Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270111048591/sk3421sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270111048591/sk3421Isup2.hkl |
CCDC reference: 862221
2,4,6-Trimethylbenzene-1,3,5-tricarboxylic acid (H3TMBTC) was synthesized according to the method of Zimmerman and co-workers with modifications (Kolotuchin et al., 1999). The product was recrystallized from acetonitrile (yield 90%) as white needles. 1H NMR (300 MHz, d6-DMSO, δ, p.p.m.): 2.33 (s, 9H, CH3), 13.51 (s, 3H, COOH).
A mixture of Cd(NO3)2.4H2O (20 mg, 0.06 mmol), H3TMBTC (10 mg, 0.05 mmol) and bpy (10 mg, 0.06 mmol) was suspended in a mixed solvent of H2O (8 ml) and EtOH (8 ml), and heated in a Teflon-lined steel bomb at 413 K for 3 d. Colourless crystals of (I) (14 mg) were collected, washed with water and dried in air (yield 51%, based on Cd)
All H atoms were generated geometrically and allowed to ride on their parent atoms in the riding-model approximation, with aromatic C—H = 0.93 Å and methyl C—H = 0.96 Å, and with Uiso(H) = 1.2Ueq(C).
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).
[Cd3(C12H9O6)2(C10H8N2)2] | F(000) = 1132 |
Mr = 1147.95 | Dx = 1.853 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 5089 reflections |
a = 14.178 (4) Å | θ = 4.4–55.6° |
b = 9.481 (3) Å | µ = 1.61 mm−1 |
c = 15.901 (4) Å | T = 298 K |
β = 105.772 (4)° | Block, colourless |
V = 2056.9 (10) Å3 | 0.10 × 0.08 × 0.06 mm |
Z = 2 |
Bruker SMART APEXII CCD area-detector diffractometer | 4037 independent reflections |
Radiation source: fine-focus sealed tube | 3371 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.031 |
ω and ϕ scans | θmax = 26.0°, θmin = 1.5° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −8→17 |
Tmin = 0.856, Tmax = 0.910 | k = −11→11 |
10768 measured reflections | l = −19→19 |
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)] = 0.028 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.068 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0327P)2] where P = (Fo2 + 2Fc2)/3 |
4037 reflections | (Δ/σ)max = 0.001 |
289 parameters | Δρmax = 0.42 e Å−3 |
0 restraints | Δρmin = −0.44 e Å−3 |
[Cd3(C12H9O6)2(C10H8N2)2] | V = 2056.9 (10) Å3 |
Mr = 1147.95 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 14.178 (4) Å | µ = 1.61 mm−1 |
b = 9.481 (3) Å | T = 298 K |
c = 15.901 (4) Å | 0.10 × 0.08 × 0.06 mm |
β = 105.772 (4)° |
Bruker SMART APEXII CCD area-detector diffractometer | 4037 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 3371 reflections with I > 2σ(I) |
Tmin = 0.856, Tmax = 0.910 | Rint = 0.031 |
10768 measured reflections |
R[F2 > 2σ(F2)] = 0.028 | 0 restraints |
wR(F2) = 0.068 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.42 e Å−3 |
4037 reflections | Δρmin = −0.44 e Å−3 |
289 parameters |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 | ||
