- Email: [email protected]
Synthesis and characterization of three open-framework zinc phosphites with (3,4)-connected frameworks
Solid State Sciences 13 (2011) 1473e1477
Contents lists available at ScienceDirect
Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie
Synthesis and characterization of three open-framework zinc phosphites with (3,4)-connected frameworks Maoping Kang a, Daibing Luo b, Xiuchao Luo a, Zhien Lin a, * a b
College of Chemistry, Sichuan University, Chengdu 610064, PR China Analytical & Testing Center, Sichuan University, Chengdu 610064, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 16 March 2011 Received in revised form 9 April 2011 Accepted 4 May 2011 Available online 17 May 2011
By using different monoamines as the structure-directing agents, three new open-framework zinc phosphite compounds, [C4H10ON]2$[Zn3(HPO3)4] (1), [CH3CH2NH3]2$[Zn3(HPO3)4] (2) and [H2N(CH3)2]2$[Zn3(HPO3)4] (3), have been synthesized under hydro/solvothermal conditions. The three compounds have different (3,4)-connected frameworks constructed from strictly alternating ZnO4 tetrahedra and HPO3 pseudo pyramids. The presence of 12-ring channels in their structures is noteworthy. The removal of organic cations in the free voids of compound 1 by an ion-exchange process will make the structure collapse. Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords: Monoamine Crystal structure Open-framework Zinc phosphite 12-Ring channel
1. Introduction Hydrothermal synthesis of open-framework inorganic solids has been the subject of intense research owing to their rich structural chemistry and potential applications in catalysis, ion-exchange and separation [1e3]. Zeolitic aluminosilicates and aluminophosphates are the most well known open-framework compounds with 4-connected frameworks [4,5]. Since the pioneering work reporting the possibility of making open-framework metal phosphites in the presence of organic cations by Zubieta in 1995 [6], some transition metals and main group elements, such as V [7e9], Cr [10], Mn [11,12], Fe [13e15], Co [16e18], Ni [19,20], Zn [21e31], Be [32], Al [33], Ga [34], and In [35], have been successfully incorporated into phosphite frameworks. The ability of these metal ions to form MO4 tetrahedra, MO5 trigonal bipyramids, and MO6 octahedra, combined with the characteristic pseudo pyramidal HPO3 unit, implies that a large number of novel framework topologies can be potentially obtained in this system. The use of amine molecules with different size and shape as the structure-directing agents in the hydrothermal synthesis has been demonstrated to be a useful method to affect the structures of metal phosphites. Many diamine, triamine and polyamine molecules have
* Corresponding author. Fax: þ86 28 85412284. E-mail address: [email protected] (Z. Lin). 1293-2558/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2011.05.001
been studied during the past years [36]. However, a very limited number of open-framework metal phosphites have been obtained in the presence of monoamine molecules as the structure-directing agents. This is surprising, considering that several metal phosphites with extra-large pores have been prepared in the presence of different monoamines, including n-propylamine, n-butylamine, cyclopentylamine, and cyclohexylamine [37e40]. In an attempt to explore the structure-directing roles of three monoamines (i.e. morpholine, ethylamine, and dimethylamine), here we report hydro/solvothermal synthesis and characterization of three new open-framework zinc phosphites, [C4H10ON]2$[Zn3(HPO3)4] (1), [CH3CH2NH3]2$[Zn3(HPO3)4] (2) and [H2N(CH3)2]2$[Zn3(HPO3)4] (3). Compounds 1 and 2 are isostructural with H2apm,Zn3(HPO3)4 and [CH3CH2CH2NH3]2,[Zn3(HPO3)4], respectively [41e43]. Compound 3 has a novel (3,4)-connected framework topology with 12-ring channels.
2. Experimental 2.1. Materials and methods Reagents were purchased commercially and used without further purification. The CHN analyses were carried out on a Euro EA3000 analyzer. Powder X-ray diffraction (XRD) data were obtained using a Rigaku D/MAX-rA diffractometer with Cu-Ka
1474
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
radiation (l ¼ 1.5418 Å). IR spectrum (KBr pellet) was recorded on an ABB Bomen MB 102 spectrometer. The thermogravimetric analysis was performed on a Mettler Toledo TGA/SDTA 851e analyzer in a flow of N2 with a heating rate of 10 C/min from 30 to 700 C. 2.2. Synthesis 2.2.1. [C4H10ON]2$[Zn3(HPO3)4] (1) A mixture of Zn(OAc)2$2H2O (0.2195 g), H3PO3 (50 wt%, 0.4959 g), morpholine (0.3982 g), 1,4-dioxane (3.1021 ml) and H2O (2.015 g) was stirred under ambient conditions. The resulting mixture was sealed in a Teflon-lined steel autoclave and heated at 160 C for 3 days and then cooled to room temperature. The resulting product was recovered by filtration, washed with distilled water and dried in air. Yield: 0.1352 g (58.5% yield based on zinc). 2.2.2. [CH3CH2NH3]2$[Zn3(HPO3)4] (2) A mixture of ZnO (0.0814 g), H3PO3 (50 wt%, 0.3344 g), ethylamine (65 wt%, 0.1396 g) and H2O (8.5 g) was stirred under ambient conditions. The resulting gel was sealed in a Teflon-lined steel autoclave and heated at 160 C for 3 days and then cooled to room temperature. The resulting product, contains a small amount of powder impurities and colorless crystals of compound 2 as the major phase, was recovered by filtration, washed with distilled water and dried in air. 2.2.3. [H2N(CH3)2]2$[Zn3(HPO3)4] (3) A mixture of Zn(OAc)2$2H2O (0.220 g), H3PO3 (0.246 g), L-Proline (0.115 g) and DMF (5.0 ml) was stirred under ambient conditions. The resulting gel was sealed in a Teflon-lined steel autoclave and heated at 80 C for 3 days and then cooled to room temperature. The resulting product, contains irregular-shape compound 3 and a large amount of two known zinc phosphite phases: [H2N(CH3)2]2Zn3(HPO3)4 and Zn2(H2O)4(HPO3)2,H2O [44,45], was recovered by filtration, washed with distilled water and dried in air. 2.3. Crystal structure determination Suitable single crystals of each compound were carefully selected under an optical microscope. Crystal structure determination by X-ray diffraction was performed on an Oxford Xcalibur diffractometer with graphite-monochromated MoKa (l ¼ 0.71073 Å) radiation at room temperature. The crystal structures were solved by direct methods. The zinc and phosphorus atoms were first located. The oxygen, nitrogen, carbon, and the hydrogen atoms attached to phosphorus atoms were found in the difference Fourier map. The hydrogen atoms attached to carbon and nitrogen atoms are added by calculation and refined using a riding model. The structures were refined on F2 by full-matrix least-squares methods using the SHELXTL program package [46]. All non-hydrogen atoms were refined anisotropically. The crystallographic data for 1e3 are summarized in Table 1. 2.4. Ion-exchange process The ion-exchange experiment of compound 1 was carried out by immersing 100 mg sample of the as-synthesized compound 1 in 10 ml of 1 M KNO3 aqueous solution at room temperature for 1 day. The exchanged solids were then recovered, washed thoroughly with water and dried in air. 3. Results and discussion Compounds 1e3 were obtained as colorless crystals under autogenous pressure. Single-crystal X-ray diffraction analysis reveals
Table 1 Crystal data and structure refinement for 1e3.
