Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807050465/bt2533sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807050465/bt2533Isup2.hkl |
CCDC reference: 667180
All reagents and solvents were used as obtained without further purification. The CHN elemental analyses were performed on a Perkin–Elmer elemental analyzer.
A mixture of copper chloride dihydrate (17.1 mg, 0.1 mmol), NaOH (8 mg, 0.2 mmol), and oxalic acid (12.7 mg, 0.1 mmol) in water (5 ml) was stirred for 15 min at 60 degree, then L1 (15 mg, 0.1 mmol) was added to the mixture. After stirring for 50 min, the blue precipitate was collected and dissolved in a minimum amount of ammonia. Blue single crystals of 1 were obtained by slow evaporation of the ammonia solution at ambient temperature. Yield: 30 mg, 44.7%. Anal. Calculated for C18H24Cu2N8O12: C, 32.16; H, 3.57; N 16.68. Found: C, 31.96; H, 3.49; N 16.61.
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H = 0.96 Å and O—H = 0.85 Å and Uiso set to 1.2 Ueq(parent atom). The coordinates of the water H atoms were calculated by the HYDROGEN program (Nardelli, 1999).
The design and synthesis of metal–organic framework structures have received enormous attention (Lehn, 1995) in recent years. It is well known that carboxylate ligands play an important role in coordination chemistry and can adopt various binding modes such as terminal monodentate, chelating to one metal center, bridging bidentate in a syn–syn, syn–anti, and anti–anti configuration to two metal centers, and bridging tridentate to two metal centers (Policar et al., 1999; Levstein & Calvo, 1990; Rueff et al., 2001). The use of organic spacers, particularly the flexible dicarboxylates bridging ligands and rigid planar bidentate diimines (bipy or pyz) as building blocks to construct various metal assemblage is of growing interest in the field of molecular materials (Oschio & Nagashima, 1990). Recently great success has been achieved by combination of the flexible aliphatic dicarboxylates and bipy as chelating bridging ligands, which resulted in compounds having 1–three-dimensional frameworks and unique physicochemical properties (Li et al., 1997, 2000; Rodriguez-Martin et al., 2001, 2002; Lightfoot & Snedden, 1999; Maji et al., 2003; Rather & Zaworotko, 2003; Zhang et al., 2003; Liu et al., 2003). In contrast to rigid spacers, the flexible ligands, which can adopt various conformations, may induce coordination polymers with novel topologies. However, the flexible ligands containing imidazolyl groups and polycarboxylate ligands have not been well studied to date (Yang et al., 2005; Ma et al., 2003, 2004; Wen et al., 2005, 2006, 2007). Bis(N-imidazolyl)methane (L1) can be used as flexible divergent ligands to construct coordination polymer materials. As an extension of our work (Jin & Chen, 2007a,b; Jin et al., 2007), the title complex is reported here.
The compound was obtained by reacting copper chloride dihydrate, oxalic acid, and bis(N-imidazolyl)methane (L1) in basic aqueous solution and it was isolated as blue crystals. (I) is a discrete dinuclear complex, and the asymmetric unit consists of one Cu ion, one oxalate, and one bis(N-imidazolyl)methane molecule. As shown in Fig. 1, Cu ion adopts square pyramidal geometry, and each copper atom is coordinated by two nitrogen atoms from two bis(N-imidazolyl)methane as bridging ligands, two oxygen atoms from one oxalate anion in chelating mode, one water molecule, completing its tretragonal pyramidal geometry in a N2O3 donor set. The Cu—N distances of 1.991 (2) and 1.977 (2) Å are normal and well consistent with those of known Cu–imidazole complexes ranging from 1.876 (13) to 2.049 (8) Å (Zhu et al., 2005). The Cu—O(water) bond distance, being 2.229 (2) Å is much longer than those of the Cu—O(carboxylate) bond distance [1.954 (2) Å]. The oxalate anion acts as a bis-unidentate ligand and forms a five-membered ring with the copper ion, while two L1 and two Cu atoms form a sixteen-membered ring. The dimeric units are connected through strong hydrogen bonds with water molecules, yielding three dimensional network structure, which is illustrated in Fig. 2.
