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Synthesis and Characterization of Novel Inclusion Complexes between Microporous Molybdenum(II) Dicarboxylates and Organic Polymers Satoshi Takamaizawa,†,‡ Masatoshi Furihata,† Sadamu Takeda,§ Kizashi Yamaguchi,‡ and Wasuke Mori*,† Department of Chemistry, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan; Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; and Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan Received February 23, 2000; Revised Manuscript Received June 21, 2000
ABSTRACT: Novel inclusion complexes between host microporous molybdenum(II) dicarboxylates (fumarate, terephthalate, trans-trans-muconate, and pyridine-2,5-dicarboxylate) and guest organic polyethers (poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG)) of various molecular weights were synthesized. The rate of complex formation depends on the shapes of the micropores and polyethers. The amount of included polyethers increased with their molecular weight, and reached a saturated amount, with the exception that molybdenum(II) pyridine-2,5-dicarboxylate did not form complexes with bulky PPG. The amount of adsorbed argon in the microporous molybdenum(II) dicarboxylates decreased with increased amounts of included polyethers. The 13C CP/MAS NMR measurement of molybdenum(II) terephthalate with PEG demonstrated that PEG chains are included in the capillaries. This is an effective method for synthesizing supramolecular complexes.
Introduction Previously, we reported that microporous complexes, dinuclear transition-metal dicarboxylates (Cu(II),1 Mo(II),2 Ru(II,III)3), reversibly adsorb a large amount of gases such as nitrogen, oxygen, argon, and xenon.4 These complexes are commonly accepted as useful adsorbents for storing methane under low pressure.5 The dinuclear metal carboxylates, which are represented by the general formula M2(O2CR)4L2 and which have a well-known lantern-like structure, are shown in Figure 1a. In the case of the linear dicarboxylate bridge, it is obvious that two-dimensional lattices are constructed (Figure 1b) and that infinite linear micropores (Figure 1c) are created by stacking the two-dimensional lattices. Physicochemical characterization has shown that these metal dicarboxylates have the same dinuclear structure as that of copper(II) acetate monohydrate,6 forming network structures with infinite linear micropores. They have homogeneous capillaries and can adsorb large amounts of gases. In 1995, after we had applied to patent some adsorbent microporous complexes,5 Kitagawa,7 Yaghi,8 and Williams9 reported the gas-adsorption phenomena of porous complexes. The production of long-range organometallic conjugation is of great interest due to the possibility of fabricating purpose-specific materials with useful properties, for example, electronic, magnetic, optical, and catalytic substances derived from long-range pπ-dπ and/or dπdπ interaction.10 Some dinuclear molybdenum(II) dicarboxylates (fumarate, terephthalate, trans-trans-muconate, pyridine-2,5-dicarboxylate, and trans-1,4-cyclohexanedicarboxylate) bearing d-d quadruple bond, capable of adsorbing gases, were successfully synthesized as novel adsorbents.2 †
Kanagawa University. Osaka University. § Hokkaido University. * Corresponding author. Phone 81-463-59-4111, Fax 81-463-589684, E-mail
[email protected]. ‡
Figure 1. (a) Lantern-like structure of M2(O2CR)4L2. (b) Infinite two-dimensional lattice with holes of molybdenum(II) dicarboxylates. (c) Linear micropores constructed by stacking two-dimensional lattices of molybdenum(II) dicarboxylates.
