КООРДИНАЦИОННАЯ ХИМИЯ, 2013, том 39, № 3, с. 141-146
УДК 541.49
DESIGN AND SYNTHESIS OF TWO-DIMENSIONAL PILLARED MOF LAYERS BY CONNECTING INFINITE ONE-DIMENSIONAL CHAINS
via 4,4-BIPYRIDINE
© 2013 L. J. Li*, L. Z. Wang, X. Y. Yang, G. Y. Wang, Ch. Tian, and J. L. Du
Key Laboratory of Chemical Biology of Hebei Province, Hebei University, Baoding, 071002 P.R. China
*E-mail: llj@hbu.edu.cn Received September 13, 2011
Two novel metal-organic frameworks, [Cd(Bna)(DMF)2(H2O)2]n • nDMF (I) (Bna = 2,2'-dihydroxy-l,l'-di-naphthyl-3,3'-dicarboxylate) and [Cd(Bna)(Bipy)(DMF)2]n (II) (Bipy = 4,4'-bipyridine) have been synthesized under mild conditions and structurally characterized. Crystal structural analyses reveal that complex I adots a 1D spiral structure with DMF guest molecules in the spiral by hydrogen bondings. Complex II is constructed by —Cd—Bna—Cd— zigzag chains, which are further connected by Bipy into a 2D sheet. X-ray powder diffraction and thermogravimetric analyses for I and II show that they are highly themally stable in the solid state.
DOI: 10.7868/S0132344X13030055
INTRODUCTION
Great progress has been made during the past two decades in the construction of metal-organic frameworks (MOFs) comprising an infinite alternate arrangement of metal ions and bridging ligands [1—3]. Because of the ability to systematically tune their porosity and the functionalities that are incorporated within the framework scaffolds [4—9]. As a result, numerous MOFs have been engineered for a number of potential applications, including gas storage [10—13], nonlinear optics [8], and catalysis [14, 15]. Lin group have particularly demonstrated the utility of binaphth-yl-derived homochiral MOFs in heterogeneous asymmetric catalysis [16, 17]. Although a number of strategies have been developed to achieve 2D or 3D structures MOFs in recent years [9] it is still a challenge to obtain MOFs with open channels and extremely large porosity. Modification of the frameworks are still at-tractting much interest.
Presently, we have been interested in constructing 2D structures MOFs containing Bna ligands, where H2Bna = 2,2'-dihydroxy-l,l'-dinaphthyl-3,3'-dicar-boxy acid, contributing to asymmetric synthesis. The design strategy is to link 1D chains, made of the combination ofBna and metal ion, to each other by using a linear ligand to form MOFs layers. The chains can be combined through linear bifunctional ligand such as 4,4'-bi-pyridine (Bipy) to generate 2D MOFs architecture.
EXPERIMENTAL
Materials and methods. All chemicals were purchased commercially and used without further puri-cation. Infrared spectra were obtained with a Nico-
let Impact 410 FTIR spectrometer in the range 400— 4000 cm-1 using the KBr pellets. A PerkinElmer TGA thermogravimetric analyzer was used to obtain ther-mogravimetric analysis (TGA) curve in air with a heating rate of 20°C/min. 1H NMR spectra were run at 25°C using a Bruker 400 (400 MHz) spectrometer. X-ray powder diffraction (XRPD) spectra were obtained with a Bruker D8 ADVANCE.
