YANG Shi JIANG Hong ZHANG Wen-Qiang TANG Xian-Hui JIN Yao LIU Yan

Synthesis, Structure, and Characterization of a Novel Coordination Polymer with Polythreading Feature①

YANG Shi JIANG Hong ZHANG Wen-Qiang TANG Xian-Hui JIN Yao LIU Yan②

(200240)

coordination polymer, polythreading, single crystal, photoluminescence;

1 INTRODUCTION

Coordination polymers (CPs), comprising of metal ions and organic ligands, appeal the great interest of chemists due to their fascinating architectures and topologies, as well as their potential applications in gas storage and separation, heterogeneous catalysis, luminescence and magnetism[1-15].The intense interest in CPs has led to the discovery of more types of topological entanglements such as polycatenation, polythreading, and polyknotting that resemble molecular catenanes, rotaxanes, and knots[16-20], of which, the particular attention has been recently paid to polythreaded coordination networks, which can be considered as periodic analogues of the molecule rotaxanes or pseudorotaxanes[21].Undoubtedly, the exploration of entangled structures can be helpful not only for both the design and analysis of crystal structures but also for understanding the relationships between the structure and function of these coordination polymers[22].To rationally design polythreading framework, herein we utilize the mix-ligand strategy to combine the dicarboxlate and tripyridyl ligands to construct polythreading structures.The 2sheet with windows is formed by the coordination of BDC2-and Zn ion, and the TPPA[23, 24]ligands acting as threads penetrate into the windows of neighboring layers.The triphenyl core has been demonstrated to exhibit excellent luminescent properties, thus endowing the whole framework functionality.

2 EXPERIMENTAL

2.1 Materials and methods

Reagents and solvents employed were commercially available.FT-IR absorption spectra of the compounds were recorded in the range of 400～4000 cm-1on a Nicolet (Impact 410) spectrometer with KBr pellets.C and H analyses were carried out with a Perkin-Elmer 240C elemental analyzer.Powder X-ray diffraction (PXRD) measurements were performed on a Bruker D8 VENTURE CMOS photon 100 diffractometer with Helios MX multilayer monochromatic Cu-radiation (= 1.54178 Å) in which the X-ray tube was operated at 40 kV and 40 mA.Luminescent spectra were recorded on a Perkin-Elmer LS55 fluorescence spectrophotometer at room temperature.

2.2 Synthesis of 1

A mixture of Zn(NO3)2·6H2O (29.7 mg, 0.1 mmol), TPPA (47.6 mg, 0.1 mmol), and H2BDC (16.6 mg, 0.1 mmol) was dissolved in 15 mL of DMF/MeCN (2/1, V/V).The final mixture was placed in a 50 mL sealed vial and heated at 100 ℃ for 3d.Block yellow crystals of 1 [Zn2(BDC)2(TPPA)]·CH3CN were collected in 80% yield (based on TPPA ligand).Calcd.for Zn2C51N5O8H36: C, 62.66; H, 3.71%.Found: C, 62.44; H, 3.45%.FT-IR (KBr, cm-1): 537 (w), 563 (s), 705 (s), 749 (s), 807 (s), 825 (m), 1187 (s), 1214 (w), 1272 (m), 1292 (s), 1436 (m), 1473 (m), 1513 (m), 1600 (s), 1924 (w), 2203 (m), 2554 (w), 2929 (w), 3037 (s), 3403 (s).

2.3 X-ray structure determination

Table 1.Selected Bond Lengths (Å) and Bond Angles (°)

Symmetry transformations used to generate the equivalent atoms for 1: #1: –+1, –, –;#2: –+2, –, –+1; #3: –+1, –, –+1; #4:+1,,; #5:–1,,

3 RESULTS AND DISCUSSION

3.1 Synthesis and characterization

As shown in Scheme 1, 1 was synthesized through solvent thermal reactions between Zn(NO3)2·6H2O, TPPA, and H2BDC.The phase purity was established by the general agreement between the experimental and simulated X-ray powder diffraction patterns (Fig.1a).The major peaks of the PXRD pattern between the simulated 1 and synthesized 1 can be matched very well.The missing of some peaks and minor shift of the peaks can be explained by the crystal orientation distribution and the flexible framework.1 shows a strong band at 1600 cm−1, characteristic of carboxylic acid(C=O) (Fig.1b).The thermogravimetric analysis of 1 was investigated under a N2atmosphere from 40 to 800 ℃, and the result indicates that the solvent molecules are released below 200 ℃, with 4.1% weight loss.The framework of 1 starts to collapse when heating upon to 330 ℃ (Fig.1c).The ultraviolet visible light absorption of 1 was mostly due to the transition of-and-of the ligand[27](Fig.1d).