Cd1 | 0.771640 (18) | 0.52474 (2) | 0.551725 (15) | 0.02109 (8) | |
Cd2 | 0.5000 | 0.5000 | 0.5000 | 0.01788 (9) | |
C1 | 0.9447 (3) | 0.4259 (4) | 0.7264 (2) | 0.0443 (10) | |
H1 | 0.8913 | 0.3833 | 0.7394 | 0.053* | |
C2 | 1.0369 (3) | 0.4064 (5) | 0.7827 (3) | 0.0509 (11) | |
H2 | 1.0451 | 0.3519 | 0.8328 | 0.061* | |
C3 | 1.1164 (3) | 0.4688 (5) | 0.7636 (3) | 0.0550 (12) | |
H3 | 1.1790 | 0.4586 | 0.8011 | 0.066* | |
C4 | 1.1013 (3) | 0.5469 (5) | 0.6875 (3) | 0.0476 (10) | |
H4 | 1.1541 | 0.5871 | 0.6722 | 0.057* | |
C5 | 1.0074 (3) | 0.5646 (4) | 0.6346 (2) | 0.0302 (8) | |
C6 | 0.9852 (3) | 0.6524 (3) | 0.5533 (2) | 0.0299 (8) | |
C7 | 1.0588 (3) | 0.7247 (4) | 0.5268 (3) | 0.0461 (10) | |
H7 | 1.1241 | 0.7165 | 0.5585 | 0.055* | |
C8 | 1.0326 (4) | 0.8079 (5) | 0.4532 (3) | 0.0559 (12) | |
H8 | 1.0801 | 0.8560 | 0.4341 | 0.067* | |
C9 | 0.9349 (3) | 0.8190 (5) | 0.4081 (3) | 0.0570 (12) | |
H9 | 0.9150 | 0.8760 | 0.3588 | 0.068* | |
C10 | 0.8681 (3) | 0.7440 (5) | 0.4378 (3) | 0.0553 (12) | |
H10 | 0.8023 | 0.7516 | 0.4072 | 0.066* | |
C11 | 0.6348 (3) | 0.7695 (3) | 0.5818 (2) | 0.0250 (7) | |
C12 | 0.6290 (2) | 0.9069 (3) | 0.62936 (19) | 0.0187 (6) | |
C13 | 0.6224 (2) | 0.9017 (3) | 0.71552 (19) | 0.0200 (7) | |
C14 | 0.6304 (2) | 1.0292 (3) | 0.7621 (2) | 0.0192 (7) | |
C15 | 0.6447 (2) | 1.1574 (3) | 0.72446 (19) | 0.0187 (7) | |
C16 | 0.6522 (2) | 1.1586 (3) | 0.63824 (19) | 0.0186 (7) | |
C17 | 0.6424 (2) | 1.0336 (3) | 0.5888 (2) | 0.0193 (7) | |
C18 | 0.6134 (3) | 0.7614 (3) | 0.7574 (2) | 0.0321 (8) | |
H20A | 0.6748 | 0.7123 | 0.7691 | 0.048* | |
H20B | 0.5633 | 0.7062 | 0.7186 | 0.048* | |
H20C | 0.5965 | 0.7766 | 0.8112 | 0.048* | |
C19 | 0.6334 (3) | 1.0220 (3) | 0.8583 (2) | 0.0235 (7) | |
C20 | 0.6568 (3) | 1.2931 (3) | 0.7774 (2) | 0.0311 (8) | |
H22A | 0.6425 | 1.2755 | 0.8321 | 0.047* | |
H22B | 0.6127 | 1.3633 | 0.7453 | 0.047* | |
H22C | 0.7231 | 1.3262 | 0.7881 | 0.047* | |
C21 | 0.6869 (2) | 1.2899 (3) | 0.60285 (19) | 0.0207 (7) | |
C22 | 0.6486 (3) | 1.0345 (4) | 0.4954 (2) | 0.0336 (9) | |
H21A | 0.7151 | 1.0179 | 0.4945 | 0.050* | |
H21B | 0.6274 | 1.1245 | 0.4694 | 0.050* | |
H21C | 0.6072 | 0.9618 | 0.4630 | 0.050* | |
N1 | 0.9293 (2) | 0.5043 (3) | 0.6533 (2) | 0.0325 (7) | |
N2 | 0.8915 (2) | 0.6606 (3) | 0.50797 (19) | 0.0350 (7) | |
O1 | 0.71997 (19) | 0.7195 (3) | 0.59759 (19) | 0.0473 (7) | |
O2 | 0.55904 (19) | 0.7180 (2) | 0.53426 (16) | 0.0409 (7) | |
O3 | 0.71851 (19) | 1.0169 (3) | 0.91004 (16) | 0.0393 (7) | |
O4 | 0.55527 (19) | 1.0209 (3) | 0.87886 (16) | 0.0401 (7) | |
O5 | 0.76949 (18) | 1.2854 (2) | 0.58802 (17) | 0.0378 (6) | |
O6 | 0.63847 (17) | 1.4037 (2) | 0.59336 (14) | 0.0276 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cd1 | 0.02155 (14) | 0.02020 (13) | 0.02218 (14) | −0.00208 (9) | 0.00709 (10) | −0.00026 (9) |