In recent studies of supramolecular chemistry, much attention has been focused on the design and construction of nanoscale structures by using the technique of supramolecular noncovalent assemblies.11 In 1990, Harada and Kamachi found that many cyclodextrins are threaded on a linear polymer such as poly(ethylene glycol).12 This substance is recognized as the first complete organic polyrotaxane made from guest organic polymers and host organic molecules. One of the extreme supramolecules can be considered as a threedimensional network structure and regularly distributes one-dimensional polymer chains. Frank et al. reported the important differences in thermophysical properties of ultrathin polymer films.13 Hence, the above three-
10.1021/ma000336t CCC: $19.00 © 2000 American Chemical Society Published on Web 07/29/2000
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Table 1. Color and Shape, Yields, and Analytical Data of Complexes 1-4 compound 1 (purple powder)
2 (red powder)
3 (purple powder)
4 (purple powder)
additive polymer PEG200 PEG600 PEG1000 PEG1500 PEG3000 PEG7500 PPG400 PPG700 PPG2000 PPG3000 PEG200 PEG600 PEG1000 PEG1500 PEG3000 PEG7500 PPG400 PPG700 PPG2000 PPG3000 PEG200 PEG600 PEG1000 PEG1500 PEG3000 PEG7500 PPG400 PPG700 PPG2000 PPG3000 PEG200 PEG600 PEG1000 PEG1500 PEG3000 PEG7500 PPG400 PPG700 PPG2000 PPG3000
formula ([Mo2L2]‚x(Mer)‚y(H2O))a x y 0.5 0.4 1.8 2.5 4.0 4.3 0.36 1.0 2.1 2.3 0.0 0.2 1.5 2.5 4.0 5.0 0.1 1.0 2.1 2.8 0.4 0.8 1.9 3.0 3.8 3.8 0.0 0.6 0.7 1.9 0.4 0.5 0.2 0.5 1.5 2.0 0.3 0.3 0.2 0.4
2.8 1.8 1.8 1.8 1.3 1.5 3.0 2.2 1.3 1.4 3.6 2.6 2.3 2.0 2.1 2.0 2.9 2.5 2.0 2.0 2.3 2.3 2.3 1.9 1.7 1.9 4.1 3.1 2.5 1.8 4.0 4.0 4.0 4.0 4.0 3.0 4.6 4.6 4.8 4.0
yieldb/%
C/%
66 (77) 93 (104) 95 (120) 85 (114) 83 (122) 88 (134) 82 (97) 88 (109) 85 (114) 86 (118) 86 (86) 108 (120) 101 (122) 84 (108) 84 (118) 88 (134) 81 (90) 88 (105) 85 (111) 90 (124) 87 (95) 88 (96) 81 (103) 81 (109) 80 (113) 90 (128) 82 (95) 81 (96) 87 (103) 78 (101) 80 (94) 87 (103) 88 (102) 86 (102) 81 (102) 110 (141) 81 (97) 80 (95) 78 (94) 77 (93)
21.96 (21.95) 22.45 (22.49) 26.24 (26.20) 27.74 (27.76) 31.02 (31.01) 31.31 (31.33) 22.04 (22.03) 25.55 (25.52) 30.30 (30.38) 30.93 (30.92) 32.81 (32.85) 34.17 (34.21) 36.30 (36.36) 37.74 (37.86) 39.26 (39.25) 40.18 (40.22) 33.89 (33.86) 36.61 (36.62) 39.46 (39.50) 40.75 (40.77) 28.91 (28.95) 29.73 (29.77) 31.70 (31.78) 33.38 (33.86) 35.14 (35.13) 34.95 (34.94) 26.38 (26.40) 29.48 (29.45) 30.38 (30.36) 34.56 (34.58) 28.96 (29.06) 29.28 (29.24) 28.93 (28.68) 29.38 (29.24) 30.86 (30.93) 32.38 (32.55) 28.51 (28.51) 28.73 (28.75) 28.25 (28.26) 29.61 (29.62)
analysisc H/% 2.29 (2.37) 1.86 (1.97) 2.80 (2.81) 3.19 (3.15) 3.66 (3.68) 3.80 (3.83) 2.47 (2.48) 2.89 (2.80) 3.40 (3.42) 3.60 (3.59) 2.32 (2.62) 2.48 (2.45) 2.95 (2.99) 3.38 (3.33) 3.87 (3.89) 4.17 (4.15) 2.59 (2.51) 3.18 (3.07) 3.68 (3.66) 4.01 (4.04) 2.71 (2.69) 2.91 (2.90) 3.43 (3.41) 3.74 (3.76) 4.00 (4.00) 4.02 (4.04) 3.03 (2.99) 3.16 (3.19) 3.13 (3.11) 3.79 (3.77) 2.32 (2.57) 2.26 (2.39) 2.37 (2.47) 2.57 (2.26) 2.87 (3.05) 3.13 (3.03) 2.72 (2.83) 2.76 (2.75) 2.78 (2.90) 2.74 (2.82)
N/%
4.43 (4.58) 4.46 (4.55) 4.44 (4.65) 4.38 (4.55) 3.99 (4.24) 3.99 (4.22) 4.34 (4.46) 4.46 (4.50) 4.30 (4.42) 4.36 (4.46)
a L and Mer mean dicarboxylate ligand and periodic glycol unit (C H O for PEG and C H O for PPG), respectively. b Yields are calculated 2 4 3 6 by the use of analytical formula with polymer (outside parentheses) and formula without polymer (inside parentheses). c Calculated values are in parentheses.
