* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Alcohol responsive 2D coordination network of 3
Artificial photosynthesis wikipedia , lookup
List of phenyltropanes wikipedia , lookup
Freshwater environmental quality parameters wikipedia , lookup
Liquid–liquid extraction wikipedia , lookup
Computational chemistry wikipedia , lookup
Drug discovery wikipedia , lookup
Structural integrity and failure wikipedia , lookup
Halogen bond wikipedia , lookup
Resonance (chemistry) wikipedia , lookup
Chemical bond wikipedia , lookup
Host–guest chemistry wikipedia , lookup
History of molecular biology wikipedia , lookup
Gas chromatography wikipedia , lookup
Solvent models wikipedia , lookup
Colloidal crystal wikipedia , lookup
Water splitting wikipedia , lookup
Self-assembled monolayer wikipedia , lookup
Organic chemistry wikipedia , lookup
Hydrogen bond wikipedia , lookup
Size-exclusion chromatography wikipedia , lookup
Pharmacometabolomics wikipedia , lookup
Strychnine total synthesis wikipedia , lookup
Implicit solvation wikipedia , lookup
Gas chromatography–mass spectrometry wikipedia , lookup
Spin crossover wikipedia , lookup
Molecular dynamics wikipedia , lookup
Biochemistry wikipedia , lookup
Electrolysis of water wikipedia , lookup
Metalloprotein wikipedia , lookup
Atomic theory wikipedia , lookup
Thermomechanical analysis wikipedia , lookup
Analytical chemistry wikipedia , lookup
Crystal structure wikipedia , lookup
Crystallographic database wikipedia , lookup
X-ray fluorescence wikipedia , lookup
Hypervalent molecule wikipedia , lookup
Homoaromaticity wikipedia , lookup
X-ray crystallography wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Crystallization wikipedia , lookup
Inorganic chemistry wikipedia , lookup
History of molecular theory wikipedia , lookup
Coordination complex wikipedia , lookup
IUPAC nomenclature of inorganic chemistry 2005 wikipedia , lookup
318 Z. Kristallogr. 2013, 228, 318–322 / DOI 10.1524/zkri.2013.1607 # by Oldenbourg Wissenschaftsverlag, München Alcohol responsive 2D coordination network of 3-(4-pyridyl)benzoate and Zinc(II) Gift Mehlana, Gaëlle Ramon and Susan A. Bourne* Centre for Supramolecular Chemistry Research, Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa Received February 8, 2013; accepted May 14, 2013 Published online: July 1, 2013 Coordination network / Guest exchange / Thermal analysis / Alcohol sorption Abstract. The solvothermal reaction of 3-(4-pyridyl)benzoic acid and zinc nitrate yielded a 2D network with an sql topology. Both elemental analysis and single crystal X-ray diffraction studies confirmed the formula of the compound as {[Zn(34pba)2] (0.5 DMF) (0.5 H2O)}n (1). At room temperature, the desolvated phase of 1, 1d, absorbs methanol, ethanol, 1-propanol and 1-butanol but not water vapour. 1. Introduction One of the most important objectives in the field of coordination networks or metal organic frameworks is the engineering of porous structures with a well defined chemical environment [1–2]. This is however very difficult to achieve in 3D structures due to catenation and interpenetration. Thus in recent years, solid state chemists have developed a series of bottom-up fabrication schemes to achieve two-dimensional open coordination networks, frequently with limited domain size, using non covalent interactions such as hydrogen bonding [3], metal directed assembly [4], and the organisation of flexible species [5]. Porous materials based on 2D frameworks have received attention owing to useful properties endowed by dynamic guest- responsive phenomena [6]. The interlayer separation plays a major role in guest inclusion while framework flexibility can be achieved as a result of sliding of the 2D layers. Most importantly the ability of the framework to open or close its channels upon exposure to guest molecules has high potential for realising new useful functions, such as switching and sensing [7]. 