Inorganic Chemistry Communications 14 (2011) 1201–1203

Contents lists available at ScienceDirect

Inorganic Chemistry Communications

j ourna l homepage: www.e lsev ie r.com/ locate / inoche

A new three-dimensional uninodal six-connected coordination polymer constructedfrom butterfly-like [Cd4(μ3-OH)2] secondary building units: Pcu net topologyand luminescence

Lin Cheng, Jian-Quan Wang, Shao-Hua Gou ⁎School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, China

⁎ Corresponding author.E-mail address: sgou@seu.edu.cn (S.-H. Gou).

1387-7003/$ – see front matter. Crown Copyright © 20doi:10.1016/j.inoche.2011.04.017

a b s t r a c t

a r t i c l e i n f o

Article history:Received 10 March 2011Accepted 15 April 2011Available online 27 April 2011

Keywords:[Cd4(μ3-OH)2]Pcu topologyCd(II) complexLuminescence

A new three-dimensional coordination polymer with the formula, [Cd4(OH)2(na)6]n (1) (na=nicotinate), hasbeen hydrothermally synthesized and structurally characterized, which can be considered as a uninodal six-connected pcu topology based on butterfly-like [Cd4(μ3-OH)2] SBUs. The polymer exhibits high thermalstability until 355 °C confirmed by thermogravimetric analysis and has potential applications as an opticalmaterial.

Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.

The construction of coordination polymers has recently become anarea of intense interests in the field of supramolecular chemistry andcrystal engineering because of their intriguing esthetic structures andtopological features as well as their potential applications in magne-tism, electric conductivity, molecular adsorption, heterogeneouscatalysis, nonlinear optics and fluorescent materials [1,2]. The abilityto rationally design and modify the crystal structures of polymericmaterials is the key to increase the potential for commercialapplications [3]. Secondary building units (SBUs), as an importantstrategy, have been applied with eminent success for understandingand predicting structural topologies of such polymers [4]. Polynuclearmetal clusters have been always employed as secondary building units(SBUs) to build coordination polymers [5] due to their followingstructure features. Firstly, the large surface areas (sometimes evennanoscale) and more coordination sites of polynuclear metal clusterscan induce them readily accommodating the steric demands of organicligands, which help to construct novel coordination polymers with six-connected or higher connected topologies. And secondly, polynuclearmetal clusters have their intrinsic properties, such as magnetism,heterogeneous catalysis andfluorescence. A tetranuclear [Zn4(μ3-OH)2]metal cluster has been used in the assembly of a rich variety ofcoordination polymers with two (2D) and three-dimensional (3D)networks, and interesting properties [6,7]. In contrast, as an analog, themulti-dimensional (2D and 3D) networks based on [Cd4(μ3-OH)2]metal clusters have been rarely reported [7].

11 Published by Elsevier B.V. All rig

On the other hand, multidentate ligands containing a carboxylateand a pyridyl group, such as nicotinate (na) and isonicotinate (ina),have been frequently introduced to the preparation of coordinationpolymers because the coordination of the pyridyl and carboxylategroups in these ligands may result in extended multi dimensionalframeworks [8]. In this paper, we reported the synthesis [9], crystalstructure [10] and fluorescent property of a new three-dimensionalcoordination polymer [Cd4(OH)2(na)6]n (1) (na=nicotinate) with auninodal six-connected pcu topology based on [Cd4(μ3-OH)2] metalclusters and nicotinate linkers.

Single-crystal X-ray diffraction reveals that 1, a three-dimensionalframework consisting of [Cd4(μ3-OH)2] cluster units and nicotinatebridges, crystallizes in the triclinic system, P-1 space group, with theasymmetric unit of two crystallographically independent Cd(II) ions,one μ3-OH group and three nicotinate ligands. Both metal atomsdisplay a distorted octahedral geometry, in which Cd1 is coordinatedby three oxygen atoms from three nicotinate, respectively, one μ3-OHgroup and two nitrogen atoms from two nicotinate ligands (Fig. 1a);while Cd2 is surrounded by three oxygen atoms from three individualnicotinate ligands, two μ3-OH groups and one nitrogen atom from onenicotinate, as shown in Fig. 1b. The butterfly-like [Cd4(μ3-OH)2] clusterunit is a centrosymmetric dimmer with a crystallographic inversioncenter at themidpoint of two Cd1 (Fig. 2a), containing four Cd(II) atomsand two symmetry-related μ3-OH groups with the Cd1-O(H) distance of2.200(2) Å, as well as the Cd2-O(H) distances of 2.367(3) and 2.228(3)Å. In the tetranuclear cluster, four metal atoms lie on an absoluteplane to form an approximate parallelogram, in which theCd1···Cd1 and Cd2···Cd2 distances are 6.556(1) and 3.547(1) Å,respectively. The two sides of the parallelogram are unequal with the

hts reserved.

