Synthesis and Molecular Structures of Two [1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene]-dichloro-Zn(II) Coordination Polymers
Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106,
Taiwan
*
Author to whom correspondence should be addressed.
Molecules 2006, 11(8), 589-596; https://doi.org/10.3390/11080589
Submission received: 5 June 2006
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Revised: 30 July 2006
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Accepted: 31 July 2006
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Published: 10 August 2006
Abstract
:Two novel coordination polymers with 3D metal-organic frameworks (MOFs) have been synthesized by reacting 1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene (L) with zinc dichloride. Both compounds have the same repeating unit consisting of a distorted tetrahedral Zn(II) center coordinated by two chlorides and two pyridyl nitrogen atoms of two bridging bismonodentate L ligands, however, different structural conformations have been found, one forming a helical chain and the other producing a square-wave chain. The intermolecular C−H∙∙∙Cl hydrogen bonds in 1 and 2 play important roles in the formation of three-dimensional coordination polymers. Compound 1 crystallized in an orthorhombic space group Pna21 with a = 7.9652(3), b = 21.4716(7), c = 8.2491(3)Å, V = 1410.81(9) Å 3 and Z = 4. Compound 2 crystallized in a monoclinic space group P21/n with a = 9.1752(3), b = 14.5976(4), c = 10.3666(3) Å , β = 98.231(2)°, V = 1374.16(7) Å 3 and Z = 4.
Introduction
The coordinative and hydrogen bond approaches have been widely used in crystal engineering in the construction of coordination compounds with one- (1D), two- (2D) or three-dimensional (3D) metal-organic frameworks (MOFs). Rigid organic ligands containing pyridine rings, such as4,4’-bipyridine, 1,2-bis(4-pyridyl)ethene and 1,2-bis(4-pyridyl)ethyne, have been proven to be useful for assembling MOFs [1,2,3,4,5] in recent years.
The organic ligand 1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene (L), containing two pyridyl groups joined by a zigzag –CH=N−N=CH− group, possesses effective sites for accommodating transition metal ions. The structure of [Co(SCN)2(L)2·2CH2Cl2]n shows a 2D non-interpenetrating MOF with a distorted square pattern as the basic building unit [6]. The isomorphous structures of [Co(NO3)2(L)1.5·CH2Cl2]n and [Cd(NO3)2(L)1.5·CH2Cl2]n with polycyclohexane structural MOFs have also been reported [7]. In this paper, we report the synthesis of compounds 1 and 2, both having the same chemical composition, [ZnCl2(L)]n, but different MOFs.
Results and Discussion
Compound 1 was synthesized by reacting of ZnCl2 with L (molar ratio 1:1) under solvothermal conditions. Figure 1 shows the crystal structure of compound 1. The structure reveals that compound 1 consists of a distorted tetrahedral Zn(II) center coordinating to two chlorides and two pyridyl nitrogen atoms from two symmetry-related L ligands [Zn(1)−Cl(1) = 2.2229(11) Å; Zn(1)−Cl(2) = 2.2123(9)Å; Zn(1)−N(1) = 2.049(3)Å; Zn(1)−N(4A) = 2.057(3)Å, symmetry operation code: A= −x+3/2, y+1/2, z−1/2]. Some selected bond lengths and angles around the Zn center are listed in Table 1. It is noteworthy that the ligand L is not planar, but twisted around the –CH=N−N=CH− with a dihedral angle of 46.65(13)° between the two pyridine rings and acts as a bis-monodentate mode to the Zn(II) ion. Hence, a 1D polymeric helical chain is formed. The distance between the neighboring zinc ions is 12.1834(4) Å.
Figure 1.
One-dimensional polymeric helical chain of compound 1. Atomic displacement ellipsoids were plotted at 50% probability level.
Figure 1.
One-dimensional polymeric helical chain of compound 1. Atomic displacement ellipsoids were plotted at 50% probability level.