For related literature, see: Jin & Chen (2007a,b); Jin et al. (2007); Lehn (1995); Levstein & Calvo (1990); Li et al. (1997, 2000); Lightfoot & Snedden (1999); Liu et al. (2003); Ma et al. (2003, 2004); Maji et al. (2003); Nardelli (1999); Oschio & Nagashima (1990); Policar et al. (1999); Rather & Zaworotko (2003); Rodriguez-Martin et al. (2002, 2001); Rueff et al. (2001); Sheldrick (1996); Siemens (1996); Wen et al. (2005, 2006, 2007); Yang et al. (2005); Zhang et al. (2003); Zhu et al. (2005).
Data collection: SMART (Siemens, 1996); cell refinement: SMART (Siemens, 1996); data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Siemens, 1996); software used to prepare material for publication: SHELXTL (Siemens, 1996).
[Cu2(C2O4)2(C7H8N4)2(H2O)2]·2H2O | Z = 1 |
Mr = 671.53 | F(000) = 342 |
Triclinic, P1 | Dx = 1.716 Mg m−3 |
a = 7.970 (4) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 9.770 (4) Å | Cell parameters from 2374 reflections |
c = 9.913 (4) Å | θ = 2.4–28.0° |
α = 117.964 (4)° | µ = 1.71 mm−1 |
β = 104.582 (5)° | T = 298 K |
γ = 91.773 (5)° | Block, blue |
V = 649.7 (5) Å3 | 0.55 × 0.53 × 0.49 mm |
Siemens SMART CCD area-detector diffractometer | 2248 independent reflections |
Radiation source: fine-focus sealed tube | 1997 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.019 |
φ and ω scans | θmax = 25.0°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −9→9 |
Tmin = 0.453, Tmax = 0.487 | k = −11→11 |
3367 measured reflections | l = −11→11 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.027 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.072 | H-atom parameters constrained |
S = 1.08 | w = 1/[σ2(Fo2) + (0.0326P)2 + 0.2553P] where P = (Fo2 + 2Fc2)/3 |
2248 reflections | (Δ/σ)max = 0.001 |
181 parameters | Δρmax = 0.37 e Å−3 |
0 restraints | Δρmin = −0.36 e Å−3 |
[Cu2(C2O4)2(C7H8N4)2(H2O)2]·2H2O | γ = 91.773 (5)° |
Mr = 671.53 | V = 649.7 (5) Å3 |
Triclinic, P1 | Z = 1 |
a = 7.970 (4) Å | Mo Kα radiation |
b = 9.770 (4) Å | µ = 1.71 mm−1 |
c = 9.913 (4) Å | T = 298 K |
α = 117.964 (4)° | 0.55 × 0.53 × 0.49 mm |
β = 104.582 (5)° |
Siemens SMART CCD area-detector diffractometer | 2248 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1997 reflections with I > 2σ(I) |
Tmin = 0.453, Tmax = 0.487 | Rint = 0.019 |
3367 measured reflections |
R[F2 > 2σ(F2)] = 0.027 | 0 restraints |
wR(F2) = 0.072 | H-atom parameters constrained |
S = 1.08 | Δρmax = 0.37 e Å−3 |
2248 reflections | Δρmin = −0.36 e Å−3 |
181 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
Cu1 | 0.86641 (4) | 0.71911 (3) | 0.95989 (3) | 0.02912 (12) | |
