Structural Variations Influenced by Ligand Conformation and

CRYSTAL GROWTH & DESIGN

Structural Variations Influenced by Ligand Conformation and Counteranions in Copper(II) Complexes with Flexible Bis-Triazole Ligand

2009 VOL. 9, NO. 1 593–601

Bin Ding,†,‡ Yuan-Yuan Liu,†,‡ Yong-Quan Huang,† Wei Shi,† Peng Cheng,*,† Dai-Zheng Liao,† and Shi-Ping Yan† Department of Chemistry, Nankai UniVersity, Tianjin 300071, P. R. China, and College of Chemistry and Life Science, Tianjin Normal UniVersity, Tianjin 300074, P. R. China ReceiVed August 14, 2008; ReVised Manuscript ReceiVed October 8, 2008

ABSTRACT: Using a flexible bis-triazole ligand 1,4-bis(triazol-1-ylmethyl)benzene (L), four new copper(II) compounds {[Cu(trans-L)(cis-L)2(H2O)2](CF3SO3)2 · 4H2O}n (1), {[Cu(cis-L)2(H2O)2](CF3SO3)2 · 2H2O}n (2), {[Cu(trans-L)2]Cl2}n (3), and {[Cu(trans-L)(cis-L)](BF4)2}n (4) have been isolated. Conformations of L in 1-4 can be tuned as a result of changing the anion or metal/ligand ratio in the reaction system, which ultimately form a series of novel framework structures varying from 1D to 3D with different supramolecular architectures. 1 is a 1D single-chain structure, in which trinuclear water clusters link adjacent triflate anions to form 1D supramolecular helix. 2 is composed of right-helical Cu(II) bis-triazole chains, which are interlinked via copper(II) ions as hingers forming a novel 2D layered structure. Eight-member supramolecular cycles constructed by coordinated water molecules and free triflate anions are found to be embedded into the 2D planes of 2. 3 contains 2D planar nanogrid networks stacked in an AB stacking fashion. Triple Cl · · · H-C hydrogen bonds reside between these 2D layers. 4 is a 3D MOF with large 1D rhombic channels with dimensionalities of 10.102 × 14.067 Å2 accommodating BF4- anions, which also represents the first case of metal bis-triazole compound with CdSO4 topology. For 1-4, FT-IR and elemental analysis has been carried out, and the conformational variation of L also has been briefly discussed. Introduction

Scheme 1

In recent years, there has been great interest in the construction of metal-organic frameworks (MOFs) due to their interesting properties such as magnetic, electronic, nonlinear optical (NLO) properties and intriguing structural motifs varying from extended coordination polymers to discrete molecular entities such as cages, metallomacrocycles, and many others.1-3 However, it is still a great challenge to exactly predict structures and compositions of MOFs built by coordination bonds and/or supramolecular contacts because even very small tuning factors can dramatically change the framework structure.4-6 Of all these factors, the choice of ligands is key. The donor atoms, functional groups and relative position can directly determine framework structures. Moreover, flexible ligands also have attracted especial interest because their flexible conformations are expected to produce many intriguing architectures such as polymorph, entanglement and so on.7,8 As the simple small molecular ligands, 1,2,4-triazole and its derivatives are very interesting not only because they can be used as spin crossover materials which has the potential application in information storage but also they can form a variety of novel structural motifs. We are interested in the exploring metal triazole9 and bis-triazole10 systems. Recently using the flexible ligand 1,2-bis(triazol-1-ylmethyl)ethane we reported a series of Zn(II) and Cd(II) complexes with interesting framework structures and supramolecular architectures.11 As a continuous investigation of previous work, herein 1,4-bis(triazol1-ylmethyl)benzene (L) with rigid benzene spacers are chosen. As illustrated in Scheme 1, the conformational flexibility of L not only arises from the relative rotation of two triazole groups about the line connecting two methylene carbon atoms (Csp3),

and the rotation of each triazole ring about the corresponding Csp3-N bond, but also the rotation of the benzene ring around the Csp3 · · · Csp3 line.12 These motions make the conformation of L highly flexible and tunable as spacers to link two metal centers. Four novel complexes, {[Cu(trans-L)(cis-L)2(H2O)2](CF3SO3)2 · 4H2O}n (1), {[Cu(cis-L)2(H2O)2] (CF3SO3)2 · 2H2O}n (2), {[Cu(trans-L)2]Cl2}n (3), and {[Cu(trans-L)(cis-L)](BF4)2}n (4) were obtained. They exhibited novel framework structures varying from 1D to 3D with interesting supramolecular architectures, which may help us further understand the nature of crystal engineering.

