Connected Coordination Networks - American Chemical Society

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Employing Zinc Clusters as SBUs To Construct (3,8) and (3,14)Connected Coordination Networks: Structures, Topologies, and Luminescence Kun-Huan He, Yun-Wu Li, Yong-Qiang Chen, Wei-Chao Song, and Xian-He Bu* Department of Chemistry, and Tianjin Key Lab on Metal and Molecule-based Material Chemistry, Nankai University, Tianjin 300071, China S Supporting Information *

ABSTRACT: Two new metal−organic frameworks (MOFs), [Zn2(OH)(cpia)(bipy)0.5]n (1) and {[Zn7(OH)2(HOMe)2(cpia)4(bib)]·5H2O}n (2) (bib = 1,4-bis(imidazol-1-yl)benzene, H3cpia = 5-(4-carboxyphenoxy)isophthalic acid, bipy = 4,4′-bipyridine), have been solvothermally synthesized and structurally characterized. Both of them are based on zinc clusters as secondary building units (SBUs). Compound 1 presents an interesting three-dimensional 2-fold interpenetrated (3,8)-connected network constructed from tetranuclear [Zn 4 (OH) 2 ] 6+ clusters with (43)2(46·618·84) topology, while compound 2 can be described as a (3,14)-connected framework built from an unprecedented heptanuclear [Zn7(OH)2(HOMe)2]12+ cluster with {(420·652·76·813)(43)4} topology. Detailed structural comparison of two compounds indicated that coligands play significant roles in tuning the nuclearity of metal clusters and the connectivity of specific networks. Furthermore, the thermal stabilities and luminescence properties of two compounds reveal that they all exhibit high thermal stability and strong luminescence emission bands in the solid state at room temperature.

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to perform high connectivity. Examples of eight-, nine-, and ten-connected MOFs are relatively scarce,6 and especially twelve- and fourteen-connected MOFs are highly rare; these may be due to the limited coordination numbers of metal centers and the steric hindrance of organic ligands.7 Following the above consideration, we report two new MOFs based on polynuclear zinc cluster SBUs, namely, [Zn2(OH)(cpia)(bipy) 0 . 5 ] n (1) and {[Zn 7 (OH) 2 (HOMe) 2 (cpia) 4 (bib)]·5H2O}n (2) (bib = 1,4-bis(imidazol-1-yl)benzene, H3cpia = 5-(4-carboxyphenoxy)isophthalic acid, bipy = 4,4′bipyridine), which are structurally characterized by singlecrystal X-ray diffraction. As will be shown, 1 is a binodal (3,8)connected network with tetranuclear SBUs as 8-connected nodes and cpia ligands as 3-connected nodes, and the Schläfli symbol is (43)2(46·618·84). While compound 2 can be described as a binodal (3,14)-connected network with heptanuclear {Zn7} SBU 14-connected nodes and cpia ligands as 3-connected nodes, and the Schläfli symbol is {(420·652·76·813)(43)4}. Up to now, the (3,14)-connected 3D framework via using covalent linkages has not been observed in MOFs.13c Furthermore, the thermal stabilities and luminscence properties for 1 and 2 have been examined. Reaction of Zn(NO3)2·6H2O and H3cpia with bipy in a mixed solvent of water and methanol afforded colorless crystals

