Synthesis, Structure and Magnetic Property of One NiII Based Coordination Polymer①

WEN Bo WANG Xiao-Dan YU Ying-Hui GAO Jin-Sheng HOU Guang-Feng

a (Engineering Research Centre of Pesticide of Heilongjiang University, Heilongjiang University, Harbin 150080, China)b (School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China)

1 INTRODUCTION

Design and construction of coordination polymers have attracted considerable attention due to their fascinating variety of structural diversity and potential applications in catalysis, magnetism, gas storage and luminescence[1–5]. The structures and properties of coordination polymers could be influenced by many factors such as the nature of ligands, metal/ligand ratio, solvent media, and so on[6–9]. The effect of ligand structure is crucial,usually considered firstly in designing novel coordination complexes with various structures. 1,n-Bis(imidazol-1-ylmethyl)benzene (n = 2, 3, 4) represents a famous type of N-containing semi-rigid ligands with a rigid phenyl center linking two coordinated imidazol groups via flexible methylene sp3-carbon atoms. Such interesting ligands have been reported to react with metal ions, furnishing discrete metallomacrocycles, 1D infinite chain, 2D polyrotaxane networks and 3D frameworks[10–15]. As is well known, one effective approach for the synthesis of new coordination polymers is the incorporation of the second building blocks, such as polyoxometalates, clusters, adjuvant/second ligands,which can afford not only intriguing architectures,but also abundant properties[16–18].

The reaction of 1,3-bis(imidazol-1-ylmethyl)benzene (m-bix), 1,3-benzenedicarboxylic acid (m-BDC) and Ni(NO3)2resulted in a new complex,[Ni(m-bix)(m-BDC)] (1), which shows a novel 6-connected 3D sxd type topological framework.Complex 1 was characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR analysis and thermal gravimetric analysis. Furthermore,the magnetic property was also investigated.

Scheme 1. Schematic representation of 1,3-bis((1H-imidazolyl)methyl)benzene(m-bix) and 1,3-benzenedicarboxylic acid (m-BDC)

2 EXPERIMENTAL

2.1 Materials and methods

All commercially available chemicals were of reagent grade and used as received without further purification. Elemental analyses were performed on a CARLO ERBA 1106 analyzer. IR spectra were recorded on a Bruker IFS 66v FT-IR spectrometer equipped with a DGTS detector (32 scans) by using KBr pellet.1H NMR spectra were performed on a Bruker AV 300 MHz spectrometer. Thermogravimetric measurements were done on a Perkin-Elmer TGA 7 analyzer. Powder X-ray diffraction (PXRD)data were recorded using a Bruker D8 system with CuΚα radiation (λ = 0.15405 nm). The temperaturedependent magnetic susceptibility of 1 was measured with crystalline powder samples with a Quantum Design MPMS XL-7 Squid magnetometer in a magnetic field of 1000 Oe from 1.8 to 300 K.

2.2 Synthesis of 1,3-bis((1H-imidazolyl) methyl)benzene (m-bix)

A mixture of imidazole (10.0 g, 150 mmol) and KOH (16.8 g, 300 mmol) in acetonitrile (200 mL)was stirred at 50 ℃ for 1 h, and then 1,3-bis(chloromethyl)benzene (13.1 g, 75 mmol) in acetonitrile(30 mL) was added. The mixture was kept stirring at room temperature for 4 hours. 15.2 g yellow crude product of m-bix was obtained after removing acetonitrile by distillation, which was recrystallized from the binary solvent of ethanol–H2O (30 mL, v:v= 1:2) to get pure m-bix (12.8 g, 72% yield)[19].Elemental analysis: Calcd. for m-bix (C14H14N4): C,70.57; H, 5.92; N, 23.51%. Found: C, 70.52; H,5.92; N, 23.55%. IR (KBr, cm-1): 3389 (m), 3189(m), 3112 (m), 2949 (w), 2254 (w), 1609 (s), 1507(m), 1442 (m), 1347 (m), 1279 (s), 1229 (m), 1086(s), 1028 (m), 918 (w), 835 (m), 772 (m), 729 (s),656 (m), 627 (w).1H NMR (CD3OD): 5.21 (4H, s),6.98 (2H, s), 7.07 (2H, s), 7.08 (3H, t), 7.18 (1H, t),7.72 (2H, s).