* To whom correspondence should be addressed. E-mail: pcheng@nankai. edu.cn. † Nankai University. ‡ Tianjin Normal University.

Experimental Section General Methods. Ligand L was prepared by literature methods.13 All commercially available chemicals are reagent grade and used as

10.1021/cg8008943 CCC: $40.75  2009 American Chemical Society Published on Web 12/02/2008

594 Crystal Growth & Design, Vol. 9, No. 1, 2009

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Table 1. Crystal Data and Structure Refinement Information for Compounds 1-4a

empirical formula formula weight crystal system space group a (Å) b (Å) c (Å) β (°) V (Å3) Z F (g/cm3) µ (mm-1) F(000) crystal size (mm3) θ (°) limiting indices reflections /collected/unique data/restraints/parameters good of fit on F2 final R indices (I > 2σ (I)) R indices (all data) largest diff. peak and hole (e. Å-3) a

1

2

3

4

C38H48CuF6N18O12S2 1190.60 monoclinic P21/c 12.065(2) 8.3587(13) 25.861(4) 99.548(3) 2571.9(7) 2 1.537 0.604 1226 0.22 × 0.20 × 0.12 1.60 to 26.38 -14 e h e 15 -10 e k e 6 -32 e l e 31 14194/5246 [R(int) ) 0.0668] 5246/10/373 1.007 R1 ) 0.0476 wR2 ) 0.0983 R1 ) 0.1207 wR2 ) 0.1244 0.400 and-0.334

C26H32CuF6N12O10S2 914.30 monoclinic C2/c 22.296(12) 9.268(5) 20.969(11) 119.640(5) 3766(3) 4 1.613 0.789 1868 0.36 × 0.22 × 0.12 2.10 to 25.03 -26 e h e 23 -9 e h e 11 -24 e l e 24 9823/3320 [R(int) ) 0.0200] 3320/4/259 1.080 R1 ) 0.0556 wR2 ) 0.1465 R1 ) 0.0625 wR2 ) 0.1508 1.092 and -0.386

C12H12ClCu0.50N6 307.50 monoclinic P21/c 7.6671(16) 21.327(4) 8.5287(18) 106.559(2) 1336.8(5) 4 1.528 1.057 630 0.32 × 0.20 × 0.12 2.67 to 25.03 -9 e h e 9 -25 e k e 19 -10 e l e 9 7140/2362 [R(int) ) 0.0220] 2362/0/178 1.071 R1 ) 0.0313 wR2 ) 0.0879 R1 ) 0.0407 wR2 ) 0.0917 0.403 and -0.467

C24H24B2CuF8N12 717.71 monoclinic C2/c 24.199(4) 9.6398(16) 15.528(3) 124.507(3) 2985.0(9) 4 1.597 0.822 1452 0.22 × 0.20 × 0.16 2.04 to 26.38 -30 e h e 18 -12 e k e 12 -14 e l e 19 8255/3047 [R(int) ) 0.0540] 3047/14/270 1.004 R1 ) 0.0494 wR2 ) 0.1102 R1 ) 0.1041 wR2 ) 0.1382 0.418 and-0.471

R1 )∑|Fo|-|Fc|/|Fo|, wR2 ) [∑w(Fo2-Fc2)2/∑w(Fo2)2]1/2.

received without further purification. Deionized water was used as solvent in this work. C, H, and N microanalyses were carried out with a Perkin-

Elmer 240 elemental analyzer. FT-IR spectra were recorded from KBr pellets in the range 4000-400 cm-1 on a Bio-Rad FTS 135 spectrometer.