2D metal organic frameworks can be created by combining bifunctional ligands coordinated meridially to a trigonal bipyriramidal or octahedral node [8–10]. To create such a system, we have focussed on an asymmetric ditopic ligand, 3-(4-pyridyl)benzoic acid, expecting that both the pyridyl and the carboxylate moiety would coordinate * Correspondence author (e-mail: [email protected]) to the metal center. Variation in the dihedral angles between the pyridyl and the benzene ring was also expected to contribute towards framework flexibility while maintaining structural integrity. Finally, we chose the Zn(II) metal ion as it can adopt different geometries due to its versatile coordination chemistry. 2. Experimental All materials were purchased from commercial sources and were used without further purification. 2.1 Synthesis: {[Zn(34pba)2] (0.5 DMF) (0.5 H2O)}n Zn(NO3)2 6 H2O (29 mg, 0.1 mmol) was dissolved in 4 ml of water. 3-(4-pyridyl) benzoic acid was dissolved in 4 ml dimethyl formamide (DMF) with heating and stirring. The two solutions were combined in a 25 ml teflon lined autoclave and sealed tightly. The mixture was then heated (ca. 2 C min1) at 105 C for 72 hours. Colourless block crystals were formed upon cooling (ca. 1 C min1) the reaction mixture to room temperature. Elemental analysis. % Calculated for C25.5H20.5N2.5O5Zn, C ¼ 60.36, H ¼ 4.07, N ¼ 6.90. % Found C ¼ 60.40, H ¼ 3.99, N ¼ 6.06 2.2 Crystal structure determination Crystal structure determination by single crystal X-ray diffraction was performed using a Bruker ApexII KAPPA CCD diffractometer at 173 K using a graphite monochoromated MoKa radiation (l ¼ 0.71073 A). Unit cell refinement and data reduction were achieved using the program SAINT [11]. The data was corrected for Lorentz- polarisation effects and absorption using the SADABS [12] program. The structure was solved by direct methods and refined using the SHELXL [13] computer programme package within the X-SEED [14] interface. Except for hydrogen atoms and atoms of the disordered DMF molecule, all atoms were refined anisotropically. Hydrogen atoms were introduced at calculated positions and refined isotropically. The bond angles and bond distances of the disorUnauthenticated Download Date | 6/12/17 7:22 AM 319 Alcohol responsive 2D coordination network of 3-(4-pyridyl)benzoate and Zinc(II) dered DMF molecule were fixed based on the average values found from the Cambridge structural Database [15]. Crystal data: Mr 507.34 g mol1, Monoclinic, space group C2/c, a ¼ 21.3002(4) Å, b ¼ 11.6040(2) Å, c ¼ 21.499(4) Å, b ¼ 118.70(3) , V ¼ 4661.0(16) Å3, Z ¼ 8, crystal size(mm) ¼ 0.200.250.33, 28437 reflections measured, No of unique relections ¼ 5338, No of unique reflections with I > 2q ¼ 4770. The final R values were R1 ¼ 0.0435, wR2 ¼ 0.1323, Max, min electron density (e A3) 2.54 (in the region of the disordered DMF molecule), 0.57. The structure was deposited at the CCDC and allocated the number CCDC 923522. found to be 424.64 and [4.4.4.4.4.4.4.4.4.4.4.4.43.43.43.*.*.*] respectively. The topological density value (TD 10) was found to be 221. The relevant outfiles are given in the Supporting information. 2.8 Sorption studies Compound 1 was activated by heating under a vaccum for 5 hrs at 130 C to generate 1d. 1d was placed in small open vials. The small vials containing the activated samples were then placed in large vials containing respective dry solvents. The large vials were capped and sealed tightly before being left at room temperature for 24 hours. 2.3 Powder X-ray diffraction (PXRD) Powder X-ray diffraction measurements were performed on a BRUKER D8 Advance X-ray diffractometer using. CuKa-radiation (l ¼ 1.5406 Å). Samples were placed on a zero background sample holder and scanned over the range of 4 to 30 with a step size of 0.01 per second at an accelerating voltage of 30 kV and a current flow of 40 mA. For variable temperature studies, samples were placed in a capillary rotation device on a HUBER Imaging Plate Guinier Camera 670 fitted with a HUBER HighTemperature Controller HTC 9634 unit. Ni-filtered CuKaradiation (l ¼ 1.5406 Å) was used to measure the PXRD patterns at elevated temperatures. 