Scheme 1.Synthesis of 1

Fig.1.(a) PXRD patterns, b) FT-IR spectra, (c) TGA curves, and (d) UV-vis spectra of 1

3.2 X-ray crystal structure

Fig.2.(a) Coordination mode of ligand TPPA, (b) structure of Zn-based paddlewheel cluster, (c) 2grid formed by Zn2+and BDC2-, (d) TPPA ligands arranged above and beneath the 2layer with one pyridine uncoordinated

The paddlewheel clusters are further bridged by BDC2-to form a 2rectangular sheet.There are large distorted rhombic windows with approximate dimensions of about 9.9 × 11.7 Å2built by four clusters and four bent BDC2-molecules (Fig.2b).Moreover, each metal in the dimeric unit bears a terminally bound pyridyl group of TPPA ligand along thedirection (Fig.2c).Two pyridine groups of each TPPA ligand bridge two zinc clusters, and the third pyridine group is uncoordinated.Therefore, the TPPA ligands are arranged above and beneath the 2layer, exhibiting an overall multi-arm sheet.Each dangling arm has a length of about 15.4 Å (Fig.2d).Each window is threaded by two arms above and below through-interactions between the neighbor phenyl rings (Fig.3a), thus resulting in the formation of a rare polythreading coordination framework (Figs.3b and 3c).

Fig.3.(a) Packing diagram of 1 showing the-interactions between the neighbor phenyl rings, (b) 3packing structure of 1, (c) schematic illustration of the polythreading structure of 1

3.3 Photoluminescence

Upon excitation at 350 nm, as shown in Fig.4, the free ligand TPPA displayed fluorescent emission at 435 nm, while the emission of 1 at 488 nm exhibits 53 nm red-shift.The observed shift in the emission for 1 originated from the coordination of nitrogen atom to the Zn(II) ions, which effectively increases the rigidity of the ligand and reduces the loss of energy.

Fig.4.Fluorescent emission spectra of 1

4 CONCLUSION

In summary, a novel coordination polymer 1 with polythreading structure was synthesized by a pot solvo- thermal reaction of Zn(II) ion, H2BDC, and TPPA.It was characterized by single-crystal and powder X-ray diffraction, TGA, FT-IR, and UV-vis.In addition, the photolumine- scence of 1 and free ligand was also investigated.

(1) Yaghi, O.M.; O’Keeffe, M.; Ockwig, N.W.; Chae, H.K.; Eddaoudi, M.; Kim, J.Reticular synthesis and the design of new materials.2003, 423, 705-714.

(2) Xuan, W.; Zhu, C.; Liu, Y.; Cui, Y.Mesoporous metal-organic framework materials.2012, 41, 1677-1695.

(3) Li, J.R.; Kuppler, R.; Zhou, H.C.Selective gas adsorption and separation in metal-organic frameworks.2009, 38, 1477-1504.

(4) Lysova, A.A.; Samsonenko, D.G.; Dorovatovskii, P.V.; Lazarenko, V.A.; Khrustalev, V.N.; Kovalenko, K.A.; Dybtsev, D.N.; Fedin, V.P.Tuning the molecular and cationic affinity in a series of multifunctional metal-organic frameworks based on dodecanuclear Zn(II) carboxylate wheels.2019, 141, 17260-17269.

(5) Jiang, H.; Zhang, W.; Kang, X.; Cao, Z.; Chen, X.; Liu, Y.; Cui, Y.Topology-based functionalization of robust chiral Zr-based metal-organic frameworks for catalytic enantioselective hydrogenation..2020, 142, 9642-9652.

(6) Gong, W.; Chen, X.; Jiang, H.; Chu, D.; Cui, Y.; Liu, Y.Highly stable Zr(IV)-based metal-organic frameworks with chiral phosphoric acids for catalytic asymmetric tandem reactions.2019, 141, 7498-7508.

(7) Allendorf, M.D.; Bauer, C.A.; Bhakta, R.K.; Houk, R.J.T.Luminescent metal-organic frameworks.2009, 38, 1330-1352.

(8) Sussardi, A.; Hobday, C.L.; Marshall, R.J.; Forgan, R.S.; Jones, A.C.; Moggach, S.A.Correlating pressure-induced emission modulation with linker rotation in a photoluminescent MOF..2020, 132, 8195-8199.

(9) Zeng, M.H.; Yin, Z.; Tan, Y.X.; Zhang, W.X.; He, Y.P.; Kurmoo, M.Nanoporous cobalt(II) MOF exhibiting four magnetic ground states and changes in gas sorption upon post-synthetic modification.2014, 136, 4680-4688.

(10) Terzopoulou, A.; Hoop, M.; Chen, X.Z.; Hirt, A.M.; Charilaou, M.; Shen, Y.; Mushtaq, F.;del Pino, A.P.; Logofatu, C.; Simonelli, L.; de Mello, A.J.; Doonan, C.J.; Sort, J.; Nelson, B.J.; Pané, S.; Puigmartí-Luis, J.Mineralization-inspired synthesis of magnetic zeolitic imidazole framework composites..2019, 58, 13550-13555.