2.3 Synthesis of [Ni(m-bix)(m-BDC)] (1)

m-Bix (0.0953 g, 0.4 mmol), m-BDC (0.0660 g,0.4 mmol) and Ni(NO3)2(0.10 g, 0.4 mmol) were dissolved in ethanol–H2O (8 mL, v:v = 1:2.5)binary solvent and then heated at 160 ℃ for three days in a sealed 18 mL Teflon-lined stainless-steel vessel under autogeneous pressure. After slowly cooling to room temperature, green block crystals were filtered and washed with distilled water and ethanol (71% yield based on Ni). Elemental analysis:Calcd. for 1: C, 57.31; H, 3.93; N, 12.15%. Found:C, 57.37; H, 3.98; N, 12.10%. IR (soid KBr pellet/cm-1): 3403 (m), 3105(m), 2348 (w), 1616 (s),1583 (m), 1538 (s), 1515 (m), 1474 (m), 1443 (m),1394(s), 1280 (w), 1228 (m), 1117 (m), 1081 (m),1022 (w), 940 (w), 828 (m), 745(m), 726 (m), 715(m), 665 (m), 630 (w).

2.4 Structure determination

Single-crystal X-ray diffraction data for complex 1 were collected on a Rigaku R-AXIS RAPID imaging plate diffractometer equipped with graphitemonochromated MoKα (λ = 0.71073 ?) radiation at 291 K. Empirical absorption corrections based on equivalent reflections were applied. The structure of complex 1 was solved by direct methods and refined by full-matrix least-squares methods on F2using SHELXS-97 crystallographic software package[20]. In the range of 3.14<θ<25.00o, a total of 7487 reflections were collected, of which 3424 were unique with Rint= 0.0278. All non-hydrogen atoms were refined anisotropically by full-matrix leastsquares techniques for 2827 observed reflections with I > 2σ(I) to the final R = 0.0335, wR = 0.0683(R = Σ||Fo| – |Fc||/Σ|Fo|, wR = {Σ[w(Fo2–Fc2)2/Σw(Fo2)2]}1/2). H atoms bound to C were placed in the calculated positions and treated as riding on their parent atoms with C-H = 0.93 ?(aromatic) or 0.97 ? (methylene), and with Uiso(H)= 1.2Ueq(C).

3 RESULTS AND DISCUSSION

3.1 Crystal structure description

Single-crystal X-ray diffraction analysis shows that the asymmetric unit of complex 1 consists of one NiIIcation, one m-BDC anion, and one m-bix ligand. As shown in Fig. 1, the NiIIcation is sixcoordinated in a distorted octahedral environment defined by four O atoms from the m-BDC anions and two N atoms from the m-bix ligands. The Ni–O bond distances are in the range of 2.042(2)～2.149(2) ? with the average distance of 2.109 ?,while the two Ni–N bond distances are 2.056(2) and 2.077(2) ?, respectively. The angles around the NiIIcation are in the range of 61.64(6)～174.86(7)°(Table 1).

Fig. 1. Asymmetric unit of complex 1 at 50% probability thermal ellipsoids. Hydrogen atoms are omitted for clarity. Symmetry codes: (i) 1–x, 0.5+y, 1.5–z; (ii) 1–x, 2–y, 2–z; (iii) –x, 2–y, 2–z

The m-BDC anion serves as a tetradentate ligand coordinating with three NiIIcations involving its two carboxyl groups in a binding mode of μ3-η1:η1:η1:η1. As shown in Fig. 2, the two carboxyl groups exhibit different coordination modes: one carboxyl group (O(1)–C(21)–O(2)) shows a bridging coordination mode, which links two NiIIcations to form a dinuclear {Ni2} moiety with Ni···Ni distance of 4.495(1) ?; however, the other carboxyl group (O(3)–C(22)–O(4)) exhibits a chelating coordination mode to connect the Niiication forming the shortest distance between two adjacent{Ni2} moieties of 8.062(1) ?. A ladder-like chain is constructed by m-BDC anions linking NiIIcations along the [1 0 0] direction. Furthermore, the m-bix molecules take cis-configuration to connect the Niiications to propagate a helical chain along the [0 1 0]direction. Notably, these m-BDC chains connect the m-bix chains to construct a novel 6-connected 3D sxd type topological framework[21,22]with a point symbol of (33·46·55·6) simplified by the TOPOS program[23](Fig. 3). Such novel sxd type topology is firstly found in 2005, which is comprised of triangles, squares and hexagons[24].

Table 1. Selected Bond Lengths (?) and Bond Angles (°) for Complex 1

Fig. 2. Coordination modes of m-BDC anion in complex 1.Symmetry codes: (i) 1–x, 0.5+y,1.5–z; (ii) 1–x, 2–y, 2–z; (iii) –x, 2–y, 2–z

Fig. 3. Schematic illustration of the 6-connected3D sxd type topological framework with apoint symbol of (33·46·55·6) of complex 1

3.2 PXRD and TGA

In order to characterize the phase purity of other crystalline materials, PXRD pattern for complex 1 was performed at room temperature (Fig. 4). The locations and intensities of diffraction peaks of experimental patterns match well with the calculated ones, indicating that complex 1 was synthesized as a single phase. The TG measurement of complex 1 was carried out under atmosphere in the temperature range of 30～750 ℃ (Fig. 5). The TG curve shows that the framework collapses starting at 390 ℃, and then loses its weight of 82.89% from 390 to 430 ℃ corresponding to the decomposition of both m-bix molecule and m-BDC anion (calcd.83.80%). The residue with weight of 17.11% can be ascribed to the NiO (calcd. 16.20%).

