to generate equivalent atoms: (#1) x + 1/2, -y + 1/2, z + 1/2; (#2) -x, -y, -z; (#3) x, -y, -z + 1; (#4) -x, -y - 1, -z + 1; (#5) -x, -y, -z.

Figure 3. View of the 3D framework along the [101] direction. The free water molecules and hydrogen atoms have been omitted for clarity.

Figure 1. Coordination environment of the Co2+ and IDC3ions. An ORTEP drawing with 30% probability displacement ellipsoids is presented. H atoms were omitted for clarity.

containing such a corrugated honeycomb network. The result indicates that the generation of such a topology is much more dependent on the geometric needs of the metal atoms as well as the coordination environments around the metal centers. {[Co3(IDC)2(4,4′-bipy)(H2O)4]‚2H2O}n (1). Singlecrystal X-ray analysis reveals that 1 is a 2-fold interpenetrated 3D framework consisting of concertina sheets linked by 4,4′-bipy. As shown in Figure 1, two crystallographically independent cobalt ions are disposed in different coordination environments. Co1 is surrounded by one nitrogen and three oxygen atoms from two individual IDC3- ligands, one nitrogen atom from a bridging 4,4′-bipy ligand, and one oxygen atom from a water molecule in a slightly distorted octahedral coordination geometry. Co2, however, resides on an inver-

sion center and is octahedrally coordinated by two nitrogen and two oxygen atoms from two individual IDC3- ligands and two oxygen atoms from two aqua molecules. The Co-N distances range between 2.067(3) and 2.130(3) Å, and the Co-O bonds range between 2.067(3) and 2.153(3) Å. These distances are comparable to reported values.6e,12 Each IDC3- anion is quasi-planar and connects three Co(II) atoms through C2 symmetry in a tri(bidentate) mode (Chart 1c). The metal-metal distances around IDC3- are nearly symmetrical (C2): Co1‚‚‚Co2 ) 5.832, Co1‚‚‚Co1A ) 5.924, and Co1A‚‚‚Co2 ) 6.328 Å. All the Co(II) atoms are interlinked by IDC3ligands to generate a concertina sheet, which is practically composed of hexagonal 24-membered rings involving six IDC3- anions and six Co2+ cations (Figure 2). Each sheet may be described topologically as a (6,3) net. In the present case, the (6,3) net is not the ubiquitous flat graphene sheet but a topologically equivalent (6,3) net of chair conformation six-rings, which form a coordination polymer analogue of the puckered layers in graphite monofluoride, CFx. The structural features of each sheet described here are somewhat similar to that described in Ni3(btc)2(µ-4AP)2 (4AP)4‚6C4H9OH‚ 2H2O.11b Two IDC3- units are linked together at Co1, and the angle subtended between their mean planes is 118.9°. This is reflected in the extreme puckering of the layers: adjacent corrugations subtend an angle of 112.7° to each other (Figure 3). The cobalts (Co2) act as linear connectors in the side of each concertina layer, and the other cobalts (Co1) at the peaks (troughs) of each corrugated layer are linked by bridging 4,4′-bipy molecules to cobalts (Co1) at the troughs (peaks) of adjacent

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Figure 4. Interpenetration of two equivalent 3D frameworks in 1. The water molecules and hydrogen atoms have been omitted for clarity.

