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Three-dimensional lanthanide metal-organic frameworks constructed from octahedral secondary building units: Pcu net topology and luminescence
Inorganic Chemistry Communications 13 (2010) 935–937
Contents lists available at ScienceDirect
Inorganic Chemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i n o c h e
Three-dimensional lanthanide metal-organic frameworks constructed from octahedral secondary building units: Pcu net topology and luminescence Gang Wang a, Tianyou Song a, Yong Fan a, Wei Wan a, Jianing Xu b,⁎, Li Wang a,⁎ a b
College of Chemistry, Jilin University, Changchun 130012, China State Key Laboratory of Inorganic Synthesis & Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, China
a r t i c l e
i n f o
Article history: Received 29 March 2010 Accepted 28 April 2010 Available online 10 May 2010 Keywords: Rare-earth Metal–organic framework Topology Luminescent property
a b s t r a c t Three isomorphous three-dimensional lanthanide metal–organic frameworks, [Ln2(NIPH)3(DMF)4] (DMF)2 (Ln = Eu, Pr and Sm, and H2NIPH = 5-nitroisophthalic acid) have been synthesized under solvothermal condition and characterized by single-crystal X-ray structure diffraction, IR spectroscopy, thermogravimetric analysis (TGA), luminescent property and elemental analyses. In their structures, two lanthanide(III) ions are bridged by four carboxylate groups and chelated by another two carboxylate groups to generate a [Ln2 (COO)6] dinuclear group, which serves as octahedral secondary building unit (SBU) to produce a pcu net. © 2010 Elsevier B.V. All rights reserved.
Secondary building units (SBUs) have served as an important concept for the classification of the metal–organic frameworks (MOFs) structures into their underlying topology [1] and design of directionality for the construction of porous coordination polymers (PCPs) [2,3]. A classic example is MOF-5 where OZn4 cationic SBUs are linked by the benzenedicarboxylate (BDC) anion to form a continuous cubic neutral framework of composition Zn4O(BDC)3 [4]. Although some SBUs have been found in porous rare earth MOFs, such as rod-shaped SBUs [5], octahedral SBUs [6] and square–planar Ln4(μ4-H2O) SBUs [7], it is still the experience accumulation stage compared with transition metal MOFs [2–4] for higher coordination numbers and flexible coordination geometry of rare earth ions[5–8]. The introduction of substituent groups such as amine, amide, and methyl and nitro group on organic linker may bring the changes of space, solubility, and coordination modes, which will make it difficult to form structural quasi-invariant MOFs [9]. Moreover, these changes may bring on significant conversion from types of SBUs. In similar experiment conditions of synthesizing rare earth MOFs, it is still rare that the effect of substituent groups for conversion from different types of SBUs. During our investigations on the reactivity of the 1,3-BDC (1,3Benzenedicarboxylic acid) with rare earth nitrate, we have recently reported a new compound [Eu2(BDC)3(DMF)2]·(DMF)1.7 with onedimensional hexagonal channel [10]. Then we conduct our studies on synthesizing rare earth MOFs using nitro group substituted 1,3-BDC as organic ligand and in the similar experiment condition, we successfully synthesized three novel lanthanide metal–organic frameworks. It is ⁎ Corresponding authors. Wang is to be contacted at Tel.: +86 431 85168471; fax: +86 431 85671974. E-mail address: [email protected] (L. Wang). 1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.04.031
