The first two-dimensional organic–inorganic hybrid constructed by oxalate-bridging scandium-substituted Keggin-type silicotungstate and [Cu(en)2]2 + coordination cations

Inorganic Chemistry Communications 20 (2012) 191–195

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The first two-dimensional organic–inorganic hybrid constructed by oxalate-bridging scandium-substituted Keggin-type silicotungstate and [Cu(en)2] 2 + coordination cations Dongdi Zhang a, b, Shaowei Zhang b, Pengtao Ma b, Jingping Wang b,⁎, Jingyang Niu b,⁎ a b

Pharmaceutical College, Henan University, Kaifeng, Henan 475004, PR China Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, PR China

a r t i c l e

i n f o

Article history: Received 13 January 2012 Accepted 8 March 2012 Available online 16 March 2012 Keywords: Keggin-type Polyoxometalate Silicotungstate RE–TM heterometals Oxalate

a b s t r a c t The hydrothermal reactions of Keggin-type silicotungstate with rare-earth–transition-metal (RE–TM) heterometals in the presence of mixed ligands of oxalate and en (en = ethylenediamine) generate a novel two-dimensional (2D) organic–inorganic hybrid oxalate-bridging scandium-substituted silicotungstate. The complex [Cu(en)2(H2O)]2 {[Cu(en)2(H2O)]2[Cu(en)2]2[(α-SiW11O39)Sc(H2O)]2(C2O4)}·8H2O (1) has been further characterized by elemental analyses, powder X-ray diffraction (PXRD), IR spectra, thermogravimetric (TG) analyses, and single-crystal X-ray diffraction. X-ray structural analysis reveals that 1 exhibits the dimeric mono-Sc substituted Keggin [Sc(α-SiW11O39)]210 − subunits linked by the oxalate ligand, which further results in the 2D network architecture interconnected by [Cu(en)2]2 + coordination cations. Notably, 1 represents the first oxalate-bridging RE–TM heterometallic hybrid built by lacunary Keggin silicotungstate-supported RE derivatives and [Cu(en)2]2 + coordination cations. Furthermore, the TG curve of 1 displays two steps of slow weight loss in the range of 25–1000 °C. © 2012 Elsevier B.V. All rights reserved.

Polyoxometalates (POMs) of the early transition metal oxide clusters (Mo, W, V, Nb and Ta) can bind most of the transition metal (TM) or rareearth (RE) cations, leading to a large family of TM-substituted POMs or RE-substituted POMs (RESPs) with potential applications in various areas such as electrochemistry, photochemistry, catalysis and magnetism [1,2]. On the other hand, the RE–TM heterometallic coordination polymers are of remarkable interest because their meaningful structural architectures and interesting properties recommend them as candidates for adsorption materials, luminescent sensors and magnetic materials [3,4]. However, only little work has devoted to the heterometallic RE– TM POMs [5–17]. In recent years, our group has also made great efforts in RE–TM heterometallic POMs and isolated several types of RE–TM POM derivatives: {[Cu(en)2]2[Dy2(H2O)2(GeW11O39)3]}14 −, [As2W18Fe2 {Y(OH2)2}2O68]6 −, {[Cu(dap)2]4.5[Dy(α-PW11O39)2]}2 −, {[Cu(en)2]1.5 [Cu(en)(2,2′-bipy)(H2O)n]RE[(α-PW11O39)2]}6 − [RE=CeIII, PrIII, NdIII, GdIII, TbIII, ErIII] [18–21]. In general, the majority of aforementioned POMs were RE–TM heterometallic phosphotungstates and germantungstates, the silicotungstate analogs are relatively less [22–26], including three unprecedented cubane- {RECu3(OH)3O} (RE = LaIII, GdIII, Eu III) substituted [α-SiW11O39] 8 − POMs [22], a 1D double-chain derivative [(γ-SiW10O36)2(Cr(OH)(H2O))3(La(H2O)7)2] 4 − [23], two [RE-(μ3-O)3-Fe] (RE = DyIII, TbIII) cluster-based [α-SiW10 O38] 12 −