2.4 Hot stage microscopy The behaviour of the compounds was monitored using a Nikon SMZ-10 stereoscopic microscope fitted with a Linkam THMS600 hot stage and a Linkam TP92 control unit. The samples were placed on a transparent glass slide and covered in silicon oil. The compound was heated from 25 to 400 C at heating rate of 10 C min1. The images were captured at different temperatures using a Sony Digital HAD colour video camera and recorded using the Soft Imaging System program [16]. 3. Results and discussion 3.1 Structural description X-ray single crystal structure analysis revealed that the compound crystallizes in the monoclinic space group C2=c. The asymmetric unit (shown in Scheme 1) consists of one Zn (II) ion, two deprotonated ligands (34pba), half uncoordinated water molecule and a disordered half DMF molecule sitting on a two-fold axis at Wyckoff position e. The Zn(II) centre is coordinated to three oxygen atoms from the 34pba carboxylate groups with bond distances ranging from 1.974 (2) Å to 2.315(2) Å and two nitrogen atoms with distances of 2.093(2), (Zn1––N1B) and 2.010(2) Å, (Zn1––N1A). The relevant bond lengths and bond angles are given in the supporting information (Tables S1 and S2). 2.5 Differential Scanning Calorimetry (DSC) In order to determine the onset temperature of guest loss DSC was performed. The sample was dried on filter paper and a sample of 0.5–1 mg placed in ventilated aluminium pans with lids and heated at 10 C min1 under nitrogen gas flow (50 mL min1). The experiment was performed using a TA instrument DSC-Q200. 2.6 Thermogravimetric analysis (TGA) Thermogravimetric analyses were performed using a TA Instrument TAQ-500. Samples of 1–2 mg were heated at 10 C min1 under nitrogen gas flow (50 mL min1). 2.7 Topological analysis The netwok topology of the compound was analysed using X-SEED, SYSTRE [17] and TOPOS [18] and checked against the Reticular Chemistry Structural Resource (RSCR) [19]. The calculated point symbol and vertex symbol were Scheme 1 The overall geometry around the Zn(II) centre is trigonal bipyramidal. The 3-(4-pyridyl) benzoate ligands show different coordination modes, that is they adopt a tridentate m2-bridging and bidentate m2-bridging modes. The dihedral angles between the pyridyl and benzene ring in the ligands are 23.2(1) and 32.7(4) for the ligand with tridenUnauthenticated Download Date | 6/12/17 7:22 AM 320 G. Mehlana, G. Ramon and S. A. Bourne Fig. 1. Coordination environment of the Zn(II) centre displaying the binding modes assumed by the carboxylate moiety. Hydrogen atoms have been omitted for clarity. a a b b Fig. 2. (a) Packing diagram of the compound viewed along [010]. The diagram illustrates interdigitated 2D layers in the channels of which water and DMF guest molecules (van der Waals radii) reside, (b) packing diagram as viewed along [001]. tate m2-bridging mode and bidentate m2-bridging mode respectively. The tridentate m2-bridging mode (equatorial position) and bidentate m2-bridging mode (axial position) act as linear linkers to join two zinc centres with Zn––Zn of 11.6(5) Å and 10.8(3) Å respectively giving rise to a 2D coordination network (Fig. 1). These 2D layers are stabilised by non classical hydrogen bonds (Table 1) which connect them together. The 2D layers are interdigitated encapsulating water and DMF as guest molecules in channels (Fig. 2). Extensive hydrogen bonding interactions exist between water and DMF guest molecules, however there are no c Fig. 3. (a) Network connectivity of the compound. (b) Network analysis of the compound. Spheres represent the 4-connected uninodal node at each Zn(II) center. (c) Four-fold non interpenetrating parallel sql nets. hydrogen bonding interactions between the solvent molecules and the 2D framework. The solvent accessible void volume in the solvent free network was determined using the SQUEEZE routine in Platon [20] as 846.7(5) Å3 which is approximately 19% of the unit cell volume. Topological analysis of the compound revealed a 4-connected uninodal sql grid net. The Symmetry operator d(C O) (Å) Angle ( ) C5A––H5A O14B C6B––H6B O15B 3 =2 x, 1=2 þ y, 1=2 z x, 1 þ y, z 3.112(3) 3.142(3) 132 119 C12B––H12 O14B 2 x, y, 1=2 z 2.829(3) 100 Table 1. Weak hydrogen bonding intramolecular interactions. Unauthenticated Download Date | 6/12/17 7:22 AM 321 Alcohol responsive 2D coordination network of 