Empirical formula Formula weight Crystal system Space group a, Å b, Å c, Å Volume, Å3 Z Dc, g/cm3 m (Mo-Ka), mm1 Total data Unique data Data, I > 2s (I) Final R1, wR2 [I > 2s (I)]
1
2
3
C8H24N2O14 P4Zn3 692.28 Orthorhombic Pna21 14.4115(4) 16.0984(5) 9.6856(3) 2247.08(12) 4 2.046 3.528 5729 3216 2843 0.0249, 0.0516
C4H20N2O12P4Zn3 608.21 Orthorhombic Pccn 9.6456(3) 23.1871(9) 8.7113(3) 1948.31(12) 4 2.074 4.046 4677 1719 1414 0.0234, 0.0587
C4H20N2O12P4Zn3 608.21 Orthorhombic Iba2 25.8033(18) 8.6742(6) 8.4557(5) 1892.6(2) 4 2.135 4.165 2072 1118 1069 0.0307, 0.0800
that compound 1 has a three-dimensional structure, which is isostructural with H2apm,Zn3(HPO3)4 [41]. As shown in Fig. 1a, the asymmetric unit consists of three crystallographically independent zinc atoms and four crystallographically independent phosphorus atoms. All the zinc atoms are tetrahedrally coordinated by oxygen atoms. The phosphorus atoms each make three PeOeZn linkages with adjacent zinc atoms, with the fourth vertex occupied by a terminal hydrogen atom [(PeH)av ¼ 1.38 Å]. The ZneO bond lengths vary from 1.853(2) to 1.961(3) Å, and the PeO bond lengths range from 1.463(1) to 1.584(2) Å. The connectivity of strictly alternating ZnO4 tetrahedra and HPO3 pseudo pyramids gives rise to a three-dimensional inorganic framework with zigzag 12-ring channels running along the [100] direction (Fig. 2a). The complicated structure can be alternatively understood from a layered structure, as shown in Fig. 2b. When the (4.6.12) layered structures are stacked along the [100] direction in an ABAB sequence, the three-dimensional structure of 1 is formed. The framework density (FD, defined as the number of polyhedra per 1000 Å3) of compound 1 is 12.5, which is similar to other openframework zinc phosphites with 12-ring channels, such as FJ-8 (FD ¼ 13.2) and FJ-15 (FD ¼ 13.4) [47,48]. The monoprotonated morpholine cations reside in the free voids of compound 1 and interact with the framework oxygen atoms through extensive hydrogen bonds. The four shortest N$$$O distances are 2.752(5) Å, 2.801(5) Å, 2.826(5) Å, and 2.908(5) Å for N2eO7, N1eO6, N1eO12, and N2eO11, respectively. A void space analysis performed by use of the program PLATON indicates that the extraframework organic cations in compound 1 occupy 47.5% of the unit cell volume [49]. The structure of compound 2 consists of an anionic zinc phosphite framework and monoprotonated ethylamine cations. The asymmetric unit of 2 contains 13 non-hydrogen atoms, of which two zinc atoms and two phosphorus atoms are crystallographically independent (Fig. 1b). Zn(1) atom locates in a general position and Zn(2) atom occupies a special position with site multiplicity of 0.5. Both the zinc atoms are tetrahedrally coordinated with four oxygen atoms. The two phosphorus atoms each share three oxygen atoms with adjacent zinc atoms, with the fourth vertex occupied by a hydrogen atom [(PeH)av ¼ 1.38 Å]. The ZneO bond lengths are in the range of 1.911(2)e1.952(2) Å, and the PeO bond lengths vary from 1.504 (2) to 1.520(2) Å, in excellent agreement with those previously reported. The stoichiometry of [Zn3(HPO3)4] results in a net charge of 2, which is balanced by two monoprotonated ethylamine cations per formula unit. The inorganic framework of 2 is made up of strictly alternating ZnO4 tetrahedra and HPO3 pseudo pyramids. The FD value of compound 2 is 14.2, which is slightly higher than that of compound
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
1475
Fig. 3. (a) The three-dimensional structure of 2 with 12-ring channel is constructed by (b) a 4.82 layered structure and (c) a corner-sharing 4-ring chain. Color code: Zn, yellow; P, green; O, red; H, gray. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 1. View of the coordination environments of zinc and phosphorus atoms in compound 1 (a), compound 2 (b), and compound 3 (c), showing the atom labeling scheme, and with 30% thermal ellipsoids. Atom labels having “A” and “B” refer to symmetry-generated atoms.