Fig. 1. Local coordination environments of Cd1 (a) and Cd2 (b) in 1. All the hydrogenatoms attached to carbon atoms are omitted for clarity. Symmetry codes, a: 1−x, 1−y,4−z; b: 1−x, y, z; c: x, 1−y, z; d: 1−x, 1−y, 3−z; e: 2−x, 1−y, 3−z.

Fig. 3. TG plot for 1.

1202 L. Cheng et al. / Inorganic Chemistry Communications 14 (2011) 1201–1203

Cd1···Cd2 separations of 3.910(1) and 3.535(1) Å, respectively,which may be attributed to the different bridging modes betweenCd1 and Cd2 besides the μ3-OH bridge: the corresponding Cd1 andCd2 atoms in the shorter side are bridged by two syn–syn carboxylatesfrom two nicotinate bridges, respectively, while the Cd1 and Cd2 atomsin the longer side are linked by one syn–syn carboxylate from onenicotinate ligand (Fig. 2a). Therefore, each [Cd4(μ3-OH)2] cluster issurrounded by six syn-syn carboxylates from six individual nicoti-nate ligands. Meanwhile, each Cd1 is further ligated by two nitrogenatoms from two nicotinate ligands, and each Cd2 is further

Fig. 2. Structures of the [Cd4(μ3-OH)2] SBU surrounded by six carboxylates (a), thelinkages of a six-connected tetranuclear SBU (b) and the pcu topology (c) in 1. Thepurple polyhedra in b represent [Cd4(μ3-OH)2] SBUs.

coordinated by one nitrogen atoms from one nicotinate ligand. Intotal, each [Cd4(μ3-OH)2] cluster unit is linked to twelve nicotinateligands (Fig. 2b).

These twelve nicotinate ligands can be equally divided into threekinds of crystallographically independent ligands, in which each pairof ligands with a crystallographic inversion center are linked to twoadjacent [Cd4(μ3-OH)2] metal cluster units. Therefore, each clusterunit is bridged to six adjacent ones by six pairs of nicotinate ligandswith a centroide-centriod separation of 11.329(1) Å (Fig. 2b),resulting in a three-dimensional network. From the topologicalview, each tetranuclear cluster unit and each pair of nicotinateligands can be considered as a six-connecting node and a two-connecting linker, respectively. Consequently, a topologic analysis of 1with the OLEX program [11] yields a pcu topology with the pointsymbol [12] of (412.63).

The thermogravimetric analysis of powder sample 1 was carriedout from 22 to 681 °C under nitrogen atmosphere at the heating rateof 10 °C min−1, as shown in Fig. 3. The TGA curve for the compoundshows that there is no weight loss between 22 and 355 °C, indicatingthat the polymer 1 remains stable up to 355 °C. Decomposition of thepolymer begins from 355 °C with two-steps weight losses. In thetemperature range 355–466 °C, the first weight loss of 58.6% of thetotal weight occurs, which can be assigned to the decomposition ofnicotinate ligands (calc. 62.2%) and the collapse of the wholeframework. The second weight loss of 2.5% between 446 and 466 °Ccorresponds to the removal of μ3-OH (calc. 2.8%) and the final residualweight is 38.9% corresponding to that of CdO (calc. 42.7%).

The solid-state luminescent spectra of both 1 and the free ligand,nicotinic acid (Hna), were investigated at room temperature, as shownin Fig. 4. In the solid state, themaximumemission band of 1 is located at371 nmupon excitation at 330 nm. Since the free ligand exhibits purplephotoluminescence emission at 380 nm (λex=330 nm), the emission

Fig. 4. Luminescent spectra of 1 and Hna in the solid state at room temperature.

1203L. Cheng et al. / Inorganic Chemistry Communications 14 (2011) 1201–1203

band at 371 nmof 1maybedue to the intraligandfluorescent emissions(π–π*). Theemission spectrumof1 showsablue-shift of 9 nmcomparedwith that of nicotinic acid, which may be assigned to ligand-to-metalcharge transfer (LMCT) [6d,13].