3-(4-pyridyl)benzoate and Zinc(II) Table 2. TGA analysis for 1 and the resulting alcohol inclusion compounds from sorption studies. Fig. 4. An overlay of the TGA and DSC for 1. TGA Experimental mass loss % Network/solvent ratio 1 based on Zn(34pba)2 : x 1 9.80 1 : 0.5 : 0.5 1d 1d-methanol –– * –– 1d-ethanol 6.55 1 : 0.70 1d-1-propanol 8.75 1 : 0.74 1d-1-butanol 8.25 1 : 0.58 1: The network : solvent ratios were calculated using experimental results of the TGA for all the compounds. The results were modelled on {[Zn(34pba)2] : solvent}n and expressed as 1 : x. *: 1d-methanol stoichiometry could not be determined as the solvated phase is not stable at room temperature. packing diagram of the nets shows a four-fold non-interpenetrating sql nets as illustrated in Fig. 3. 3.2 Thermal analysis and sorption studies Fig. 5. Variable temperature PXRD of the compound illustrating the phase change that takes place between 250 and 290 C upon heating. Thermal analysis by TGA shows that the compound is stable at room temperature (Fig. 4). An initial weight loss of 9.80% is observed over a temperature range of 90– 250 C which corresponds to loss of both the water and the DMF from the host framework. This weight loss is a reasonably good match to the solvent content modelled in the crystal structure (calc: 8.90%). However, we have noted that the 0.5 DMF molecules modelled per formula unit in the crystal structure may be too low, as both the TGA results and the % N in the elemental analysis support a higher guest occupancy. This may indicate that guest occupancy varies between single crystals. Fig. 6. PXRD of 1, 1d, the alcohol inclusion compounds (1d-methanol, 1d-ethanol, 1d-propanol and 1d-butanol) and 1d-water. Unauthenticated Download Date | 6/12/17 7:22 AM 322 Decomposition of the guest-free compound occurs above 380 C. The DSC shows two endotherms at 135 and 230 C which corresponds to successive release of water and DMF molecules from the host channels. The DSC analysis also displays an exotherm after complete loss of guest molecules at approximately 280 C. This event is further supported by variable temperature PXRD studies which show that the compound undergoes phase transformation between 250 and 290 C (Fig. 5). Sorption studies were carried out as described in the experimental section. The PXRD of the desolvated phase is very similar to that of the as-made compound (Fig. 6) which is an indication that structural integrity is maintained after desolvation. We confirmed that desolvation had taken place by means of TGA. The activated sample (1d) was exposed to solvent vapours (water, methanol, ethanol, 1-propanol or 1-butanol) at room temperature in a controlled environment. The amount of the solvents absorbed is given in the supporting information in Table 2 and in Figs. S1–S5. Interestingly the activated phase absorbed the alcohols but did not absorb water as evidenced by no change in the diffraction pattern of the desolvated phase on exposure to water vapour. This result is further supported by TGA which is featureless until decomposition, indicating that no water was absorbed. Similar results have been reported using a square-grid Cd(II) MOF [21] and a lanthanide-carboxylate-MOF [22]. Figure 6 shows the PXRD traces of the resultant alcohol inclusion compounds. The alcohol inclusion compounds exhibit diffraction peaks at lower 2q values than 1 and 1d. This is due to the expansion of the 2D layers to accommodate guest molecules. The ability of the ligand to vary its dihedral angle by the rotation of the benzene and pyridyl rings may help to explain why alcohol molecules are able to move into the host framework. 