Hydrogen bonding has been widely used in constructing coordination polymers [8,9,10]. Intermolecular C−H∙∙∙Cl hydrogen bonds were observed in our coordination polymers. The packing diagram viewed along the c axis is shown in Figure 2. Two Cl‾ anions produce four intermolecular C−H∙∙∙Cl interactions in the crystal packing [C(8)−H∙∙∙Cl(1), 3.554(4)Å; C(9)−H∙∙∙Cl(1), 3.629(4)Å; C(1)−H∙∙∙Cl(2), 3.546(4)Å and C(12)−H∙∙∙Cl(2), 3.445(4)Å]. These C−H∙∙∙Cl hydrogen bonds formed between adjacent 1D polymer helical chains result in a 3D network.
| Bond Length [Å] | Bond Angle [°] | ||
|---|---|---|---|
| Zn(1)-Cl(1) | 2.2229(11) | N(1)-Zn(1)-N(4A) | 99.56(13) |
| Zn(1)-Cl(2) | 2.2123(9) | N(1)-Zn(1)-Cl(2) | 110.25(10) |
| Zn(1)-N(1) | 2.049(3) | N(4A)-Zn(1)-Cl(2) | 104.18(9) |
| Zn(1)-N(4A) | 2.057(3) | N(1)-Zn(1)-Cl(1) | 107.14(9) |
| N(2)-C(6) | 1.281(5) | N(4A)-Zn(1)-Cl(1) | 107.54(9) |
| N(2)-N(3) | 1.415(4) | Cl(2)-Zn(1)-Cl(1) | 125.13(4) |
| N(3)-C(7) | 1.272(5) | C(6)-N(2)-N(3) | 109.6(3) |
| C(4)-C(6) | 1.477(5) | C(7)-N(3)-N(2) | 112.1(3) |
| C(7)-C(11) | 1.467(5) | N(2)-C(6)-C(4) | 120.0(4) |
| N(3)-C(7)-C(11) | 119.5(4) | ||
Symmetry transformations used to generate equivalent atoms: A = -x+3/2, y+1/2, z-1/2
Figure 2.
The packing diagram of compound 1, viewed along the c axis. Dotted lines indicate hydrogen bonds.
Figure 2.
The packing diagram of compound 1, viewed along the c axis. Dotted lines indicate hydrogen bonds.
Compound 2, synthesized under solvothermal conditions by the reaction of ZnCl2 with NaSCN and L in a 1:2:1 molar-ratio, has an unexpected but interesting structure. The molecular drawing of the 1D polymeric chain of compound 2 is shown in Figure 3. The structure reveals that the zinc ions in compound 2 also have a distorted tetrahedral geometry and bond to two chlorides and two pyridyl nitrogen atoms from two symmetry-related L ligands [Zn(1)-Cl(1) = 2.2205(6)Å; Zn(1)-Cl(2) = 2.2336(7)Å; Zn(1)-N(1) = 2.047(2)Å; Zn(1)-N(4A) = 2.052(2)Å, symmetry operation code: A= -x+3/2, y+1/2, -z+1/2]. Some selected bond lengths and angles around the Zn center are listed in Table 2. It is noteworthy that the geometry of ligand L is nearly planar and the dihedral angle between two pyridine rings is 2.96(16)°, which is much smaller than the 46.65(13)° one in compound 1. The bond angle of N(1)-Zn(1)-N(4A) is 116.22(8)°, which is significantly larger than that of 99.56(13)° observed in compound 1. The structure of compound 2 reveals a 1D square-wave arrangement with the separation of neighboring zinc ions of 12.4319(6) Å.
Figure 3.
One-dimensional polymeric square-wave chain of compound 2. Atomic displacement ellipsoids were drawn at 50% probability level.
Figure 3.
One-dimensional polymeric square-wave chain of compound 2. Atomic displacement ellipsoids were drawn at 50% probability level.
| Bond Length [Å] | Bond Angle [°] | ||
|---|---|---|---|
| Zn(1)-Cl(1) | 2.2205(6) | N(1)-Zn(1)-N(4A) | 116.22(8) |
| Zn(1)-Cl(2) | 2.2336(7) | N(1)-Zn(1)-Cl(2) | 104.83(6) |
| Zn(1)-N(1) | 2.047(2) | N(4A)-Zn(1)-Cl(2) | 107.56(6) |
| Zn(1)-N(4A) | 2.052(2) | N(1)-Zn(1)-Cl(1) | 103.00(6) |
| N(2)-C(6) | 1.262(3) | N(4A)-Zn(1)-Cl(1) | 105.31(6) |
| N(2)-N(3) | 1.415(3) | Cl(2)-Zn(1)-Cl(1) | 120.49(3) |
| N(3)-C(7) | 1.274(3) | C(6)-N(2)-N(3) | 111.7(2) |
| C(4)-C(6) | 1.473(3) | C(7)-N(3)-N(2) | 111.5(2) |
| C(7)-C(11) | 1.466(3) | N(2)-C(6)-C(4) | 121.3(2) |
| N(3)-C(7)-C(11) | 120.7(2) | ||
Symmetry transformations used to generate equivalent atoms: A = -x+3/2, y+1/2, -z+1/2.