Fig. 4. Powder X-ray diffraction patterns and the simulated patterns of complex 1

Fig. 5. TGA curve of complex 1 from 25 to 750 ℃ under atmosphere

3.3 Magnetic property

The temperature dependent magnetic susceptibility of complex 1 was carried out on crystal samples under an applied field of 1000 Oe in the range of 1.8～300 K. The plots of χmT and χmversus T for complex 1 are shown in Fig. 6. The χmT value at 300 K is 1.59 cm3K mol-1, which is larger than the spin-only value of 1.002 cm3K mol-1and less than two independent S = 1 NiIIcenters. Therefor, the value falls into a reasonable range for complexes containing NiIIcenters[25]. As the temperature decreases from 300 K down to 40 K, χmT value gradually decreases from 1.59 cm3K mol-1to 1.28 cm3K mol-1, and then it dramatically decreases to 0.44 cm3K mol-1at 1.8 K. This curve represents an antiferrromagnetic interaction between NiIIcenters in complex 1. The inverse susceptibility 1/χmplot as a function of temperature is linear, closely following the Curie-Weiss law.

Fig. 6. Plots (left) of temperature dependence of χm (black) and χmT (blue)for complex 1; plots (right) of temperature dependence of 1/χm

4 CONCLUSION

One metal-organic framework based on semirigid m-bix ligand and m-BDC as the second ligand has been synthesized and characterized, exhibiting a novel 6-connected 3D sxd type topological structure.Magnetic measurement shows antiferromagnetic interactions between NiIIcenters in complex 1.Other metal centered complexes containing m-bix ligand and aromatic polycarboxylates with intri-guing structures as well as their physical properties are also under investigation.

(1) Wu, H. H.; Gong, Q. H.; Olson, D. H.; Li, J. Commensurate adsorption of hydrocarbons and alcohols in microporous metal organic frameworks.Chem. Rev. 2012, 112, 836-868.

(2) Zhang, J. P.; Zhang, Y. B.; Lin J. B.; Chen, X. M. Metal azolate frameworks: from crystal engineering to functional materials. Chem. Rev. 2012, 112,1001-1033.

(3) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O'Keeffe, M.; Yaghi, O. M. Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage. Science 2002, 295, 469-472.

(4) Haldoupis, E.; Nair, S.; Sholl, D. S. Finding MOFs for highly selective CO2/N2adsorption using materials screening based on efficient assignment of atomic point charges. J. Am. Chem. Soc. 2012, 134, 4313-4323.

(5) Mckinlay, A. C.; Morris, R. E.; Horcajada, P.; Férey, G.; Gref, R.; Couvreur, P.; Serre, C. BioMOFs: metal-organic frameworks for biological and medical applications. Angew. Chem., Int. Ed. 2010, 49, 6260-6266.

(6) Hou, G. F.; Bi, L. H.; Li, B.; Wang, B.; Wu, L. X. Polyoxometalate charge directed coordination assemblies: macrocycles and polymer chains.CrystEngComm. 2011, 13, 3526-3535.

(7) Perry, J. J.; Kravtsov, V. C.; McManus, G. J.; Zaworotko, M. J. Bottom up synthesis that does not start at the bottom:quadruple covalent gross-linking of nanoscale faceted polyhedra. J. Am. Chem. Soc. 2007, 129, 10076-10077.

(8) Xiang, J.; Luo, Y. A novel layer cadmium coordination polymer containing tetranuclear [Cd4(tpt)2(Cl)4]4+as a secondary building unit (SBU)bridged by pyridine 2,4-dicarboxylic acid. Chin. J. Struct. Chem. 2014, 33, 345-352.

(9) Hou, G. F.; Yu, Y. H.; Wang, X.; Gao, J. S.; Wen, B.; Wang, X. D.; Yan, P. F. Syntheses, structures and characterizations of three Ag(I) complexes constructed by length modulated pyrazole-based ligands. J. Coord. Chem. 2013, 66, 3402-3411.

(10) Mei, C. Z.; Wang, H. R.; Xiong, H. L.; Meng, R. J.; Shan, W. W.; Li H. H. Hydrothermal synthesis and crystal structure of one 3D coordination polymer of nickel(II) achieved from 5-iodo-isophthalic acid ligand. Chin. J. Struct. Chem. 2014, 33, 563-568.