N1 | 0.7745 (3) | 0.3018 (2) | 0.5408 (2) | 0.0287 (5) | |
N2 | 0.8596 (3) | 0.5362 (2) | 0.7528 (2) | 0.0285 (5) | |
N3 | 0.5694 (3) | 0.1755 (2) | 0.2769 (2) | 0.0276 (5) | |
N4 | 0.3642 (3) | 0.2364 (2) | 0.1309 (2) | 0.0296 (5) | |
O1 | 1.1180 (2) | 0.7196 (2) | 1.0468 (2) | 0.0360 (4) | |
O2 | 1.3453 (2) | 0.8662 (2) | 1.2644 (2) | 0.0414 (5) | |
O3 | 0.9116 (2) | 0.9180 (2) | 1.1597 (2) | 0.0450 (5) | |
O4 | 1.1263 (3) | 1.0719 (3) | 1.3829 (3) | 0.0731 (8) | |
O5 | 0.7390 (3) | 0.5676 (2) | 1.0311 (2) | 0.0476 (5) | |
H11 | 0.7729 | 0.4808 | 1.0134 | 0.071* | |
H12 | 0.7205 | 0.6120 | 1.1217 | 0.071* | |
O6 | 0.6384 (3) | 0.7255 (3) | 0.3125 (3) | 0.0540 (6) | |
H13 | 0.5560 | 0.7690 | 0.2849 | 0.081* | |
H14 | 0.7054 | 0.8012 | 0.3997 | 0.081* | |
C1 | 0.6634 (4) | 0.1548 (3) | 0.4106 (3) | 0.0338 (6) | |
H1A | 0.7356 | 0.0746 | 0.3750 | 0.041* | |
H1B | 0.5795 | 0.1197 | 0.4486 | 0.041* | |
C2 | 0.7277 (3) | 0.4185 (3) | 0.6587 (3) | 0.0305 (6) | |
H2 | 0.6164 | 0.4162 | 0.6720 | 0.037* | |
C3 | 0.9981 (3) | 0.4921 (3) | 0.6917 (3) | 0.0363 (6) | |
H3 | 1.1099 | 0.5524 | 0.7345 | 0.044* | |
C4 | 0.9473 (3) | 0.3485 (3) | 0.5607 (3) | 0.0388 (7) | |
H4 | 1.0155 | 0.2923 | 0.4966 | 0.047* | |
C5 | 0.4070 (3) | 0.2121 (3) | 0.2547 (3) | 0.0304 (6) | |
H5A | 0.3350 | 0.2192 | 0.3176 | 0.036* | |
C6 | 0.5059 (3) | 0.2145 (3) | 0.0727 (3) | 0.0337 (6) | |
H6 | 0.5134 | 0.2241 | −0.0147 | 0.040* | |
C7 | 0.6329 (3) | 0.1769 (3) | 0.1621 (3) | 0.0329 (6) | |
H7 | 0.7422 | 0.1561 | 0.1481 | 0.040* | |
C8 | 1.1908 (3) | 0.8376 (3) | 1.1850 (3) | 0.0282 (5) | |
C9 | 1.0674 (3) | 0.9537 (3) | 1.2509 (3) | 0.0376 (6) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.02589 (18) | 0.02280 (18) | 0.02358 (18) | 0.00912 (12) | 0.00161 (12) | 0.00222 (13) |
N1 | 0.0313 (11) | 0.0211 (10) | 0.0221 (11) | 0.0085 (9) | 0.0015 (9) | 0.0044 (9) |
N2 | 0.0268 (10) | 0.0248 (11) | 0.0233 (11) | 0.0069 (9) | 0.0035 (9) | 0.0053 (9) |
N3 | 0.0298 (11) | 0.0194 (10) | 0.0231 (11) | 0.0072 (8) | 0.0017 (9) | 0.0052 (8) |
N4 | 0.0274 (10) | 0.0269 (11) | 0.0254 (11) | 0.0068 (9) | 0.0029 (9) | 0.0083 (9) |
O1 | 0.0299 (9) | 0.0274 (10) | 0.0279 (10) | 0.0134 (8) | 0.0017 (8) | −0.0011 (8) |
O2 | 0.0283 (10) | 0.0393 (11) | 0.0388 (11) | 0.0068 (8) | −0.0026 (8) | 0.0115 (9) |
O3 | 0.0334 (10) | 0.0353 (11) | 0.0360 (11) | 0.0169 (8) | 0.0021 (9) | −0.0027 (9) |
O4 | 0.0508 (13) | 0.0559 (14) | 0.0430 (13) | 0.0166 (11) | 0.0006 (11) | −0.0239 (11) |
O5 | 0.0670 (13) | 0.0411 (11) | 0.0494 (12) | 0.0287 (10) | 0.0295 (11) | 0.0269 (10) |
O6 | 0.0396 (11) | 0.0561 (14) | 0.0495 (13) | 0.0163 (10) | 0.0099 (10) | 0.0142 (11) |