noted that all of them show the fascinating conversion from infinite rodshaped building units in [Eu2(BDC)3(DMF)2]·(DMF)1.7 to octahedral SBUs owing to affect of substituent group. In our experiments, M(NO3)3·6H2O (M= Eu, Pr, and Sm), 5-nitroisophthalic acid and 4, 4’-bipyridine were selected as starting materials in DMF and water to prepare three isomorphous 3-D frameworks [Eu2(NIPH)3(DMF)4]∙ (DMF)2 1-Eu, [Pr2(NIPH)3(DMF)4]∙(DMF)2 2-Pr and [Sm2(NIPH)3 (DMF)4]∙(DMF)2 3-Sm (see Table 1) which have octahedral SBUs [11]. The following description and discussion will be focused on 1-Eu. Compound 1-Eu crystallizes in C2/c space group, while the asymmetric unit of the compound 1 contains one Eu ion, one and half NIPH ligands, and three DMF molecules. Each Eu atom is coordinated by
Table 1 Crystal data and structure refinement information for the complexes. Compound
1
2
3
Emprical formula Formula weight Space group a (Å) b (Å) c (Å) β (°) V(Å3) Z Dcal (mg∙cm−3) R1,wR2a (I N 2σ(I)) R1,wR2a [all data] GOF
C42 H51 N9 O24 Eu2 1369.84 C2/c(15) 21.621(5) 16.786(5) 16.385(5) 119.553(5) 5172 (3) 4 1.759 0.0235; 0.0604 0.0264; 0.0639 1.073
C42 H51 N9 O24 Pr2 1347.74 C2/c(15) 21.801(5) 16.882(5) 16.522(5) 119.499(5) 5293(3) 4 1.691 0.0390; 0.0908 0.0625; 0.1038 1.011
C42 H51 N9 O24Sm2 1366.62 C2/c(15) 21.6771(6) 16.8297(5) 16.4199(5) 119.53 5211.9(3) 4 1.742 0.0169; 0.0407 0.0189; 0.0417 1.039
a
R1 = ∑||Fo| − |Fc||/∑|F|, wR2 = {∑[w(Fo2 − Fc2)2]/∑(Fo2)2}1/2.
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G. Wang et al. / Inorganic Chemistry Communications 13 (2010) 935–937
Fig. 1. The crystal structure of complex 1-Eu is constructed by [Ln2(COO)6] dinuclear group (a), which serves as octahedral secondary building unit (b).
eight oxygen atoms with a distorted square antiprismatic geometry. One basal face of the antiprism is defined by four carboxylate oxygen atoms from four NIPH ligands. The other base is completed by another four oxygen atoms from a chelating carboxylate group and two DMF molecules. The above Eu–O distances in the range of 2.335(2)–2.522(2) Å fall in the usual range for Eu compounds with carboxylate ligands. The binuclear units can be regarded as six-connecting octahedral SBUs (see Figs. 1 and 2a), and as observed in 1-Eu, each SBU is connected with six identical motifs through six NIPH ligands to yield a 3D framework. The compound 1-Eu has an open framework, quadrilateral channels along the [010] direction (see Fig. 2b) and irregular-shaped pore along the [001] direction (see Fig. 2c) and two kinds of irregular-shaped pore at direction in Fig. 2d, respectively.
Fig. 3. The 3-D pcu net in the structure of 1-Eu ([Ln2(COO)6] dinuclear groups: pink atoms; NIPH: light green bonds).
The binuclear [Ln2(COO)6] motif with four bridging and two chelating carboxylate groups has been recognized in a few discrete complex molecules with monocarboxylate ligands [12] and a limited number of 3-D rare earth MOFs with multicarboxylate ligands [6,13].
Fig. 2. (a) The structural detail of dinuclear group; (b) view down [010] of 1-Eu showing the quadrilateral pore and dinuclear group; (c) view down [001] of 1-Eu showing the irregular-shaped pore and alternating arrangement of NIPH; and (d) a structure view of 1-Eu showing two kinds of irregular-shaped pore. Hydrogen atoms, terminal DMF molecules, and solvent molecules are omitted for clarity.
G. Wang et al. / Inorganic Chemistry Communications 13 (2010) 935–937
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compound emitted red light in solid state at room temperature. Future work will focus on the effect of other substituent groups, such as 5-hydroxy-1,3-benzenedicarboxylic acid, 5-methylisophthalic acid, and 5-tert-butylisophthalic acid. Acknowledgement The authors thank the National Natural Science Foundation of China (Grant No. 20901028) for financial support. Furthermore, PXRD patterns and TG curve of compound 1-Eu can be seen in supporting information. Appendix A. Supplementary material
Fig. 4. Solid-state emission spectrum of compound 1-Eu.