1. Two distinct structural motifs, a 4.82 layered network and a corner-sharing 4-ring chain, are involved in the construction of the framework structure. As shown in Fig. 3, the two building units are cross-linked with each other via ZneOeP linkages, forming a three-dimensional structure with 12-ring channels. The monoprotonated ethylamine cations are well ordered in the free region of compound 2 due to the extensive hydrogen bonding between the amino groups and the framework oxygen atoms. The shortest
Fig. 2. (a) The three-dimensional structure of 1 with 12-ring channel is constructed by (b) the layered structures stacked along the [001] direction in an ABAB sequence. Color code: Zn, yellow; P, green; O, red; H, gray. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
1476
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
N$$$O distances are in the range of 2.876(3)e2.986(3) Å. A void space analysis performed by use of the program PLATON indicates that the extraframework organic cations in compound 2 occupy 38.3% of the unit cell volume. It should be noted that compound 2 is isostructural with another open-framework zinc phosphite, [CH3CH2CH2NH3]2,[Zn3(HPO3)4] [42,43]. The two compounds have the same framework topology with 12-ring channels. The main difference lies in their extraframework cations. In compound 2, the extraframework cations are monoprotonated ethylamine molecules, whereas in [CH3CH2CH2NH3]2,[Zn3(HPO3)4], the extraframework cations are monoprotonated propylamine molecules. In addition, all three unit cell axes in compound 2 are shorter than those in [CH3CH2CH2NH3]2,[Zn3(HPO3)4] due to the smaller size of structure-directing agents. The asymmetric unit of compound 3 contains 13 non-hydrogen atoms, of which 10 atoms belong to the host framework (two Zn, two P, and six O atoms) and 3 atoms belong to the guest species (Fig.1c). Both the zinc atoms are tetrahedrally coordinated by oxygen atoms with ZneO bond lengths varying from 1.918(4) to 1.967(4) Å. The phosphorus atoms each share three oxygen atoms with adjacent zinc atoms [PeO: 1.493(5)e1.529(4) Å], with the fourth vertex occupied by a terminal hydrogen atom [(PeH)av ¼ 1.15 Å]. The stoichiometry of [Zn3(HPO3)4] results in a net charge of 2, which is balanced by two monoprotonated dimethylamine cations per formula unit. It should be noted that no dimethylamine molecule was used as the starting material in the reaction system. They should be formed in situ by the decomposition of DMF molecules under solvothermal conditions. The structure of compound 3 has a new (3,4)-connected framework with FD value of 14.8. The three-dimensional structure of compound 3 can be described in terms of two distinct building units: a 63 layered network and a corner-sharing 4-ring chain. As shown in Fig. 4, the linkages between Zn(1)O4 tetrahedra and HP(1)O3 pseudo pyramids produce 63 layered networks, and the linkages between Zn(2)O4 tetrahedra and HP(2)O3 pseudo pyramids give rise to corner-sharing 4-ring chains. The 63 layered networks are crosslinked by corner-sharing 4-ring chains through ZneOeP linkages, producing the three-dimensional structure with 12-ring channels running along the [001] direction, wherein the organic cations reside. An intriguing structural feature of 3 is its resemblance to that of [H2N(CH3)2]2[M3(HPO3)4] (M ¼ Zn, Co) [44,50]. The two compounds contain the same amine (i.e. dimethylamine) as the structure-directing agent and their (3,4)-connected structures both contain corner-sharing 4-ring chains as the building units. One main difference between the two structures is that, in the structure of [H2N(CH3)2]2[M3(HPO3)4], the corner-sharing 4-ring chains are connected by metal ions to produce its three-dimensional structure, whereas in compound 3, the structure is built up by the linkages of 63 layered networks and the corner-sharing 4-ring chains. Among the three open-framework zinc phosphites, only compound 1 was obtained as a pure phase. The powder XRD pattern of the bulk product was in good agreement with the one simulated on the basis of the single-crystal structure. CHN analyses confirmed its stoichiometry (Anal. Found: C, 7.68; H, 3.19; N, 4.51%. Calcd: C, 7.90; H, 3.31; N, 4.61%). IR spectroscopy contained the bands at 1640, 1470, and 1400 cm1 caused by the bending vibrations of eNH2 and eCH2 groups, confirming the presence of amine cations in the structure. Thermogravimetric analysis of compound 1 was carried out in N2 with a heating rate of 10 C/min. It remained stable up to 270 C. On further heating, a two-step weight loss between 270e400 C and 510e600 C was observed, corresponding to the decomposition of two morpholine molecules per formula unit. The total weight loss for the two steps compared well with that calculated on the basis of the above interpretation (observed:
Fig. 4. (a) The three-dimensional structure of 3 with 12-ring channel is constructed by (b) a 63 layered structure and (c) a corner-sharing 4-ring chain. Color code: Zn, yellow; P, green; O, red; H, gray. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
24.83%; expected: 25.17%). To evaluate the ion-exchange property of compound 1, 100 mg sample of the as-synthesized compound 1 was immersed in 10 ml of 1 M KNO3 aqueous solution at room temperature for 1 day. XRD pattern of the exchange solid indicated that a new hydrated zinc phosphite, Zn2(H2O)4(HPO3)2$H2O, formed after the ion-exchange process [45]. 4. Conclusions In summary, three new opens-framework zinc phosphites were obtained as good quality single crystals under hydro/solvothermal conditions. These compounds have different three-dimensional inorganic frameworks with large 12-ring channels, wherein the protonated monoamines reside. While the structures of compounds 1 and 2 are closely related to the known (3,4)-connected zinc phosphites, compound 3 has a novel (3,4)-connected framework topology. The attempt to remove the organic cations in compound 1 by an ion-exchange process causes the structure collapse. The use of other monoamine as the structure-directing agent under similar hydro/solvothermal conditions may result in other novel open-framework metal phosphites with unique structures and physical properties. Acknowledgments We thank the support of this work by the NNSF of China (Grant 20801037). Appendix. Supplementary material Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.solidstatesciences.2011.05.001.
