ARTICLE pubs.acs.org/crystal
Assembly of Three NiII Bis(triazole) Complexes by Exerting the Linkage and Template Roles of Keggin Anions Xiu-li Wang,* Jin Li, Ai-xiang Tian, Dan Zhao, Guo-cheng Liu, and Hong-yan Lin Department of Chemistry, Bohai University, Jinzhou 121000, People’s Republic of China
bS Supporting Information ABSTRACT: Three inorganic organic hybrid compounds based on Keggin-type polyoxometalate (POM) and NiII-bis(triazole) complexes, namely, [Ni2(L1)4(SiW12O40)] 3 H2O (1), [Ni2(H2O)4(L2)4(HL2)2][PMo12O40]2 3 2H2O (2), and [Ni3(L1)5][PMo12O40]2 3 14H2O (3) (L1 = 1,4-bis(1,2,4-triazol-1-yl)butane, L2 = 1,6-bis(1,2,4-triazol-1-yl)hexane), have been obtained under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compound 1 exhibits a (66) three-dimensional (3D) Ni-L1 framework with hexagonal channels, in which [SiW12O40]4 anions have been accommodated as tetradentate linkages. In compound 2, the Ni-L2 motif exhibits a 3D supramolecular network templated by [PMo12O40]3 (PMo12) anions. In compound 3, the Ni-L1 motif is a two-dimensional (2D) layer, which is linked by PMo12a anions to construct a 3D framework. The 3D frameworks interpenetrate with each other to form a 2-fold interpenetrating structure, which exhibits two kinds of channels. The other discrete PMo12b anions, acting as inorganic templates, are embedded in the larger channels. The Keggin anions in 3 exert not only linkage but also template roles. In addition, electrochemical properties of 1-bulk modified carbon paste electrode (1 CPE) and 3 CPE have been studied in 1 M H2SO4 aqueous solution.
’ INTRODUCTION Polyoxometalates (POMs), as an outstanding class of inorganic metal-oxide clusters, have attracted extensive attention owing to not only their controllable shape, size, composition, and structural diversity but also their promising properties, such as photochemical activity, magnetism, and catalytic activity.1 In recent years, the introduction of transition-metal complexes (TMCs) to POMs has become an appealing field, aiming for construction of high dimensional frameworks with novel topology and some potential properties. Thus, a series of these compounds have been reported.2 4 In these compounds, POMs usually act as two kinds of roles: linkages and templates. First, as is well-known, POMs comprise abundant terminal/bridging oxygen atoms acting as potential coordination sites to link TMCs, which lend itself to play the linkage role, and many POM-based compounds with high dimensionality and connectivity have been obtained.3 Second, POMs act as only inorganic templates, without utilizing the coordination ability of terminal/bridging oxygen atoms.4,5 As inorganic templates, POMs have their obvious merits: (a) They have high negative charges, which can assemble the cationic metal organic subunits and conduce to construct different interesting frameworks.4b (b) They exhibit controllable shapes and sizes, such as Wells-Dawson (13.45 10.36 Å), Keggin (10.45 10.45 Å), Anderson (9.07 9.07 Å), which result in the construction of different metal organic structures.4d,6 Thus, POMs acting as inorganic templates bring an appealing route to obtain fascinating metal organic frameworks. However, the reports on POMs-templated r 2011 American Chemical Society
compounds are relatively limited.4,5 In this work, we try to further exert the linkage and template roles of POMs and construct new compounds in the POMs/TMCs system. Notably, it is really rare that both of the roles of POMs, linkage and template, coexist in one compound. Thus, it would be an appealing field to construct POMbased compounds by exerting the linkage and template roles of POMs, especially converging these two roles in one compound. At present, organonitrogen ligands have become the preferred choice to assemble POM-based compounds; in particular, the flexible bis(triazole) ligands have drawn chemists’ attention owing to their special characters:3c,7 (i) The flexible bis(triazole) ligands can donate four N-donor atoms, which can enhance their coordination ability with TM ions and consequently contribute the formation of TMCs. (ii) The flexibility and conformational freedom of (CH2)n spacers can allow them to meet the requirements of the coordination geometries of the transition metal (TM) ions and POMs freely, conducing to exert the template and linkage roles of POMs. Thus, in this work, we choose flexible bis(triazole) ligands to construct POM-based TMCs by exerting the linkage and template roles of POMs. In this paper, we report three novel inorganic organic hybrid compounds based on Keggin-type POMs, NiII and flexible Received: March 1, 2011 Revised: May 24, 2011 Published: May 31, 2011 3456
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Crystal Growth & Design bis(triazole) ligands: [Ni2(L1)4(SiW12O40)] 3 H2O (1), [Ni2(H2O)4(L2)4(HL2)2][PMo12O40]2 3 2H2O (2), and [Ni3(L1)5][PMo12O40]2 3 14H2O (3), (L1 = 1,4-bis(1,2,4-triazol-1-yl)butane, L2 = 1,6-bis(1,2,4-triazol-1-yl)hexane). The Keggin anions in these three compounds play different roles, for example, the linkage role in compound 1 and the template role in 2, while converging these two roles in 3.