The binuclear units can be regarded as six-connecting octahedral SBUs (Fig. 1), and each SBU in 1-Eu is connected with six identical motifs through six NIPH ligands to yield a 3D framework. Furthermore, the net topology of 1-Eu adopts the pcu net (41263) for octahedral nodes (see Fig. 3). The solid-state luminescent property of 1-Eu was investigated. When excited by ultraviolet light, the Eu3+ coordination compound 1-Eu emitted red light. The emission spectrum was measured in the 550–750 nm range (λex = 395 nm) and showed five major peaks assigned to the 5D0 → 7FJ (J = 0–4) transitions, namely, 5D0 → 7F0 (577 nm), 5 D 0 → 7 F 1 (593 nm) 5 D 0 → 7 F 2 (617 nm) 5 D 0 → 7 F 3 (651 nm) and 5D0 → 7F4 (698 nm) (see Fig. 4). The presence of the weak symmetry forbidden 5D0 → 7F0 emission indicates that the Eu (III) ions occupy low-symmetry coordination sites with no inversion centers, in agreement with the result of X-ray structural analysis. The intensity ratio 5D0 → 7F2/5D0 → 7F1 was 2.6, much higher than 0.67, a typical value for a centrosymmetric Eu3+ center [14]. This high ratio therefore indicates that the Eu 3+ ion adopted a noncentrosymmetric coordination environment, with no center of inversion, as observed on the single-crystal structure [15]. The TGA study of compound 1-Eu is performed under an air atmosphere in range from 25 to 800 °C (as shown in Fig. S2). The gradual weight loss of 30.78% from 25 to 412 °C corresponds to the loss of two guest DMF molecules and four terminal coordinated DMF molecules. The sharp weight loss above 412 °C corresponds to the decomposition of compound 1-Eu and the remaining weight of 24.68% is the Eu and O components, Eu2O3. To summarize, we have described three isomorphous threedimensional lanthanide metal–organic frameworks, derived from 5-nitroisophthalic acid ligand. The noninterpenetrated 3-D framework is based on the octahedral [Ln2(COO)6] secondary building units and it exhibits pcu net with octahedral nodes. The Eu(III)
CCDC 764879-764881 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via http:// www.ccdc.cam.ac.uk/conts/retrieving.html, or Email:deposit@ccdc. cam.ac.uk. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2010.04.031. References [1] (a) A.K. Cheetham, G. Férey, T. Loiseau, Angew. Chem. Int. Ed. 38 (1999) 3268; (b) M.E. Davis, Nature 417 (2002) 813. [2] (a) O.M. Yaghi, H. Li, C. Davis, D. Richardson, T.L. Groy, Acc. Chem. Res. 31 (1998) 474; (b) S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed. 43 (2004) 233. [3] (a) M. Eddaoudi, D.B. Moler, H. Li, B. Chen, T.M. Reineke, M. O'Keeffe, O.M. Yaghi, Acc. Chem. Res. 34 (2001) 319; (b) N.W. Ockwig, O. Delgado-Friedrichs, M. O'Keeffe, O.M. Yaghi, Acc. Chem. Res. 38 (2005) 176. [4] H. Li, M. Eddaoudi, M. O'Keeffe, O.M. Yaghi, Nature 402 (1999) 276. [5] L. Pan, K.M. Adams, H.E. Hernandez, X. Wang, C. Zheng, Y. Hattori, K. Kaneko, J. Am. Chem. Soc. 125 (2003) 3062. [6] T.M. Reineke, M. Eddaoudi, D. Moler, M. O'Keeffe, O.M. Yaghi, J. Am. Chem. Soc. 122 (2000) 4843. [7] S. Ma, X. Wang, D. Yuan, H. Zhou, Angew. Chem., Int. Ed. 47 (2008) 4130. [8] T. Devic, C. Serre, N. Audebrand, J. Marrot, G. Férey, J. Am. Chem. Soc. 127 (2005) 12788. [9] H. Deng, C.J. Doonan, H. Furukawa, R.B. Ferreira, J. Towne, C.B. Knobler, B. Wang, O.M. Yaghi, Science 327 (2010) 846. [10] G. Wang, T. Song, Y. Fan, J. Xu, M. Wang, L. Wang, L. Zhang, L. Wang, Inorg. Chem. Commun. 