layers to result in a three-dimensional architecture (Figure 3) with cavities running parallel to [101] (11.741 Å × 12.807 Å) and [101 h ] (12.807 Å × 11.350 Å) (based on dCo‚‚‚Co) directions. The void space in the single framework is so large that two 3D frameworks interpenetrate each other through the large cavities as shown in Figure 4. Lattice water molecules occupy the residual space and form hydrogen bonds with the carboxylate groups and coordinated water, as well as with other cavity water molecules (O7‚‚‚O2, 2.857(5) Å; O6‚‚‚O7#1, 2.999(6) Å; O7‚‚‚O7#2, 2.831(9) Å; symmetry codes (#1) x - 1/2, -y + 1/2, z + 1/2 and (#2) -x + 1, -y, -z). {[Co3(IDC)2(4,4′-Bipy)3]‚6H2O‚DMF}n (2). Singlecrystal X-ray analysis reveals that in compound 2, all the Co(II) ions are integrated by IDC3- ligands into a graphene-like (6,3) net (Figure 5b). The resulting 2D honeycomb-like sheets are further pillared by 4,4′-bypy to afford a 3D open framework (Figure 6). The infinite hexagonal sheet is also made up of edge-sharing 24membered rings of six IDC3- units joining six Co2+ cations. Similar to that in compound 1, each IDC3- ion is quasi-planar and acts as a three-connecting ligand (Chart 1c). As shown in Figure 5a, there are three crystallographically independent Co(II) atoms in the asymmetric unit, all located on inversion centers. The Co1 center has a slightly distorted [CoN2O4] octahedral coordination sphere with four oxygen atoms from two IDC3- ligands in the equatorial positions and two nitrogen atoms from two 4,4′-bypy ligands in the apical positions (Co-O ) 2.066(3)-2.075(3) Å, Co-N ) 2.166(4) Å). Both Co2 and Co3 centers have slightly distorted [CoN4O2] coordination spheres with two nitrogen and two oxygen atoms from two IDC3- ligands occupying the equatorial positions and two nitrogen atoms of two 4,4′bypy ligands occupying the apical positions (Co-O ) 2.107(4)-2.125(4) Å, Co-N ) 2.049(4)-2.195(4) Å). The metal-metal distances around IDC3- are very close to those in compound 1: Co1‚‚‚Co2 ) 5.807, Co1‚‚‚Co2 ) 5.909, and Co1A‚‚‚Co2 ) 6.319 Å. Two types of pillared 4,4′-bypy ligands are observed in the compound 2. One type is that two pyridine rings are coplanar; the other is that two pyridine rings are severely distorted with the dihedral angle of 27.3°. The honeycomb layers are stacked in an AAA manner along the a axis to produce

Figure 5. (a) ORTEP drawing of 2 with 30% probability displacement ellipsoids (H atoms were omitted for clarity) and (b) 2D honeycomb-like network with 24-membered metallacycles composed of six IDC3- anions and six Co2+ cations (4,4′bipy and encapsulated solvent have been omitted).

a 3D hexagonal channel (12.638 Å × 11.613 Å, based on dCo‚‚‚Co) (Figure 7a). The disordered aqua and DMF molecules reside in the tunnels. When these extraframework species are not considered, the accessible volume within the crystal is calculated to be 39.3% by using the program PLATON.13 Figure 7b shows the channel window along the b axis. Infrared Spectrum, Thermal Gravimetric Analysis, and X-ray Powder Diffraction. The IR spectra of compounds 1 and 2 both exhibit strong characteristic absorption around 1605-1607 (νasym(CO2)) and 1388-1399 cm-1 (νsym(CO2)) for the carboxyl groups. The strong and broad bands centered at 3410 and 3419 cm-1 are attributed to the νO-H stretching of coordinated water and crystallization water in 1 and 2. The thermal gravimetric analysis (TGA) diagram of 1 reveals two distinct weight loss regions centered around 200 and 400 °C (Figure 8). The first weight loss of 14.0% from 132 to 210 °C is attributed to the release

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Figure 6. View of the three-dimensional metal-organic framework of 2. The encapsulated solvent molecules and hydrogen atoms have been omitted for clarity.