⁎ Corresponding authors. Fax: + 86 378 3886876. E-mail addresses: [email protected] (J. Wang), [email protected] (J. Niu). 1387-7003/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2012.03.006

fragments [24], two inorganic sandwich-type assemblages [{Ce(H2 O)7}2Mn4Si2W18O68(H2O)2]6 − [25], and {Nd2(H2O)12Cu4(H2O)2(SiW9 O34)2}6 − [26]. Furthermore, the investigations on silicotungstates containing RE–TM heterometals and organic multicarboxylic ligands are rather rare. To our knowledge, till now, only a family of organic–inorganic hybrid silicotungstate derivatives with RE–TM heterometals and mixed ligands {[Cu(en)2][Cu (en)2(H2O)][(α-SiW11O39)RE(H2O)(pzda)]}26 − (RE=YIII, DyIII, YbIII, LuIII) and {[Cu(en)2]2[Cu(pzda)2][(α-H2Si W11O39) Ce(H2O)]2}4 − have been just separated by us [27]. As an extension of our work, we expect to discover novel organic multicarboxylic bridged Sc–Cu heterometallic silicotungstates by the reaction of K4[α-SiW12O40]·17H2O, ScIII cations, CuII cations and mixed ligands (H2C2O4 and en) under hydrothermal conditions based on the following considerations: (i) The saturated Keggin-type [α-SiW12O40]4 − polyoxoanions (POAs) easily degrade and isomerize to a variety of silicotungstate derivatives, such as [β-SiW12O40]4 −, [α-SiW11O39]8 −, [γ-SiW10 O36]8 −, [αSiW9O34]10 −, [β-SiW8O31]10 −, [γ-SiW8O31]10 −, etc. (ii) Probably due to its comparatively shorter radius, as far as we know, rare or no reports on scandiumIII-substituted complexes have been documented. (iii) Compared with other TM caions, CuII ions exhibit more flexible various coordination modes (square, trigonal bipyramid, square pyramid and octahedron), moreover, the presence of the Jahn–Teller effect of the octahedron and pseudo-Jahn–Teller effect of the square pyramid for CuII cations can give different linkage modes to overcome steric hindrance, and thus form novel structures. Hence, CuII cations can be the good candidates as TM cation sources. (iv) As well known, the oxyphilic RE cations are

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readily bonded to the surface O atoms of the highly negative POMs, which makes the reactions of RE cations with carboxylic ligands become extremely difficult; moreover, the steric hindrance of RESPs is unfavorable to combining the relatively large ligands. Consequently, the oxalate ligand has been selected as multicarboxylic ligands to overcome these difficulties due to its small size and high affinity for RE cations [28]. (v) Our previous efforts demonstrate that some organic N-ligands can act as good donors to coordinate to electrophilic TM cations, readily generating TM complexes, which can work as the bridges to generate highdimensional structures [21]. Therefore, the use of aliphatic diamine ligand en has been fully considered during our preparation of novel RE–TM-heterometal-containing POMs. (vi) In addition, the hydrothermal method has been proved to be an effective strategy in preparing organic–inorganic hybrids because the solubility of starting materials can be increased and a variety of inorganic and organic components can be employed as well as its advantages with respect to growth and isolation of good single crystals. On the basis of the aforementioned points, by trial and error, a novel organic–inorganic hybrid silicotungstate with Sc–Cu heterometals and mixed ligands has been successfully isolated, which is formulated as [Cu(en)2(H2O)]2{[Cu(en)2(H2O)]2[Cu(en)2]2 [(α-SiW11O39)Sc(H2O)]2(C2O4)}·8H2O (1). X-ray structural analysis reveals that 1 shows the dimeric mono-Sc substituted Keggin [Sc(α-SiW11O39)]210 − subunits connected by the oxalate ligand, further leading to the 2D network architecture linked by [Cu(en)2] 2 + coordination cations. It is worth noting that 1 represents the first oxalatebridging RE–TM heterometallic hybrid constructed by lacunary Keggin silicotungstate-supported RE derivatives and [Cu(en)2] 2 + coordination cations. Compound 1 can be hydrothermally prepared by the reaction of K4 [α-SiW12O40]·17H2O [29] with ScCl3 6H2O and CuCl2 2H2O in the presence of H2C2O4 and en [30]. The experimental PXRD pattern of 1 was in good agreement with the simulated PXRD pattern from the single-crystal X-ray diffraction, suggesting the good phase purity for 1 (Fig. 1). The differences in intensity between them may be due to the variation in preferred orientation of the powder sample during collection of the experimental PXRD pattern. Bond–valence sum calculations [31] indicate that the oxidation states of W, Sc and Cu elements in 1 are +6, +3 and +2, respectively. Single-crystal X-ray analysis reveals [32] that 1 crystallizes in the orthorhombic space group Pbca. The skeleton of 1 consists of one {[Cu(en)2(H2O)]2[Cu(en)2]2[(α-SiW11O39)Sc(H2O)]2(C2O4)} 4 − POA (Fig. 2), two free [Cu(en)2(H2O)]2 + ions and eight lattice water molecules. Because of the coexistence of octahedral and square pyramidal geometries of the CuII cations, the Jahn–Teller effect of the octahedral and pseudo-Jahn–Teller effect of the square pyramid and different linkage modes can overcome larger steric hindrance and help to stabilize the formed larger aggregates. As a result, in the structural description of the compound, the Cu–O weak interactions will be considered because the evident Jahn–Teller distortion of CuII cations in the crystal field leads to the elongation of the Cu–O distances, and this phenomenon is very common in the POM chemistry [20,33–35]. Three crystallographic independent copper ions exhibit two types of coordination geometries. The Cu1 ion exhibits in the six-coordinate octahedral geometry constituted