n recent years, cluster-based metal−organic frameworks (MOFs) have attracted considerable attention because of their enormous variety of fascinating structural topologies and potential applications as functional materials.1 Up to the present, a large number of cluster-based MOFs with rich physical or chemical properties, such as magnetism, luminescence, selective guest inclusion, gas storage, and separation, have been obtained via the rationally designed metal clusters directional self-assembly approach.2 More efforts have therefore been made on this field: for example, Yaghi and co-workers have constructed a large family of isoreticular MOFs by combination of linear dicarboxylate ligands bearing different lengths and [Zn4O(COO)6] clusters, which exhibit tunable pore sizes, shapes, and functionalities.2 It is noteworthy that utilizing polynuclear clusters as SBUs can reduce the interpenetration and increase the critical pore size. As well as the increase of the pore size, the polynuclear metal clusters can also serve as high-connected nodes, which can also form possibly novel high-connected topological nets due to metal clusters bearing different sizes and connectivity.3 In this case, metal cluster entities as SBUs have been proved to be an effective and powerful synthetic strategy in constructing new MOFs,4 in which neutral zinc carboxylate clusters are most commonly used, such as penta-, hexa-, octa-, and undecanuclears, and even higher zinc cluster SBUs have also been constructed in recent years.5 Therefore, to obtain such highconnected MOFs, an effective synthetic strategy is employing polynuclear clusters with larger sizes and polycoordinating sites © 2012 American Chemical Society

Received: February 14, 2012 Revised: April 28, 2012 Published: May 3, 2012 2730

dx.doi.org/10.1021/cg300218z | Cryst. Growth Des. 2012, 12, 2730−2735

Crystal Growth & Design

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Figure 1. (a) Portion view of the coordination details of 1 showing six cpia3− ligands and two bipy spacers around each tetranuclear ZnII cluster. (b) Schematic presentation of the 8-connected node (red).

Figure 2. (a) Perspective view of a single 3D network from the interpenetrating 3D framework in 1 along the ac plane. (b) (3,8) network topology of 1. The 8-connected red nodes represent the tetranuclear ZnII clusters, while the 3-connected blue ones represent the cpia3− bridges.

bridging carboxylate groups of cpia3− and nitrogen atoms of bipy ligands. Thus, the structure of 1 can be described as a 3D framework composed of [Zn4(CO2)6(μ3-OH)2] subunits connecting through cpia3− and bipy ligands (Figure 2a). Each cpia3− ligand connects three {Zn4}-based SBUs as a 3connected node, each bipy ligand links two {Zn4}-based SBUs as a linear linker, while each {Zn4}-based SBU is surrounded by six cpia3− ligands and two bipy ligands to afford an 8-connected node (Figure 1b). So the resulting structure of 1 is an extended neutral 3D (3,8)-connected network. Topology analysis by the topos4.0 program9 suggests the (3,8)-connected net has a (43)2(46·618·84) topology symbol (Figure 2b). Because of the spacious nature of the single network, the potential voids are filled via mutual interpenetration of an identical 3D framework generating a 2-fold interpenetrating architecture (Supporting Information Figure S3). Single-crystal X-ray determination reveals that complex 2 contains hydroxyl-bridged heptanuclear [Zn7(OH)2(HOMe)2]12+ clusters, which are further connected via cpia3− and nitrogen atoms of the bib ligands to result in a

of compound [Zn2(μ3-OH)(cpia)(bipy)0.5]n (1), which was structurally characterized by single-crystal X-ray diffraction.8 The result of X-ray crystallographic analysis reveals that complex 1 crystallizes in the triclinic space group P1̅. The asymmetrical unit of 1 consists of two crystallographic independent ZnII atoms, one cpia3− ligand, half a bipy ligand, and one μ3-OH. As shown in Supporting Information Figure S1, each Zn1 in 1 is coordinated by two carboxylate oxygen atoms (Zn1−O 1.967(3) Å) of two cpia3− ligands, two oxygen atoms (Zn1−O 1.926(3) Å) of two μ3-OH, and one nitrogen atom (Zn1− N 2.016(3) Å) of one bipy ligand to furnish a tetrahedral coordination geometry. Zn2 is a six coordinated distorted octahedral coordination geometry (Figure 1a), which is completed by four carboxylate oxygen atoms (Zn2−O 2.073(4)−2.180(3) Å) of three cpia3− ligands and two oxygen atoms (Zn2−O 2.091(3)−2.099(4) Å) of two μ3-OH ligands. Zn1, Zn2 and symmetry-related Zn1A, Zn2A are associated together by two μ3-OH and six carboxylate groups of six cpia3− ligands to form a {Zn4}-based SBU [Zn4(CO2)6(μ3-OH)2]. These {Zn4}-based SBUs propagate into a 3D network via 2731



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Figure 3. (a) Portion view of the coordination details of 2 showing twelve cpia3− ligands and two bib spacers around each heptanuclear ZnII cluster. (b) Schematic presentation of the 14-connected node (red).