Synthesis of H2Bna carried out acording to the following scheme:
COOH
OH
COOH
OH OH
COOH
(H2Bna)
A mixture of 3-hydroxy-2-naphthoic acid (9.4 g, 50 mmol) and FeCl3 • 6H2O (20.3 g, 56 mmol) was grinded sufficiency, the mixture was conducted in microwave tube at 70°C and 700 W for 35 min. The mixture was kept at room temperature with occasional grinding for a certain period of the reaction time until the reaction was completed. The residue was puried by column chromatography on silica gel with petroleum ether-ethyl acetate (5 : 1) to afford the product H2Bna in 74% yield (7.0 g). Mp > 290°C; 1H NMR ((CD3)2CO; 400 MHz; 8, ppm): 7.14-7.17 (m., 2H, Ar-H), 7.39-7.42 (m., 4H, Ar-H), 8.09-8.11 (m., 2H, Ar-H), 8.84 (s., 2H, Ar-H); IR (KBr; v, cm-1):
c(22)
o(6)
c(16)
Fig. 1. The coordination environment around Cd(II) in I with the thermal ellipsoid at the 30% probability level. Symmetry code: (A) -x - 1/2, y - 1/2, - z + 1/2.
3059, 1661, 1499, 1455, 1272, 1228, 1150, 1072, 886, 796, 736.
For C22H14O6 anal. calcd., %: Found, %:
C, 81.48; C, 81.62;
H, 2.36. H, 2.28.
Synthesis of [Cd(Bna)(DMF)2(H2O)2]„ • nDMF (I).
A mixture of H2Bna (7.5 mg, 0.02 mmol) and NaOH (1.6 mg, 0.04 mmol) was warmed to dissolved in 5 mL ethanol. After removing the solvents under a reduced pressure, the residue was dissolved in 2 mL DMSO as the under layer in a tube. A mixture of 1 mL DMSO and H2O (1 : 1) was carefully layered as the middle layer in the tube. 24.2 mg (0.08 mmol) Cd(NO3)2 ■ 6H2O was dissolved in 2 mL DMF and H2O (1 : 1) as the up layer. The tube was then sealed. Diffusion between the three phases over a period produced transparent block colourless crystals of I. IR (KBr; v, cm-1): 1658, 1570, 1461, 1392, 1309, 1018, 940,861,751,599.
For C31H37N3O11Cd
anal. calcd., %:C, 50.24; H, 5.00; N, 5.68; Cd, 15.19. Found, %: C, 50.33; H, 4.86; N, 5.48; Cd, 15.15.
Synthesis of [Cd(Bna)2(Bipy)(DMF)2]„ (II). 34 mg
(0.12 mmol) Cd(NO)3 • 4H2O was dissolved in a mixture of 2 mL DMSO and H2O (v/v = 1/2) as the under layer in a tube. A mixture of 1 mL DMF and H2O (v/v = 1/1) was carefully layered as the middle layer in the tube. A mixture of H2Bna (7.5 mg, 0.02 mmol) and 8 mg (0.04 mmol) Bipy was dissolved in 2 mL DMF as
the up layer. The tube was then sealed. Diffusion between the three phases over a period of 3 months produced transparent rhombic block crystals of II. IR (KBr; v, cm-1): 1640, 1581, 1399, 1455, 1110, 1110, 816, 758, 673,598.
For C38H34N4O8Cd
anal. calcd., %: C, 57.93; H, 4.32; N, 7.11; Cd, 14.28. Found, %: C, 57.45; H, 4.56; N, 7.08; Cd, 14.32.
X-ray determination of structure. The single crystal data of the complexes I and II were collected on a Bruker Smart Apex II CCD diffractometer using the graphite monochromated MoZ„ radiation (X = = 0.71073 A). The data of I were collected at 296(2) K. A total of 17626 reections, including 6315 unique reflections (Rjnt = 0.0163) were measured in the 1.97° < 9 <
< 28.34°. The data of II were collected at 296 K. A total of12540 reflections, including 4205 unique reflections (Rint = 0.0290) were measured in the 1.97° < 9 <
< 28.34°. Both structures were solved with a direct method using SHELXS-97 and were rened by full-matrix least-square methods using SHELXTL-97. All H atoms were placed geometrically. The crystallo-graphic data and structure experimental details of the complexes I and II are given in Table 1, and selected bond lengths and bond angles are presented in Table 2.
Supplementary material for structures I and II has been deposited with the Cambridge Crystallo-graphic Data Centre (nos. 836989 (I) and 836988 (II); deposit@ccdc. cam.ac.uk or http://www.ccdc.cam. ac.uk).
