Novel Cluster Coordination Polymers Based on Tetranuclear Nest-Shaped [WOS3Cu3] Heterothiometallitic Secondary Building Units and 4,4′-Bipyridine Ligand Kai Liang,*,†,‡ He-Gen Zheng,*,‡ Ying-Lin Song,§ Yi-Zhi Li,‡ and Xin-Quan Xin‡
CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 2 373-376
Shanghai Key Laboratory of Molecular Catalysis and InnoVatiVe Material, Department of Chemistry, Fudan UniVersiy, Shanghai 200433, P. R. China, State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing UniVersity, Nanjing 210093, P. R. China, and Department of Physics, Harbin Institute of Technology, Harbin 150001, P. R. China ReceiVed September 11, 2006; ReVised Manuscript ReceiVed NoVember 5, 2006
ABSTRACT: Two novel cluster coordination polymers, {[W4O4S12Cu12Cl2(4,4′-bipy)12]2Cl.4H2O}n (1) and {[(n-Bu)4N]2[W2O2S6Cu6Br4(4,4′-bipy)3]}n (2) (4,4′-bipy ) 4,4′-bipyridine), based on tetranuclear nest-shaped heterothiometallatillic secondary building units [WOS3Cu3] have been synthesized and characterized by X-ray diffraction. Compound 1 shows a 3D 3-fold interpenetrated cationic diamondoid structure, whereas compound 2 shows a 1D anionic zigzag pattern. Both of them exhibit excellent third-order nonlinear optical (NLO) properties. Introduction The field of inorganic-organic composite coordination polymer design is attractive because of its potential application in porous materials, nonlinear optical materials, and catalytic reactions.1 Most of coordination polymers were prepared by simple assembly of metal ions with organic ligands.2 However, the concept of the secondary build units (SBUs) as the metal ion replacement is applied with eminent success to the design of highly porous and rigid metal-organic frameworks (MOFs).3 The heterothiometallic clusters W(Mo)/Cu/S have received a great deal of attention because these clusters exhibit various skeletal structures and strong third-order nonlinear optical (NLO) effects.4 A series of heterothiometallates such as cubanelike, half-open cubanelike, hexagonal prism-shaped, nest-shaped, twin-nest-shaped, butterfly-shaped, twenty-nuclear supracagelike structure have been prepared in the early stage. Interestingly, in some cases, several inorganic heterothiometallic polymeric clusters utilizing the heterothiometallates and bridging inorganic anions (S2-, Cl-, Br-, I-, SCN-, CN-) have appeared.5 However, few examples are known in which heterothiometallic clusters W(Mo)/Cu/S are assembled with organic bridging ligands.6 We herein report the crystal structures and third-order NLO properties of an unprecedented 3D 3-fold interpenetrated cationic diamondoid cluster coordination polymer {[W4O4S12Cu12Cl2(4,4′-bipy)12]2Cl·4H2O}n 1 and 1D anionic zigzag cluster coordination polymer {[(n-Bu)4N]2[W2O2S6Cu6Br4(4,4′-bipy)3]}n 2 based on [WOS3Cu3] secondary build units and 4,4′-bipy ligands. Experimental Section General Methods. All reactions and manipulations were performed under nitrogen gas. Solvents were used without purification. The starting material (NH4)2WO2S2 was prepared according to the literature,7 and other chemicals were used as commercially available. Elemental analyses were performed on Perkin-Elmer 240C microanalyzers. IR spectra were recorded on a Brucker Vector 22 FT-IR spectrophotom* To whom correspondence should be addressed. Fax: 86-21-65641740. Tel: 86-21-65643458. E-mail:
[email protected] (K.L.); hegenz@ yahoo.com (H.-G.Z.). † Fudan University. ‡ Nanjing University. § Harbin Institute of Technology.