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Table 1. Crystal Data and Structure Refinement Parameters for Compounds 1 3 1
2
3
formula
C32H48Ni2-
C60H110Ni2N36-
C40H88Ni3N30-
fw
N24O40SiW12 3760.65
O86P2Mo24 5193.76
O94P2Mo24 5034.03
space group
P21/n
P21/c
P1
a [Å]
11.201(5)
13.8427(12)
13.0024(8)
b [Å]
14.943(5)
18.2148(15)
13.4765(9)
Materials and Measurements. All chemicals were reagent grade,
c [Å]
21.483(5)
26.861(2)
19.0107(13)
commercially available, and used as received without further purification. The N-donor ligands L1 and L2 were prepared according to the reported procedure.8 Fourier transform infrared (FT-IR) spectra (KBr pellets) were taken on a Magna FT-IR 560 spectrometer and the elemental analyses (C, H, and N) were carried out on a Perkin-Elmer 240C elemental analyzer. Thermogravimetric analysis was carried out with a Pyris Diamond TG/DTA instrument under a N2 atmosphere with a heating rate of 10 °C 3 min 1. Powder X-ray diffraction (PXRD) patterns were measured on a Shmadzu XRD-6000 X-ray diffractometer. A CHI 440 Electrochemical Quartz Crystal Microbalance was used for the electrochemical experiments. A conventional three-electrode cell was used at room temperature. Chemically bulk-modified carbon-paste electrode (CPE) was used as the working electrode. An SCE and a platinum wire were used as reference and auxiliary electrodes, respectively. Synthesis of [Ni2(L1)4(SiW12O40)] 3 H2O (1). A mixture of NiCl2 3 6H2O (0.12 g, 0.5 mmol), L1 (0.043 g, 0.2 mmol), H4SiW12O40 3 24H2O (0.2 g, 0.07 mmol), and H2O (10 mL) was stirred for 60 min in air, then transferred and sealed in a 23 mL Teflon reactor with a starting pH of 1.3 adjusted with 1.0 mol/L NaOH, which was heated at 160 °C for 2 days leading to the formation of blue block crystals of 1, with a final pH of 0.9. Yield 18% based on Ni. Anal. Calc. for C32H50SiN24Ni2O41W12 (3778.67): C, 10.17; H, 1.33; N, 8.90%. Found: C, 10.28; H, 1.28; N, 9.01%. IR (KBr, cm 1): 3495m, 2356w, 1636m, 1528m, 1450m, 1370w, 1283m, 1210s, 1138m, 1022s, 975s, 925s, 790s, 667w.
R [°]
90
90
76.2940(10)
β [°]
92.096(5)
94.1720(10)
85.2840(10)
γ [°] V (Å3)
90 3593(2)
90 6754.9(10)
74.7680(10) 3121.9(4)
’ EXPERIMENTAL SECTION
Synthesis of [Ni2(H2O)4(L2)4(HL2)2][PMo12O40]2 3 2H2O (2).