13 (2010) 95. [11] As a typical preparation procedure for 1-Eu, a mixture of Eu(NO3)3∙6H2O (45 mg, 0.1 mmol), 4, 4'-bipyridyl (10 mg, 0.06 mmol), and 5-nitroisophthalic acid (42 mg, 0.2 mmol) was dissolved in DMF (3 ml) and ethanol (1 ml) at room temperature. The mixture in a 50 mL tube was left undisturbed at 60 °C for 4 days to give colorless crystals in 48 % yield (based on Eu). Elemental analysis calc. for C42H51Eu2N9O24: C, 36.83; H, 3.75; N, 9.20%; found: C, 36.85; H, 3.76; N, 9.23%. IR data (KBr pellet, cm-1): 426(s), 530(m), 615(s), 707(s), 748(m), 1103(m), 1381(s), 1547(s), 1605(s), 1670(s), 3431(m). The procedure of synthesis 2-Pr and 3-Sm was the same as that for 1-Eu except that Eu(NO3)3·6H2O was replaced by Pr(NO3)3·6H2O (44 mg, 0.1 mmol) and Sm(NO3)3·6H2O (44 mg, 0.1 mmol). [12] (a) A. de Bettencourt-Dias, S. Viswanathan, Chem. Commun. (2004) 1024; (b) S. Viswanathan, A. de Bettencourt-Dias, Inorg. Chem. 45 (2006) 10138. [13] B.T.N. Pham, L.M. Lund, D. Song, Inorg. Chem. 47 (2008) 6329. [14] S.I. Klink, L. Grave, D.N. Reinhoudt, F.C.J.M. van Veggel, J. Phys. Chem., A 104 (2000) 5457. [15] J. Xia, B. Zhao, H. Wang, W. Shi, Y. Ma, H. Song, P. Cheng, D. Liao, S. Yan, Inorg. Chem. 46 (2007) 3450.
Contents lists available at ScienceDirect
Inorganic Chemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i n o c h e
Three-dimensional lanthanide metal-organic frameworks constructed from octahedral secondary building units: Pcu net topology and luminescence Gang Wang a, Tianyou Song a, Yong Fan a, Wei Wan a, Jianing Xu b,⁎, Li Wang a,⁎ a b
College of Chemistry, Jilin University, Changchun 130012, China State Key Laboratory of Inorganic Synthesis & Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, China
a r t i c l e
i n f o
Article history: Received 29 March 2010 Accepted 28 April 2010 Available online 10 May 2010 Keywords: Rare-earth Metal–organic framework Topology Luminescent property
a b s t r a c t Three isomorphous three-dimensional lanthanide metal–organic frameworks, [Ln2(NIPH)3(DMF)4] (DMF)2 (Ln = Eu, Pr and Sm, and H2NIPH = 5-nitroisophthalic acid) have been synthesized under solvothermal condition and characterized by single-crystal X-ray structure diffraction, IR spectroscopy, thermogravimetric analysis (TGA), luminescent property and elemental analyses. In their structures, two lanthanide(III) ions are bridged by four carboxylate groups and chelated by another two carboxylate groups to generate a [Ln2 (COO)6] dinuclear group, which serves as octahedral secondary building unit (SBU) to produce a pcu net. © 2010 Elsevier B.V. All rights reserved.