Figure 1. (a) Coordination geometry of copper(II) center in (b) The 1D chain structure with trinuclear water clusters. Cyan, Cu; blue, N; gray, C; red, O; white, H; red dot line, hydrogen bonding.

Structural Variations in Cu(II) Complexes

Crystal Growth & Design, Vol. 9, No. 1, 2009 595

Figure 2. (a) 3D supramolecular architecture of 1 (terminal ligands are omitted for clarity) and (b) 1D supramolecular helical chain constructed via trinuclear water clusters and free triflate anions (Cyan, Cu; blue, N; gray, C; red, O; yellow, S; green, F; red dot line, hydrogen bonding).

Figure 3. Coordination geometry of copper(II) center in 2. Preparation of Compounds 1-4. {[Cu(trans-L)(cis-L)2(H2O)2](CF3SO3)2 · 4H2O}n (1). Compound 1 was prepared by refluxing L (3.0 mmol) and Cu(CF3SO3)2 (1.0 mmol) in 15 mL of aqueous solution for 1 h. The precipitate was filtrated and blue crystals were isolated from the filtrate after several days. Yield: 60% (based on L). Anal. Calc. C38H48F6CuN18O12S2 (1190.60): C, 38.33; H, 4.06; N, 21.17. Found: C, 38.54; H, 4.27; N, 21.38%. IR data (cm-1): 3444 (bs), 1653 (s), 1541 (m), 1384 (s), 1283 (vs), 1193 (m), 1126 (s), 1103 (m), 1036 (s), 896 (m), 867 (m), 779 (m), 734 (m), 632 (m), 498 (w). {[Cu(cis-L)2(H2O)2](CF3SO3)2 · 2H2O}n (2). Compound 2 was prepared by refluxing L (2.0 mmol) and Cu(CF3SO3)2 (1.0 mmol) in 15 mL of water solution for 1 h. The precipitate was filtrated, and blue crystals were isolated from the filtrate after several days. Yield: 52% (based on L). Anal. Calc. C26H32CuF6N12O10S2: (914.30): C, 34.16; H, 3.53; N, 18.38. Found: C, 34.37; H, 3.55; N, 18.62%. IR data (cm-1): 3141 (bs), 1619 (s), 1384 (s), 1271 (m), 1173 (m), 1025 (w), 773 (m), 669 (m), 647 (m), 561 (w).

{[Cu(trans-L)2]Cl2}n (3). Compound 3 was prepared by refluxing L (2.0 mmol) and CuCl2 · 2H2O (1.0 mmol) in 15 mL of water solution for 1 h. The precipitate was filtrated, and blue crystals were isolated from the filtrate after several days. Yield: 45% (based on L). Anal. Calc. C24H24Cl2CuN12 (614.98): C, 46.87; H, 3.93; N, 27.34. Found: C, 46.95; H, 3.97; N, 27.50%. IR data (cm-1): 1623 (bm), 1531 (s), 1400 (m), 1280 (m), 1206 (m), 1126 (vs), 1012 (m), 991 (m), 896 (w), 870 (m), 776 (m), 734 (m), 676 (w). {[Cu(trans-L)(cis-L)](BF4)2}n (4). Compound 4 was prepared by refluxing L (2.0 mmol) and Cu(BF4)2 (1.0 mmol) in 15 mL of water solution for 1 h. The precipitate was filtrated, and blue crystals were isolated from the filtrate after several days. Yield: 38% (based on L). Anal. Calc. C24H24B2CuF8N12: (717.71): C, 40.17; H, 3.37; N, 23.42. Found: C, 40.37; H, 3.54; N, 23.52%. IR data (cm-1): 3445 (w), 1634 (s), 1507 (m), 1400 (m), 1280 (m), 1126 (m), 1081 (s), 879 (m), 722 (m), 673 (m). X-ray Crystallography. Diffraction intensities for complexes 1-4 were collected on a Bruker SMART 1000 CCD diffractometer with graphite-monochromated Mo KR radiation (λ ) 0.71073 A) by using the ω-φ scan technique. Lorentz polarization and absorption corrections were applied. The structures were solved by direct methods and refined with the full-matrix least-squares technique using the SHELXS97 and SHELXL-97 programs.14 An empirical absorption correction was applied (SADABS).14c Anisotropic thermal parameters were assigned to all non-hydrogen atoms. The organic hydrogen atoms were generated geometrically; the hydrogen atoms of the water molecules were located from difference maps and refined with isotropic thermal parameters. Analytical expressions of neutral-atom scattering factors were employed, and anomalous dispersion corrections were incorporated. The crystallographic data and details of refinements for compounds 1-4 are summarized in Table 1, selected bond lengths and angles are listed in Table S1. CCDC-605864 (1), -605866 (2), -605865 (3), and -605863 (4) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge