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
D. Maspoch, D. Ruiz-Molina, J. Veciana, Chem. Soc. Rev. 36 (2007) 770. S. Natarajan, S. Mandal, Angew. Chem. Int. Ed. 47 (2008) 4798. J. Jiang, J. Yu, A. Corma, Angew. Chem. Int. Ed. 49 (2010) 3120. M. Davis, Nature 417 (2002) 813. J. Yu, R. Xu, Chem. Soc. Rev. 35 (2006) 593. G. Bonavia, J. DeBord, R.C. Haushalter, D. Rose, J. Zubieta, Chem. Mater. 7 (1995) 1995. Z. Shi, G. Li, D. Zhang, J. Hua, S. Feng, Inorg. Chem. 42 (2003) 2357. R.-K. Chiang, N.-T. Chuang, J. Solid State Chem. 178 (2005) 3040. X. Jing, L. Zhang, S. Gong, G. Li, M. Bi, Q. Huo, Y. Liu, Micropor. Mesopor. Mater. 116 (2008) 101. S. Fernández, J.L. Mesa, J.L. Pizarro, L. Lezama, M.I. Arriortua, T. Rojo, Angew. Chem. Int. Ed. 41 (2002) 3683. S. Fernández, J.L. Mesa, J.L. Pizarro, L. Lezama, M.I. Arriortua, R. Olazcuaga, T. Rojo, Chem. Mater. 12 (2000) 2092. S. Fernández, J.L. Pizarro, J.L. Mesa, L. Lezama, M.I. Arriortua, R. Olazcuaga, T. Rojo, Inorg. Chem. 40 (2001) 3476. S. Fernández, J.L. Mesa, J.L. Pizarro, L. Lezama, M.I. Arriortua, T. Rojo, Chem. Mater. 14 (2002) 2300. W. Liu, H.-H. Chen, X.-X. Yang, J.-T. Zhao, Eur. J. Inorg. Chem. (2005) 946. J. Qiao, L. Zhang, Y. Yu, G. Li, T. Jiang, Q. Huo, Y. Liu, J. Solid State Chem. 182 (2009) 1929. L. Zhao, J. Li, P. Chen, G. Li, J. Yu, R. Xu, Chem. Mater. 20 (2008) 17. C.-C. Cheng, W.-K. Chang, R.-K. Chiang, S.-L. Wang, J. Solid State Chem. 183 (2010) 304. X. Liu, Y. Xing, X. Wang, H. Xu, X. Liu, K. Shao, Z. Su, Chem. Commun. 46 (2010) 2614. Z.-E. Lin, J. Zhang, S.-T. Zheng, G.-Y. Yang, J. Mater. Chem. 14 (2004) 1652. J. Liang, J. Li, J. Yu, Q. Pan, Q. Fang, R. Xu, J. Solid State Chem. 178 (2005) 2673. J.A. Rodgers, W.T.A. Harrison, Chem. Commun. (2000) 2385. W.T.A. Harrison, M.L.F. Phillips, J. Stanchfield, T.M. Nenoff, Inorg. Chem. 40 (2001) 895. W.T.A. Harrison, M.L.F. Phillips, T.M. Nenoff, J. Chem. Soc. Dalton Trans. (2001) 2459.
1477
[24] W.T.A. Harrison, R.M. Yeates, M.L.F. Phillips, T.M. Nenoff, Inorg. Chem. 42 (2003) 1493. [25] J.-X. Pan, S.-T. Zheng, G.-Y. Yang, Cryst. Growth Des. 5 (2005) 237. [26] D. Zhang, H. Yue, Z. Shi, M. Guo, S. Feng, Solid State Sci. 8 (2006) 192. [27] L. Chen, X. Bu, Chem. Mater. 18 (2006) 1857. [28] S. Mandal, S. Natarajan, Inorg. Chem. 47 (2008) 5304. [29] Y. Yang, Y. Zhao, J. Yu, S. Wu, R. Wang, Inorg. Chem. 47 (2008) 769. [30] Z. Lin, H.P. Nayek, S. Dehnen, Inorg. Chem. 48 (2009) 3517. [31] J.-D. Feng, K.-Z. Shao, S.-W. Tang, R.-S. Wang, Z.-M. Su, CrystEngComm 12 (2010) 1401. [32] W. Fu, L. Wang, Z. Shi, G. Li, X. Chen, Z. Dai, L. Yang, S. Feng, Cryst. Growth Des. 4 (2004) 297. [33] A. Lu, H. Song, N. Li, S. Xiang, N. Guan, H. Wang, Chem. Mater. 29 (2007) 4142. [34] L. Wang, T. Song, Y. Fang, Y. Wang, J. Xu, S. Shi, T. Zhu, J. Solid State Chem. 179 (2006) 865. [35] L. Wang, T. Song, J. Xu, Y. Wang, Z. Tian, S. Shi, Micropor. Mesopor. Mater. 96 (2006) 287. [36] T. Rojo, J.L. Mesa, J. Lago, B. Bazan, J.L. Pizarro, M.I. Arriortua, J. Mater. Chem. 19 (2009) 3793. [37] J. Liang, J. Li, J. Yu, P. Chen, Q. Fang, F. Sun, R. Xu, Angew. Chem. Int. Ed. 45 (2006) 2546. [38] Y. Yang, N. Li, H. Song, H. Wang, W. Chen, S. Xiang, Chem. Mater. 19 (2007) 1889. [39] Y.-L. Lai, K.-H. Lii, S.-L. Wang, J. Am. Chem. Soc. 129 (2007) 5350. [40] J. Li, L. Li, J. Liang, P. Chen, J. Yu, Y. Xu, R. Xu, Cryst. Growth Des. 8 (2008) 2318. [41] Z. Lin, S. Dehnen, J. Solid State Chem. 182 (2009) 3143. [42] D. Zhang, Z. Shi, W. Dong, W. Fu, L. Wang, G. Li, S. Feng, J. Solid State Chem. 177 (2004) 343. [43] S. Mandal, S. Natarajan, Solid State Sci. 8 (2006) 388. [44] L. Chen, X. Bu, Inorg. Chem. 45 (2006) 4654. [45] C.Y. Ortiz-Avila, P.J. Squattrito, M. Shieh, A. Clearfield, Inorg. Chem. 28 (1989) 2608. [46] G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112e122. [47] Z.-E. Lin, J. Zhang, S.-T. Zheng, G.-Y. Yang, Eur. J. Inorg. Chem. (2004) 953. [48] J.-X. Pan, S.-T. Zheng, G.-Y. Yang, Micropor. Mesopor. Mater. 75 (2004) 129. [49] A.L. Spek, Acta Crystallogr. Sect. A A46 (1990) C34. [50] Z. Lin, H.P. Nayek, S. Dehnen, Z. Anorg, Allg. Chem. 635 (2009) 2391.