C1 | 0.0451 (15) | 0.0194 (12) | 0.0249 (13) | 0.0063 (11) | 0.0005 (11) | 0.0065 (11) |
C2 | 0.0291 (13) | 0.0274 (13) | 0.0257 (13) | 0.0063 (11) | 0.0065 (11) | 0.0067 (11) |
C3 | 0.0276 (13) | 0.0396 (16) | 0.0280 (14) | 0.0039 (11) | 0.0053 (11) | 0.0076 (12) |
C4 | 0.0318 (14) | 0.0427 (16) | 0.0285 (14) | 0.0147 (12) | 0.0102 (11) | 0.0061 (12) |
C5 | 0.0283 (13) | 0.0287 (14) | 0.0271 (13) | 0.0072 (11) | 0.0075 (11) | 0.0086 (11) |
C6 | 0.0337 (14) | 0.0369 (15) | 0.0280 (14) | 0.0102 (11) | 0.0086 (11) | 0.0141 (12) |
C7 | 0.0283 (13) | 0.0317 (14) | 0.0298 (14) | 0.0099 (11) | 0.0073 (11) | 0.0085 (11) |
C8 | 0.0266 (13) | 0.0239 (13) | 0.0273 (13) | 0.0052 (10) | 0.0043 (11) | 0.0092 (11) |
C9 | 0.0362 (15) | 0.0269 (14) | 0.0312 (15) | 0.0074 (11) | 0.0068 (12) | 0.0014 (12) |
Cu1—O3 | 1.9537 (19) | O3—C9 | 1.262 (3) |
Cu1—O1 | 1.9717 (19) | O4—C9 | 1.227 (3) |
Cu1—N2 | 1.977 (2) | O5—H11 | 0.8499 |
Cu1—N4i | 1.991 (2) | O5—H12 | 0.8499 |
Cu1—O5 | 2.229 (2) | O6—H13 | 0.8500 |
N1—C2 | 1.342 (3) | O6—H14 | 0.8500 |
N1—C4 | 1.373 (3) | C1—H1A | 0.9700 |
N1—C1 | 1.456 (3) | C1—H1B | 0.9700 |
N2—C2 | 1.313 (3) | C2—H2 | 0.9300 |
N2—C3 | 1.376 (3) | C3—C4 | 1.345 (4) |
N3—C5 | 1.345 (3) | C3—H3 | 0.9300 |
N3—C7 | 1.362 (3) | C4—H4 | 0.9300 |
N3—C1 | 1.456 (3) | C5—H5A | 0.9300 |
N4—C5 | 1.322 (3) | C6—C7 | 1.350 (4) |
N4—C6 | 1.372 (3) | C6—H6 | 0.9300 |
N4—Cu1i | 1.991 (2) | C7—H7 | 0.9300 |
O1—C8 | 1.273 (3) | C8—C9 | 1.542 (4) |
O2—C8 | 1.224 (3) | ||
O3—Cu1—O1 | 83.29 (7) | N3—C1—H1A | 109.5 |
O3—Cu1—N2 | 169.00 (9) | N1—C1—H1A | 109.5 |
O1—Cu1—N2 | 90.02 (8) | N3—C1—H1B | 109.5 |
O3—Cu1—N4i | 91.17 (8) | N1—C1—H1B | 109.5 |
O1—Cu1—N4i | 165.88 (8) | H1A—C1—H1B | 108.1 |
N2—Cu1—N4i | 93.33 (8) | N2—C2—N1 | 111.1 (2) |
O3—Cu1—O5 | 97.83 (9) | N2—C2—H2 | 124.4 |
O1—Cu1—O5 | 101.59 (8) | N1—C2—H2 | 124.4 |
N2—Cu1—O5 | 92.04 (9) | C4—C3—N2 | 109.8 (2) |
N4i—Cu1—O5 | 92.01 (9) | C4—C3—H3 | 125.1 |
C2—N1—C4 | 107.3 (2) | N2—C3—H3 | 125.1 |
C2—N1—C1 | 127.3 (2) | C3—C4—N1 | 106.0 (2) |
C4—N1—C1 | 125.3 (2) | C3—C4—H4 | 127.0 |
C2—N2—C3 | 105.8 (2) | N1—C4—H4 | 127.0 |
C2—N2—Cu1 | 125.91 (17) | N4—C5—N3 | 110.4 (2) |
C3—N2—Cu1 | 127.46 (17) | N4—C5—H5A | 124.8 |
C5—N3—C7 | 107.7 (2) | N3—C5—H5A | 124.8 |
C5—N3—C1 | 124.9 (2) | C7—C6—N4 | 109.4 (2) |
C7—N3—C1 | 127.2 (2) | C7—C6—H6 | 125.3 |
C5—N4—C6 | 106.1 (2) | N4—C6—H6 | 125.3 |
C5—N4—Cu1i | 126.32 (17) | C6—C7—N3 | 106.4 (2) |
C6—N4—Cu1i | 127.45 (18) | C6—C7—H7 | 126.8 |
C8—O1—Cu1 | 113.30 (15) | N3—C7—H7 | 126.8 |
C9—O3—Cu1 | 113.63 (16) | O2—C8—O1 | 126.3 (2) |
Cu1—O5—H11 | 118.7 | O2—C8—C9 | 119.4 (2) |