Ding et al.

Figure 4. (a) 2D homochiral helical structure using the copper atoms as the hinges. (b) Space-filling view of 2D layer (Cyan, Cu).

Figure 5. (a) 8-Membered supramolecular cycles embedded in the 2D layers. (b) Side view of the 2D layer (Cyan, Cu; blue, N; gray, C; red, O; yellow, S; green, F; red dot line, hydrogen bonding). from The Cambridge Crystallographic Data Centre via www.ccdc. cam.ac.uk/data_request/cif.

Results and discussion Structural Description of 1-4. As shown in Figure 1, the asymmetric unit in 1 consists of one copper(II) center, one transL, two cis-L, two free triflate anions, two coordinated, and four lattice water molecules. The Cu(II) ion, lying a crystallographic inversion center, is six-coordinated to two water molecules axially and four nitrogen atoms from four ligands in a squareplanar fashion. The axial Cu(1)-O(1) distance (2.411(1) Å) is much longer than those Cu-O distances (1.967(5) to 1.977(5) Å) in the previous Cu(II)-triazole ligand complex [Cu3(µ3OH)L3(ClO4)(H2O)2](ClO4) · 2H2O (L ) 3-acetylamino-1,2,4triazolate), which can be attributed to Jahn-Teller elongation.8c trans-L ligands bridge copper(II) centers to form a 1D singlechain structure while cis-L ligands only act as unidendate terminal ligands. O(1) from coordination water molecules and

O(5), O(6) from lattice water molecules generate strong intermolecular hydrogen bonds and construct trinuclear water clusters, in which O(1) acts as hydrogen donor and O(5), O(6) act as hydrogen bonding acceptors. The hydrogen bond distances are 2.824(4) Å (O(1)-H(1B) · · · O(6)) and 2.737(3) Å (O(1)H(1A) · · · O(5)). The average distance of trimer water cluster is 2.781(4) Å, which is similar to O · · · O distance (2.75 Å) in the structure of ice(Ic).15 It is notable that trinuclear water clusters furthermore link adjacent triflate anions to form 1D helical supramolecular chains along the crystallographic b axis (Figure 2), which cross-link the 1D metal-ligand single-chains of 1 into a 3D supramolecular architecture. O(5), O(6) from trinuclear clusters act as hydrogen bonding donors and O(2), O(4) from triflate anions act as hydrogen bonding acceptors. The corresponding hydrogen bonding distances are 2.840(5) Å (O(5)H(5B) · · · O(2)) and 2.966(3) Å (O(6)-H(6A) · · · O(4)). Additionally N(5) and N(6) from unidendate cis-L ligands and O(5), O(6) from trinuclear clusters also generate intermolecular



Figure 6. (a) Coordination geometry of copper(II) center in 3. (b) 2D grid layer of 3. cyan, Cu; green, Cl; blue, N; gray, C. (c) the space-filling view of ABAB... packing structure for 3 (Cyan, Cu; blue, N; gray, C; red, O; green, Cl).