Scheme 1
dimensional supramolecule with specific nanoscale structure points the way to a new supramolecular architecture and enables the construction of specific surface and new physical properties. For the purpose mentioned above, we present a model supramolecule consisting of two independent molecules: a coordinating polymer (transition metal complex) and a one-dimensional organic polymer. We previously reported the first formation of a supramolecule of the inclusion complex between molybdenum(II) fumarate and poly(ethylene glycol) (PEG).14 Here, we fully report the formation of an inclusion complex between microporous molybdenum(II) dicarboxylates and poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) through the use of supramolecular assemblies with the
aid of the micropores of these transition metal complexes. We report on the synthesis of the inclusion complex and the effects of the molecular weight and bulkiness of polyethers on the formation of the supramolecule. Results and Discussion Synthesis, Elemental Analysis, and Raman Spectrum. These target inclusion complexes were prepared by the one-pot method (Scheme 1). The compounds were produced as insoluble precipitates. We attempted to prepare the target supramolecules by ligand-exchange reaction between molybdenum(II) acetate and dicarboxylic acid in an alcohol media in the presence of polyether. The reaction conditions (reaction scale, concentration (wt %), and reaction time) were kept the same in all syntheses. The color and shapes, yields, and analytical data based upon molybdenum(II) acetate are described in Table 1. The yields are according to the formation of molybdenum(II) dicarboxylate. The use of formulas containing polyethers gives reasonable yields, while yields over 100% were obtained when the formulas of molybdenum(II) dicarboxylates were used without polyether. The amount of included periodic glycol (ethylene glycol or propylene glycol) units per dinuclear molybdenum(II) atoms was calculated by elemental
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Table 2. Results of Raman Measurement of Complexes 1-4 (ν(Mo-Mo)/cm-1) included polymer complex
PEG 7500
PPG 3000
no polymera
1 2 3 4
397 399 390 389
399 399 391 390
398 399 389 386
a
Previous results in ref 2.
analyses. The water molecules of the complexes are due to the hygroscopicity of the molybdenum complex and terminal OH groups of polyethers. In the Raman spectra of molybdenum(II) dicarboxylates with PEG 7500 and PPG 3000, the strongest band occurred around 400 cm-1 in the solid; these bands are assigned to the A1g mode consisting predominantly of Mo-Mo stretching.15 Raman shifts are summarized in Table 2. In comparisons with the molybdenum(II) dicarboxylates (host complexes) reported previously, the dinuclear molybdenum(II) moiety was maintained in the molybdenum(II) dicarboxylates containing polyethers. Inclusion Complex Formation. Elemental analyses gave the formulas of molybdenum(II) dicarboxylates containing PEG and PPG. The molecular weight dependencies of the amount of included PEG and PPG are shown in Figures 2a and 3a, respectively. The amount of included periodic glycol units increased with an increase in the molecular weight of polyether, finally reaching the saturated amount at the molecular weight of polyethers over 3000. The length of the included polymer is a prior factor of supramolecular formation. The longer chain is advantageous for interaction with the capillary, whose wall is made from hydrocarbon skeletons. In the PEG complexes of 1-4, the curves clearly show the saturated amounts, which are four units per Mo2 for complexes 1-3 and two units per Mo2 for complex 4. The saturated amounts at PPG 3000 are two for complexes 1-3 and the exceptionally slight 0.4 for complex 4. The saturated amounts of PPG units are half of those for the PEG complexes, except for complex 4. This result demonstrates that supramolecular formation is strongly affected by the bulkiness of the linear polymer. We want to emphasize that the amounts of included polyethers are very large and the amounts of glycol units are just natural numbers per dinuclear molybdenum(II) unit (i.e., micropore unit). Complex 4 demonstrated abnormal behavior in the inclusion complex formation in that the amount of included PEG is small. In particular, complex 4 seems to exclude PPG chains out of the micropores in the complex formation. This result agrees with the fact that complex 4 adsorbs n-butane but no neopentane16 in its micropores, while complexes 1-3 adsorb neopentane and n-butane. In complex 4, the structure of the capillary is most likely linearly zigzag and narrow by the offset stacking of the host lattices. The low wavenumber (386-390 cm-1) in the Raman spectra may indicate an axial coordination of the pyridine nitrogen to molybdenum atom in the neighboring dinuclear moiety. The capillary shape of the microporous complexes also influences the inclusion complex formation. The concentration of PEG (0.070 mol of ethylene glycol unit) is much smaller than that of the methanol molecules (4.7 mol) in the reaction mixture. Although the methanol molecules surround a trace amount of PEG molecules, the microporous molybdenum(II) dicar-
Figure 2. PEG molecular weight dependencies of the amount of included PEG units (upper) and maximum amount of occluded Ar (lower). The values of molybdenum(II) dicarboxylates in ref 2 are plotted at Mw ) 0.