Fig. 1. Comparison of the simulated and experimental PXRD patterns of 1.

Fig. 2. Polyhedral/ball-and-stick representation of the molecular structural unit of 1, H atoms, lattice water molecules and the free [Cu3(en)2(H2O)]2 + ions are omitted for clarity.

by four N atoms from two en ligands [Cu–N: 1.98(2)–2.02(2) Å], one terminal O atom from the [Sc(α-SiW11O39)] 5 − POA [Cu–O: 2.53(15) Å] and one O atom from the oxalate ligand [Cu–O: 2.88(14) Å]. The decorated [Cu2(en)2(H2 O)]2 + ion adopts the same geometry to the [Cu1(en)2] 2 + ion with four N atoms from two en ligands [Cu–N: 1.96(2)–2.03(2) Å], one terminal O atom from the [Sc(α-SiW11O39)]5 − POA [Cu–O: 2.82(17) Å] and one O atom from the water ligand [Cu–O: 2.63(19) Å]. The free [Cu3(en)2(H2O)] 2 + ion displays square pyramid geometry, which is defined by four N atoms from the chelating en ligands [Cu–N: 1.99(19)–2.02(3) Å] and one water ligand [Cu–O: 2.40(18) Å]. The dimeric {[(α-SiW11O39)Sc (H2O)]2(C2O4)}12 − POA consists of two mono-Sc substituted [Sc(α-SiW11O39)]5 − subunits and one bridged C2O42 − ligand. The [Sc(α-SiW11O39)]5 − subunit formed by the incorporation of the Sc1III cation into the monovacant [α-SiW11O39]8 − POA, which is derived from the classical Keggin-type [α-SiW11O39] 8 − by removal of a W = Od group. The Sc1III cation displays a rare sevencoordinated monocapped trigonal prism geometry bonding to four available O atoms of the lacunary site of the [α-SiW11O39] 8 − POA, two O atoms from the C2O42 − ligand and one O atom from the water ligand with Sc1III–O distances of 2.02(19)–2.59(3) Å (Fig. 3). In the coordination configuration of the Sc1III cation, the O16, O35, O40 group and O12, O28, O41 group constitute the two bottom surfaces of the trigonal prism with the dihedral angle for the two bottom planes of 5.4°, and the distances of the Sc1III cation and the two bottom planes are 1.34 and 1.36 Å, respectively. The O28, O35, O40, O41 group, O12, O16, O40, O41 group and O12, O16, O28, O35 group form the three side planes of the trigonal prism and their standard deviations from their leastsquares are 0.06, 0.07 and 0.01 Å, respectively. The distances between the Sc1III cation and the three side planes are 0.71, 1.04 and 0.71 Å, respectively. In addition, the O1W occupies the cap position covering the side plane defined by the O28, O35, O40, O41 group and the distance between the “cap” and the plane is 1.87 Å. The above-mentioned data

Fig. 3. The coordination environment of the Sc1III cation in 1.