eter with use of KBr pellets. For UV-visible spectra, a Shimadzu UV3100 UV-VIS-NIR recording spectrophotometer was used. Synthesis of {[W4O4S12Cu12Cl2(4,4′-bipy)12]2Cl‚4H2O}n (1). (NH4)2WO2S2 (0.16 g, 0.5 mmol), CuCl (0.10 g,1mmol), (n-Bu)4NCl (0.28 g, 1 mmol), and 4,4′-bipyridine (0.16 g, 1 mmol) were dissolved in 15 cm3 of DMF and the solution was stirred under a N2 atmosphere for 12 h. The final reaction solution was filtered and the yellow filtrate was carefully added to 10 cm3 of MeCN on the top. Three weeks later, some white precipitate was filtered and the clear filtrate was allowed to stand for 2 months at ambient temperature to give orange crystals (yield 10%). Calcd for C120H104Cl4Cu12N24O8S12W4: C, 35.72; H, 2.60; N, 8.33. Found: C, 35.68; H, 2.56; N, 8.41. IR (KBr): 3422 (w), 1658 (s), 1601 (s), 1530 (m), 1483 (m), 1408 (s), 1285(m), 1216 (m), 1066 (m), 922(m), 808 (s), 626 (m), 428 (s) cm-1. Synthesis of {[(n-Bu)4N]2[W2O2S6Cu6Br4(4,4′-bipy)3]}n (2). (NH4)2WO2S2 (0.16 g, 0.5 mmol), CuBr (0.14 g, 1 mmol), (n-Bu)4NBr (0.32 g, 1 mmol), and 4,4′-bipy (0.16 g, 1 mmol) were added to CH2Cl2 (20 mL) and stirred in a reaction tube for 12 h at room temperature; the solution was filtered, and a dark red filtration solution was obtained. The dropwise addition of ether (10 mL) to the top of the solution led to some red diamondoid crystals that were filtered several days later (yield 25%). Calcd for C62H96Br4Cu6N8O2S6W2: C, 33.15; H, 4.31; N, 4.99. Found: C, 33.27; H, 4.42; N, 5.31. IR (KBr, cm-1): 3449 (m), 3052 (w), 2925 (w), 1728 (m), 1661 (s), 1602 (s), 1530 (m), 1486 (m), 1411 (s), 1217 (m), 1067 (m), 921 (s), 809 (s), 630 (m), 430 (m). X-ray Crystallography. X-ray intensity data of compounds 1 and 2 were collected on a Bruker Smart APEX CCD diffractometer with graphite-monochromated MoKR radiation (λ ) 0.71073 Å) with the ω scan mode at room temperature. Empirical absorption corrections were applied to the data using the SADABS program.8 The structures were solved by direct methods and refined by the full-matrix method on the basis of F2. All calculations were performed using the SHELXTL program.8 The crystallographic and refinement data for compounds 1 and 2 are listed in Table 1. Nonlinear Optical Measurements. The DMF solution of the cluster coordination polymer 1 (4.46 × 10-5 mol dm-3) or 2 (1.25 × 10-4 mol dm-3) was placed in a 2 mm quartz cuvette for optical property measurements, which were performed with linearly polarized 8 ns pulses at 532 nm, generated from a Q-switched frequency-doubled Nd:YAG laser. The compound 1 and compound 2 are stable toward air and laser light under the experimental conditions. The spatial profiles of the optical pulses were of nearly Gaussian transverse mode. The pulsed laser was focused onto the sample cell with a 30 cm focal length mirror. The energy of the input and output pulses were measured simultaneously by precision laser detectors (818J-09B energy probes), which were linked to a computer by an RS232 interface, whereas the incident pulse energy was varied by a Newport Com. Attenuator. The interval between the laser pulses was chosen to be 1 s to avoid the influence of thermal
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Liang et al.
Table 1. Crystallographic Data for 1 and 2
empirical formula fw cryst syst space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z λ (Å) Dcalcd (g cm-3) F(000) µ(Mo KR) (cm-1) T (K) S Rint Ra wRb a
1
2
C120H104N24O8S12Cl4Cu12W4 4034.67 monoclinic C2/c 17.7743(16) 25.311(2) 16.5981(15) 90.00 105.408(2) 90.00 7198.9(11) 2 0.71073 1.861 3920 5.218 293 1.016 0.028 0.0409 0.1024
C31H48N4OS3Br2Cu3W 1123.20 triclinic P1h 9.8430(10) 12.9740(10) 17.362(2) 97.650(10) 101.500(10) 108.650(10) 2011.8(4) 2 0.71073 1.854 1098 6.585 293 0.949 0.043 0.0348 0.0674
R ) ∑||Fo| - |Fc||/∑|Fo|. bwR ) {∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]}1/2.
