КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 12, с. 734-740
УДК 541.49
IONOTHERMAL SYNTHESIS OF TWO CHIRAL THREE-DIMENSIONAL METAL-ORGANIC FRAMEWORKS BASED ON D-CAMPHORIC ACID © 2014 L. Li, S. Chen, Y. J. Ning, Y. Bai*, and D. B. Dang*
Henan Key Laboratory of Polyoxometalate Chemistry, Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004 P.R. China *E-mail: baiyan@henu.edu.cn; dangdb@henu.edu.cn Received April 28, 2014
Two three-dimensional chiral metal-organic frameworks [PMIm][Co2(D-Cam)2(CH3COO)] (I) and [BMIm][Mn2(D-Cam)2(CH3COO)] ■ H2O (II) (PMIm = 1-propyl-3-methylimidazolium, BMIm = 1-bu-tyl-3-methylimidazolium, D-Cam = D-camphoric acid) have been synthesized under the ionothermal conditions and structurally characterized by IR spectroscopy, elemental analysis, XRPD, and X-ray single-crystal structure analysis (CIF files CCDC nos. 979650 (I) and 979649 (II)). Two structures exhibit similar three-dimentional frameworks constructed by the coordination interactions of binuclear metal secondary building units and two bridging ligands of D-Cam and CH3COO-, in which [PMIm]+ cations for I and [BMIm]+ cations for II as templates are filled in the void of frameworks.
DOI: 10.7868/S0132344X14120081
INTRODUCTION
The science of metal-organic frameworks (MOFs) with multitopic organic linkers and metal nodes is an area of great interest owing to their potential to exhibit structure-dependent behavior, such as magnetic, optical, catalytic and adsorbent properties [1—5]. So far, investigations have mainly involved the construction of MOFs under hydrothermal, solvothermal conditions or room-temperature crystallization [6]. In contrast, the use of ionic liquids (ILs) in the design and synthesis of MOFs has been much less explored, despite their excellent properties including the low melting points, low vapor pressure, high thermal stability, ionic conductivity, and their abilities to dissolve a wide range of organic and inorganic compounds [7—9]. In the coordination chemistry-based self-assembly, ionic liquids can be functioned as reaction media and structure templates, which may result in a rich diversity of microarchitectures and topologies [10—13].
As an important part of MOFs, chiral MOFs are of particular interest showing promise in not only the intriguing variety of architectures and topologies, but also their applications such as in nonlinear optics, enantio-merically selective catalysis and separation [14—16]. An efficient strategy constructing chiral MOFs is the incorporation of enantiopure organic ligands. D-cam-phoric acid (D-Cam), as a kind of chiral ligands, has comparatively small volume and versatile coordination behavior. A series of homochiral MOFs based on D-Cam have been reported via hydrothermal synthesis [17—20], however, homochiral MOFs synthesized in ILs are relatively few [21]. In 2008, Xianhui Bu re-
ports a homochiral framework (EMIm)[Co2(D-Cam)2(Ac)] (EMIm = 1-ethyl-3-methylimidazolium, Ac = acetate) through ionothermal synthesis [22]. As part of our continuing investigations on the construction of functional MOFs [14, 17, 23, 24], herein we have successfully synthesized two 3D chiral metal-organic frameworks [PMIm] [Co2(D-Cam)2(CH3COO)] (I) and [BMIm][Mn2(D-Cam)2(CH3COO)] ■ H2O (II) through the use of [PMIm]Br (1-propyl-3-methylim-idazolium bromide) and [BMIm]Br (1-butyl-3-me-thylimidazolium bromide) as solvents.
EXPERIMENTAL
All chemicals were of reagent grade quality obtained from commercial sources and used without further purification. [PMIm]Br and [BMIm]Br were prepared according to the literature method [25]. Elemental analyses (C, H, and N) were carried out on a PerkinElmer 240C analytical instrument. IR spectra were recorded from KBr pellets with a Nicolet 170 SXFT-IR spectrophotometer in the 4000-400 cm-1 region. Powder X-ray diffraction patterns were recorded on a D/max-g A rotating anode X-ray diffractome-ter with a sealed Cu tube (X = 1.54178 A).