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Fig. 4. The 2D network of 1, H atoms, lattice water molecules and the free [Cu3(en)2(H2O)]2 + ions are omitted for clarity.

indicate that the monocapped trigonal prism is somewhat distorted. Interestingly, the C2O42 − ligands are combined with two ScIII cations and two CuII ions presenting a novel dimeric motif. Analogous oxalatebridging RE-substituted Keggin-type phosphotungstates {[(α-PW11O39) RE(H2O)]2 (C2O4)}10 − (RE=YIII, DyIII, HoIII, ErIII) (A) have been previously observed by us [28], however, this similar oxalate-bridging dimers have not been discovered as far as we know. Comparing 1 with A, three obvious differences are observed: (i) 1 was obtained under hydrothermal conditions other than the conventional aqueous solution; (ii) 1 was synthesized by the reaction of [α-SiW12O40]4 − with ScIII and CuII cations in the presence of oxalate and en, while A were obtained by the reaction of [α-PW11O39]7 − with YIII cations using NaOH and H2C2O4 to adjust the pH to 5.4; (iii) most important of all, the oxalate ligand in 1 binds ScIII and CuII ions as a tetradentate ligand whereas the oxalate ligand in A as a bidentate ligand connects two REIII ions to form the dinuclear RE–oxalate complexes. It is also of interest to compare 1 to {[Cu(en)2] [Cu(en)2(H2O)][(α-SiW11O39)RE(H2O)(pzda)]}26 − (RE=YIII, DyIII, YbIII, LuIII) (B), which are the only example of a series of pzda2 − ligands bridging monovacant Keggin-type silicotungstates containing both RE–TM heterometals and mixed ligands (H2pzda and en) to date and have been isolated by our group [27]. From a synthetic point of view, B and 1 were synthesized hydrothermally by the reaction of [α-SiW12O40]4 − with REIII and CuII cations in the presence of mixed organic ligands, which further corroborate the hydrothermal method is an effective strategy in producing novel organic–inorganic hybrid POM derivatives. Additionally, both of them contain the [α-SiW11O39] 8 − units, RE–TM heterometals and [Cu(en)2] 2 + ions. On the other hand, the major discrepancies are as follows: (i) adjacent [Sc(α-SiW11O39)]5 − POAs are interconnected by oxalate ligands in 1, in contrast, adjacent [RE(αSiW11O39)2] 13 − POAs in B are linked by H2pzda organic ligands; (ii) unlike B, the dimeric {[(α-SiW11O39)Sc(H2O)]2(C2O4)}12 − POAs are linked by [Cu(en)2] 2 + ions in 1, leading to a 2D network. It is worth mentioning here that the oxalate ligands in 1 act as the tetradentate mode to bind two ScIII cations and two CuII ions, such coordination mode has not been known as far as we are aware. The most remarkable structural feature of 1 is that the adjacent {[(α-SiW11O39)Sc(H2O)]2(C2O4)}12 − subunits are connected by [Cu1(en) 2] 2 + coordinated cations resulting in the 2D network in the ac plane(Fig. 4), which represents the first organic–inorganic hybrid 2D RE–TM heterometallic silicotungstate with mixed organic ligands. Topologically, if each {[(α-SiW11O39)Sc(H2O)]2(C2O4)} 12 − subunit is considered as a 4-