(11) Fu, H.R.; Xu, Z.X.; Zhang, J.Water-stable metal-organic frameworks for fast and high dichromate trapping via single-crystal-to-single-crystal ion exchange.2015, 27, 205-210.

(12) Zhuo, C.; Wang, F.; Zhang, J.Mixed short and long ligands toward the construction of metal-organic frameworks with large pore openings..2019, 19, 3120-3123.

(13) An, Z.; Zhou, T.Mixed-ligands self-assembly strategy affording a new 4-fold interpenetrated 3Co(II)-based coordination polymer: synthesis, crystal structure and magnetic property.2019, 38, 777-782.

(14) Liu, Z.Y.; Fu, M.; Wang, X.G.; Wang, L.L.; Yang, E.C.; Zhao, X.J.Two preparation methods-dominated CdII-based coordination polymers with mixed adenine nucleobase and 5-nitroisophathalate ligands: synthesis, structure and fluorescence.2019, 38, 613-620.

(15) Liu, N.; Xing, G.E.; Huang, X.X.; Guo, J.A new Zn(II) coordination polymer constructed from 4-(1H-pyrazol-3-yl)pyridine as fluorescent sensor for Fe3+.2019, 38, 660-666.

(16) Kitagawa, S.; Kitaura, R.; Noro, S.I.Functional porous coordination polymers..2004, 43, 2334-2375.

(17) Liu, G.; Li, Y.; Lu, Z.; Li, X.; Wang, X.L.; Wang, X.; Chen, X.Versatile carboxylate-directed structures of ten 1→ 3Ni(II) coordination polymers: fluorescence behaviors and electrochemical activities.2019, 21, 5344-5355.

(18) Qian, L.L.; Han, S.S.; Zheng, L.Y.; Yang, Z.; Li, K.; Li, B.L.; Wu, B.Syntheses, structures and properties of structural diversity of 3coordination polymers based on bis(imidazole) and dicarboxylate.2019, 162, 303-310.

(19) Zhang, L.; Ma, J.; Yang, J.; Pang, Y.; Ma, J.Series of 2and 3coordination polymers based on 1,2,3,4-benzenetetracarboxylate and N-donor ligands: synthesis, topological structures, and photoluminescent properties.2010, 49, 1535-1550.

(20) Gu, Z.; Xu, X.; Zhou, W.; Pang, C.; Bao, F.; Li, Z.A new type of entangled coordination network: coexistence of polythreading and polyknotting involved molecular braids.2012, 48, 3212-3214.

(21) Carlucci, L.; Ciani, G.; Proserpio, D.M.Polycatenation, polythreading and polyknotting in coordination network chemistry.2003, 246, 247-289.

(22) Yao, Q.; Ju, Z.; Jin, X.; Zhang, J.Novel polythreaded coordination polymer: from an armed-polyrotaxane sheet to a 3polypseudorotaxane array, photo- and thermochromic behaviors.2009, 48, 1266-1268.

(23) Hu, B.; Chen, X.; Wang, Y.; Lu, P.; Wang, Y.Structure-property investigations of substituted triarylamines and their applications as fluorescent pH sensors..2013, 8, 1144-1151.

(24) Wang, T.; Liu, L.; Xu, K.; Xie, H.; Shen, H.; Zhao, W.X.Synthesis and characterization of trinuclear N-heterocyclic carbine-palladium(II) complexes and their applications in the Suzuki-Miyaura cross-coupling reaction.2016, 6, 100690-100695.

(25) Sheldrick, G.M..University of Göttingen, Germany 1997.

(26) Dolomanov, O.V.; Bourhis, L.J.; Gildea, R.J.; Howard, J.A.K.; Puschmann, H.OLEX2: a complete structure solution, refinement and analysis program.2009, 42, 339−341.

(27) Mohamed, G.; El-Gamel, N.Synthesis, investigation and spectroscopic characterization of piroxicam ternary complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with glycine and dl-phenylalanine.2004, 60, 3141-3154.

(28) Farha, O.K.; Malliakas, C.D.; Kanatzidis, M.G.; Hupp, J.T.Control over catenation in metal-organic frameworks via rational design of the organic building block.2010, 132, 950-952.

(29) Yang, H.; Peng, F.; Dang, C.; Wang, Y.; Hu, D.; Zhao, X.; Feng, P.; Bu, X.Ligand charge separation to build highly stable quasi-isomer of MOF-74-Zn.2019, 141, 9808-9812.

14 May 2020;

29 June 2020(CCDC 2003289)

① This research was supported by the National Science Foundation of China (Nos.91956124, 21875136), the National Key Basic Research Program of China (2016YFA0203400), and Shanghai Rising-Star Program (19QA1404300)

.Liu Yan.Female, professor.E-mail:liuy@sjtu.edu.cn

10.14102/j.cnki.0254–5861.2011–2877