The packing diagram viewed along the c axis is shown in Figure 4. Similar to compound 1, compound 2 also shows intermolecular C−H∙∙∙Cl hydrogen bonds [C(3)−H∙∙∙Cl(2), 3.509(4)Å and C(9)−H∙∙∙Cl(2), 3.507(3)Å] to form a 3D network. The pyridyl rings in the adjacent polymeric chains are nearly parallel. They have the shortest distances of 3.85Å and 4.22Å respectively. The result indicates the presence of weak π-π stacking. In contrast, compound 1 does not show π-π interactions in the crystal packing, because the two pyridyl rings attached to the –CH=N−N=CH− are twisted.
Figure 4.
The packing diagram of compound 2, viewed along the c axis. Dotted lines indicate hydrogen bonds.
Figure 4.
The packing diagram of compound 2, viewed along the c axis. Dotted lines indicate hydrogen bonds.
Conclusions
We have successfully synthesized two novel coordination polymers. Although the compounds have the same chemical composition, [ZnCl2(L)]n, they show different structural conformations with one forming a helical chain and the other a square-wave chain, determined by X-ray crystallography. The intermolecular C−H∙∙∙Cl hydrogen bonds in 1 and 2 play important roles in the formation of 3D coordination polymers.
Experimental
General
Solvents and metal salts for syntheses (analytical grade) were used without further purification. The ligand L was prepared according to the literature [7]. IR spectra were recorded using KBr discs on a Nicolet FT-IR CGB- 2400 FT-IR spectrophotometer. Elemental analysis (EA) were performed on a Heraeus CHN-Rapid elemental analyzer.
Synthesis of compound 1
A mixture of ZnCl2 (27.2 mg, 0.2 mmol) and L (42.0 mg, 0.2 mmol) in ethanol (5 mL) was placed in a 23 mL Teflon-lined stainless steel autoclave container and heated at 150 °C for 48 h. Afterwards the mixture was cooled to room temperature at a rate of 5°C/h . The resulting colorless crystals were collected in 50% yield. IR (νmax, cm–1): 1632.9 (s), 1605.0 (s), 1467.1 (m), 1432.9 (s), 1311.4 (m), 1215.4 (w), 1192.3 (m), 1126.7 (w), 1103.1 (w), 1057.3 (m), 1031.7 (w), 966.6 (w), 935.1 (w), 882.8 (w), 815.3 (w), 697.1 (m), 653.7 (m); Elemental analysis: Calcd.: C, 41.59; H, 2.91; N, 16.17. Found: C, 41.82; H, 2.88; N, 16.52.
Synthesis of compound 2
A mixture of ZnCl2 (27.2 mg, 0.2 mmol), NaSCN (42.4mg, 0.4 mmol) and L (42.0 mg, 0.2 mmol) in ethanol (5 mL) was placed in a 23 ml Teflon-lined stainless steel autoclave container and heated at 150 °C for 48 h. Afterwards the mixture was cooled to room temperature at a rate of 5°C/h. The light brown crystals were collected in 55% yield. IR (νmax, cm–1): 1632.0 (s), 1605.0 (s), 1473.8 (s), 1430.9 (s), 1309.9 (m), 1215.4 (m), 1187.9 (m), 1126.2 (m), 1101.6 (m), 1057.3 (s), 1030.8 (m), 971.0 (m), 948.8 (m), 883.7 (s), 814.3 (s), 699.1 (vs), 652.8 (s); Elemental analysis: Calcd.: C, 41.59; H, 2.91; N, 16.17. Found: C, 41.93; H, 2.90; N, 16.49.