and long-term effects. The third-order NLO absorptive and refractive properties of compounds 1 and 2 were determined by performing Z-scan measurements.9 The sample was mounted on a translation stage that was controlled by the computer to move along the axis of the incident laser beam (Z-direction) with respect to the focal point instead of being positioned at its focal point. For determining both the sign and magnitude of the nonlinear refraction, a 0.2 mm diameter aperture was placed in front of the transmission detector and the transmittance recorded as a function of the sample position on the Z axis (closedaperture Z-scan). For measuring the nonlinear absorption, the Zdependent sample transmittance was taken without the aperture (open aperture Z-scan).
bipy ligands and two µ-Cl atoms. In the whole molecule, there is 3-fold interpenetrated diamondoid structure (Figure 3). The whole void of the cell is 191 Å3,12 and the disordered H2O molecules and chloride ions are in voids. The cluster coordination polymer 2 consists of interesting infinite zigzag anionic chains [W2O2S6Cu6Br4(4,4′-bipy)3]2-n
Results and Discussion Compounds 1 and 2 are synthesized by self-assembly of (NH4)2WO2S2, CuX, (n-Bu)4NX (X ) Cl, 1; X ) Br, 2), and 4,4′-bipy with the same mol ratio 1:2:2:2. However, to our surprise, an X-ray single-crystal structure determination reveals that compound 1 is a cationic 3-fold interpenetrated diamondoid structure and that compound 2 is anionic zigzag structure. Although every attempt is tried, only the compound [CuI(4,4′bipy)]n10 was obtained when we used CuI instead. Single-crystal structure analysis of compound 1 reveals that it has a 3-fold interpenetrated cationic diamondoid structure. As shown in Figure 1, it is composed of the nest-shaped secondary building units [WOS3Cu3], which are connected by 4,4′-bipy molecules and µ-Cl atoms via three Cu atoms. The bond lengths and angles of the secondary building units are all within the normal range. The coordination environment of three Cu atoms is different: Cu(1) is coordinated by N(1) and N(2) atoms from two bridged 4,4′-bipy ligands, Cu(2) is coordinated by a N(3) atom from one bridged 4,4′-bipy ligand and a N(5) atom from a monodentate 4,4′-bipy ligand, whereas Cu(3) is coordinated by one µ-Cl(1) atom and one N(4) atom from a bridged 4,4′-bipy ligand. Thus, a diamondoid structure has been formed (Figure 2). Although some 3-fold diamondoid structures have been reported,11 the most unique feature of this diamondoid structure is that it has three types of six-membered rings. The first six-membered ring comprised [WOS3Cu3] secondary building units and two parallel double bridged 4,4′-bipy ligands, two single bridged 4,4′-bipy ligands, and two µ-Cl atoms; the second six-membered ring comprised two parallel double bridged 4,4′bipy ligands and four single bridged 4,4′-bipy ligands; and the third six-membered ring comprised four single bridged 4,4′-
Figure 1. ORTEP diagram of the asymmetric unit of the cluster coordination polymer 1.
Figure 2. Diamondoid structure of the cationic cluster coordination polymer 1. Hydrogen atoms are omitted for clarity. Color code: W, violet; S, yellow; Cu, orange; Cl, green; O, red; C, gray; N, blue.
Cluster Coordination Polymers Based on [WOS3Cu3] Units
Figure 3. Three-fold interpenetrated cationic diamondoid framework formed by compound 1. The red, green, and blue colors each represent one independent cationic cluster coordination polymer; hydrogen atoms are omitted for clarity.
Figure 4. ORTEP diagram of the asymmetric unit of 2.
and (n-Bu)4N+ cations. The cations have expected structure as well as normal distances and angles, which will not be discussed further. As shown in Figure 4, the asymmetric unit of the anionic part of cluster coordination polymers 2 consists of the nestshaped secondary building units [WOS3Cu3], 4,4′-bipy ligands, and Br atoms. Two [WOS3Cu3] units and two 4,4′-bipy molecules form octanuclear metallacycles, and the distance between the adjacent metallacycles is about 11.2 Å. There are face-to-face weak π-π interactions between the two 4,4′-bipy rings in the metallacycles, and the center-to-center distance between two parallel 4,4′-bipy planes is about 3.9 Å. The coordination circumstance of the three Cu atoms is different: Cu(1) is tetrahedrally coordinated by N(1) and N(2) atoms from two 4,4′-bipy ligands and S(1), S(3) atoms from WOS32-; the Cu(2) atom is coordinated by N(3), S(1), S(2), and Br(1) atoms,
Figure 5. One-dimensional anionic zigzag structure of 2.