A mixture of NiCl2 3 6H2O (0.12 g, 0.5 mmol), L2 (0.052 g, 0.2 mmol), H3PMo12O40 3 36H2O (0.2 g, 0.08 mmol), and H2O (10 mL) was stirred for 60 min in air, and then transferred and sealed in a 23 mL Teflon reactor with a starting pH of 1.43 adjusted with 1.0 mol/L NaOH, which was heated at 150 °C for 3 days leading to the formation of green block crystals of 2, with a final pH of 1.0. Yield 35% based on Ni. Anal. Calc. for C60H110Mo24N36Ni2O86P2 (5193.76): C, 13.87; H, 2.13; N, 9.71%. Found: C, 13.61; H, 2.18; N, 9.63%. IR (KBr, cm 1): 3512m, 2356m, 1636w, 1527m, 1448w, 1387w, 1280m, 1213w, 1139m, 1058s, 961s, 889m, 809s, 675w. Synthesis of [Ni3(L1)5][PMo12O40]2 3 14H2O (3). A mixture of NiCl2 3 6H2O (0.12 g, 0.5 mmol), L1 (0.046 g, 0.2 mmol), H3PMo12O40 3 36H2O (0.2 g, 0.08 mmol), and H2O (10 mL) was stirred for 60 min in air, then transferred and sealed in a 23 mL Teflon reactor with a starting pH of 2.1 adjusted with 1.0 mol/L NaOH, which was heated at 160 °C for 3 days leading to the formation of green block crystals of 3, with a final pH of 1.5. Yield 20% based on Ni. Anal. Calc. for C40H88Mo24N30Ni3O94P2 (5034.03): C, 9.54; H, 1.76; N, 8.35%. Found: C, 9.65; H, 1.68; N, 8.43%. IR (KBr, cm 1): 3460m, 2360w, 1615m, 1525m, 1440m, 1395w, 1285s, 1215m, 1140m, 1068s, 970s, 895m, 805s, 684w. Preparations of 1 , 2 and 3 CPEs. The compound 1 bulkmodified CPE (1 CPE) was fabricated as follows:9 0.50 g of graphite powder and 0.030 g of 1 were mixed and ground together by agate mortar and pestle for approximately 30 min to achieve an even, dry mixture; to the mixture 0.15 mL of paraffin oil was added and stirred with a glass rod; then the homogenized mixture was used to pack 3 mm inner diameter glass tubes to a length of 0.8 cm, the tube surface was wiped with weighing paper, and the electrical contact was established with the copper stick through the back of
3
D/g cm Z F(000) μ/mm
1
R1a/wR2b
3.476
2.554
2.678
2
2
1
3372
5008
2412
19.749
2.553
2.905
0.0695/0.1868
0.0561/0.1045
0.0560/0.1456
1.079 2.386
1.108 1.319
1.040 1.545
[I > 2σ(I)] GOF on F2 Δ F max (e Å 3) Δ F min (e Å 3)
R1 = Σ(||Fo| Fo|2)2]1/2. a
1.770
|Fc||)/Σ|Fo|.
1.588 b
wR2 = [Σw(|Fo|2
1.571
|Fc|2)2/(Σw|
the electrode. The same procedure was used for preparation of bare CPE, 2 CPE, and 3 CPE. X-ray Crystallographic Study. X-ray diffraction analysis data for compounds 1 3 were collected with a Bruker Smart Apex 1000 CCD diffractometer with Mo KR (λ = 0.71073 Å) by ω scan mode. The structures were solved by direct methods and refined on F2 by the fullmatrix least-squares methods using the SHELXTL package.10 All nonhydrogen atoms were refined anisotropically, all the H atoms attached to carbon atoms were generated geometrically, while the H atoms attached to water molecules were not located but were included in the structure factor calculations. A summary of crystal data and structure refinements for the title compounds are given in Table 1. Selected bond distances (Å) and angles (ο) of the three compounds are listed in the Supporting Information Table S1, and hydrogen-bonding parameters (Å, °) are summarized in Table S2. Crystallographic data for the structures reported in this paper have been deposited in the Cambridge Crystallographic Data Center with CCDC reference nos. 798671 for 1, 798672 for 2, and 798687 for 3.
’ RESULTS AND DISCUSSION Structural Description of 1. Compound 1 consists of one crystallographically independent NiII ion, one SiW12 anion, three types of L1 ligands with different conformation modes (L1a, L1b, and L1c), and one water molecule, as shown in Figures 1 and S1. In the SiW12 anion, the central four μ4 oxygen atoms are observed to be disordered over eight positions with each oxygen site half-occupied, a usual problem for POM clusters.11 The Ni1 ions are six-coordinated by two Ot (terminal oxygen) atoms from two SiW12 anion and four N atoms from three L1 ligands (L1a, L1b, and L1c), showing an octahedral coordination geometry {NiN4O2}. The bond distances and angles around the nickel ions are 1.98(2) 2.02(2) Å for Ni N, 2.43(8) and 2.48(8) Å for Ni O, and 86.8(8) 178.6(8)° for N Ni N, 3457
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comparable to those in the six-coordinated NiII complexes.12 The Ni1 ions are linked by L1a and L1b ligands to generate a 2D sheet with hexagonal grids (Figure 2). Furthermore, the 2D sheet extends into a 66 3D metal organic framework (MOF) through the L1c ligands linking with Ni1 ions (Figure 3). The SiW12 anion, acting as a fourconnected ligand, offers four Ot atoms to incorporate in hexagonal channels of the 3D MOF. Thus, the Keggin anions in compound 1 exert their linkage role, utilizing their terminal oxygen atoms.