Figure 4. (a) Projection view of the 3D framework of 2 along the bc plane. (b) (3,14) network topology of 2. The 14-connected red nodes represent the heptanuclear ZnII clusters, while the 3-connected blue ones represent the cpia3− bridges.

μ3-OH group, and one μ3-HOMe ligand to complete a square pyramidal geometry. Zn3 and Zn4 are both four-coordinated and exhibit distorted tetrahedral geometries: Zn3 is surrounded by two carboxylate oxygen atoms from different cpia3− ligands, one μ3-OH group, and one nitrogen atom from one bib ligand, while Zn4 is coordinated with one μ3-OMe and three carboxylate oxygen atoms from different cpia3− ligands. The nonbonding Zn1···Zn2, Zn1···Zn3, Zn1···Zn4, Zn2···Zn3, and Zn2···Zn4 distances are 3.003, 3.533, 3.336, 3.29, and 3.523 Å, respectively, which is considerably shortened by the presence of a Zn−O−Zn linkage. There are two μ3-OH groups and two μ3HOMe, which connect seven Zn II ions to form a [Zn7(OH)2(HOMe)2]12+ cluster with 9.6 × 9.1 × 7.5 Å3. The Zn−O bond lengths for Zn1, Zn2, Zn3, and Zn4 ions are varying from 1.894(5) to 2.138(4) Å, which are comparable to those documented values in the previous heptanuclear {Zn7} clusters.11 The average Zn1−O bond length (2.116(4) Å) is

3D coordination framework. The asymmetric unit of 2 consists of three and a half ZnII cations, two cpia3− ligands, one μ3hydroxyl, one μ3-HOMe coordination molecule, half a bib ligand, and two and a half lattice water molecules (Supporting Information Figure S2). The heptanuclear clusters contain 4-, 5-, and 6-coordinated ZnII ions, which results from the various linking modes of cpia3− (Supporting Information Figure S4) ligands, such as η1:η1:η1:η1:η0:η1:μ5 and η1:η1:η0:η1:η1:η0:μ3 coordinated fashions. Furthermore, the η1:η1:η1:η1:η1:η1:μ6 coordinated fashion of the cpia3− ligand is unique and the largest coordination mode ever seen in Co(II) complexes.10 All ZnII cations exhibit three different coordination geometries. The Zn1 atom is located at general positions and coordinated by two carboxylate oxygen atoms from different cpia3− ligands, two μ3-OH groups, and two μ3-HOMe ligands to complete a distorted octahedral environment. Zn2 is coordinated to three carboxylate oxygen atoms from two different cpia3− ligands, one 2732