boxylates selectively include polyether chains in their micropores. These inclusion phenomena suggest that the microporous complexes have the capability of molecular recognition. Correlation of Inclusion Complex Formation and Gas Adsorption Behavior. We previously examined the gas adsorption isobars for complexes 1-4 and found that gases such as nitrogen, argon, oxygen, and methane were adsorbed into the complexes and that the amount of adsorbed gases finally reached the maximum around the boiling point of the gases. The adsorbed argon was saturated at the temperature of liquid nitrogen with the amounts of 1.2, 1.9, 1.2, and 1.0 mol of argon per mole of molybdenum atoms for complexes 1-4, respectively.2 The maximum amounts of adsorbed argon for the inclusion complexes were evaluated from the saturated amount of isobars (p ) 20 Torr). Maximum amounts of occluded argon gas of complexes 1-4 are summarized in Table 3 with the calculated amounts of included polyethers extracted from Table 1. The dependence on molecular weight of the amounts of adsorbed argon gas is shown in Figures 2b and 3b. The saturated amount of adsorbed argon gradually decreases with an increase in the amount of included PEG; no argon gas is adsorbed at a molecular weight of PEG over 1500. The rate of decrease of the amount of adsorbed argon is slightly greater in comparison with
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Figure 4. 13C-CP/MAS NMR spectra of complex 2 in the shift of benzene region: (a) dried 2,2 (b) 2 adsorbing n-butane,2 (c) 2 including PEG 3000.
Figure 3. PPG molecular weight dependencies of the amount of included PPG units (upper) and maximum amount of occluded Ar (lower). The values of molybdenum(II) dicarboxylates in ref 2 are plotted at Mw ) 0. Table 3. Periodic Glycol Units and Maximum Amount of Occluded Argon Gas of Complexes 1-4 complex polymer
1
2
3
4
no additiona PEG 200 PEG 600 PEG 1000 PEG 1500 PEG 3000 PEG 7500
nob (1.2)c 0.5 (1.3) 0.4 (0.3) 1.8 (0.1) 2.5 (0.0) 4.0 (0.0) 4.3 (0.0)
no (1.9) 0.0 (2.4) 0.2 (1.5) 1.5 (0.5) 2.5 (0.1) 4.0 (0.0) 5.0 (0.0)
no (1.2) 0.4 (1.6) 0.8 (1.2) 1.9 (0.1) 2.5 (0.0) 3.8 (0.0) 3.8 (0.1)
no (1.0) 0.4 (1.0) 0.5 (0.1) 0.2 (0.1) 0.5 (0.0) 1.5 (0.1) 2.0 (0.1)
PPG 400 PPG 700 PPG 2000 PPG 3000
0.3 (1.4) 1.0 (1.0) 2.1 (0.3) 2.3 (0.1)
0.1 (2.0) 1.0 (1.2) 2.1 (0.1) 2.8 (0.1)
0.0 (1.4) 0.6 (1.3) 0.7 (1.0) 1.9 (0.3)
0.3 (1.2) 0.3 (1.0) 0.2 (0.6) 0.4 (0.6)
a Previous results in ref 2. b Amounts of included glycol extracted from Table 1 (glycol per dinuclear molybdenum). c Amounts of adsorbed argon (mole per mole of molybdenum atoms).