Cu1—O5—H12 | 117.8 | O1—C8—C9 | 114.3 (2) |
H11—O5—H12 | 110.1 | O4—C9—O3 | 125.5 (3) |
H13—O6—H14 | 103.0 | O4—C9—C8 | 119.0 (2) |
N3—C1—N1 | 110.6 (2) | O3—C9—C8 | 115.4 (2) |
O3—Cu1—N2—C2 | −164.4 (4) | C1—N1—C2—N2 | −177.8 (2) |
O1—Cu1—N2—C2 | 143.2 (2) | C2—N2—C3—C4 | 0.4 (3) |
N4i—Cu1—N2—C2 | −50.5 (2) | Cu1—N2—C3—C4 | 170.18 (19) |
O5—Cu1—N2—C2 | 41.6 (2) | N2—C3—C4—N1 | −0.6 (3) |
O3—Cu1—N2—C3 | 27.7 (5) | C2—N1—C4—C3 | 0.5 (3) |
O1—Cu1—N2—C3 | −24.6 (2) | C1—N1—C4—C3 | 178.1 (2) |
N4i—Cu1—N2—C3 | 141.7 (2) | C6—N4—C5—N3 | −0.1 (3) |
O5—Cu1—N2—C3 | −126.2 (2) | Cu1i—N4—C5—N3 | 176.06 (15) |
O3—Cu1—O1—C8 | 1.64 (18) | C7—N3—C5—N4 | 0.1 (3) |
N2—Cu1—O1—C8 | 172.90 (18) | C1—N3—C5—N4 | 174.5 (2) |
N4i—Cu1—O1—C8 | 69.1 (4) | C5—N4—C6—C7 | 0.1 (3) |
O5—Cu1—O1—C8 | −95.02 (19) | Cu1i—N4—C6—C7 | −176.04 (17) |
O1—Cu1—O3—C9 | −2.0 (2) | N4—C6—C7—N3 | 0.0 (3) |
N2—Cu1—O3—C9 | −54.8 (5) | C5—N3—C7—C6 | 0.0 (3) |
N4i—Cu1—O3—C9 | −169.0 (2) | C1—N3—C7—C6 | −174.2 (2) |
O5—Cu1—O3—C9 | 98.9 (2) | Cu1—O1—C8—O2 | −179.4 (2) |
C5—N3—C1—N1 | −92.8 (3) | Cu1—O1—C8—C9 | −1.1 (3) |
C7—N3—C1—N1 | 80.5 (3) | Cu1—O3—C9—O4 | −179.4 (3) |
C2—N1—C1—N3 | 86.0 (3) | Cu1—O3—C9—C8 | 1.9 (3) |
C4—N1—C1—N3 | −91.2 (3) | O2—C8—C9—O4 | −0.9 (4) |
C3—N2—C2—N1 | −0.1 (3) | O1—C8—C9—O4 | −179.3 (3) |
Cu1—N2—C2—N1 | −170.06 (16) | O2—C8—C9—O3 | 177.9 (2) |
C4—N1—C2—N2 | −0.3 (3) | O1—C8—C9—O3 | −0.6 (4) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O6—H14···O4ii | 0.85 | 1.98 | 2.804 (3) | 164 |
O6—H13···O2iii | 0.85 | 1.97 | 2.797 (3) | 165 |
O5—H12···O6iv | 0.85 | 1.98 | 2.823 (3) | 169 |
O5—H11···O1v | 0.85 | 2.05 | 2.895 (3) | 170 |
Symmetry codes: (ii) −x+2, −y+2, −z+2; (iii) x−1, y, z−1; (iv) x, y, z+1; (v) −x+2, −y+1, −z+2. |
Experimental details
Crystal data | |
Chemical formula | [Cu2(C2O4)2(C7H8N4)2(H2O)2]·2H2O |
Mr | 671.53 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 298 |
a, b, c (Å) | 7.970 (4), 9.770 (4), 9.913 (4) |
α, β, γ (°) | 117.964 (4), 104.582 (5), 91.773 (5) |
V (Å3) | 649.7 (5) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 1.71 |
Crystal size (mm) | 0.55 × 0.53 × 0.49 |
Data collection | |
Diffractometer | Siemens SMART CCD area-detector |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.453, 0.487 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3367, 2248, 1997 |
Rint | 0.019 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.027, 0.072, 1.08 |
No. of reflections | 2248 |
No. of parameters | 181 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.37, −0.36 |
Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Siemens, 1996).