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2D (3,6)-connected and the 2D (3,8)-connected networks can decompose into interconnected 63 and 44 networks, respectively. Furthermore, Zeng et al. have reported a unique (3,13)connected framework constructed from the (3,12)-connected net by decorating the nodes using an additional bipy spacer,13c and they provide a good topological identification method for the high-connected coordination network. Therefore, this unique (3,8) and (3,14)-connected structural evolution can be well operated on the basis of (3,6) and (3,12)-connected frameworks by additional two spacer ligands replacement, respectively. Our results further definitely confirm that utilizing a polynuclear metal cluster as an SBU is a rational and effective strategy for the design and construction of high-connected new MOFs with unusual network topology.15 To confirm the phase purity of complexes 1 and 2, the PXRD patterns were recorded. They were comparable to the corresponding simulated ones calculated from the single-crystal diffraction data (Figures S6 and S7 in the Supporting Information), indicating a pure phase of each bulky sample. To characterize the compounds more fully in terms of thermal stability, their thermal behaviors were studied by TGA. Thermal gravimetric analysis (TGA) experiments of 1 and 2 were performed under N2 atmosphere with a heating rate of 10 °C/min. Complex 1 is stable up to ca. 210 °C. The TGA curve (Supporting Information Figure S8) of 1 shows that the first weight loss takes place at 220−360 °C and corresponds to the loss of bipy molecules (obsd, 30.17%; calcd, 30.24%). From then on, almost no weight loss is observed until 380 °C, at which temperature it starts to decompose along with the loss of cpia3− ligands (obsd, 31.24%; calcd, 31.02%). In the case of 2, which is stable up to ca. 410 °C, the first weight loss of 4.78% (calcd 4.38%), in the range of 200−400 °C, corresponds to the removal of the lattice water molecules (Supporting Information Figure S9). The remaining substance is stable up to ca. 410 °C, further weight loss is observed at about 420 °C due to the decomposition of the overall framework, and then the sheet starts to decompose along with the loss of cpia3− and bib ligands (obsd, 73.55%; calcd, 73.28%). Metal−organic coordination complexes constructed from d10 metal atoms (or d10 metal clusters) and conjugated organic ligands are promising candidates for hybrid photoactive materials with potential applications such as light-emitting diodes (LEDs).16 The solid-state luminescent emission spectra of 1, 2, and free H3cpia ligand were studied at room temperature (Supporting Information Figures S10 and S11). As shown in Supporting Information Figure S11, the free H3cpia ligand exhibits emission, with the maxima at 363 nm upon excitation at 310 nm, which is ascribed to the π* → n or π* → π electronic transition. Compared with the luminescence of free ligand, the emissions of 1 (λem = 460 nm, λex = 320 nm) and 2 (λem = 503 nm, λex = 310 nm) undergo a red-shift from 363 to 460 and 503 nm, respectively. We can presume that these emissions are neither metal-to-ligand charge transfer (MLCT) nor ligand-to-metal transfer (LMCT) in nature, because in the luminescent polynuclear metal systems, Zn(II) ion is difficult to oxidize or reduce due to its d10 configuration, and the emission of bulk ZnO material was observed at λem = 380 nm.17 Therefore, emissions observed at 460 nm for 1 and 503 nm for 2 might be assigned to a combination of the charge transfer process and intraligand emission states (π* → n or π* → π), as reported for other ZnII complexes with N-donor ligands.18 Further, it can be observed that the emission spectra for 1 and 2 exhibit red-shifts with respect to the free cpiaH3