Secondary building units (SBUs) have served as an important concept for the classification of the metal–organic frameworks (MOFs) structures into their underlying topology [1] and design of directionality for the construction of porous coordination polymers (PCPs) [2,3]. A classic example is MOF-5 where OZn4 cationic SBUs are linked by the benzenedicarboxylate (BDC) anion to form a continuous cubic neutral framework of composition Zn4O(BDC)3 [4]. Although some SBUs have been found in porous rare earth MOFs, such as rod-shaped SBUs [5], octahedral SBUs [6] and square–planar Ln4(μ4-H2O) SBUs [7], it is still the experience accumulation stage compared with transition metal MOFs [2–4] for higher coordination numbers and flexible coordination geometry of rare earth ions[5–8]. The introduction of substituent groups such as amine, amide, and methyl and nitro group on organic linker may bring the changes of space, solubility, and coordination modes, which will make it difficult to form structural quasi-invariant MOFs [9]. Moreover, these changes may bring on significant conversion from types of SBUs. In similar experiment conditions of synthesizing rare earth MOFs, it is still rare that the effect of substituent groups for conversion from different types of SBUs. During our investigations on the reactivity of the 1,3-BDC (1,3Benzenedicarboxylic acid) with rare earth nitrate, we have recently reported a new compound [Eu2(BDC)3(DMF)2]·(DMF)1.7 with onedimensional hexagonal channel [10]. Then we conduct our studies on synthesizing rare earth MOFs using nitro group substituted 1,3-BDC as organic ligand and in the similar experiment condition, we successfully synthesized three novel lanthanide metal–organic frameworks. It is ⁎ Corresponding authors. Wang is to be contacted at Tel.: +86 431 85168471; fax: +86 431 85671974. E-mail address: [email protected] (L. Wang). 1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.04.031
noted that all of them show the fascinating conversion from infinite rodshaped building units in [Eu2(BDC)3(DMF)2]·(DMF)1.7 to octahedral SBUs owing to affect of substituent group. In our experiments, M(NO3)3·6H2O (M= Eu, Pr, and Sm), 5-nitroisophthalic acid and 4, 4’-bipyridine were selected as starting materials in DMF and water to prepare three isomorphous 3-D frameworks [Eu2(NIPH)3(DMF)4]∙ (DMF)2 1-Eu, [Pr2(NIPH)3(DMF)4]∙(DMF)2 2-Pr and [Sm2(NIPH)3 (DMF)4]∙(DMF)2 3-Sm (see Table 1) which have octahedral SBUs [11]. The following description and discussion will be focused on 1-Eu. Compound 1-Eu crystallizes in C2/c space group, while the asymmetric unit of the compound 1 contains one Eu ion, one and half NIPH ligands, and three DMF molecules. Each Eu atom is coordinated by
Table 1 Crystal data and structure refinement information for the complexes. Compound
1
2
3
Emprical formula Formula weight Space group a (Å) b (Å) c (Å) β (°) V(Å3) Z Dcal (mg∙cm−3) R1,wR2a (I N 2σ(I)) R1,wR2a [all data] GOF
C42 H51 N9 O24 Eu2 1369.84 C2/c(15) 21.621(5) 16.786(5) 16.385(5) 119.553(5) 5172 (3) 4 1.759 0.0235; 0.0604 0.0264; 0.0639 1.073
C42 H51 N9 O24 Pr2 1347.74 C2/c(15) 21.801(5) 16.882(5) 16.522(5) 119.499(5) 5293(3) 4 1.691 0.0390; 0.0908 0.0625; 0.1038 1.011
C42 H51 N9 O24Sm2 1366.62 C2/c(15) 21.6771(6) 16.8297(5) 16.4199(5) 119.53 5211.9(3) 4 1.742 0.0169; 0.0407 0.0189; 0.0417 1.039
a
R1 = ∑||Fo| − |Fc||/∑|F|, wR2 = {∑[w(Fo2 − Fc2)2]/∑(Fo2)2}1/2.