In conclusion, we have synthesized and characterized a new three-dimensional coordination polymer based on butterfly-like [Cd4(μ3-OH)2] SBUs with a uninodal six-connected pcu topology. Compound 1displays fluorescent properties indicating that it may have potentialapplications as an optical material.

Acknowledgements

The authors are grateful to the financial support from NationalNatural Science Foundation of China (No. 21001024) and the Fundingfrom Southeast University (No. 4007041121 and No. 9207040016).

Appendix A. Supplementary material

CCDC reference numbers 814814 contain the supplementarycrystallographic data for this paper. These data can be obtained free ofcharge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from theCambridge Crystallographic Data Centre, 12, Union Road, CambridgeCB21EZ, UK; Fax: (internat.)+44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk]. Supplementarydata associatedwith this article canbe found,in the online version, at doi:10.1016/j.inoche.2011.04.017.

References

[1] a O.M. Yaghi, H. Li, C. Davis, D. Richardson, T.L. Groy, Synthetic strategies,structure patterns, and emerging properties in the chemistry of modularporous solids, Acc. Chem. Res. 31 (1998) 474–484;

b D. Braga, F. Grepioni, G.R. Desiraju, Crystal engineering and organometallicarchitecture, Chem. Rev. 98 (1998) 1375–1405;

c A.K. Cheetham, G. Ferey, T. Loiseau, Open-framework inorganic materials,Angew. Chem. Int. Ed. 38 (1999) 3268–3292;

d G.S. Papaefstathiou, L.R. MacGillivray, Inverted metal-organic frameworks: solid-state hosts with modular functionality, Coord. Chem. Rev. 246 (2003) 169–184;

e D. Bradshaw, J.B. Claridge, E.J. Cussen, T.J. Prior, M.J. Rosseinsky, Design,chirality, and flexibility in nanoporous molecule-based materials, Acc. Chem.Res. 38 (2005) 273–282.

[2] a W.B. Lin, O.R. Evans, R.G. Xiong, Z.Y. Wang, Supramolecular engineering ofchiral and acentric 2D networks: synthesis, structures, and second-ordernonlinear optical properties of bis(nicotinato)zinc and bis{3-[2-(4-pyridyl)ethenyl]benzoato}cadmium, J. Am. Chem. Soc. 120 (1998) 13272–13273;

b K. Biradha, Y. Hongo, M. Fujita, Crystal-to-crystal sliding of 2D coordination layerstriggered by guest exchange, Angew. Chem. Int. Ed. 41 (2002) 3395–3398;

c M.B. Zhang, J. Zhang, S.T. Zheng, G.Y. Yang, A 3D coordination framework basedon linkages of nanosized hydroxo lanthanide clusters and copper centers byisonicotinate ligands, Angew. Chem. Int. Ed. 44 (2005) 1385–1388;

d D.F. Sun, S. Ma, Y. Ke, T.M. Petersen, H.C. Zhou, Synthesis, characterization, andphotoluminescence of isostructural Mn, Co, and Zn MOFs having a diamondoidstructure with large tetrahedral cages and high thermal stability, Chem.Commun. (2005) 2663–2665;

e S. Hasegawa, S. Horike, R. Matsuda, S. Furukawa, K. Mochizuki, Y. Kinoshita, S.Kitagawa, Three-dimensional porous coordination polymer functionalizedwith amide groups based on tridentate ligand: Selective sorption and catalysis,J. Am. Chem. Soc. 129 (2007) 2607–2614;

f L. Chen, J. Kim, T. Ishizuka, Y. Honsho, A. Saeki, S. Seki, H. Ihee, D. Jiang,Noncovalently netted, photoconductive sheets with extremely high carriermobility and conduction anisotropy from triphenylene-fused metal trigonconjugates, J. Am. Chem. Soc. 131 (2009) 7287–7292;

g Q.T. He, X.P. Li, Y. Liu, Z.Q. Yu, W. Wang, C.Y. Su, Copper(I) cuboctahedralcoordination cages: host-guest dependent redox activity, Angew. Chem. Int. Ed.48 (2009) 6156–6159;

h M.H. Zeng, Q.X. Wang, Y.X. Tan, S. Hu, H.X. Zhao, L.S. Long, J. Am. Chem. Soc. 132(2010) 2561–2563.