slightly longer than those of Zn2−O (2.051(5) Å), Zn3− O (1.925(4) Å), and Zn4−O (1.933(5) Å). More interestingly, the Zn1 in an inversion center is shared by two [Zn4(OH)(HOMe)]6+ tetrahedrons to form an uncommon heptanuclear [Zn7(OH)2(HOMe)2(OCO)12] clusters. Each heptanuclear zinc cluster in 2 is 14-coordinated to fourteen neighboring clusters by twelve cpia3− ligands and two μ2-bib ligands to extend into an infinite 3-D MOF (Figure 4a). The Zn1···Zn1 distances of neighboring heptanuclear clusters linked by cpia3− carboxylate groups are 11.419 and 14.219 Å, respectively, which are much shorter than those distances linked via μ2-bib ligands (19.543 Å). The construction of high-connected coordination frameworks by using polynuclear zinc clusters as SBUs will produce intriguing architectures with high-connected topologies and excellent properties, which has already been proven.12 In this paper, the in situ synthesis of heptanuclear zinc cluster units results in a fascinating structure and unique topology. To fully understand the structure of 2, the topological approach is applied to simplify such a complicated 3D coordination framework. In this 3D framework, each heptanuclear zinc cluster motif can be regarded as the SBU in the construction of this complicated network, which is surrounded by fourteen organic ligands (twelve cpia3− ligands and two bib ligands) (Figure 3a). As such, each cpia3− ligand is connected to three heptanuclear zinc clusters and results in a 3-connected node with the Schläfli symbol of (43). The vertex symbols of two independent cpia3− nodes are equivalent, that is, (4·4·43) for the type (I) and type (II) ligands (see Figure S4b, S4c for the definition of the ligand types). In addition, each bib links two heptanuclear zinc clusters as a linear linker. So each heptanuclear zinc cluster as a 14-connected node is further linked by two other heptanuclear zinc clusters and twelve 3connected nodes (Figure 4b). As a consequence, the resulting 3D framework can be simplified as a (3,14)-connected net with a topology symbol of {(420·652·76·813)(43)4} (TD10 = 5375), which represents a new topology analyzed by the Topos 4.0 program.12i,j To the best of our knowledge, such a topology has not been observed in MOFs according to the Reticular Chemistry Structure Resource database,12g and also represents the first 14-connected high node coordination network utilizing polynuclear zinc clusters as a SBU. Previous examples with binodal high-connected (3,12), (3,13), (3,24), and (3,36) frameworks based on triangles as 3-connected nodes are very rare.13 But the (3,14)-connected 3D framework using a covalent linkage has not been observed in coordination networks. As we know, the study and analysis of the network topology is a powerful tool for simplifying the structure of complicated compounds. Hill et al. have proposed a simpler and more readily visualized description in terms of 2-D subnet tectons to analyze high-connected uninodal frameworks based on 44- and 63-nets.14 In addition, Su et al. have proposed an easier topological identification method for such binodal (3,12)-connected 3D frameworks based on a CdI2-type network.13b Such analysis provides a good way to understand topological identification from the uninodal framework to the binodal framework and other complicated 3D frameworks with high connectivity. To further study and analyze the network topology for 2, this approach is used here. First, the 3D framework can decompose into a 2D (3,6)-connected framework and a 2D (3,8)-connected network when the 14connected node divides into a 6-connected node plus a 8connected node (Supporting Information Figure S5). Then, the 2733