RESULTS AND DISCUSSION
There are one [Cd(Bna)(DMF)2(H2O)2] and one non-coordinated DMF guest molecules in the asymmetric unit of complex I. As shown in Fig. 1, the Cd(II) atom in I is coordinated by two oxygen atoms from two carboxylic groups of two independent Bna2-ligands (Cd-O 2.246(2) and 2.260(2) A), two oxygen atoms from two DMF (Cd-O 2.273(3) and 2.263(2) A) and two oxygen atoms from two H2O (Cd-O 2.256(3) and 2.359(2) A), where the latter two occupy the apical positions to fulfill the octahedron coordination motif. The dihedral angle between the pair of naphthyl rings of the ligand is 88.1° and nearly perpendicular to each other. The selected bond distances and angles of complex I are listed in Table 2. The extended structure of I features 1D spirals with Cd2+ ions as the nodes (Fig. 2a). Here is an 1D chanel in the spiral, and the non-coordinated guest DMF molecule is located in the chanel by hydrongen bonded to the coordinated water (O—O 2.640 A). Hydrogen bondings are also found between water molecules from adjacent spiral lines (O—O 2.799 A) (Fig. 2b). It is interesting that the ligands from the two neighboring spiral are enanti-omer, leading to the opposite chirality of these two
KOOP^HH^HOHHAtf XHMH3 TOM 39 № 3 2013
Table 1. Crystallographic data and details of the experiment for complexes I and II
Parameter Value
I II
Formula weight 740.05 787.09
Crystal system Monoclinic Orthorhombic
Space group P21/n C222j
a, A 12.9178(4) 11.7689(11)
b, A 11.4056(4) 13.8060(13)
c, A 23.0528(7) 20.708(2)
P, deg 90.9520(10) 90
Volume, A3 3396.02(19) 3364.6(6)
Z 4 4
Pcalcd mg/m3 1.447 1.554
p., mm-1 0.704 0.711
/(000) 1520 1608
Crystal size, mm 0.46 x 0.26 x 0.21 0.27 x 0.09 x 0.08
9 Range for data collection, deg 1.77 to 28.31 1.97 to 28.34
Limiting indices -17 < h < 17, -15 < k < 14, -20 < l < 30 -15 < h < 15, -8 < k < 18, -27 < l < 27
Reflections collected 21088 12540
Independent reflections 8212 (Rint = 0.0170) 4205 (Rint = 0.0290)
Completeness to 9, % 97.3 100.0
Goodness-of-fit on F2 1.053 1.596
Parameters 440 237
Final R indices (I> 2ct(I)) R1 = 0.0398 wR2 = 0.1085 R1 = 0.0297 wR2 = 0.0568
R indices (all data) R1 = 0.0498 wR2 = 0.1171 R1 = 0.0349 wR2 = 0.0577
Largest diff. peak and hole, e A-3 1.013 and -0.410 0.939 and -0.333
neighboring spiral lines. These spirals with opposite chirality pack alternatively along y axis (Fig. 2b), makes the structure of complex I achiral.
There are 1/2[Cd(Bna)(Bipy)(DMF)2] in the asymmetric unit of complex II. As shown in Fig. 3, the Cd(II) atom in II is coordinated by two oxygen atoms from two carboxylic groups of two independent Bna2-ligands (Cd—O 2.3054(19) A), two oxygen atoms from two DMF (Cd-O 2.330(2) A) and two nitrogen atoms from two Bipy (Cd-N 2.321(2) and 2.378(2) A), where the latter two N occupy the apical positions to fulfill the octahedron coordination motif. The dihedral angle between the pair of naphthyl rings of the ligand is 78.6°. The selected bond distances and angles are listed in Table 2. The Cd2+ ions connect the adjacent Bna2- ligands to form an infinite 1D zigzag line (Fig. 4a), and then coordinate with Bipy molecules at apical positions to extend to a 2D sheet
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