the saturation point for the amount of included PEG observed at the molecular weight of PEG over 3000. In the unsaturated inclusion complex with PEG 1500, PEG chains effectively sealed the micropores of molybdenum(II) dicarboxylates. This correlation between PEG inclusion and gas adsorption suggests that PEG chains occupy the space for adsorbate argon atoms. In the PPG inclusion complexes, the amount of adsorbing argon slowly decreased as the amount of the included PPG
slowly increased. Finally, a slight amount of argon gas was adsorbed at a molecular weight of PPG 3000. The bulkiness of the PPG chains may be disadvantageous in sealing the micropores. The polymer-inclusion phenomena are significantly different from the gas-adsorption phenomena. The saturated amounts of argon gas are roughly 2 mol per 1 mol of molybdenum atoms for complex 2 and 1 mol per 1 mol of molybdenum atoms for complexes 1, 3, and 4. The saturated amounts of PEG units are ca. four units per dinuclear molybdenum for complexes 1-3 and two units per dinuclear molybdenum for complex 4. In the PPG complexes 1-3, the saturated amounts of PPG units are half of those for the PEG complexes 1-3. Considering the amount of space for adsorbing gas molecules, the PEG and PPG chains are highly packed in the linear micropores. Judging from the large amount of included PEG units for 1-3, the PEG chains may be included as a couple of chains in the capillaries of 1-3. 13C-CP/MAS NMR Spectra of the Complexes Including Polyether. Solid-state magic angle spinning (MAS) NMR was used to probe the local structure of the host lattice of complexes and the environment of the guest molecules. The 13C-CP/MAS NMR investigation of the complexes was conducted at a spinning speed of 5 kHz at room temperature. Isotropic chemical shifts (δiso) were easily distinguished from spinning sidebands by employing different spinning speeds. In previous work measuring the 13C-CP/MAS NMR of microporous molybdenum(II) dicarboxylates, a clear change was observed in the shift region of the benzene ring for complex 2 with adsorbed n-butane compared with the dried complex.2 The three 13C-CP/MAS NMR spectra for the shift region of the benzene ring (120-140 ppm) of dried complex 2 (a), complex 2 adsorbing n-butane (b), and complex 2 including PEG 3000 (c) are shown in Figure 4. Spectrum c indicates a significant change in the chemical environment of the C2 carbon of the benzene ring of the terephthalate ligand by including the PEG chains in complex 2. The signal of the C2 carbon shifts to a lower field by 0.8 ppm from dried complex 2, while other signals, including carboxyl carbon, remain almost constant. This behavior is highly similar to that of complex 2 in the adsorbing gas state. This result shows that the guest molecules of n-butane and PEG in the capillary apparently interact with C2
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Figure 6. Schematic drawing of molybdenum(II) dicarboxylates including PEG chains in the linear micropores.
Concluding Remarks Figure 5. 13C-CP/MAS NMR spectra of complex 2 including PEG 3000 in the shift region of benzene and PEG.
carbons. These results strongly indicate that PEG chains are included homogeneously in capillaries surrounded by a quartet of terephthalate ligands in the same manner as the adsorbed gas molecules. Because of the presence of guest molecules, two sharp lines were observed at 24.8 and 13.4 ppm for the methylene and methyl groups of n-butane occluded in 2. The full width at half-maximum (fwhm) values of the methyl and methylene groups were 0.6 and 0.8 ppm, respectively, which are considerably narrower than the width of 1.9 and 3.2 ppm of benzene signals. Each width and intensity ratio of 1:2 of the C1 and C2 signals of benzene ring of terephthalate ligand were determined by deconvolution of the spectrum shown in Figure 4 with assuming Lorenztian line shape. This suggests a rapid rotation of the n-butane molecule in 2. The 13C-CP/MAS NMR spectrum of n-butane molecule occluded in 1 is very similar to the case of 2. In the 13C-CP/MAS NMR spectrum of 2 including PEG 3000, a single sharp line was observed at 70.5 ppm as shown in Figure 5. The fwhm of the signal was 3.0 ppm, in contrast to a broad signal for neat PEG. In neat PEG, a broad signal of the amorphous part is usually observed; its fwhm is approximately 50 ppm, corresponding to a mixture of different PEG chain conformations.17 The sharp signal of PEG in the inclusion complexes suggests a uniform molecular conformation in the lattices of the complex. In the 13C-CP/MAS NMR spectrum of the inclusion complex 1 is very similar to the case of 2; a single sharp line was observed at 70.8 ppm (4.0 ppm of fwhm). A systematic study of the 13C-CP/MAS NMR shift of ethylene oxide oligomers by Saito et al. showed that the tg conformer (-Ot-Cg-C-) gives the 13C signal at 71 ppm whereas the gg conformer (-Og-Cg-C-) gives it at 67 ppm.18 This indicates the tg conformation of PEG in the lattices of complexes 1 and 2. PEG chains are most likely included with an tg linear structure twisted from tt planar zigzag conformation. This result is reasonable because the tg conformation is very common in PEG,17-19 and the rotation of the C-C bond from trans to gauche do not significantly disperse the MO energies.20 The deduced structure of molybdenum(II) dicarboxylates including polyethers is depicted in Figure 6. Considering the linear structure of PEG and PPG, polyether chains are regularly distributed in the lattices of the complex.