Structural Description of 2. Crystal structure analysis reveals that compound 2 consists of one crystallographically independent NiII ion, three types of L2 ligands with different conformation modes (L2A, L2B, and L2C), one kind of PMo12 anions, and six water molecules (Figures 4 and S2). The Ni1 ions are six-coordinated by two O atoms from two water molecules and four N atoms from three L2 ligands (L2A, L2B, and L2C), showing an octahedral coordination geometry {NiN4O2}. The bond distances and angles around the Ni1 ions are 2.079(9) 2.085(10) Å for Ni N, 2.116(8) and 2.159(8) Å for Ni OW, 89.7(3) 173.7(4)° for N Ni N, 86.0(3) 177.1(3)° for N Ni OW, and 86.6(3)° for OW Ni OW. Each Ni1 ion was coordinated by two L2 ligands in a monodentate mode (L2A and L2C), while two L2B ligands bridge two Ni1 ions. Thus, a binuclear circle is generated with a 26-membered ring [Ni2N8C16] (Figure S3, Supporting Information). The binuclear circles are ultimately extended to a 1D chain by hydrogen bonding interactions [C(24) 3 3 3 N(9) = 2.6314 Å]. A bigger 50-membered supramolecular ring [Ni2N18C32] forms between two adjacent binuclear circles (Figure S4, Supporting Information). The 26-membered and 50membered rings arrange vertically. The 1D chains are extended to a 2D net by hydrogen bonding interactions [C(12) 3 3 3 O(2W) = 2.876 Å], as shown in Figure 5. Then, a 3D supramolecular framework was further constructed also through hydrogen-bonding interactions [N(16) 3 3 3 C(27) = 3.0580 Å] (Figure 6). Two neighboring 2D nets are in a staggered arrangement. The PMo12 anions are sandwiched by two neighboring 2D nets (Figure 7), just like a “hamburger”. Hydrogen bonding interactions [C(9) 3 3 3 O(34) = 3.2023 Å and C(7) 3 3 3 O(20) = 3.2881 Å] exist between the PMo12 anions and 2D nets, which play an important role in the formation and stabilization of the 3D supramolecular structure. The PMo12 anion plays the inorganic template role for construction of this 3D supramolecular structure. Structural Description of 3. Crystal structure analysis reveals that compound 3 consists of two crystallographically independent NiII ions, 3 types of L1 ligands with different conformation modes (L1A, L1B, and L1C), 2 kinds of PMo12 anions (PMo12a and PMo12b), and 14 water molecules (Figures 8 and S5). In the PMo12 anion, the central four μ4 oxygen atoms are also observed to be disordered over eight positions with each oxygen site half-occupied. The Ni1 ions are six-coordinated by one Ot atom from one PMo12a anion, three N atoms from three L1 ligands (L1A, L1B, and L1C), and two O atoms from water molecules, showing an octahedral coordination geometry {NiN3O3}. The bond distances and angles around the nickel ions are 2.059(10) 2.080(9) Å for Ni N, 2.080(8) 2.105(8) Å for Ni O, 90.1(4) 174.3(4)° for N Ni N, 85.4(3) 177.6(4)° for N Ni O, and 86.7(3) 175.5(3)° for O Ni O.12b,13 The Ni2 ions also show an octahedral coordination geometry {NiN4O2}, which is completed by four
Figure 1. Stick/polyhedral view of the asymmetric unit of compound 1 and the coordination sites of the NiII ions. The hydrogen atoms and crystal water molecules are omitted for clarity.
Figure 2. Representation of the Ni-L1 2D net in 1.