Crystal Growth & Design, Vol. 7, No. 2, 2007 375
whereas Cu(3) is triangularly coordinated by S(2), S(3), and Br(2) atoms. The most attractive character of the anionic part is that it exhibits an infinite zigzag chain, from which a single 4,4′-bipy bridge and a double parallel 4,4′-bipy bridge are alternately connected through [WOS3Cu3] SBUs (Figure 5). To the best of our knowledge, this structure characterization has not been found in the one-dimensional chain coordination polymers. In the whole molecule, the cations and anions are stacked alternately (see the Supporting Information). The UV-vis spectrum (see the Supporting Information) of compounds 1 and 2 has relatively low linear absorption in the visible and near-IR regions, promising low intensity loss and little temperature change caused by photon absorption when light propagates in the materials. UV-vis absorption spectra demonstrate that the NLO responses are clear without interference of other absorption at λ ) 532 nm used in the Z-scan technique. The third-order NLO properties of both of compounds were investigated by Z-scan method.9 The typical third-order NLO absorptive and refractive effects of 1 and 2 have been shown in which the filled squares represent experimental data, whereas the solid lines represent the theoretical curve on the basis of experimental data (see the Supporting Information). A reasonably good fit between the experimental data and theoretical curve was obtained, which suggest that the experimentally obtained NLO effects are effectively a third-order process. The NLO absorptive coefficients R2 and the NLO refractive indices n2 of compound 1 were calculated to be 2.67 × 10-6 m W-1 M-1 and 4.91 × 10-13 m2 W-1 M-1, respectively. The NLO absorptive coefficients R2 and the NLO refractive indices n2 of compound 2 were calculated to be 3.36 × 10-6 m W-1 M-1 and 2.88 × 10-13 m2 W-1 M-1, respectively. Comparing the NLO characteristics exhibited by compounds 1 and 2, compound 1 containing 3D framework topologies has a better NLO refractive effect than compound 2 containing 1D framework topologies, whereas compound 2 containing a 1D framework has better NLO absorptive effects than compound 1 containing a 3D framework. The results indicate that both compounds have strong NLO absorptive and self-focusing effects, and are better than those of some semiconductors or organic polymers.13 Both cluster coordination polymers using 4,4′-bipy organic linkers have larger NLO coefficients than some cluster monomeric species containing other organic ligands, such as [WOS3Cu3I(py)5] (R2 ) 1.5 × 10-6 m W-1 M-1; n2 ) 1.88 × 10-13 m2 W-1 M-1),14 [WOS3Cu3Br(2,2′-bipy)2] (R2 ) 6 × 10-7 m W-1 M-1; n2 ) 1.81 × 10-14 m2 W-1 M-1)15 and [WOS3Cu3(4pic)6]·Br (R2 ) 3.15 × 10-7 m W-1 M-1; n2 ) 1.57 × 10-14 m2 W-1 M-1).16 Conclusions In summary, two new cluster coordination polymers, {[W4O4S12Cu12Cl2(4,4′-bipy)12]2Cl·4H2O}n (1) and {[(n-Bu)4N]2[W2O2S6Cu6Br4(4,4′-bipy)3]}n (2), have been synthesized using
376 Crystal Growth & Design, Vol. 7, No. 2, 2007
the heterothiometallic tetranuclear nest-shaped [WOS3Cu3] as SBUs. Compound 1 possess a 3D 3-fold interpenetrated cationic diamondoid structure, whereas compound 2 shows a 1D anionic zigzag pattern. This study demonstrates that the tetranuclear nest-shaped heterothiometallatillic secondary building units [WOS3Cu3] can be utilized to produce diverse cluster coordination polymers. Current efforts toward the other pentamuclear planar secondary building units [WS4Cu4] are underway. Acknowledgment. This research was supported by the National Natural Science Fund and Postdoctoral Foundation of China. Supporting Information Available: Selected bond lengths and angles of 1 and 2; UV-vis spectra of 1 and 2; schematic diagram of 1; packing diagram of 2 and the third-order NLO absorptive and refractive diagram of 1 and 2; X-ray crystallographic files in CIF format for 1 and 2. This material is available free of charge via the Internet at http://pubs.acs.org.
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