connected node, the 2D network of 1 can be described as a (4,4)topological network with the Schläfli symbol of (4 4 ·6 2 ) (Fig. 5). The IR spectrum of 1 shows the related characteristic νas(Si–Oa), terminal νas(W–Ot), corner-sharing νas(W–Ob) and edge-sharing νas(W–Oc) asymmetrical vibration peaks derived from Keggin POA frameworks, [36] similar to those of parent monovacant POAs [αSiW11O39] 8 − due to the fact that the POAs display the same Cs symmetry, suggesting that the POM moiety of 1 still retains the basic framework of the Keggin structure (Fig. 6). The Si–O mode, observed as a single signal at 925 cm− 1 for the saturated Keggin [α-SiW12O40]4 − POA [29,36], shifts to 1003 cm− 1 in the spectrum of 1, which is mainly due to a consequence of the distortion of the SiO4 groups encapsulated in Keggin POAs [21,37]. The W–O stretching vibration bands resulting from the Keggin-type structure, namely, νas(W–Ot), νas(W–Ob–W) and νas(W–Oc–W) appear at 952, 897, 833, 791 and 702 cm− 1, respectively. Compared to the monovacant POM K8[(α-SiW11O39)]·13H2O, the νas(W–Ot) vibration peak for 1 red-shifts to 7 cm− 1, the possible major reason for this may be that the ScIII cations have stronger interactions to the terminal oxygen atoms of the POAs, impairing the W–Ot bonds, reducing the W–Ot bond force constant and leading to the decrease of the W–Ot vibration frequency [21,37]. The νas(Si–Oa), and νas(W–Ob–W) vibration frequencies for 1 have different blue-shifts of 7 and 9 cm− 1, respectively, as a result of the lower symmetry of

Fig. 5. The (44·62) topology network.

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Notably, 1 represents the first 2D oxalate-bridging RE–TM heterometallic hybrid constructed by lacunary Keggin silicotungstate-supported RE derivatives and [Cu(en)2]2 + coordination cations, which endows us with great opportunities and challenges in exploiting and synthesizing more novel organic–inorganic hybrid multi-dimensional RE–TM heterometallic hybrid POM derivatives by means of the appropriate choice of different POMs and/or organic ligands in the following time. Acknowledgments This work was supported by the Natural Science Foundation of China, Special Research Fund for the Doctoral Program of Higher Education, Innovation Scientists and Technicians Troop Construction Projects of Henan Province and Natural Science Foundation of Henan Province. Appendix A. Suppleentary material

Fig. 6. IR spectra of 1 and the free H2C2O4 ligand.

[α-SiW11O39]8 − POA in 1 than in K8[(α-SiW11O39)]·13H2O [21,37]. As we all know, for the coordination modes of carboxylate group, the difference between the asymmetric (νasym) and symmetric (νsym) carboxylate stretches (Δν = νasym − νsym) is often used [27,38]. Strong absorption bands at 1690 and 1350 cm− 1 can be regarded as the asymmetric and symmetric stretching vibrations of the carboxylate group of the free oxalate ligand (Fig. 6). These bands are observed in 1655 and 1371 cm− 1 for 1, indicating that the oxalate ligands coordinate to the ScIII and CuII ions. The Δν values indicate the presence of bridging coordination mode for the oxalate ligand [27,38]. In addition, the –NH2 and – CH2 bending vibration bands are observed at 1632–1500 cm− 1 and 1460–1400 cm− 1 and the –OH stretching vibration bands appear at 3433 cm− 1. The occurrence of these resonance signals demonstrates the presence of en ligands, [21,37] being in good agreement with the results obtained from X-ray single-crystal structural analyses. To investigate the thermal stability of 1, TG analysis was performed under N2 atmosphere in the range of 25–1000 °C (Fig. 7). The TG curve of 1 displays two steps of slow weight loss in the range of 25–1000 °C, the first weight loss is approximately 4.22% between 25 and 275 °C, being attributed to the removal of 8 crystal water molecules and 6 coordinated water molecules (calcd. 3.66%). The second weight loss of 11.85% between 275 and 1000 °C is followed by the decomposition of the oxalate ligand and 12 en organic ligands (calcd. 11.74%). In conclusion, an organic–inorganic hybrid oxalate-bridging Sc–Cu heterometallic silicotungstate with mixed ligands has been obtained.