[3] J.Y. Lee, D.H. Olson, L. Pan, T.J. Emge, J. Li, Microporous metal-organic frameworks withhigh gas sorption and separation capacity, Adv. Funct. Mater. 17 (2007) 1255–1262.

[4] a O.M. Yaghi, M. O'Keeffe, N.W. Ockwig, H.K. Chae, M. Eddaoudi, J. Kim, Reticularsynthesis and the design of new materials, Nature 423 (2003) 705–714;

b M. Eddaoudi, D.B. Moler, H. Li, B. Chen, T.M. Reineke, M. O'Keeffe, O.M. Yaghi,Modular chemistry: secondary building units as a basis for the design of highlyporous and robust metal-organic carboxylate frameworks, Acc. Chem. Res. 34(2001) 319–330;

c M. Eddaoudi, J. Kim, J.B. Wachter, H.K. Chae, M. O'Keeffe, O.M. Yaghi, Porousmetal-organic polyhedra: 25 angstrom cuboctahedron constructed from 12 Cu2

(CO2)4 paddle-wheel building blocks, J. Am. Chem. Soc. 123 (2001) 4368–4369;d F. Nouar, J.F. Eubank, T. Bousquet, L. Wojtas, M.J. Zaworotko, M. Eddaoudi,

Supermolecular building blocks (SBBs) for the design and synthesis of highlyporous metal-organic frameworks, J. Am. Chem. Soc. 130 (2008) 1833–1835;

e M.Y. Wu, F.L. Jiang, W. Wei, Q. Gao, Y.G. Huang, L. Chen, M.C. Hong, A porouspolyhedral metal-organic framework based on Zn2(COO)3 and Zn2(COO)4SBUs, Cryst. Growth Des. 9 (2009) 2559–2561;

g H.P. Chun,H.J. Jung, Targeted synthesis of a prototypeMOFbasedonZn4(O)(O2C)6units and a nonlinear dicarboxylate ligand, Inorg. Chem. 48 (2009) 417–419;

f T. Basu, H.A. Sparkes, M.K. Bhunia, R. Mondal, Identification of reactionconditions that can reproducibly lead to a particular vertex geometry: questfor a robust and reproducible metal-carboxylate noncluster-type SBU, Cryst.Growth Des. 9 (2009) 3488–3496.

[5] a for examples:D.R. Xiao, E.B. Wang, H.Y. An, Y.G. Li, Z.M. Su, C.Y. Sun, A bridgebetween pillared-layer and helical structures: a series of three-dimensionalpillared coordination polymers with multiform helical chains, Chem. Eur. J. 12(2006) 6528–6541;

b J. Yang, G.D. Li, J.J. Cao, Q. Yue, G.H. Li, J.S. Chen, Structural variation from 1D to3D: effects of ligands and solvents on the construction of lead(II)-organiccoordination polymers, Chem. Eur. J. 13 (2007) 3248–3261;

c X.M. Zhang, R.Q. Fang, H.S. Wu, A twelve-connected Cu6S4 cluster-basedcoordination polymer, J. Am. Chem. Soc. 127 (2005) 7670–7671;

d Y.Q. Wang, J.Y. Zhang, Q.X. Jia, E.Q. Gao, C.M. Liu, Unprecedented self-catenatedeight-connected network based on novel azide-bridged tetramanganese(II)clusters, Inorg. Chem. 48 (2009) 789–791.

[6] a for examples:J. Tao, M.L. Tong, J.X. Shi, X.M. Chen, S.W. Ng, Bluephotoluminescent zinc coordination polymers with supertetranuclear cores,Chem. Commun. (2000) 2043–2044;

b L. Xu, E.Y. Choi, Y.U. Kwon, Ionothermal synthesis of 3D zinc coordinationpolymer: [Zn2(BTC)(OH)(I)](BMIM) containing novel tetra nuclear buildingunit, Inorg. Chem. Commun. 11 (2008) 150–154;

c E.C. Yang, Y.N. Chan, H. Liu, Z.C. Wang, X.J. Zhao, Unusual Polymeric ZnII/CdII