Figure 7. Triple Cl · · · H-C hydrogen bondings reside in the neighboring ABAB... stacking layers for 3 (the neighboring AB layers are represented in blue or red; green, Cl; purple dot line, hydrogen bond).

hydrogen bonds (O(5)-H(5A) · · · N(6) ) 2.806(1) Å, (O(6)H(6B) · · · N(5) ) 2.968(1) Å), which furthermore stabilize the 3D supramolecular architecture. When the ratio of Cu(CF3SO3)2 to L change from 1:3 to 1:2, complex 2 with 2D (4,4) layer structure is obtained. 2 contains one copper(II) center, two cis-L, two free triflate anions, two coordinated and two lattice water molecules (Figure 3). For 2 the elongated octahedral coordination environment around copper(II) ions are close to those of 1. However there is a little difference about the basic structural units of 1 and 2. In 2 the copper(II) ion lies in the general position and only comprises two lattice water molecules in comparison to that of 1. The main difference between 1 and 2 is that all L ligands adopt cis coordination mode in 2 while 1 simultaneously contains one trans- and two cis-L ligands. The most interesting thing is that Cu(II) ions in 2 link two ligands to form right-handed helical chains along the b axis. The width of the helix is calculated to be 11.7 Å, and the pitch

is 9.3 Å (neighboring Cu · · · Cu distances). The 1D helical structure in 2 also can be compared to previously reported 1D right-helical compound [Zn(bte)(Cl)2] (bte ) 1,2-bis(1,2,4triazole-1-yl)ethane),11 in which Zn(II) center is only fourcoordinated. Furthermore the 1D helical chains are in an orderly arrangement with Cu(II) centers as hinges to form a 2D (4,4) layer plane along the crystallographic ac plane (Figure 4). However, to the best of our knowledge, 2 also represents a scarcely reported case of 2D complexes containing right-handed helical chains in the metal bis-triazole systems. The result also reveals that these bis-traizole ligands may have autoresolved into separate right-handed crystals from the solution.16,17 In compound 2 coordinated water molecules and oxygen atoms from triflate anions generate 8-member supramolecular cycles (Figure 5), which are found to be embedded in the 2D plane via linking copper centers in the 2D plane. The hydrogen bonding distances are 2.77(7) Å (O(1)-H(1A) · · · O(3)) and


Ding et al.

Figure 8. (a)Coordination geometry of copper(II) center in 4. (b)The 3D MOF of 4 along the b axis with BF4- anions occupying the channels (Cyan, Cu; blue, N; gray, C; green F; red, B). (c) (65,8) CdSO4 topology of the MOF 4.

2.77(8) Å (O(2)-H(2A) · · · O(4)), respectively (These hydrogen bondings are definded by platon program).14d When CuCl2 is used in the reaction system to instead of Cu(CF3SO3)2, a 2D complex 3 with (4,4) net is obtained. The asymmetric unit of 3 contains one copper(II) center, two trans-L and two chloride atoms. Cu(II) center is also four-coordinated to four nitrogen atoms from four trans-L in the equatorial plane and two chloride ions occupying the axial positions. Cu-N distances (Cu(1)-N(1A) (2.022(3) Å), Cu(1)-N(5) (2.032(19) Å) are also close to those of 1 and 2 while axial weak Cu-Cl distance (2.840(3) Å) is much longer than those Cu-Cl distances (2.279(2) and 2.257(3) Å) in the previous Cu(II) complexes.8d Therefore the coordination environment of copper ions also can be described as the “4 + 2” coordination mode.

In 3 each trans-L ligand links two Cu(II) ions by its aromatic nitrogen atoms acting as a bridging bidentate ligand. Each Cu(II) ion is linked by four trans-L ligands with four neighboring Cu(II) ions to form a rhombohedral grid with a metal ion at each corner and a molecule of L at each edge linking two metal ions (Figure 6). All Cu ions in each layer are strictly coplanar, thus affording a 2D network with (4,4) topology structure. The 2D grid motif has the dimensionalities of 14.5 Å × 14.5 Å (metal-metal distances). The 2D grid layers are closely stacked in an offset way (Figure 6c). Two neighboring offset planes have triple Cl · · · H-C hydrogen bondings, in which chloride atoms act as three hydrogen-bondings acceptors to link two hydrogen atoms from the same plane and one hydrogen atom from neighboring plane