Contents lists available at ScienceDirect
Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie
Synthesis and characterization of three open-framework zinc phosphites with (3,4)-connected frameworks Maoping Kang a, Daibing Luo b, Xiuchao Luo a, Zhien Lin a, * a b
College of Chemistry, Sichuan University, Chengdu 610064, PR China Analytical & Testing Center, Sichuan University, Chengdu 610064, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 16 March 2011 Received in revised form 9 April 2011 Accepted 4 May 2011 Available online 17 May 2011
By using different monoamines as the structure-directing agents, three new open-framework zinc phosphite compounds, [C4H10ON]2$[Zn3(HPO3)4] (1), [CH3CH2NH3]2$[Zn3(HPO3)4] (2) and [H2N(CH3)2]2$[Zn3(HPO3)4] (3), have been synthesized under hydro/solvothermal conditions. The three compounds have different (3,4)-connected frameworks constructed from strictly alternating ZnO4 tetrahedra and HPO3 pseudo pyramids. The presence of 12-ring channels in their structures is noteworthy. The removal of organic cations in the free voids of compound 1 by an ion-exchange process will make the structure collapse. Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords: Monoamine Crystal structure Open-framework Zinc phosphite 12-Ring channel
1. Introduction Hydrothermal synthesis of open-framework inorganic solids has been the subject of intense research owing to their rich structural chemistry and potential applications in catalysis, ion-exchange and separation [1e3]. Zeolitic aluminosilicates and aluminophosphates are the most well known open-framework compounds with 4-connected frameworks [4,5]. Since the pioneering work reporting the possibility of making open-framework metal phosphites in the presence of organic cations by Zubieta in 1995 [6], some transition metals and main group elements, such as V [7e9], Cr [10], Mn [11,12], Fe [13e15], Co [16e18], Ni [19,20], Zn [21e31], Be [32], Al [33], Ga [34], and In [35], have been successfully incorporated into phosphite frameworks. The ability of these metal ions to form MO4 tetrahedra, MO5 trigonal bipyramids, and MO6 octahedra, combined with the characteristic pseudo pyramidal HPO3 unit, implies that a large number of novel framework topologies can be potentially obtained in this system. The use of amine molecules with different size and shape as the structure-directing agents in the hydrothermal synthesis has been demonstrated to be a useful method to affect the structures of metal phosphites. Many diamine, triamine and polyamine molecules have
* Corresponding author. Fax: þ86 28 85412284. E-mail address: [email protected] (Z. Lin). 1293-2558/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2011.05.001
been studied during the past years [36]. However, a very limited number of open-framework metal phosphites have been obtained in the presence of monoamine molecules as the structure-directing agents. This is surprising, considering that several metal phosphites with extra-large pores have been prepared in the presence of different monoamines, including n-propylamine, n-butylamine, cyclopentylamine, and cyclohexylamine [37e40]. In an attempt to explore the structure-directing roles of three monoamines (i.e. morpholine, ethylamine, and dimethylamine), here we report hydro/solvothermal synthesis and characterization of three new open-framework zinc phosphites, [C4H10ON]2$[Zn3(HPO3)4] (1), [CH3CH2NH3]2$[Zn3(HPO3)4] (2) and [H2N(CH3)2]2$[Zn3(HPO3)4] (3). Compounds 1 and 2 are isostructural with H2apm,Zn3(HPO3)4 and [CH3CH2CH2NH3]2,[Zn3(HPO3)4], respectively [41e43]. Compound 3 has a novel (3,4)-connected framework topology with 12-ring channels.
2. Experimental 2.1. Materials and methods Reagents were purchased commercially and used without further purification. The CHN analyses were carried out on a Euro EA3000 analyzer. Powder X-ray diffraction (XRD) data were obtained using a Rigaku D/MAX-rA diffractometer with Cu-Ka
1474
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
radiation (l ¼ 1.5418 Å). IR spectrum (KBr pellet) was recorded on an ABB Bomen MB 102 spectrometer. The thermogravimetric analysis was performed on a Mettler Toledo TGA/SDTA 851e analyzer in a flow of N2 with a heating rate of 10 C/min from 30 to 700 C. 2.2. Synthesis 2.2.1. [C4H10ON]2$[Zn3(HPO3)4] (1) A mixture of Zn(OAc)2$2H2O (0.2195 g), H3PO3 (50 wt%, 0.4959 g), morpholine (0.3982 g), 1,4-dioxane (3.1021 ml) and H2O (2.015 g) was stirred under ambient conditions. The resulting mixture was sealed in a Teflon-lined steel autoclave and heated at 160 C for 3 days and then cooled to room temperature. The resulting product was recovered by filtration, washed with distilled water and dried in air. Yield: 0.1352 g (58.5% yield based on zinc). 2.2.2. [CH3CH2NH3]2$[Zn3(HPO3)4] (2) A mixture of ZnO (0.0814 g), H3PO3 (50 wt%, 0.3344 g), ethylamine (65 wt%, 0.1396 g) and H2O (8.5 g) was stirred under ambient conditions. The resulting gel was sealed in a Teflon-lined steel autoclave and heated at 160 C for 3 days and then cooled to room temperature. The resulting product, contains a small amount of powder impurities and colorless crystals of compound 2 as the major phase, was recovered by filtration, washed with distilled water and dried in air. 2.2.3. [H2N(CH3)2]2$[Zn3(HPO3)4] (3) A mixture of Zn(OAc)2$2H2O (0.220 g), H3PO3 (0.246 g), L-Proline (0.115 g) and DMF (5.0 ml) was stirred under ambient conditions. The resulting gel was sealed in a Teflon-lined steel autoclave and heated at 80 C for 3 days and then cooled to room temperature. The resulting product, contains irregular-shape compound 3 and a large amount of two known zinc phosphite phases: [H2N(CH3)2]2Zn3(HPO3)4 and Zn2(H2O)4(HPO3)2,H2O [44,45], was recovered by filtration, washed with distilled water and dried in air. 2.3. Crystal structure determination Suitable single crystals of each compound were carefully selected under an optical microscope. Crystal structure determination by X-ray diffraction was performed on an Oxford Xcalibur diffractometer with graphite-monochromated MoKa (l ¼ 0.71073 Å) radiation at room temperature. The crystal structures were solved by direct methods. The zinc and phosphorus atoms were first located. The oxygen, nitrogen, carbon, and the hydrogen atoms attached to phosphorus atoms were found in the difference Fourier map. The hydrogen atoms attached to carbon and nitrogen atoms are added by calculation and refined using a riding model. The structures were refined on F2 by full-matrix least-squares methods using the SHELXTL program package [46]. All non-hydrogen atoms were refined anisotropically. The crystallographic data for 1e3 are summarized in Table 1. 2.4. Ion-exchange process The ion-exchange experiment of compound 1 was carried out by immersing 100 mg sample of the as-synthesized compound 1 in 10 ml of 1 M KNO3 aqueous solution at room temperature for 1 day. The exchanged solids were then recovered, washed thoroughly with water and dried in air. 3. Results and discussion Compounds 1e3 were obtained as colorless crystals under autogenous pressure. Single-crystal X-ray diffraction analysis reveals
Table 1 Crystal data and structure refinement for 1e3.