4. Conclusions A novel 2D compound with an sql net based on 34pba and Zn(II) was synthesised and its properties evaluated. Structural integrity is maintained upon desolvation and the compound undergoes a structural rearrangement above 250 C. The dried phase of the compound absorbs alcohols at room temperature. This has been attributed to the presence of open metal sites and the ability of the 2D layers to glide past one another allowing for the entry of guest molecules. The failure of the compound to absorb water at room temperature also reveals its selective nature. Acknowledgements. Funding for this project was received from the South African National Research Foundation and the Swedish International Development Agency (SIDA). G.M. is grateful for the financial support he received from the University of Cape Town Chemistry Equity Development programme and University of Cape Town 2013 JW Jagger Centenary Gift Scholarship. G. Mehlana, G. Ramon and S. A. Bourne References [1] O. M. Yaghi, M. O’Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi, J. Kim, Reticular synthesis and the design of new materials. Nature 2003, 423, 705–714. [2] Kitagawa, S. Kitaura, R. Noro, S. Functional porous coordination polymers. Angew. Chem. Int. Ed. 2004, 43, 2334–2375. [3] S. Griessl, M. Lackinger, M. Edelwirth, M. Hietschold, W. M. Heckl, Self-assembled two-dimensional molecular host-guest architectures from trimesic acid. Single Molecules 2002, 3, 25–31. [4] A. Dmitriev, H. Spillmann, N. Lin, J. V. Barth, K. Kern, Modular assembly of two-dimensional metal-organic coordination networks at a metal surface. Angew. Chem. Int. Ed. 2003, 42, 2670–2673. [5] G. Schull, L. Douillard, C. Fiorini-Debuisschert, F. Charra, F. Mathevet, D. Kreher, A.-J. Attias, Single-molecule dynamics in a self-assembled 2D molecular sieve. Nano Lett. 2006, 6, 1360–1363. [6] S. J. Ghosh, W. Kaneko, D. Kiriya, M. Ohba, S. Kitagawa, A bistable porous coordination polymer with a bond-switching mechanism showing reversible structural and functional transformations. Angew. Chem. Int. Ed. 2008, 47, 8843–8847. [7] E. J. Cussen, J. B. Claridge, M. J. Rosseinsky, C. J. Kepert, Flexible sorption and transformation behaviour in a microporous metal-organic framework. J. Am. Chem. Soc. 2002, 124, 9574– 9581. [8] B. Ye, M. L. Tong, X. M. Chen, Metal-organic molecular architectures with 2,20 -bipyridyl-like and carboxylate ligands. Coord. Chem. Rev. 2005, 249, 545–565. [9] A. J. Fletcher, K. M. Thomas, M. J. Rosseinsky, Flexibility in metal-organic framework materials: Impact on sorption properties. J. Sol. State Chem. 2005, 178, 2491–2510. [10] S. Horike, D. Tanaka, K. Nakagawa, S. Kitagawa, Selective guest sorption in an interdigitated porous framework with hydrophobic pore surfaces. Chem Commun. 2007, 3395–3397. [11] SAINT, Version 7.60a; Bruker AXS Inc: Madison, WI, USA, 2006 [12] G. M. Sheldrick, SADABS, Version 2.05, 2007. [13] G. M. Sheldrick, SHELXL-97, Program for crystal structure solution, 1997. [14] L. J. Barbour, X-Seed: A software tool for supramolecular crystallography. J. Supramol. Chem. 2001, 1, 189–191. [15] F. H. Allen, The Cambridge Structural Database: a quarter of a million crystal structures and rising. Acta Crystallogr., Sect. B. 2002, 58, 380–388. [16] Soft Imaging System GmbH: Digital solutions for Imaging and Microscopy, Version 3.1 for Windows, # 1987–2000. [17] O. D. Friedrichs, SYSTRE 1.1.4beta, http://gavrog.org/, 2013. [18] V. A. Blatov, V. Peskov, Acta Crystallogr. Sect. B. A comparitive crystallochemical analysis of binary compounds and simple anhydrous salts containing pyramidal anions LO3 (L¼S, Se, Te, Cl, Br, I). 2006, 62, 457–466; V. A. Blatov, Ac. Pavlov St. 1, 443001, Samara, Russia, TOPOS 4.0, http://www.topos.ssu.samara.ru/, accessed May 2012. [19] M. O’Keeffe, M. A. Peskov, S. Ramsden, O. M. Yaghi, The Reticular Chemistry Structure Resource (RCSR) database of, and symbols for, crystal nets. Acc. Chem. Res. 2008, 41, 1782–1789; Reticular Chemistry Structure Resource, http://rcsr.anu.edu.au/, 2009. [20] A. L. Spek, Structure validation in chemical crystallography. Acta Crystallogr., Sect. D. 2009, 65, 148–155. [21] T. Borjigin, F. Sun, J. Zhang, K. Cai, H. Ren, G. Zhu, A microporous metal-organic framework with high stability for GC separation of alcohols from water. Chem. Commun. 2012, 48, 7613–7615. [22] Z. Lin, R. Zou, J. Liang, W. Xia, D. Xia, Y. Wang, J. Lin, T. Hu, Q. Chen, X. Wang, Y. Zhao, A. K. Burrell, Pore sizecontrolled gases and alcohols separation within ultramicroporous homochiral lanthanide–organic frameworks. J. Mater. Chem. 2012, 22, 7813–7818. Unauthenticated Download Date | 6/12/17 7:22 AM