In this work, we have demonstrated that the microporous molybdenum(II) dicarboxylates includes polyethers, such as poly(ethylene glycol) and poly(propylene glycol). This system is the first example of supramolecules between microporous transition metal complexes and organic polymers. This is recognized as an effective method for synthesizing hybrid supramolecules assembled through noncovalent interaction using so-called “molecular recognition”. The inclusion complex formation was strongly affected by both the structures of the guest polymers and the host micropores. The functions and shapes of the supramolecules can be controlled by the selection of the set of host complexes and guest molecules. Complex chemistry consists of the characteristics of transition metals (inorganic species) and organic ligands (organic species). Considering the distinguishable features of inorganic compounds and organic compounds, the network structure containing transition metal complexes is expected to have a wide range of features, from organic to inorganic. Even if only the host complex was considered, the possibilities of long-range organometallic conjugation is of great interest due to the ability of constructing purpose-oriented materials with useful properties, for example electronic, magnetic, optical, and catalytic materials derived from long-range pπ-dπ and/ or dπ-dπ interaction.10 Thus, the present design strategy can not only produce a new specific surface by the use of molecular recognition but also provide functional substances combined with novel physical properties including electronic and magnetic properties interacting between the host lattice and guest molecule.21 This is a new method for making purpose-built materials with useful properties. Experimental Section Measurements. The C, H, and N analyses were conducted using a commercial microanalyzer. Absorption isobars were determined gravimetrically at 20 Torr of argon from 77 to 220 K with the aid of an electric balance (Cahn, model Cahn-1000). Raman spectra were taken with a Jasco NR-1800 using a Spectra-Physics argon ion laser as the source of 514.5 nm radiation within 5 mW. A solid sample was placed in a hole formed in a glass plate and was irradiated. 13C-CP/MAS NMR spectra were measured at room temperature and at a resonance frequency of 75.47 MHz with a Bruker DSX300 spectrometer with a conventional zirconium rotor (7 mm) and a hole-free cap. N2 gas evaporated from a container of liquid N2 was used as a bearing and driving gas for magic angle spinning. The contact time was 1 ms, and the π/2 pulse length was 5 µs for both 13C and 1H nuclei. The accumulation number was between 400 and 1600, and the repetition time was 4 s.
Macromolecules, Vol. 33, No. 17, 2000 The chemical shift was measured from TMS, and hexamethylbenzene was used as an external reference. Materials. Poly(ethylene glycol) (PEG) of weight-averaged molecular weights 200 (lot. no. LEL4655), 600 (LEJ5165), 1000 (LEF1597), 1500 (LEG1485), 3000 (LEG1371), and 7500 (LEM0708) and poly(propylene glycol) (PPG) of weight-averaged molecular weights 400 (TPP2740), 700 (TPR1335), 2000 (DLG6991), and 3000 (ESM2679) were purchased from Wako Pure Chemical Industries, Ltd., and used without further purification. Other materials and solvents were purchased from commercial sources. Molybdenum(II) acetate was prepared as previously reported.22 Preparation of Inclusion Complexes. All procedures were performed in an argon atmosphere by Schlenk techniques; the solvent was dried and distilled under argon before use. Some liquid polyethers with low molecular weight were degassed and replaced by argon before use. The inclusion complexes between molybdenum(II) dicarboxylates and polyethers of various molecular weights (PEG: 200, 600, 1000, 1500, 3000, and 7500; PPG: 400, 700, 2000, and 3000) were synthesized by the one-pot method in an argon atmosphere as described next. A methanol solution (150 mL) of dicarboxylic acid (1.40 mmol), molybdenum(II) acetate (0.70 mmol), and polyether (3.08 g of PEG or 4.07 g of PPG: 70 mmol of the periodic glycol unit) was stirred for 3 days at room temperature. After a while, the yellow solution became a deep colored solution, and then it became a heterogeneous mixture. The resulting precipitate was collected by filtration, washed with methanol, and dried under a vacuum at 80 °C, producing a purple or red powder.