Empirical formula Formula weight Crystal system Space group a, Å b, Å c, Å Volume, Å3 Z Dc, g/cm3 m (Mo-Ka), mm1 Total data Unique data Data, I > 2s (I) Final R1, wR2 [I > 2s (I)]
1
2
3
C8H24N2O14 P4Zn3 692.28 Orthorhombic Pna21 14.4115(4) 16.0984(5) 9.6856(3) 2247.08(12) 4 2.046 3.528 5729 3216 2843 0.0249, 0.0516
C4H20N2O12P4Zn3 608.21 Orthorhombic Pccn 9.6456(3) 23.1871(9) 8.7113(3) 1948.31(12) 4 2.074 4.046 4677 1719 1414 0.0234, 0.0587
C4H20N2O12P4Zn3 608.21 Orthorhombic Iba2 25.8033(18) 8.6742(6) 8.4557(5) 1892.6(2) 4 2.135 4.165 2072 1118 1069 0.0307, 0.0800
that compound 1 has a three-dimensional structure, which is isostructural with H2apm,Zn3(HPO3)4 [41]. As shown in Fig. 1a, the asymmetric unit consists of three crystallographically independent zinc atoms and four crystallographically independent phosphorus atoms. All the zinc atoms are tetrahedrally coordinated by oxygen atoms. The phosphorus atoms each make three PeOeZn linkages with adjacent zinc atoms, with the fourth vertex occupied by a terminal hydrogen atom [(PeH)av ¼ 1.38 Å]. The ZneO bond lengths vary from 1.853(2) to 1.961(3) Å, and the PeO bond lengths range from 1.463(1) to 1.584(2) Å. The connectivity of strictly alternating ZnO4 tetrahedra and HPO3 pseudo pyramids gives rise to a three-dimensional inorganic framework with zigzag 12-ring channels running along the [100] direction (Fig. 2a). The complicated structure can be alternatively understood from a layered structure, as shown in Fig. 2b. When the (4.6.12) layered structures are stacked along the [100] direction in an ABAB sequence, the three-dimensional structure of 1 is formed. The framework density (FD, defined as the number of polyhedra per 1000 Å3) of compound 1 is 12.5, which is similar to other openframework zinc phosphites with 12-ring channels, such as FJ-8 (FD ¼ 13.2) and FJ-15 (FD ¼ 13.4) [47,48]. The monoprotonated morpholine cations reside in the free voids of compound 1 and interact with the framework oxygen atoms through extensive hydrogen bonds. The four shortest N$$$O distances are 2.752(5) Å, 2.801(5) Å, 2.826(5) Å, and 2.908(5) Å for N2eO7, N1eO6, N1eO12, and N2eO11, respectively. A void space analysis performed by use of the program PLATON indicates that the extraframework organic cations in compound 1 occupy 47.5% of the unit cell volume [49]. The structure of compound 2 consists of an anionic zinc phosphite framework and monoprotonated ethylamine cations. The asymmetric unit of 2 contains 13 non-hydrogen atoms, of which two zinc atoms and two phosphorus atoms are crystallographically independent (Fig. 1b). Zn(1) atom locates in a general position and Zn(2) atom occupies a special position with site multiplicity of 0.5. Both the zinc atoms are tetrahedrally coordinated with four oxygen atoms. The two phosphorus atoms each share three oxygen atoms with adjacent zinc atoms, with the fourth vertex occupied by a hydrogen atom [(PeH)av ¼ 1.38 Å]. The ZneO bond lengths are in the range of 1.911(2)e1.952(2) Å, and the PeO bond lengths vary from 1.504 (2) to 1.520(2) Å, in excellent agreement with those previously reported. The stoichiometry of [Zn3(HPO3)4] results in a net charge of 2, which is balanced by two monoprotonated ethylamine cations per formula unit. The inorganic framework of 2 is made up of strictly alternating ZnO4 tetrahedra and HPO3 pseudo pyramids. The FD value of compound 2 is 14.2, which is slightly higher than that of compound
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
1475
Fig. 3. (a) The three-dimensional structure of 2 with 12-ring channel is constructed by (b) a 4.82 layered structure and (c) a corner-sharing 4-ring chain. Color code: Zn, yellow; P, green; O, red; H, gray. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 1. View of the coordination environments of zinc and phosphorus atoms in compound 1 (a), compound 2 (b), and compound 3 (c), showing the atom labeling scheme, and with 30% thermal ellipsoids. Atom labels having “A” and “B” refer to symmetry-generated atoms.