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Aguado, S.; Pinel, C. Angew. Chem., Int. Ed. 2009, 48, 7502. (d) Kitagawa, S.; Kitaura, R.; Noro, S. i. Angew. Chem., Int. Ed. 2004, 43, 2334. (e) Zhao, J. A.; Mi, L. W.; Hu, J. Y.; Hou, H. W.; Fan, Y. T. J. Am. Chem. Soc. 2008, 130, 15222. (4) (a) An, J.; Geib., S. J.; Rosi, N. L. J. Am. Chem. Soc. 2009, 131, 8376. (b) Lama, P.; Bharadwaj, P. K. Cryst. Growth Des. 2011, 11, 5434. (5) (a) Allendorf, M. D.; Bauer, A. A.; Bhakta R. K. Houk, R. J. T. Chem. Soc. Rev. 2009, 38, 1330. (b) Zhang, Y. N.; Liu, P.; Wang, Y. Y.; Wu, L. Y.; Pang, L. Y.; Shi, Q. Z. Cryst. Growth Des. 2011, 11, 1531. (c) Wang, M. X.; Long, L. S.; Huang, R. B.; Zheng, L. S. Chem. Commun. 2011, 47, 9834. (6) (a) Wang, X. L.; Qin, C.; Wang, E. B.; Su, Z. M.; Xu, L.; Batten, S. R. Chem. Commun. 2005, 4789. (b) Amatas, N. G.; Burkholder, E.; Zubieta, J. J. Solid State Chem. 2005, 178, 2430. (c) Williams, C. A.; Blake, A. J.; Hubberstey, P.; Schröder, M. Chem. Commun. 2005, 5435. (d) Hou, L.; Zhang, J. P.; Chen, X. M.; Ng, S. W. Chem. Commun. 2008, 4019. (e) Shi, W. J.; Hou, L.; Zhao, W.; Wu, L. Y.; Wang, Y. Y.; Shi, Q. Z. Inorg. Chem. Commun. 2011, 14, 1915. (f) He, K. H.; Song, W.-C.; Li, Y. W.; Chen, Y. Q.; Bu, X. H. Cryst. Growth Des. 2012, 12, 1064. (7) (a) Fang, Q. R.; Zhu, G. S.; Jin, Z.; Xue, M.; Wei, X.; Wang, D. J.; Qiu, S. L. Angew. Chem., Int. Ed. 2006, 45, 6126. (b) Wang, X. L.; Qin, C.; Wang, E. B.; Su, Z. M.; Xu, L.; Batten, S. R. Chem. Commun. 2005, 4789. (c) Su, Z.; Song, Y.; Bai, Z. S.; Fan, J.; Liu, G. X.; Sun, W. Y. CrystEngComm 2010, 12, 4339. (d) Hao, Z. M.; Fang, R. Q.; Wu, H. S.; Zhang, X. M. Inorg. Chem. 2008, 47, 8197. (8) Crystal data for 1: C20H12NO8Zn2, Mr = 525.09, triclinic, P1̅, a = 9.7156 (19) Å, b = 10.047(2) Å, c = 11.134(2) Å, α = 67.25(3)°, β = 77.74(3)°, γ = 66.87(3)°, V = 919.4(4) Å3, Z = 2, Dcalcd = 1. 897 g·cm−3, F(000) = 526, reflections collected/unique: 3219/2562, Rint = 0.0660, final R1 = 0.0444 (I > 2σ(I)), wR2 = 0.0773 (alldata), GOF = 1.072. For 2: C74H58N4O37Zn7, Mr = 2053.12, triclinic, P1̅, a = 11.419(2) Å, b = 12.719(3) Å, c = 13.441(3) Å, α = 96.63(3)°, β = 111.56(3)°, γ = 90.80(3)°, V = 1800.1(8) Å3, Z = 1, Dcalcd = 1. 887 g·cm−3, F(000) = 1018, reflections collected/unique: 6320/5025, Rint = 0.037, final R1 = 0.046 (I > 2σ(I)), wR2 = 0.1509 (all data), GOF = 1.025. (9) (a) O’Keeffe, M.; Yaghi, O. M. Reticular Chemistry Structure Resource; Arizona State University: Tempe, AZ, 2005; http:// okeeffews1.la.asu.edu/rcsr/home.htm. (b) Baburin, I. A.; Blatov, V. A.; Carluccib, L.; Ciani, G.; Proserpio, D. M. J. Solid State Chem. 2005, 178, 2452. (c) Blatov, V. A. 2006, http://www.topos.ssu.samara.ru/ starting.html. (10) (a) Lama, P.; Aijaz, A.; Neogi, S.; Barbour, L. J.; Bharadwaj, P. K. Cryst. Growth Des. 2010, 10, 3410. (b) Lama, P.; Aijaz, A.; Sañudo, E. C.; Bharadwaj, P. K. Cryst. Growth Des. 2010, 10, 283. (11) (a) Li, J. R.; Tao, Y.; Yu, Q.; Bu, X. H. Chem. Commun. 2007, 1527. (b) Wei, J. J.; Liu, Q. Y.; Wang, Y. L.; Zhang, N.; Wang, W. F. Inorg. Chem. Commun. 2012, 15, 61. (c) Ng, M. T.; Deivaraj, T. C.; Vittal, J. J. Inorg. Chim. Acta 2003, 348, 173. (12) (a) Yang, S. Y. L.; Long, L. S.; Huang, R. B.; Zheng, L. S. Chem. Commun. 2002, 472. (b) Lan, Y. Q.; Li, S. L.; Shao, K. Z.; Wang, X. L.; Du, D. Y.; Su, Z. M.; Wang, D. J. Cryst. Growth Des. 2008, 8, 3490. (c) Wang, J.; Lin, Z. J.; Ou, Y. C.; Yang, N. L.; Zhang, Y. H.; Tong, M. L. Inorg. Chem. 2008, 47, 190. (d) Fang, Q. R.; Zhu, G. S.; Xue, M.; Zhang, Q. L.; Sun, J. Y.; Guo, X. D.; Qiu, S. L.; Xu, S. T.; Wang, P.; Wang, D. J.; Wei, Y. Chem.Eur. J. 2006, 12, 3754. (e) Blatov, V. A. IUCr CompComm Newsl. 2006, 7, 4. (f) Blatov, V. A. TOPOS4.0, A multipurpose Crystallochemical Analysis with the Program Package; Samara State University: Russia, 2004. (g) Reticular Chemistry Structure Resource (RCSR), http://rcsr.anu.edu.au/. (13) (a) Hou, L.; Zhang, W. X.; Zhang, J. P.; Xue, W.; Zhang, Y. B.; Chen, X. M. Chem. Commun. 2010, 6311. (b) Yang, Q. Y.; Li, K.; Luo, J.; Pan, M.; Su, C. Y. Chem. Commun. 2011, 4234. (c) Zeng, M. H.; Zou, H. H.; Hu, S.; Zhou, Y. L.; Du, M.; Sun, H. L. Cryst. Growth Des. 2009, 9, 4239. (14) Hill, R. J.; Long, D. L.; Champness, N. R.; Hubberstey, P.; Schröder, M. Acc. Chem. Res. 2005, 38, 337.