X-ray techniques
Suitable single crystals were mounted on a glass fiber. The data collection was carried out on a NONIUS Kappa CCD diffractometer with Mo-Kα (λ = 0.71073 Å) radiation with the crystal cooled to 150K in a stream of N2 from Oxford Cryostream-700 cooler. A preliminary orientation matrix and the unit cell parameters were determined from the 15 frames, each frame corresponding to a 1° ω scan in 20 sec. Data were measured (program COLLECT [11]) by using an ω scan of 0.5° per frame for 20 sec. until a complete data had been collected. Program DENZO-SMN [12] was used for cell refinement and data reduction. The SORTAV [13] program was used to apply absorption correction. The structure was solved by direct method with the SHELXS97 [14] and refined on F2 with SHELXL97 [15]. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were constrained to the ideal geometry applying an appropriate riding model. The molecular graphic were plotted using SHELXTL [16] and MERCURY [17]. Crystallographic data are listed in Table 3. CCDC-605741 and 605742 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html. [or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336033; e-mail: [email protected]].
| Compound | 1 | 2 |
|---|---|---|
| Formula | C12H10N4Cl2Zn | C12H10N4Cl2Zn |
| Formula weight | 346.51 | 346.51 |
| Crystal system | Orthorhombic | monoclinic |
| Space group | Pna21 | P21/n |
| Formula per unit cell, Z | 4 | 4 |
| Unit-cell dimensions | a = 7.9652(3) Å | a = 9.1752(3) Å |
| b = 21.4716(7) Å | b = 14.5976(4) Å | |
| c = 8.2491(3) Å | c = 10.3666(3) Å | |
| α = β = γ = 90° | α = γ = 90°, β = 98.231(2)° | |
| Unit-cell volume, V (Å 3) | 1410.81(9) | 1374.16(7) |
| Dcalcd. (g/cm3) | 1.631 | 1.675 |
| Absorption coefficient, μ(mm-1) | 2.109 | 2.165 |
| F(000) | 696 | 696 |
| Crystal size (mm) | 0.50 x 0.08 x 0.05 | 0.25 x 0.15 x 0.03 |
| θ ranges (o) for data collection | 1.90 ~ 27.50 | 2.43 ~ 27.50 |
| Index ranges | -10 ≦ h ≦ 10 | -11 ≦ h ≦ 11 |
| -27 ≦ k ≦ 23 | -17 ≦ k ≦ 18 | |
| -10 ≦ l ≦ 10 | -13 ≦ l ≦ 13 | |
| Reflections collected | 9123 | 9083 |
| Independent reflections | 3184 (Rint = 0.0641) | 3145 (Rint = 0.0453) |
| Completeness to θ=27.50 (%) | 100.0 | 99.7 |
| Absorption correction | Multi-scan | Multi-scan |
| Max. and min. transmission | 0.900 and 0.418 | 0.939 and 0.700 |
| Refinement method | Full-matrix L. S. on F2 | Full-matrix L. S. on F2 |
| Data / restraints / parameters | 3184 / 1 / 172 | 3145 / 0 / 173 |
| Goodness-of-fir on F2 | 1.007 | 1.013 |
| Final R indices [I > 2σ(I)] | R1 = 0.0398, wR2 = 0.0695 | R1 = 0.0326, wR2 = 0.0598 |
| R indices (all data) | R1 = 0.0718, wR2 = 0.0765 | R1 = 0.0694, wR2 = 0.0672 |
| Largest diff. peak and hole (e/ Å 3) | 0.320 and -0.394 | 0.347 and -0.363 |
Acknowledgements
The authors would like to thank the National Science Council, Republic of China, for support under grant NSC 932622E027027CC3.
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MDPI and ACS Style
Lee, G.-H.; Wang, H.-T. Synthesis and Molecular Structures of Two [1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene]-dichloro-Zn(II) Coordination Polymers. Molecules 2006, 11, 589-596. https://doi.org/10.3390/11080589
AMA Style
Lee G-H, Wang H-T. Synthesis and Molecular Structures of Two [1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene]-dichloro-Zn(II) Coordination Polymers. Molecules. 2006; 11(8):589-596. https://doi.org/10.3390/11080589
Chicago/Turabian StyleLee, Gene-Hsiang, and Hsin-Ta Wang. 2006. "Synthesis and Molecular Structures of Two [1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene]-dichloro-Zn(II) Coordination Polymers" Molecules 11, no. 8: 589-596. https://doi.org/10.3390/11080589