1. Two distinct structural motifs, a 4.82 layered network and a corner-sharing 4-ring chain, are involved in the construction of the framework structure. As shown in Fig. 3, the two building units are cross-linked with each other via ZneOeP linkages, forming a three-dimensional structure with 12-ring channels. The monoprotonated ethylamine cations are well ordered in the free region of compound 2 due to the extensive hydrogen bonding between the amino groups and the framework oxygen atoms. The shortest
Fig. 2. (a) The three-dimensional structure of 1 with 12-ring channel is constructed by (b) the layered structures stacked along the [001] direction in an ABAB sequence. Color code: Zn, yellow; P, green; O, red; H, gray. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
1476
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
N$$$O distances are in the range of 2.876(3)e2.986(3) Å. A void space analysis performed by use of the program PLATON indicates that the extraframework organic cations in compound 2 occupy 38.3% of the unit cell volume. It should be noted that compound 2 is isostructural with another open-framework zinc phosphite, [CH3CH2CH2NH3]2,[Zn3(HPO3)4] [42,43]. The two compounds have the same framework topology with 12-ring channels. The main difference lies in their extraframework cations. In compound 2, the extraframework cations are monoprotonated ethylamine molecules, whereas in [CH3CH2CH2NH3]2,[Zn3(HPO3)4], the extraframework cations are monoprotonated propylamine molecules. In addition, all three unit cell axes in compound 2 are shorter than those in [CH3CH2CH2NH3]2,[Zn3(HPO3)4] due to the smaller size of structure-directing agents. The asymmetric unit of compound 3 contains 13 non-hydrogen atoms, of which 10 atoms belong to the host framework (two Zn, two P, and six O atoms) and 3 atoms belong to the guest species (Fig.1c). Both the zinc atoms are tetrahedrally coordinated by oxygen atoms with ZneO bond lengths varying from 1.918(4) to 1.967(4) Å. The phosphorus atoms each share three oxygen atoms with adjacent zinc atoms [PeO: 1.493(5)e1.529(4) Å], with the fourth vertex occupied by a terminal hydrogen atom [(PeH)av ¼ 1.15 Å]. The stoichiometry of [Zn3(HPO3)4] results in a net charge of 2, which is balanced by two monoprotonated dimethylamine cations per formula unit. It should be noted that no dimethylamine molecule was used as the starting material in the reaction system. They should be formed in situ by the decomposition of DMF molecules under solvothermal conditions. The structure of compound 3 has a new (3,4)-connected framework with FD value of 14.8. The three-dimensional structure of compound 3 can be described in terms of two distinct building units: a 63 layered network and a corner-sharing 4-ring chain. As shown in Fig. 4, the linkages between Zn(1)O4 tetrahedra and HP(1)O3 pseudo pyramids produce 63 layered networks, and the linkages between Zn(2)O4 tetrahedra and HP(2)O3 pseudo pyramids give rise to corner-sharing 4-ring chains. The 63 layered networks are crosslinked by corner-sharing 4-ring chains through ZneOeP linkages, producing the three-dimensional structure with 12-ring channels running along the [001] direction, wherein the organic cations reside. An intriguing structural feature of 3 is its resemblance to that of [H2N(CH3)2]2[M3(HPO3)4] (M ¼ Zn, Co) [44,50]. The two compounds contain the same amine (i.e. dimethylamine) as the structure-directing agent and their (3,4)-connected structures both contain corner-sharing 4-ring chains as the building units. One main difference between the two structures is that, in the structure of [H2N(CH3)2]2[M3(HPO3)4], the corner-sharing 4-ring chains are connected by metal ions to produce its three-dimensional structure, whereas in compound 3, the structure is built up by the linkages of 63 layered networks and the corner-sharing 4-ring chains. Among the three open-framework zinc phosphites, only compound 1 was obtained as a pure phase. The powder XRD pattern of the bulk product was in good agreement with the one simulated on the basis of the single-crystal structure. CHN analyses confirmed its stoichiometry (Anal. Found: C, 7.68; H, 3.19; N, 4.51%. Calcd: C, 7.90; H, 3.31; N, 4.61%). IR spectroscopy contained the bands at 1640, 1470, and 1400 cm1 caused by the bending vibrations of eNH2 and eCH2 groups, confirming the presence of amine cations in the structure. Thermogravimetric analysis of compound 1 was carried out in N2 with a heating rate of 10 C/min. It remained stable up to 270 C. On further heating, a two-step weight loss between 270e400 C and 510e600 C was observed, corresponding to the decomposition of two morpholine molecules per formula unit. The total weight loss for the two steps compared well with that calculated on the basis of the above interpretation (observed:
Fig. 4. (a) The three-dimensional structure of 3 with 12-ring channel is constructed by (b) a 63 layered structure and (c) a corner-sharing 4-ring chain. Color code: Zn, yellow; P, green; O, red; H, gray. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
24.83%; expected: 25.17%). To evaluate the ion-exchange property of compound 1, 100 mg sample of the as-synthesized compound 1 was immersed in 10 ml of 1 M KNO3 aqueous solution at room temperature for 1 day. XRD pattern of the exchange solid indicated that a new hydrated zinc phosphite, Zn2(H2O)4(HPO3)2$H2O, formed after the ion-exchange process [45]. 4. Conclusions In summary, three new opens-framework zinc phosphites were obtained as good quality single crystals under hydro/solvothermal conditions. These compounds have different three-dimensional inorganic frameworks with large 12-ring channels, wherein the protonated monoamines reside. While the structures of compounds 1 and 2 are closely related to the known (3,4)-connected zinc phosphites, compound 3 has a novel (3,4)-connected framework topology. The attempt to remove the organic cations in compound 1 by an ion-exchange process causes the structure collapse. The use of other monoamine as the structure-directing agent under similar hydro/solvothermal conditions may result in other novel open-framework metal phosphites with unique structures and physical properties. Acknowledgments We thank the support of this work by the NNSF of China (Grant 20801037). Appendix. Supplementary material Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.solidstatesciences.2011.05.001.