ligand, may be due to the chelating and/or bridging effect of the deprotonated cpia3− ligands and the coordination effects of cpia3− ligands to the Zn(II) ions.19 On the other hand, a strong luminescence emission may be attributed to the rigidity of the bipy and bib ligands with regard to the metal clusters, which effectively increases the rigidity and conjugation upon metal coordination and then affects the loss of energy via a radiationless pathway of the intraligand (π* → n or π* → π) excited state.19e‑f In summary, we have obtained two 3D ZnII complexes by using 2-connected rigid N-donor coligands and one 3connected aromatic multicarboxylates H3cpia ligand. 1 is a binodal (3,8)-connected network with (43)2(46·618·84) topology based on tetranuclear [Zn4(OH)2]6+ clusters. 2 shows a binodal (3,14)-connected network with {(420·652·76·813)(43)4} topology based on an unprecedented heptanuclear [Zn7(OH)2(HOMe)2]12+ clusters as SBU. They all display strong luminescent emission. Therefore, the present work will largely enrich binodal (3,8) and (3,14)-connected nets and bring us a new effective synthetic strategy to access (3,8)connected or other kinds of high-connected new MOFs. This leads us to predict that in these or other systems incorporating polynuclear metal clusters as SBU, multicarboxylate ligands and N-donor coligands can play important roles in the construction of high-connected MOFs whose 3D structures can be rationally designed and experimentally controlled. These results will also further facilitate the exploration of high-connected MOFs based on polynuclear Zn clusters, which can be used as new types of functional materials in fields such as gas storage, separation, magnetism, and luminescence.

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ASSOCIATED CONTENT

S Supporting Information *

Syntheses of compounds 1 and 2, selected bond lengths and angles, simulated and experimental X-ray powder diffraction patterns, and IR and X-ray crystallographic files in cif format for 1 and 2. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +86-22-23502458. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Science Foundation of China (21031002 and 51073079), the 973 Program of China (2012CB821700), and the Natural Science Fund of Tianjin, China (10JCZDJC22100).

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REFERENCES

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Connected Coordination Networks - American Chemical Society

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