Synthesis of complex I. A mixture of Co(CH3COO)2 ■ 4H2O (0.37 g, 1.5 mmol), D-Cam (0.20 g, 1.0 mmol), and [PMIm]Br (1.80 g, 8.8 mmol) in a 25 mL Teflon-lined stainless-steel autoclave was heated to 120°C for 5 days in a furnace. The resulting mixture was naturally cooled to get purple crystals of I
suitable for single-crystal X-ray diffraction. The total yield was 60% based on D-Cam.
For C29H44N2O10Co2 (M = 698.53)
anal. calcd., %: C, 49.86; H, 6.35; N, 4.01.
Found, %: C, 49.77; H, 6.31; N, 3.95.
IR (KBr; v, cm-1): 3428 m, 3143 w, 3103 w, 3052 w, 2967 m, 2928 w, 2881 w, 1630 s, 1566 s, 1448 m, 1401 v.s,
1364 m, 1291 w, 1175 m, 1130 w, 799 w, 782 w.
Synthesis of complex II was carried out in a similar manner to that of I, except that [BMIm]Br (1.80 g) was used instead of [PMIm]Br, Mn(CH3COO)2 ■ 4H2O (0.37 g, 1.5 mmol) instead of Co(CH3COO)2 ■ 4H2O. The yellow crystals ofII are suitable for single-crystal X-ray diffraction. The total yield was 71% based on D-Cam.
For C30H48N2O11Mn2 (M = 722.59)
anal. calcd., %: C, 49.87; H, 6.70; N, 3.88.
Found, %: C, 49.81; H, 6.62; N, 3.94.
IR (KBr; v, cm-1): 3455 m, 3154 w, 3091 w, 3060 m, 2964 m, 2938 w, 2877 w, 1627 s, 1552 s, 1460 m, 1401 v.s,
1365 m, 1319 m 1291 w, 1175 m, 1129 w, 798 m, 784 m.
X-ray crystallography. A suitable crystal of size 0.17 x 0.13 x 0.09 mm for I and 0.25 x 0.22 x 0.18 mm for II were chosen for the crystallographic study and mounted on a Bruker Smart APEX II CCD diffracto-meter. All diffraction measurements were performed at room temperature using graphite-monochroma-tized Mo^a radiation (X = 0.71073 A). The structure was solved by Direct Methods and refined on F2 by using full-matrix least-squares methods with the SHELXL-97 program [26, 27]. Space group, lattice parameters and other relevant information are listed in Table 1 and selected bond lengths and angles are given in Table 2.
Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (nos. 979650 (I) and 979649 (II); deposit@ccdc.cam. ac.uk or http://www.ccdc.cam.ac.uk).
RESULT AND DISCUSSION
The IR spectra of complexes I and II give clear evidences of characteristic bands of carboxylates. The bands at 1566, 1401 cm-1 for I and 1552, 1401 cm-1 for II show the antisymmetric and symmetric stretching vibrations of COO- [28, 29]. The peaks from 3052 to 3143 cm-1 for I and 3060 to 3154 cm-1 for II should be attributed to the stretching vibrations of C-H for imi-dazolium. The bands at 2967 cm-1 for I and 2964 cm-1 for II are assigned to C-H stretching vibrations of methyl and methylene [30]. These results were finally confirmed by X-ray crystallography.