Figure 3. SiW12 anions incorporated in hexagonal channels of the 3D MOF. 3458
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Figure 7. The inorganic template role of the PMo12 anion for construction of 3D supramolecular structure through hydrogen bonding interactions. Figure 4. Stick/polyhedral view of the asymmetric unit of 2 and the coordination environments of the NiII ions. The hydrogen atoms and crystal water molecules are omitted for clarity.
Figure 5. Representation of the Ni-L2 2D supramolecular net.
Figure 8. Stick/polyhedral view of the asymmetric unit of 3 and the coordination sites of the NiII ions. The hydrogen atoms and crystal water molecules are omitted for clarity.
Figure 6. Representation of the Ni-L2 3D supramolecular framework.
Figure 9. Representation of the Ni-L1 2D net.
nitrogen atoms from two L1 ligands (L1A and L1B), two O atoms from water molecules. The bond distances and angles around the Ni2 ions are 2.095(9) and 2.105(8) Å for Ni N, 2.115 (7) Å for Ni O, 88.6(3) 179.998(2)° for N Ni N, 88.4(3) 92.5(3)° for N Ni O, and 180.0(2)° for O Ni O. A notable feature in the structure of 3 is that the Ni1, Ni2 ions and three types of L1 ligands form an interesting 2D net with two different kinds of grid-like chains (a and b) (Figure 9): Tetragonal grids, with a dimension of ca. 14.228 13.254 Å, form the chain a, while hexagonal grids with chair conformation (Figure S6, Supporting Information) form the chain b. The chains a and b
share two Ni ions. The PMo12a anion, offering two terminal O atoms (O39), acts as a two-connected ligand to link two 2D nets via Ni1 ion (Figure 8, 10, and S7, Supporting Information). Thus, a (4 3 63 3 82)2(42 3 62 3 82) 3D MOF is formed, in which Keggin anions PMo12a exert their linkage role. Furthermore, two sets of these 3D MOFs exist, which interpenetrate with each other to form a 2-fold interpenetrating structure, as shown in Figure 11. Interestingly, the 2-fold interpenetrating structure has two different sizes of channels (channel A and channel B). The PMo12b anions acting as inorganic template incorporate only into the bigger hexagonal channels (channel B), while the tetragonal 3459
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Crystal Growth & Design channels only accommodate the water molecules. In a word, the Keggin anions in compound 3 act as not only linkages but also templates. Both of the roles contribute to construct the interesting structure of 3. In contrast, the PMo12a anions in compound 3 act as bidentate linkages, while the anions in compound 1 act as tetradentate linkages. The coordination sites offered by Keggin anions in 3 are less than 1, which may be caused by the template roles of other discrete PMo12b anions in 3. If the coordination sites offered by some Keggin anions in 3 become more, the space would be too congested to accommodate the template anions. FT-IR Spectra. The IR spectra of compounds 1 3 are shown in Figure S8, Supporting Information, the characteristic bands at 975, 925, 790, and 1022 cm 1 for 1 are assigned to νas(W Ot),
Figure 10. The PMo12a anion offering two terminal O atoms to link the 2D nets va Ni1 ion.
Figure 11. The 2-fold interpenetrated structure and two different sizes of nanotube channels (code A and code B). PMo12b anions (yellow balls) incorporating only into the code B channels. (The red rectangle represents the 2D net with two different kinds of grid-like chains, and the purple elliptical represents the 1D chains linking the 2D nets.)