Complexes with 2,6-diaminopurine by synergistic coordination of nucleobasesand polycarboxylate anions: binding behavior, self-assembled pattern of thenucleobase, and luminscent properties, Cryst. Growth Des. 9 (2009)4933–4944;

d Y.H. Xu, Y.Q. Lan, X.L. Wang, H.Y. Zang, K.Z. Shao, Y. Liao, Z.M. Su, Self-assemblyof zinc polymers based on a flexible linear ligand at different pH values:syntheses, structures and fluorescent properties, Solid State Sci. 11 (2009)635–642;

e A.M. Spokoyny, O.K. Farha, K.L. Mulfort, J.T. Hupp, C.A. Mirkin, Porosity tuning ofcarborane-based metal-organic frameworks (MOFs) via coordination chem-istry and ligand design, Inorg. Chim. Acta 364 (2010) 266–271;

f D. Liu, Z.G. Ren, H.X. Li, J.P. Lang, N.Y. Li, B.F. Abraha, Single-crystal-to-single-crystal transformations of two three-dimensional coordination polymersthrough regioselective [2+2] photodimerization reactions, Angew. Chem. Int.Ed. 49 (2010) 4767–4770.

[7] a Y.H. He, Y.L. Feng, Y.Z. Lan, Y.H. Wen, Syntheses, structures, and photolumines-cence of four d10 metal-organic frameworks constructed from 3,5-bis-oxyacetate-benzoic acid, Cryst. Growth Des. 8 (2008) 3586–3594;

b J. Tao, X. Yin, Z.B. Wei, R.B. Huang, L.S. Zheng, Hydrothermal syntheses, crystalstructures and photoluminescent properties of three metal-cluster basedcoordination polymers containing mixed organic ligands, Eur. J. Inorg. Chem.(2004) 125–133.

[8] a Y.H. Liu, H.L. Tsai, Y.L. Lu, Y.S. Wen, J.C. Wang, K.L. Lu, Assembly of a robust,thermally stable porous cobalt(II) nicotinate framework based on a dicobaltcarboxylate unit, Inorg. Chem. 40 (2001) 6426–6431;

b L. Cheng, W.X. Zhang, B.H. Ye, J.B. Lin, X.M. Chen, Spin canting and topologicalferrimagnetism in two manganese(II) coordination polymers generated by insitu solvothermal ligand reactions, Eur. J. Inorg. Chem. (2007) 2668–2676.

[9] A mixture of nicotinic acid (0.024 g, 0.2 mmol), Cd(NO3)2⋅4H2O (0.031 g, 0.1mmol), NaOH (0.008 g, 0.2 mmol) and H2O (10 mL) were heated in a 25 mLTeflon-lined vessel at 160 °C for 3 days, followed by slow cooling (5 °C h-1) toroom temperature. After filtration and washing with H2O, yellow block crystalswere collected and dried in air (0.015 g, yield ca. 49.3% based on Cd). Anal. Calcd(%) for C36H26Cd4N6O14: C, 35.55; H, 2.15; N, 6.91. Found: C, 37.36; H, 2.29; N,7.20. Main IR (KBr, cm–1): 3228(b), 2885(m), 2830(m), 1611(s), 1550(s), 1421(vs), 1385(s), 1230(w), 1059(m), 1020(w), 822(w), 772(m), 834(m), 689(m),527(w).Crystal data for 1: C36H26Cd4N6O14, Mr = 1216.26, triclinic, spacegroup P-1, a=9.140(1) Å, b=10.143(1) Å, c=11.329(1) Å,α=105.678(1), β=98.382(1), γ = 104.532(1), V = 952.8(2) Å3, Z = 1, Dcalcd. = 2.120 g/cm3, μ =2.280mm-1, R1[IN2σ(I)] = 0.0282, wR2(for all data) = 0.0712. The structure wassolved by direct methods and refined by full-matrix least-squares fitting on F2 bySHELXL-97 [10].

[10] G.M. Sheldrick, A short history of SHELX, Acta Cryst. A64 (2008) 112–122.[11] O.V. Dolomanov, OLEX, http://www.ccp14.ac.uk/ccp/webmirrors/lcells/index.htm.[12] V.A. Blatov, M. O'Keeffe, D.M. Proserpio, Vertex-, face-, point-, Schläfli-, and

Delaney-symbols in nets, polyhedra and tilings: recommended terminology,CrystEngComm. 12 (2010) 44–48.

[13] V.W.W. Yam, K.K.W. Lo, Luminescent polynuclear d10 metal complexes, Chem.Soc. Rev. 28 (1999) 323–334.