Table 1. Crystallographic data and refinement parameters for complexes of I and II
Malue
Parameter
I II
Formula weight 698.52 722.58
Temperature, K 295(2) 296(2)
Crystal system Orthorhombic Orthorhombic
Space group P212121 P212121
a, A 13.3950(8) 13.085(6)
b, A 13.5119(8) 14.106(7)
c, A 17.6200(10) 18.175(9)
V, A3 3189.1(3) 3354(3)
Z 4 4
Pcalcd g cm-3 1.455 1.431
p., mm-1 1.097 0.812
F(000) 1464 1520
9 Range for data collection, deg 1.90-25.00 1.83-24.99
Scan mode O 0
Number of unique reflections (N1) 5611 (Rint = 0.0519) 5905 (Rint = 0.0388)
Number of reflections with I > 2ct(I) (N2) 4081 4967
Number of parameters refined 388 424
GOOF (F2) 1.079 1.058
R1 for N2 0.0539 0.0360
wR2 for N1 0.1577 0.0994
APmaxAPmirn « A-3 0.966/-0.386 0.280/-0.400
Table 2. Selected bond lengths (A) and bond angles (deg) of I*
Bond d, A Bond d, A
Co(1)-O(2) Co(1)-O(3A) Co(1)-O(5B) Co(1)-O(8) Co(1)-O(10C) Mn(1)-O(1) Mn(1)-O(3A) Mn(1)-O(6B) Mn(1)-O(8) Mn(1)-O(9) 2.044(5) 2.049(5) 2.037(5) 2.014(5) 2.002(4) I 2.098(2) 2.133(3) 2.110(3) 2.084(3) 2.070(3) Co(2)-O(1) Co(2)-O(4A) Co(2)-O(6B) Co(2)-O(7) Co(2)-O(9) I Mn(2)-O(2) Mn(2)-O(4A) Mn(2)-O(5B) Mn(2)-O(7) Mn(2)-O(10C) 2.035(5) 2.039(5) 2.039(5) 2.033(5) 2.023(4) 2.126(3) 2.01(3) 2.093(3) 2.142(3) 2.070(2)
Angle ro, deg Angle ro, deg
O(2)Co(1)O(3A) O(8)Co(1)O(2) O(5B)Co(1)O(3A) O(10B)Co(1)O(3A) O(10C)Co(1) O(5B) O(1)Co(2)O(4A) O(7)Co(2)O(1) O(7)Co(2)O(4A) O(4A)Co(2)O(6B) O(9)Co(2)O(6B) O(1)Mn(1)O(3A) O(8)Mn(1)O(1) O(6B)Mn(1)O(3A) O(9)Mn(1)O(3A) O(9)Mn(1)O(6B) O(4A)Mn(2)O(2) O(2)Mn(2)O(7) O(5B)Mn(2)O(4A) O(10C)Mn(2)O(4A) O(5B)Mn(2)O(7) 88.5(2) 159.6(2) 164.00(19) 99.8(2) 96.2(2) 88.4(2) 164.3(2) 87.5(2) 160.33(19) 102.62(18) I 87.80(11) 155.06(12) 158.05(12) 102.31(12) 99.63(12) 86.25(11) 158.83(12) 156.03(12) 101.99(11) 89.55(12) O(5B)Co(1)O(2) O(10C)Co(1)O(2) O(8)Co(1)O(3A) O(8)Co(1)O(5B) O(10C)Co(1)O(8) O(1)Co(2)O(6B) O(9)Co(2)O(1) O(9)Co(2)O(4A) O(7)Co(2)O(6B) O(9)Co(2)O(7) I O(1)Mn(1)O(6B) O(9)Mn(1)O(1) O(8)Mn(1)O(3A) O(8)Mn(1)O(6B) O(9)Mn(1)O(8) O(5B)Mn(2)O(2) O(10C)Mn(2)O(2) 0(4A)Mn(2)O(7) O(10C)Mn(2)O(5B) O(10C)Mn(2)O(7) 89.2(2) 97.0(2) 88.7(2) 87.9(2) 103.4(2) 89..(2) 101.34(19) 97..(2) 89..(2) 94.2(2) 88.86(12) 97.67(11) 87.47(11) 86.47(12) 107.27(11) 88.75(12) 100.71(11) 86.78(11) 101.97(11) 100.29(11)
* Symmetry codes: (A) 0.5 + x, 3.5 - y, 3 - z; (B) - 0.5 + x, 2.5 - y, 3 - z; (C) 2.5 - x, 3 - y, - 0.5 + z for I.
Single-crystal X-ray diffraction analysis has revealed that both I and II exhibit crystalline 3D metal-organic frameworks constructed by the coordination interactions of binuclear metal secondary building units (SBUs) and two bridging ligands (D-Cam and CH3COO) with [PMIm]+ cations for I, [BMIm]+ cations for II as templates. The coordination environment of the metal atoms is depicted in Fig. 1 and Fig. 2,
respectively. Each metal atom has a distorted square pyramid geometry and is coordinated by five oxygen atoms from four D-Cam anions ((Co(1): O(2) and O(3A) of Cam-1, O(5B) and O(8) of Cam-2; Co(2): O(1) and O(4A) of Cam-1, O(6B) and O(7) of Cam-2)) and one CH3COO- anion (O(10C) for Co(1) and O(9) for Co(2)). In complex II, the oxygen donors are O(1) and O(3A) of Cam-1, O(6B) and O(8) of Cam-2, O(9)
Fig. 1. The structure of I and the coordination environment of
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