Crystal Growth & Design, Vol. 9, No. 1, 2009 599 Scheme 2

(Figure 7). Cl · · · H distances are 2.67(9) Å (Cl(1) · · · H(1)), 2.72(1) Å (Cl(1) · · · H(11)), and 2.81(2) Å (Cl(1) · · · H(12)), respectively. The nonclassical Cl · · · H-C hydrogen bonds weaken the axial Cu-Cl bonds and may play an important role for stabling the offset packing way of 2D planes.18 When BF4- anions are used, an unprecedented 3D MOFs {[Cu(trans-L)(cis-L)](BF4)2}n (4) is obtained. In 4 the asymmetric unit contains one [Cu(trans-L)(cis-L)] cation unit and two BF4- anions. The copper(II) ion, lying in the inversion center, is four-coordinated to four nitrogen atoms of four ligands and strictly coplanar with four N atoms. As can be seen in Figure 8a, each copper(II) center links four trans-L ligands to four neighboring copper(II) ions, thus extending into a 3D metal-organic framework. In the 3D MOF, 1D rhombic channel with dimensionalities of 10.102(23) Å × 14.067(33) Å (metal-metal distances) exist along the crystallographic b axis. Four fluoride atoms of BF4- anions and C(5), C(6) atoms of benzene ring in L ligands are disordered. The disordered BF4- anions occupy the 1D channel (Figure 8b), The F(1) atoms have weak interactions with central copper(II) ions and Cu-F distance is 2.449(2) Å; therefore, the coordination environment of copper ions can also be described as the “4 + 2” coordination mode (a normal Cu-F bond length should be below 2.3 Å). As for the topological geometry, the copper ion can be seen as four connected nodes and the ligand can be regarded as twoconnected linker. As is shown in Figure 8c, the structure of 4 can be simplified into a (65,8) CdSO4 topological geometry sustained by 4-connected nodes.19 The compounds with CdSO4 topological geometry have been reported, while for triazole complexes 4 may represent the first case with CdSO4 topological geometry. One 1D, two 2D, and one 3D coordination polymers with L have been isolated and structurally characterized. Scheme 3 lists the supramolecular environment around L ligands in 1-4 and corresponding hydrogen bonds paramaters are listed in Table S2. The basic structural units of 1-4 can be seen as similar Cu(L)4(H2O)2 (1 and 2), Cu(L)4(Cl)2 (3), and Cu(L)4(BF4)2 (4), respectively (considering Cu-Cl and Cu-F weak interactions).

The axial ligands variation of 1-4 can also be thought to spatial effect of anions. The very large volume of CF3SO3- make axial sites of basic structural units of 1 and 2 are occupied by aqua ligands and CF3SO3- acts as free anion while Cl- and BF4occupy the axial sites in 3 and 4 because of relatively small volumes. However the axial Cu-Cl and Cu-F bonds are weak, which is greatly affected by the supramolecular interactions between anions and ligands. The most typical example is that in 3 triple C-H · · · Cl hydrogen bonds obviously weaken Cu-Cl bonds. For 4 C-H · · · F interactions can also be observed, which also directed the conformation of L and weaken Cu-F bonds. It is also interesting that when a different initial amount of ligand is used in 1 and 2 a different amount of lattice water molecules is involved in the system. (For 1 four lattice water molecules per unit are involved forming trinuclear water clusters, which further link free CF3SO3- anions forming 1D supramolecular helix, whereas for 2 two lattice water molecules per unit are involved. No water clusters are observed, and eight-member supramolecular cycles constructed by coordinated water molecules and free triflate anions are found to be embedded into the 2D planes of 2.) The structural types and variations of supramolecular architectures in 1-4 are shown in Scheme 2. In the M/L ratio of 1:2, pure cis or trans ligands give 2D MOFs with 8-member supramolecular cycles (2) or triple Cl · · · H-C hydrogen bondings (3), whereas mixed cis and trans ligands give 3D MOFs (4), and the ratio of cis/trans is 1:1. While we changed the ratio of Cu/L from 1:2 to 1:3 in the existence of CF3SO3- anions, mixed cis and trans L ligands give 1D MOFs with 1D supramolecular helical chains (1). The ratio of cis/trans L varies from 1:1 in 4 to 1:2 in 1. Though the copper(II) centers in 1-4 adopt similar octahedral coordination geometries, ascrbing to the flexible nature and long spacers of L, when different anions or M/L ratio are introduced, different supramolecular architectures in 1-4 can be obtained. Further the supramolecular interactions involving L also dramaticelly change and greatly affect the conformations of L, which ultimately can obtain different novel metal-organic frameworks. As is shown in