(11) Wang, Y.; Liu, Z. Q.; Wang, S. N.; Liu, G. X.; Chen, Y. C.; Wang, X. X.; Ye, M. A novel cadmium(II) complex based on asymmetric dicarboxylate and N-auxiliary ligand: synthesis, crystal structure and properties. Chin. J. Struct. Chem. 2013, 32, 903-907.

(12) Li, X. M.; Ji, J. Y.; Wang, Z. T.; Liu, B. Hydrothermal synthesis and crystal structure of a three-dimensional cadmium(II) complex. Chin. J. Struct.Chem. 2012, 31, 1464-1468.

(13) Tripuramallu, B. K.; Manna, P.; Reddy, S. N.; Das, S. K. Factors affecting the conformational modulation of flexible ligands in the self-assembly process of coordination polymers: synthesis, structural characterization, magnetic properties, and theoretical studies of [Co(pda)(bix)]n,[Ni(pda)(bix)(H2O)]n, [Cu(pda)(bix)2(H2O)2]n·8nH2O, [Co2(μ-OH)(pda)(ptz)]n·nH2O, [Co(hfipbb)(bix)0.5]n, and [Co(2,6-pydc)(bix)1.5]n·4nH2O.Cryst. Growth Des. 2012, 12, 777-792.

(14) Sun, X. L.; Song, W. C.; Zang, S. Q.; Du, C. X.; Hou, H. W.; Mark, T. C. W. Hierarchical assembly of a homochiral triple concentric helical system in a novel 3D supramolecular metal-organic framework: synthesis, crystal structure, and SHG properties. Chem. Commun. 2012, 48, 2113-2115.

(15) Wu, H.; Liu, H. Y.; Liu, Y. Y.; Yang, J.; Liu, B.; Ma, J. F. An unprecedented 2D → 3D metal-organic polyrotaxane framework constructed from cadmium and a flexible star-like ligand. Chem. Commun. 2011, 47, 1818-1820.

(16) Sha, J. Q.; Sun, J. W.; Wang, C.; Li, G. M.; Yan, P. F.; Li, M. T. Syntheses study of keggin POM supporting MOFs system. Cryst. Growth Des. 2012,12, 2242-2250.

(17) Liu, Y. Y.; Wang, Z. H.; Yang, J.; Liu, B.; Liu, Y. Y.; Ma, J. F. A series of coordination polymers based on reduced Schiff basemultidentate anions and bis(imidazole) ligands: syntheses, structures and photoluminescence. CrystEngComm. 2011, 13, 3811-3821.

(18) Hou, G. F.; Bi, L. H.; Li, B.; Wu, L. X. Reaction controlled assemblies of polyoxotungstates (-molybdates) and coordination polymers. Inorg. Chem.2010, 49, 6474-6483.

(19) Hou, G. F.; Wang, X. D.; Yu, Y. H.; Gao, J. S.; Wen, B.; Yan, P. F. A new topology constructed from an octamolybdate and metallomacrocycle coordination complex. CrystEngComm. 2013, 15, 249-251.

(20) Sheldrick, G. M. A short history of SHELX. Acta Cryst. 2008, A64, 112-122.

(21) Wang, Y.; Liu, Z. Q.; Zhou, J. H.; Wang, T.; Wang, S. N.; Liu, G. X.; Wang, X. X.; Gao, Y.; Xu, J. A series of transition coordination polymers assembled by asymmetric dicarboxylic acid and flexible bridging ligand: structural diversities, topologies and properties. Inorg. Chim. Acta 2013,400, 160-178.

(22) Wu, Y. P.; Li, D. S.; Fu, F.; Dong, W. W.; Yang, G. P.; Wang, Y. Y.; Shi, Q. Z. Characterization of three new divalent zinc coordination polymers involving flurinated carboxylate tecton via the modulation of heterocyclic N-donor co-ligands. Polyhedron 2012, 188-195.

(23) Blatov, V. A. IUCr CompComm Newsletter, 2006, 7, 4; http://www.topos.ssu.samara.ru.

(24) Hoffart, D. J.; Loeb, S. J. Metal-organic rotaxane frameworks: three-dimensional polyrotaxanes from lanthanide-ion nodes, pyridinium N-oxide axles, and crown-ether wheels. Angew. Chem., Int. Ed. 2005, 49, 901-904.

(25) Zhu, H. L.; Qi, J. L.; Lin, J. L.; Xu, W.; Wu, J.; Zheng, Y. Q. Novel topological supramolecular architectures based on partially protonated butane-1,2,3,4-tetracarboxylato complexes: synthesis, structures and magnetic properties. Inorg. Chim. Acta 2013, 404, 49-57.