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Fig. 1. The crystal structure of complex 1-Eu is constructed by [Ln2(COO)6] dinuclear group (a), which serves as octahedral secondary building unit (b).
eight oxygen atoms with a distorted square antiprismatic geometry. One basal face of the antiprism is defined by four carboxylate oxygen atoms from four NIPH ligands. The other base is completed by another four oxygen atoms from a chelating carboxylate group and two DMF molecules. The above Eu–O distances in the range of 2.335(2)–2.522(2) Å fall in the usual range for Eu compounds with carboxylate ligands. The binuclear units can be regarded as six-connecting octahedral SBUs (see Figs. 1 and 2a), and as observed in 1-Eu, each SBU is connected with six identical motifs through six NIPH ligands to yield a 3D framework. The compound 1-Eu has an open framework, quadrilateral channels along the [010] direction (see Fig. 2b) and irregular-shaped pore along the [001] direction (see Fig. 2c) and two kinds of irregular-shaped pore at direction in Fig. 2d, respectively.
Fig. 3. The 3-D pcu net in the structure of 1-Eu ([Ln2(COO)6] dinuclear groups: pink atoms; NIPH: light green bonds).
The binuclear [Ln2(COO)6] motif with four bridging and two chelating carboxylate groups has been recognized in a few discrete complex molecules with monocarboxylate ligands [12] and a limited number of 3-D rare earth MOFs with multicarboxylate ligands [6,13].
Fig. 2. (a) The structural detail of dinuclear group; (b) view down [010] of 1-Eu showing the quadrilateral pore and dinuclear group; (c) view down [001] of 1-Eu showing the irregular-shaped pore and alternating arrangement of NIPH; and (d) a structure view of 1-Eu showing two kinds of irregular-shaped pore. Hydrogen atoms, terminal DMF molecules, and solvent molecules are omitted for clarity.
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compound emitted red light in solid state at room temperature. Future work will focus on the effect of other substituent groups, such as 5-hydroxy-1,3-benzenedicarboxylic acid, 5-methylisophthalic acid, and 5-tert-butylisophthalic acid. Acknowledgement The authors thank the National Natural Science Foundation of China (Grant No. 20901028) for financial support. Furthermore, PXRD patterns and TG curve of compound 1-Eu can be seen in supporting information. Appendix A. Supplementary material
Fig. 4. Solid-state emission spectrum of compound 1-Eu.
The binuclear units can be regarded as six-connecting octahedral SBUs (Fig. 1), and each SBU in 1-Eu is connected with six identical motifs through six NIPH ligands to yield a 3D framework. Furthermore, the net topology of 1-Eu adopts the pcu net (41263) for octahedral nodes (see Fig. 3). The solid-state luminescent property of 1-Eu was investigated. When excited by ultraviolet light, the Eu3+ coordination compound 1-Eu emitted red light. The emission spectrum was measured in the 550–750 nm range (λex = 395 nm) and showed five major peaks assigned to the 5D0 → 7FJ (J = 0–4) transitions, namely, 5D0 → 7F0 (577 nm), 5 D 0 → 7 F 1 (593 nm) 5 D 0 → 7 F 2 (617 nm) 5 D 0 → 7 F 3 (651 nm) and 5D0 → 7F4 (698 nm) (see Fig. 4). The presence of the weak symmetry forbidden 5D0 → 7F0 emission indicates that the Eu (III) ions occupy low-symmetry coordination sites with no inversion centers, in agreement with the result of X-ray structural analysis. The intensity ratio 5D0 → 7F2/5D0 → 7F1 was 2.6, much higher than 0.67, a typical value for a centrosymmetric Eu3+ center [14]. This high ratio