Fig. 7. The TG curve of 1 on crystalline samples in a N2 atmosphere in the range of 25–1000 °C.

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derivatives: [Cu(en)2]2H6[Ce(α-PW11O39)2]·8H2O and [Cu(dap)2 (H2O)] [Cu(dap)2]4.5[Dy(α-PW11O39)2]·4H2O, Inorg. Chem. Commun. 14 (2011) 324–329. J.Y. Niu, S.W. Zhang, H.N. Chen, J.W. Zhao, P.T. Ma, J.P. Wang, 1-D, 2-D and 3-D organic–inorganic hybrids assembled from Keggin-type polyoxometalates and 3d-4f heterometals, Cryst. Growth Des. 11 (2011) 3769–3777. B. Nohra, P. Mialane, A. Dolbecq, E. Rivière, J. Marrot, F. Sécheresse, Heterometallic 3d-4f cubane clusters inserted in polyoxometalate matrices, Chem. Commun. (2009) 2703–2705. J.D. Compain, P. Mialane, A. Dolbecq, I. Mbomekallé, M.J. Marrot, F. Sécheresse, C. Duboc, E. Rivière, Structural, magnetic, EPR, and electrochemical characterizations of a spin-frustrated trinuclear CrIII polyoxometalate and study of its reactivity with lanthanum cations, Inorg. Chem. 49 (2010) 2851–2858. Z.M. Zhang, Y.G. Li, S. Yao, E.B. Wang, Hexameric polyoxometalates decorated by six 3d-4f heterometallic clusters, Dalton Trans. (2011) 6475–6479. W.L. Chen, Y.G. Li, Y.H. Wang, E.B. Wang, An inorganic aggregate based on a sandwich-type polyoxometalate with lanthanide and potassium cations: from 1D chiral ladder-like chains to a 3D open framework, Eur. J. Inorg. Chem. (2007) 2216–2220. Z.M. Zhang, Y.G. Li, W.L. Chen, E.B. Wang, X.L. Wang, Two-dimensional (3,6)-topological inorganic aggregate based on the sandwich-type polyoxometalate and lanthanide linkers, Inorg. Chem. Commun. 11 (2008) 879–882. S.W. Zhang, J.W. Zhao, P.T. Ma, J.Y. Niu, J.P. Wang, Rare-earth–transition-metal organic–inorganic hybrids based on Keggin-type polyoxometalates and pyrazine2,3-dicarboxylate, Chem. Asian J. 7 (2012) 966–974. S.W. Zhang, Y. Wang, J.W. Zhao, P.T. Ma, J.P. Wang, J.Y. Niu, Two types of oxalatebridging rare-earth-substituted Keggin-type phosphotungstates {[(α-PW11O39) RE(H2O)]2(C2O4)}10 − and {(α-x-PW10O38) RE2(C2O4)(H2O)2}3 −, Dalton Trans. 41 (2012) 3764–3772. C. Rocchiccioli-Deltcheff, M. Fournier, R. Franck, R. Thouvenot, Vibrational investigations of polyoxometalates. 2. Evidence for anion–anion interactions in molybdenum(VI) and tungsten(VI) compounds related to the Keggin structure, Inorg. Chem. 22 (1983) 207–216. Compound 1 can be prepared as follows: K4[α-SiW12O40]·17H2O (0.50 g, 0.15 mmol), ScCl3 6H2O (0.10 g, 0.39 mmol), CuCl2 2H2O (0.11 g, 0.65 mmol), H2C2O4 (0.03 g, 0.33 mmol) and ethylenediamine (0.2 mL, 2.96 mmol) were successively added in H2O (10 mL). After stirring for 45 min, the resulting mixture was transferred and sealed in a 25-mL Telfon-lined stainless steel autoclave, kept at 170 °C for 117 h and then slowly cooled to room temperature. Purple block crystals were collected by filtering, washed with distilled water and dried in air. Yield: ca. 13% (based on K4[α-SiW12O40]·17H2O). anal. calc. (%) for C26H124Cu6N24O96Sc2Si2W22: C, 4.54; H, 1.82; N, 4.89; Si, 0.82; Sc, 1.31; Cu, 5.54; W, 58.78. Found (%): C, 4.37; H, 1.96; N, 5.05; Si, 0.94; Sc, 1.19; Cu, 5.39; W, 58.92.