Acknowledgment. The authors thank Professor M. Kamachi for his helpful discussion. The present work was supported by Grant-in-Aids for Specially Promoted Research No. 06101004 (Akira Nakamura) and Scientific Research Nos. 10149253 and 10554041 from the Ministry of Education, Science, Sports and Culture of Japan. References and Notes (1) Mori, W.; Inoue, F.; Yoshida, K.; Nakayama, H.; Takamizawa, S.; Kishita, M. Chem. Lett. 1997, 1219. Mori, W.; et al., submitted. (2) Takamizawa, S.; Mori, W.; Furihata, M.; Takeda, S.; Yamaguchi, K. Inorg. Chim. Acta 1998, 283, 268.
Novel Inclusion Complexes 6227 (3) (a) Takamizawa, S.; Yamaguchi, K.; Mori, W. Inorg. Chem. Commun. 1998, 1, 177. (b) Takamizawa, S.; Ohmura, T.; Yamaguchi, K.; Mori, W. Mol. Cryst. Liq. Cryst., in press. (4) (a) Mori, W.; Takamizawa, S. Kagaku Kogyo 1998, 51, 210 (Japanese). (b) Mori, W.; Takamizawa, S. Catal. Catal. 2000, 42, 40 (Japanese). (c) Takamizawa, S. Kagaku Kogyo 2000, 53, 136 (Japanese). (d) Mori, W.; Takamizawa, S. J. Solid State Chem., in press. (5) Mori, W.; Takamizawa, S.; Fujiwara, M.; Seki, K. Patent Nos. JP 09132580, 1995, and EP 0727608, 1996. (6) van Niekerk, J. N.; Schoening, F. R. L. Acta Crystallogr. 1953, 6, 227. (7) Kondo, M.; Yoshitomi, T.; Seki, K.; Matsuzaka, H.; Kitagawa, S. Angew. Chem., Int. Ed. Engl. 1997, 36, 1725. (8) Li, H.; Eddaoudi, M.; Groy, T. L.; Yaghi, O. M. J. Am. Chem. Soc. 1998, 120, 8571. (9) Chui, S. S.-Y.; Lo, S. M.-F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. Science 1999, 283, 148. (10) Nakamura, A. Bull. Chem. Soc. Jpn. 1995, 68, 1515. Nishino, M.; Takamizawa, S.; Kitagawa, Y.; Takano, Y.; Onishi, T.; Nagao, H.; Yoshioka, Y.; Mashima, K.; Nakamura, A.; Yamaguchi, K. Bull. Chem. Soc. Jpn., submitted. (11) Lehn, J. M. Science 1985, 227, 849. (12) Harada, A.; Kamachi, M. Macromolecules 1990, 23, 2821. Harada, A.; Kamachi, M. Nature 1992, 356, 325. Harada, A.; Li, Y.; Kanachi, M. J. Am. Chem. Soc. 1994, 116, 3192. (13) Frank, C. W.; Rao, V.; Despotopoulou, M. M.; Pease, R. F. W.; Hinsberg, W. D.; Miller, R. D.; Rabolt, J. F. Science 1996, 273, 912. (14) Takamizawa, S.; Furihata, M.; Takeda, S.; Yamaguchi, K.; Mori, W. Polym. Adv. Technol., in press. (15) Bratton, W. K.; et al. J. Coord. Chem. 1971, 1, 121. (16) Takamizawa, S.; et al., in preparation. (17) Ueda, T.; Ohki, H.; Nakamura, N.; Chihara, H. Bull. Chem. Soc. Jpn. 1991, 64, 2416. (18) Tanabe, R.; Saito, H. Bull. Chem. Soc. Jpn. 1985, 58, 3215. (19) Mark, J. E.; Flory, P. J. J. Am. Chem. Soc. 1965, 87, 1415. (20) Beamson, G.; Pickup, B. T.; Li, W.; Mai, S.-M. J. Phys. Chem. B 2000, 104, 2656. (21) (a) Yamaguchi, K.; Takamizawa, S.; Kitagawa, Y.; Onishi, T.; Nagao, H.; Yoshioka, Y.; Okamura, T.; Ueyama, N. J. Chem. Phys., submitted. (b) Nagao, H.; Kitagawa, Y.; Onishi, T.; Shigeta, Y.; Takamizawa, S.; Yoshioka, Y.; Yamaguchi, K. J. Chem. Phys., submitted. (22) Stephenson, T. A.; Bannister, E.; Wilkinson, G. J. Chem. Soc. 1964, 2538.
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