Ding et al. Scheme 3

Scheme 3, trinuclear water clusters are important for the formation of cis-L. For 1-4 it can be thought that the ratio of cis- and transligands, coordination bonds, and supramolecular contacts all lie in a dynamic equilibrium in the solution. It is also obvious that some factors such as variations of ratio between metal salts/ ligands and counterions can affect the dynamic equilibrium in the solution which ultimately induce that 1-4 crystallize in different structural dimensionalities and supramolecular architectures from the solutions. Though the influences on the final conformation ratio of cis- and trans-ligands in the crystal structure are rather intricate, the results also still reveal that the strategy via tuning the ratio between metal salts/ligands and counterions is an effective tool for constructing new MOFs and the potential of L for preparation of solids with intriguing structural motifs which may cause interesting functional materials. Interestingly it is noted that this work also can be compared with previous result, in which using three different anions three

1D copper(II) compounds [Cu(L)(H2O)2(NO3)2], [Cu(L)2(CH3CN)2](ClO4)2(H2O)2, and [Cu(L)2(H2O)2](ClO4)2(DMF)3 also have been isolated by Li et al.20 The result is quite different from the framework structure of 1-4, which also again proved that the strategy of tuning anions and ligand conformations indeed is effective to obtain various different interesting framework structures in the crystal engineering. Synthesis and General Characterization. Although we have tried varying the rate of Cu(CF3SO3)2 with ligand from 1:1 to 1:2 to 1:3, only the 1:2 complexes and 1:3 complexes were obtained. For 3 and 4 we also tried different ratio of ligand/ metal in the preparation process, however under similar conditions only powder or microcrystals can be obtained. All the complexes are stable in room temperature, and not soluble in general organic solvent. The presence of BF4- anions is evidenced by the strong bands at ca. 1080.9 cm-1 in 4.21 The FT-IR spectra of 1 and 2 have


strong peaks at 3443.7 and 3141.4 cm-1, respectively, which can be attributed that O-H stretch of lattice and coordinated water molecules. The intermolecular hydrogen bonds make the peaks become wider. For 1-4 the peak at ca. 800 cm-1 can be assigned to an out-of-ring C-H bend vibration while the bands in the range of 1600∼1500 cm-1 can be assigned to the stretch vibrations of CdN (triazole) and CdC (benzene ring).21


(6) (7)

Conclusion In summary, 1D, 2D, and 3D coordination polymers based on cis and trans bis-triazole ligands were isolated and characterized by X-ray single-crystal diffraction. The structural motifs of polymers are profoundly influenced by diversity in ligand conformation. For bis-triazole systems, it is still of great interest to understand the flexibility of the ligand. However the differences among these structures indicate that variations of the counteranions and ligand conformation play an important role in controling the formation of the frameworks and specific supramolecular architecture constructed from the bis-triazole ligands.

(8)

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Acknowledgment. This work was supported by the National Natural Science Foundation of China (20631030 and 20425103) and the State Key Project of Fundamental Research of MOST (2007CB815305 and 2007AA05Z109), P. R. China. Supporting Information Available: Additional tables and CIF files of data. This material is available free of charge via the Internet at http://pubs.acs.org.

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CG8008943

Structural Variations Influenced by Ligand Conformation and

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