therefore indicates that the Eu 3+ ion adopted a noncentrosymmetric coordination environment, with no center of inversion, as observed on the single-crystal structure [15]. The TGA study of compound 1-Eu is performed under an air atmosphere in range from 25 to 800 °C (as shown in Fig. S2). The gradual weight loss of 30.78% from 25 to 412 °C corresponds to the loss of two guest DMF molecules and four terminal coordinated DMF molecules. The sharp weight loss above 412 °C corresponds to the decomposition of compound 1-Eu and the remaining weight of 24.68% is the Eu and O components, Eu2O3. To summarize, we have described three isomorphous threedimensional lanthanide metal–organic frameworks, derived from 5-nitroisophthalic acid ligand. The noninterpenetrated 3-D framework is based on the octahedral [Ln2(COO)6] secondary building units and it exhibits pcu net with octahedral nodes. The Eu(III)
CCDC 764879-764881 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via http:// www.ccdc.cam.ac.uk/conts/retrieving.html, or Email:deposit@ccdc. cam.ac.uk. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2010.04.031. References [1] (a) A.K. Cheetham, G. Férey, T. Loiseau, Angew. Chem. Int. Ed. 38 (1999) 3268; (b) M.E. Davis, Nature 417 (2002) 813. [2] (a) O.M. Yaghi, H. Li, C. Davis, D. Richardson, T.L. Groy, Acc. Chem. Res. 31 (1998) 474; (b) S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed. 43 (2004) 233. [3] (a) M. Eddaoudi, D.B. Moler, H. Li, B. Chen, T.M. Reineke, M. O'Keeffe, O.M. Yaghi, Acc. Chem. Res. 34 (2001) 319; (b) N.W. Ockwig, O. Delgado-Friedrichs, M. O'Keeffe, O.M. Yaghi, Acc. Chem. Res. 38 (2005) 176. [4] H. Li, M. Eddaoudi, M. O'Keeffe, O.M. Yaghi, Nature 402 (1999) 276. [5] L. Pan, K.M. Adams, H.E. Hernandez, X. Wang, C. Zheng, Y. Hattori, K. Kaneko, J. Am. Chem. Soc. 125 (2003) 3062. [6] T.M. Reineke, M. Eddaoudi, D. Moler, M. O'Keeffe, O.M. Yaghi, J. Am. Chem. Soc. 122 (2000) 4843. [7] S. Ma, X. Wang, D. Yuan, H. Zhou, Angew. Chem., Int. Ed. 47 (2008) 4130. [8] T. Devic, C. Serre, N. Audebrand, J. Marrot, G. Férey, J. Am. Chem. Soc. 127 (2005) 12788. [9] H. Deng, C.J. Doonan, H. Furukawa, R.B. Ferreira, J. Towne, C.B. Knobler, B. Wang, O.M. Yaghi, Science 327 (2010) 846. [10] G. Wang, T. Song, Y. Fan, J. Xu, M. Wang, L. Wang, L. Zhang, L. Wang, Inorg. Chem. Commun. 13 (2010) 95. [11] As a typical preparation procedure for 1-Eu, a mixture of Eu(NO3)3∙6H2O (45 mg, 0.1 mmol), 4, 4'-bipyridyl (10 mg, 0.06 mmol), and 5-nitroisophthalic acid (42 mg, 0.2 mmol) was dissolved in DMF (3 ml) and ethanol (1 ml) at room temperature. The mixture in a 50 mL tube was left undisturbed at 60 °C for 4 days to give colorless crystals in 48 % yield (based on Eu). Elemental analysis calc. for C42H51Eu2N9O24: C, 36.83; H, 3.75; N, 9.20%; found: C, 36.85; H, 3.76; N, 9.23%. IR data (KBr pellet, cm-1): 426(s), 530(m), 615(s), 707(s), 748(m), 1103(m), 1381(s), 1547(s), 1605(s), 1670(s), 3431(m). The procedure of synthesis 2-Pr and 3-Sm was the same as that for 1-Eu except that Eu(NO3)3·6H2O was replaced by Pr(NO3)3·6H2O (44 mg, 0.1 mmol) and Sm(NO3)3·6H2O (44 mg, 0.1 mmol). [12] (a) A. de Bettencourt-Dias, S. Viswanathan, Chem. Commun. (2004) 1024; (b) S. Viswanathan, A. de Bettencourt-Dias, Inorg. Chem. 45 (2006) 10138. [13] B.T.N. Pham, L.M. Lund, D. Song, Inorg. Chem. 47 (2008) 6329. [14] S.I. Klink, L. Grave, D.N. Reinhoudt, F.C.J.M. van Veggel, J. Phys. Chem., A 104 (2000) 5457. [15] J. Xia, B. Zhao, H. Wang, W. Shi, Y. Ma, H. Song, P. Cheng, D. Liao, S. Yan, Inorg. Chem. 46 (2007) 3450.