of all the water molecules (calcd ) 14.4%). We note that the crystallization water is released at the same time as the coordinated water, supporting the structural evidence of a hydrogen-bonding network in 1. The second weight loss, covering a temperature range from 400 to 700 °C, suggests the destruction of the framework by the oxidation of the organic component. For 2, the weight loss of 10.01% from 63 to 160 °C is equivalent to the loss of the six free water molecules per formula unit (calcd ) 9.54%). The framework of 2 is stable up to 260 °C at which point the loss of solvent DMF and simultaneous decomposition starts. The original sample and dehydrated sample of 2 were characterized by X-ray powder diffraction (XRPD) at room temperature (Figure 9). The patterns calculated from the single-crystal X-ray data of 2 were in good agreement with the observed ones. Compared to the original sample, the dehydrated solid obtained by heating crystals of 2 up to 180 °C shows very similar XRPD patterns as far as line positions are concerned (Figure 9c), but the intensity is weakened. After immersion in H2O/DMF (3:1) for 24 h, the dehydrated sample of 2 exhibits almost identical XRPD patterns to those of the original sample. These results illustrate that the main framework of 2 is retained upon removal of all the water molecules and the dehydration/hydration of 2 is reversible. Magnetic Properties. The temperature-dependent magnetic susceptibility of 1 and 2 were measured from 2 to 300 K in a constant magnetic field of 1 and 0.5 T, respectively. The 1/χm and µeff per Co(II) ion versus T curves are shown in Figure 10. At 300 K, µeff is 4.33 µB for 1 and 4.39 µB for 2, both larger than the expected 3.87 µB for magnetically isolated high-spin CoII ions (SCo ) 3/2, g ) 2.0). The larger values of 1 and 2 are the result of contributions to the susceptibility from orbital angular momentum at high temperature. Between 10 and 300 K, the magnetic susceptibility, χm, can be fitted to the Curie-Weiss law, χm ) Cm/(T - θ) with Cm ) 2.61 ( 0.01 cm3 mol-1 K and θ ) -32.9 ( 0.4 K for 1 and Cm ) 2.75 ( 0.01 cm3 mol-1 K and θ ) -40.8 ( 0.4 K for 2, respectively. These results indicate the antiferromagnetic interactions between cobalt(II) centers in both complexes.

Figure 7. Packing of the 3D open framework of 2 showing the channels formed by the AAA stacking viewed (a) from the a axis and (b) from the b axis. The framework is represented by its van der Waals surfaces (O, red; C, gray; N, dark blue; Co, blue; H, white).

Figure 8. TGA curves for compounds 1 and 2.

Conclusion Two three-dimensional frameworks, {[Co3(IDC)2(4,4′bipy)(H2O)4]‚2H2O}}n (1) and {[Co3(IDC)2(4,4′-bipy)3]‚

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figurations. The differences are attributed to the geometric needs of metal atoms, as well as the coordination environments around the metal centers. It is also noted that the pillared architecture of 2 contains 3D cavities. This kind of material possesses potential application in the areas of gas storage, heterogeneous catalysis, and ion exchange.14 Variable-temperature (4-300 K) magnetic susceptibility measurements indicate that 1 and 2 exhibit antiferromagnetic interactions between the Co(II) paramagnetic centers. This predictable designing of metal-organic frameworks with special topology by judicious combination of suitable metal “nodes” and organic molecular “spacers” may have promising application in coordination polymer chemistry. Acknowledgment. We thank the National Natural Science Foundation of China (Grants 90206040, 20325106, 20333070), the Natural Science Foundation of Fujian Province, and the “one-hundred Talent” Project from CAS for financial support. Figure 9. XRPD patterns for compound 2: (a) calculated patterns from single-crystal X-ray data; (b) taken at room temperature; (c) after heating at 180 °C for 60 min; (d) after immersion in H2O/DMF (3:1) for 24 h.

Figure 10. Plots of experimental µeff vs T (0) and 1/χm vs T (O) of (a) 1 and (b) 2. The solid red line shows the CurieWeiss fitting.

6H2O‚DMF}n (2), were constructed from H3IDC ligand in the presence of auxiliary 4,4′-bpy ligand. Both 1 and 2 contain 2D honeycomb networks, which are linked by 4,4′-bpy to form 3D architectures. Interestingly, The honeycomb networks in 1 and 2 adopt different con-

Supporting Information Available: X-ray crystallographic file in CIF format for 1 and 2. This material is available free of charge via the Internet at http://pubs.acs.org.

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CG0501128