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νas(W Ob W), νas(W Oc W) and νas(Si Oa),14 961, 889, 809, and 1058 cm 1 for 2, and 970, 895, 805, and 1068 cm 1 for 3 are attributed to νas(Mo Ot), νas(Mo Ob Mo), νas(Mo Oc Mo), and νas(P Oa),15 respectively. Furthermore, the bands at 1800 1100 cm 1 are ascribed to stretching vibrations of νas(CdN) and νas(NdN) of the triazole-ring and 3200 2700 cm 1 are attributed to the CH2 stretching vibrations in L1 or L2 molecules.3c,7c In addition, a weak broad band at 3400 3600 cm 1 should be attributed to the vibration of ν(OH) of water molecules. Thermalgravimetric Analyses and PXRD. The thermogravimetry (TG) analyses of 1, 2, and 3 were carried out in flowing N2 with a heating rate of 10 °C 3 min 1 in the temperature range of 40 720 °C, as shown in Figure S9, Supporting Information. The TG curves of compounds 1 3 show two distinct weight loss steps: The first weight loss steps occur below 300 °C corresponding to the loss of water molecules. The second weight loss step of compound 1 in the range of 300 660 °C can be attributed to the decomposition of L1 ligands. The observed weight loss (29.49%) is consistent with the calculated value (29.96%). In the TG curves for compounds 2 and 3, the second weight loss step from 300 to 600 °C can be ascribed to the loss of organic molecules, 25.05% (25.45%) for 2 and 19.56% (calcd 19.10%) for 3.16 The phase purities of the compounds 2 and 3 were confirmed by PXRD measurements (Figure S10, Supporting Information). The difference in reflection intensities between the experimental and the simulated patterns is due to the different orientation of the crystals in the powder samples. Electrochemical Behaviors of the 1 CPE and 3 CPE in Aqueous Electrolyte. The redox properties of compounds 1, 2, and 3 were investigated in 1 M H2SO4 aqueous solution. The electrochemical behaviors of the compounds 2 (Figures S11 and 12, Supporting Information) and 3 bulk-modified carbon paste electrode (2 CPE and 3 CPE) are similar except for some slight potential shift, and 3 CPE has been taken as an example. The cyclic voltammetry for 1 CPE at different scan rates are presented in the potential range of 200 to 700 mV (Figure 12a). There exhibits two reversible redox peaks I I’ and II II’ with the mean peak potentials E1/2 = (Epa + Epc)/2 are approximately 458 (I I’) and 615 (II II’) mV, respectively, which correspond to the redox of SiW12 polyanion.14,17 As shown in Figure 12b, in the potential range of +700 to 120 mV for 3 CPE, there are three reversible redox peaks I I’, II II’, and III III’ with the mean peak potentials of approximately 350, 189, and 46 mV, respectively, which can be attributed to the three consecutive two-electron processes of the PMo12
Figure 12. (a) Cyclic voltammograms of the 1 CPE in the 1 M H2SO4 aqueous solution at different scan rates (from inner to outer: 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 250, 300, 350, 400, 450, 500, 550, 600 mV s 1). (b) Cyclic voltammograms of the 3 CPE in the 1 M H2SO4 aqueous solution at different scan rates (from inner to outer: 40, 60, 80, 100, 120, 140, 160, 180, 200, 250, 300, 350, 400, 450, 500 mV s 1). 3460
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Figure 13. (a) Cyclic voltammograms of the 1 CPE in 1 M H2SO4 aqueous solution containing 0.0 0.60 mM KNO2 and a bare CPE in 1.0 mM KNO2 + 1 M H2SO4 aqueous solution. Potentials vs SCE. Scan rate: 140 mV s 1. (b) Cyclic voltammograms of the 3 CPE in 1 M H2SO4 aqueous solution containing 0.0 0.875 mM KNO2 and a bare CPE in 1.0 mM KNO2 + 1 M H2SO4 aqueous solution. Potentials vs SCE. Scan rate: 140 mV s 1.
polyanions.18 The peak currents are proportional to the scan rates up to 600 mV s 1 for 1 CPE and 500 mV s 1 for 3 CPE, which indicates that the redox processes of the 1 CPE and 3 CPE are surface-controlled (Figures S13 14). In this work, we studied the electrocatalytic reduction of nitrite at 1 CPE and 3 CPE in the acid solution. It is known that direct electroreduction of nitrite requires a large overpotential at most electrode surfaces, and so no obvious response was observed for nitrite at the bare CPE in the potential range of 700 to 200 mV and +700 to 120 mV in 1 M H2SO4 aqueous solution. As can be seen from Figure 13, with the addition of nitrite, all the reduction peak currents increase markedly, while the corresponding oxidation peak currents decrease dramatically, which indicates that the two reduced species of SiW12 in 1 CPE and the three reduced species of PMo12 in 3 CPE all show good electrocatalytic activity toward the reduction of nitrite.14,17 19 It is noteworthy that the third reduced species of 3 CPE showed the best electrocatalytic activity; that is, the catalytic activity is enhanced with increasing extent of polyanion reduction (Figure S15, Supporting Information).