D—H···A | D—H | H···A | D···A | D—H···A |
O6—H14···O4i | 0.85 | 1.98 | 2.804 (3) | 163.5 |
O6—H13···O2ii | 0.85 | 1.97 | 2.797 (3) | 165.1 |
O5—H12···O6iii | 0.85 | 1.98 | 2.823 (3) | 169.3 |
O5—H11···O1iv | 0.85 | 2.05 | 2.895 (3) | 170.4 |
Symmetry codes: (i) −x+2, −y+2, −z+2; (ii) x−1, y, z−1; (iii) x, y, z+1; (iv) −x+2, −y+1, −z+2. |
The design and synthesis of metal–organic framework structures have received enormous attention (Lehn, 1995) in recent years. It is well known that carboxylate ligands play an important role in coordination chemistry and can adopt various binding modes such as terminal monodentate, chelating to one metal center, bridging bidentate in a syn–syn, syn–anti, and anti–anti configuration to two metal centers, and bridging tridentate to two metal centers (Policar et al., 1999; Levstein & Calvo, 1990; Rueff et al., 2001). The use of organic spacers, particularly the flexible dicarboxylates bridging ligands and rigid planar bidentate diimines (bipy or pyz) as building blocks to construct various metal assemblage is of growing interest in the field of molecular materials (Oschio & Nagashima, 1990). Recently great success has been achieved by combination of the flexible aliphatic dicarboxylates and bipy as chelating bridging ligands, which resulted in compounds having 1–three-dimensional frameworks and unique physicochemical properties (Li et al., 1997, 2000; Rodriguez-Martin et al., 2001, 2002; Lightfoot & Snedden, 1999; Maji et al., 2003; Rather & Zaworotko, 2003; Zhang et al., 2003; Liu et al., 2003). In contrast to rigid spacers, the flexible ligands, which can adopt various conformations, may induce coordination polymers with novel topologies. However, the flexible ligands containing imidazolyl groups and polycarboxylate ligands have not been well studied to date (Yang et al., 2005; Ma et al., 2003, 2004; Wen et al., 2005, 2006, 2007). Bis(N-imidazolyl)methane (L1) can be used as flexible divergent ligands to construct coordination polymer materials. As an extension of our work (Jin & Chen, 2007a,b; Jin et al., 2007), the title complex is reported here.
The compound was obtained by reacting copper chloride dihydrate, oxalic acid, and bis(N-imidazolyl)methane (L1) in basic aqueous solution and it was isolated as blue crystals. (I) is a discrete dinuclear complex, and the asymmetric unit consists of one Cu ion, one oxalate, and one bis(N-imidazolyl)methane molecule. As shown in Fig. 1, Cu ion adopts square pyramidal geometry, and each copper atom is coordinated by two nitrogen atoms from two bis(N-imidazolyl)methane as bridging ligands, two oxygen atoms from one oxalate anion in chelating mode, one water molecule, completing its tretragonal pyramidal geometry in a N2O3 donor set. The Cu—N distances of 1.991 (2) and 1.977 (2) Å are normal and well consistent with those of known Cu–imidazole complexes ranging from 1.876 (13) to 2.049 (8) Å (Zhu et al., 2005). The Cu—O(water) bond distance, being 2.229 (2) Å is much longer than those of the Cu—O(carboxylate) bond distance [1.954 (2) Å]. The oxalate anion acts as a bis-unidentate ligand and forms a five-membered ring with the copper ion, while two L1 and two Cu atoms form a sixteen-membered ring. The dimeric units are connected through strong hydrogen bonds with water molecules, yielding three dimensional network structure, which is illustrated in Fig. 2.