M. Kang et al. / Solid State Sciences 13 (2011) 1473e1477
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
D. Maspoch, D. Ruiz-Molina, J. Veciana, Chem. Soc. Rev. 36 (2007) 770. S. Natarajan, S. Mandal, Angew. Chem. Int. Ed. 47 (2008) 4798. J. Jiang, J. Yu, A. Corma, Angew. Chem. Int. Ed. 49 (2010) 3120. M. Davis, Nature 417 (2002) 813. J. Yu, R. Xu, Chem. Soc. Rev. 35 (2006) 593. G. Bonavia, J. DeBord, R.C. Haushalter, D. Rose, J. Zubieta, Chem. Mater. 7 (1995) 1995. Z. Shi, G. Li, D. Zhang, J. Hua, S. Feng, Inorg. Chem. 42 (2003) 2357. R.-K. Chiang, N.-T. Chuang, J. Solid State Chem. 178 (2005) 3040. X. Jing, L. Zhang, S. Gong, G. Li, M. Bi, Q. Huo, Y. Liu, Micropor. Mesopor. Mater. 116 (2008) 101. S. Fernández, J.L. Mesa, J.L. Pizarro, L. Lezama, M.I. Arriortua, T. Rojo, Angew. Chem. Int. Ed. 41 (2002) 3683. S. Fernández, J.L. Mesa, J.L. Pizarro, L. Lezama, M.I. Arriortua, R. Olazcuaga, T. Rojo, Chem. Mater. 12 (2000) 2092. S. Fernández, J.L. Pizarro, J.L. Mesa, L. Lezama, M.I. Arriortua, R. Olazcuaga, T. Rojo, Inorg. Chem. 40 (2001) 3476. S. Fernández, J.L. Mesa, J.L. Pizarro, L. Lezama, M.I. Arriortua, T. Rojo, Chem. Mater. 14 (2002) 2300. W. Liu, H.-H. Chen, X.-X. Yang, J.-T. Zhao, Eur. J. Inorg. Chem. (2005) 946. J. Qiao, L. Zhang, Y. Yu, G. Li, T. Jiang, Q. Huo, Y. Liu, J. Solid State Chem. 182 (2009) 1929. L. Zhao, J. Li, P. Chen, G. Li, J. Yu, R. Xu, Chem. Mater. 20 (2008) 17. C.-C. Cheng, W.-K. Chang, R.-K. Chiang, S.-L. Wang, J. Solid State Chem. 183 (2010) 304. X. Liu, Y. Xing, X. Wang, H. Xu, X. Liu, K. Shao, Z. Su, Chem. Commun. 46 (2010) 2614. Z.-E. Lin, J. Zhang, S.-T. Zheng, G.-Y. Yang, J. Mater. Chem. 14 (2004) 1652. J. Liang, J. Li, J. Yu, Q. Pan, Q. Fang, R. Xu, J. Solid State Chem. 178 (2005) 2673. J.A. Rodgers, W.T.A. Harrison, Chem. Commun. (2000) 2385. W.T.A. Harrison, M.L.F. Phillips, J. Stanchfield, T.M. Nenoff, Inorg. Chem. 40 (2001) 895. W.T.A. Harrison, M.L.F. Phillips, T.M. Nenoff, J. Chem. Soc. Dalton Trans. (2001) 2459.
1477
[24] W.T.A. Harrison, R.M. Yeates, M.L.F. Phillips, T.M. Nenoff, Inorg. Chem. 42 (2003) 1493. [25] J.-X. Pan, S.-T. Zheng, G.-Y. Yang, Cryst. Growth Des. 5 (2005) 237. [26] D. Zhang, H. Yue, Z. Shi, M. Guo, S. Feng, Solid State Sci. 8 (2006) 192. [27] L. Chen, X. Bu, Chem. Mater. 18 (2006) 1857. [28] S. Mandal, S. Natarajan, Inorg. Chem. 47 (2008) 5304. [29] Y. Yang, Y. Zhao, J. Yu, S. Wu, R. Wang, Inorg. Chem. 47 (2008) 769. [30] Z. Lin, H.P. Nayek, S. Dehnen, Inorg. Chem. 48 (2009) 3517. [31] J.-D. Feng, K.-Z. Shao, S.-W. Tang, R.-S. Wang, Z.-M. Su, CrystEngComm 12 (2010) 1401. [32] W. Fu, L. Wang, Z. Shi, G. Li, X. Chen, Z. Dai, L. Yang, S. Feng, Cryst. Growth Des. 4 (2004) 297. [33] A. Lu, H. Song, N. Li, S. Xiang, N. Guan, H. Wang, Chem. Mater. 29 (2007) 4142. [34] L. Wang, T. Song, Y. Fang, Y. Wang, J. Xu, S. Shi, T. Zhu, J. Solid State Chem. 179 (2006) 865. [35] L. Wang, T. Song, J. Xu, Y. Wang, Z. Tian, S. Shi, Micropor. Mesopor. Mater. 96 (2006) 287. [36] T. Rojo, J.L. Mesa, J. Lago, B. Bazan, J.L. Pizarro, M.I. Arriortua, J. Mater. Chem. 19 (2009) 3793. [37] J. Liang, J. Li, J. Yu, P. Chen, Q. Fang, F. Sun, R. Xu, Angew. Chem. Int. Ed. 45 (2006) 2546. [38] Y. Yang, N. Li, H. Song, H. Wang, W. Chen, S. Xiang, Chem. Mater. 19 (2007) 1889. [39] Y.-L. Lai, K.-H. Lii, S.-L. Wang, J. Am. Chem. Soc. 129 (2007) 5350. [40] J. Li, L. Li, J. Liang, P. Chen, J. Yu, Y. Xu, R. Xu, Cryst. Growth Des. 8 (2008) 2318. [41] Z. Lin, S. Dehnen, J. Solid State Chem. 182 (2009) 3143. [42] D. Zhang, Z. Shi, W. Dong, W. Fu, L. Wang, G. Li, S. Feng, J. Solid State Chem. 177 (2004) 343. [43] S. Mandal, S. Natarajan, Solid State Sci. 8 (2006) 388. [44] L. Chen, X. Bu, Inorg. Chem. 45 (2006) 4654. [45] C.Y. Ortiz-Avila, P.J. Squattrito, M. Shieh, A. Clearfield, Inorg. Chem. 28 (1989) 2608. [46] G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112e122. [47] Z.-E. Lin, J. Zhang, S.-T. Zheng, G.-Y. Yang, Eur. J. Inorg. Chem. (2004) 953. [48] J.-X. Pan, S.-T. Zheng, G.-Y. Yang, Micropor. Mesopor. Mater. 75 (2004) 129. [49] A.L. Spek, Acta Crystallogr. Sect. A A46 (1990) C34. [50] Z. Lin, H.P. Nayek, S. Dehnen, Z. Anorg, Allg. Chem. 635 (2009) 2391.