’ CONCLUSION Three new inorganic organic hybrid compounds constructed from NiII-bis(triazole) networks and Keggin anions have been successfully isolated under hydrothermal conditions. The Keggin anions play the linkage and template roles in the formation of compounds 1 3. Compound 1 exhibits a 3D Ni-L1 framework with hexagonal channels, in which the tetradentate SiW12 anions are incorporated. In compound 2, PMo12 anions act as inorganic templates, inducing the construction of a 3D supramolecular network based on Ni-L2 motif. In compound 3, the PMo12a anion, acting as a bidentate inorganic linkage, links the Ni-L1 2D nets to form a (4 3 63 3 82)2(42 3 62 3 82) 3D framework. The 3D frameworks interpenetrate with each other to form a 2-fold interpenetrating structure, containing two different sizes of channels. The PMo12b guests act as templates embedding in the bigger hexagonal channels of this 2-fold interpenetrating structure. Compound 3 is the first POM-templated compound, in which the Keggin anions also act as inorganinc linkages to construct a 2-fold interpenetrating 3D framework. This work may provide informative examples in preparing POM-based compounds, exerting the linkage and template roles of POMs. Thus, further study on other types of POMs and organic ligands is underway.
’ ASSOCIATED CONTENT
bS
Supporting Information. Three X-ray crystallographic files (CIF); selected bond distances and angles, and figures for compounds 1 3. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*Tel: +86-416-3400158. Fax: +86-416-3400158. E-mail: wangxiuli@ bhu.edu.cn.
’ ACKNOWLEDGMENT We are thankful for financial support from the National Natural Science Foundation of China (No. 20871022), New Century Excellent Talents in University (NCET-09-0853), and Talentsupporting Foundation of Liaoning Province (No. 2009R03). ’ REFERENCES (1) (a) Yamase, T. Chem. Rev. 1998, 98, 307. (b) Ritchie, C.; Ferguson, A.; Nojiri, H.; Miras, H.; Song, Y. F.; Long, D. L.; Cronin, L. Angew. Chem., Int. Ed. 2008, 47, 5609. (c) Xi, Z. W.; Zhou, N.; Sun, Y.; Li, K. L. Science 2001, 292, 1139. (d) Botar, B.; Geletili, Y. V.; K€ogerler, P.; Musaew, D. G.; Hill, C. L. J. Am. Chem. Soc. 2006, 128, 11268. (e) Kamata, K.; Sumida, Y.; Yamaguchi, K.; Hikichi, S.; Mizuno, N. Science 2003, 300, 964. (2) (a) Hagrman, D.; Zubieta, C.; Rose, D. J.; Zubieta, J.; Haushalter, R. C. Angew. Chem., Int. Ed. 1997, 36, 873. (b) Shivaiah, V.; Das, K. S. Inorg. Chem. 2005, 44, 8846. (c) Jiang, C. J.; Lesbani, A.; Kawamoto, R.; Uchida, S.; Mizuno, N. J. Am. Chem. Soc. 2006, 128, 14240. (3) (a) Ren, Y. P.; Kong, X. J.; Hu, X. Y.; Sun, M.; Long, L. S.; Huang, R. B.; Zheng, L. S. Inorg. Chem. 2006, 45, 4016. (b) Sha, J. Q.; Peng, J.; Liu, H. S.; Chen, J.; Dong, B. X.; Tian, A. X.; Su, Z. M. Eur. J. Inorg. Chem. 2007, 46, 1268. (c) Tian, A. X.; Ying, J.; Peng, J.; Sha, J. Q.; Han, Z. G.; Ma, J. F.; Su, Z. M.; Hu, N. H.; Jia, H. Q. Inorg. Chem. 2008, 47, 3274. (d) Zhai, Q. G.; Wu, X. Y.; Chen, S. M.; Zhao, Z. G.; Lu, C. Z. Inorg. Chem. 2007, 46, 5046. (e) Lin, H. S.; Maggard, P. A. Inorg. Chem. 2008, 47, 8044. (f) Cao, R. G.; Liu, S. X.; Xie, L. H.; Pan, Y. B.; Cao, J. F.; Ren, Y. H.; Xu, L. Inorg. Chem. 2007, 46, 3541. (g) Bontchev, R. P.; Venturini, E. L.; Nyman, M. Inorg. Chem. 2007, 46, 4483. (h) Zang, H. Y.; Lan, Y. Q.; Yang, G. S.; Wang, X. L.; Shao, K. Z.; Xu, G. J.; Su, Z. M. CrystEngComm 2010, 12, 434. (i) Yang, H. X.; Gao, S. Y.; L, J.; Xu, B.; L, J. X.; Cao, R. Inorg. Chem. 2010, 49, 736. 3461
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