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IR (KBr pellets): 3433 (w), 1655 (m), 1631 (m), 1457 (m), 1394 (m), 1371 (m), 1275 (w), 1120 (w), 1038 (s), 1003 (w), 952 (s), 897 (s), 833 (s), 791 (m), 702 (m) cm− 1. I.D. Brown, D. Altermatt, Bond–valance parameters obtained from a systematic analysis of the inorganic crystal structure database, Acta Crystallogr. B41 (1985) 244–247. Crystal data for 1: C26H124Cu6N24O96Sc2Si2W22, Mr = 6881.53, orthorhombic space group Pbca, a = 21.262(8) Å, b = 26.615(9) Å, c = 21.497(7) Å, V = 12165 (7) Å3, Z = 4, Dc = 3.757 g·m− 3, μ = 21.964 mm− 1, GOF = 1.011, R1 = 0.0598, wR2 = 0.1342 [I > 2σ(I)] and R1 = 0.1172, wR2 = 0.1525 (all data). Intensity data for 1 were collected on Bruker Apex-II CCD diffractometer with Mo Kα monochromated radiation (λ = 0.71073 Å) at 293(2) K. Routine Lorentz polarization and empirical absorption corrections were applied. The structure was solved by direct methods and refined by full-matrix least-squares methods on F2 with the SHELXTL-97 program package. No hydrogen atoms associated with the water molecules were located from the difference Fourier map. Positions of the hydrogen atoms attached to the carbon and nitrogen atoms were geometrically placed. All hydrogen atoms were refined isotropically as a riding mode using the default SHELXTL parameters. The restrains are used to resolve the ADP errors of some N and C atoms by the ISOR and SIMU instructions, and the distance of C10 and C11 atoms is bundled in the normal ranges by the DFIX instruction. B. Li, J.W. Zhao, S.T. Zheng, G.Y. Yang, Combination chemistry of hexa-coppersubstituted polyoxometalates driven by the CuII-polyhedra distortion: from tetramer, 1D chain to 3D framework, Inorg. Chem. 48 (2009) 8294–8303. Q.X. Han, P.T. Ma, J.W. Zhao, Z.L. Wang, W.H. Yang, P.H. Guo, J.P. Wang, J.Y. Niu, Three novel inorganic–organic hybrid arsenomolybdate architectures constructed from monocapped trivacant [AsIIIAsVMo9O34]6 − fragments with [Cu(L)2]2 + linkers: from dimer to two-dimensional framework, Cryst. Growth Des. 11 (2011) 436–444. J.W. Zhao, S.T. Zheng, W. Liu, G.Y. Yang, Hydrothermal synthesis and structural characterization of two 1-D and 2-D Dawson-based phosphotungstates, J. Solid State Chem. 181 (2008) 637–645. L.S. Felices, P. Vitoria, J.M. Gutiérrez-Zorrilla, L. Lezama, S. Reinoso, Hybrid inorganic– metalorganic compounds containing copper(II)-monosubstituted Keegin polyanions and polymeric copper(II) complexes, Inorg. Chem. 45 (2006) 7748–7757. J.W. Zhao, S.T. Zheng, G.Y. Yang, 0-D and 1-D inorganic–organic composite polyoxotungstates constructed from in-situ generated monocopperII-substituted Keggin polyoxoanions and copperII–organoamine complexes, J. Solid State Chem. 181 (2008) 2205–2216. H.Y. An, Z.B. Han, T.Q. Xu, Three-dimensional architectures based on lanthanidesubstituted double-Keggin-type polyoxometalates and lanthanide cations or lanthanide-organic complexes, Inorg. Chem. 49 (2010) 11403–11414.