Cd2 | 0.01812 (18) | 0.01808 (17) | 0.01859 (17) | −0.00225 (12) | 0.00696 (14) | −0.00367 (12) |
C1 | 0.041 (2) | 0.048 (2) | 0.040 (2) | −0.0086 (19) | 0.003 (2) | 0.0099 (19) |
C2 | 0.053 (3) | 0.053 (3) | 0.039 (2) | 0.001 (2) | 0.000 (2) | 0.009 (2) |
C3 | 0.035 (3) | 0.071 (3) | 0.050 (3) | 0.006 (2) | −0.003 (2) | 0.003 (2) |
C4 | 0.027 (2) | 0.065 (3) | 0.049 (3) | 0.001 (2) | 0.007 (2) | 0.002 (2) |
C5 | 0.0260 (19) | 0.0292 (18) | 0.036 (2) | −0.0014 (15) | 0.0090 (16) | −0.0087 (15) |
C6 | 0.032 (2) | 0.0268 (18) | 0.035 (2) | −0.0022 (15) | 0.0163 (17) | −0.0075 (15) |
C7 | 0.036 (2) | 0.048 (2) | 0.058 (3) | −0.0074 (19) | 0.019 (2) | −0.002 (2) |
C8 | 0.060 (3) | 0.048 (3) | 0.074 (3) | −0.008 (2) | 0.042 (3) | 0.008 (2) |
C9 | 0.061 (3) | 0.054 (3) | 0.060 (3) | −0.003 (2) | 0.025 (3) | 0.023 (2) |
C10 | 0.050 (3) | 0.061 (3) | 0.053 (3) | −0.007 (2) | 0.010 (2) | 0.022 (2) |
C11 | 0.039 (2) | 0.0168 (16) | 0.0227 (18) | −0.0039 (15) | 0.0138 (16) | −0.0011 (13) |
C12 | 0.0167 (16) | 0.0179 (15) | 0.0204 (16) | −0.0003 (12) | 0.0031 (13) | −0.0024 (12) |
C13 | 0.0175 (17) | 0.0217 (16) | 0.0211 (16) | −0.0024 (13) | 0.0056 (14) | 0.0008 (13) |
C14 | 0.0201 (17) | 0.0230 (16) | 0.0162 (16) | −0.0002 (13) | 0.0078 (13) | 0.0004 (12) |
C15 | 0.0198 (17) | 0.0184 (15) | 0.0189 (16) | 0.0011 (12) | 0.0072 (13) | −0.0017 (12) |
C16 | 0.0183 (17) | 0.0150 (15) | 0.0221 (16) | 0.0013 (12) | 0.0046 (14) | 0.0022 (12) |
C17 | 0.0190 (17) | 0.0209 (16) | 0.0177 (16) | −0.0029 (13) | 0.0045 (13) | −0.0010 (12) |
C18 | 0.043 (2) | 0.0249 (18) | 0.030 (2) | −0.0046 (16) | 0.0114 (17) | 0.0017 (15) |
C19 | 0.032 (2) | 0.0185 (16) | 0.0213 (17) | 0.0016 (14) | 0.0101 (16) | −0.0006 (12) |
C20 | 0.046 (2) | 0.0240 (17) | 0.0258 (19) | −0.0034 (15) | 0.0131 (17) | −0.0038 (14) |
C21 | 0.0240 (19) | 0.0200 (16) | 0.0166 (16) | −0.0031 (13) | 0.0031 (14) | −0.0013 (12) |
C22 | 0.052 (3) | 0.0308 (19) | 0.0212 (18) | −0.0103 (17) | 0.0152 (17) | −0.0028 (14) |
N1 | 0.0265 (17) | 0.0343 (17) | 0.0352 (18) | −0.0037 (12) | 0.0055 (14) | 0.0013 (13) |
N2 | 0.0296 (18) | 0.0413 (18) | 0.0340 (17) | −0.0069 (14) | 0.0084 (14) | 0.0057 (14) |
O1 | 0.0378 (17) | 0.0308 (14) | 0.077 (2) | 0.0007 (12) | 0.0224 (15) | −0.0187 (13) |
O2 | 0.0514 (18) | 0.0197 (12) | 0.0406 (15) | −0.0079 (12) | −0.0060 (14) | −0.0061 (11) |
O3 | 0.0292 (15) | 0.0654 (19) | 0.0221 (13) | 0.0013 (12) | 0.0050 (12) | 0.0056 (12) |
O4 | 0.0339 (16) | 0.0654 (18) | 0.0265 (14) | 0.0012 (13) | 0.0175 (12) | 0.0068 (12) |
O5 | 0.0302 (15) | 0.0278 (13) | 0.0614 (17) | −0.0011 (11) | 0.0224 (13) | 0.0086 (12) |
O6 | 0.0317 (14) | 0.0189 (12) | 0.0317 (13) | 0.0048 (10) | 0.0075 (11) | 0.0055 (9) |
Cd1—O1 | 2.184 (2) | C11—C12 | 1.519 (4) |
Cd1—O3i | 2.208 (2) | C12—C13 | 1.399 (4) |
Cd1—O5ii | 2.343 (2) | C12—C17 | 1.400 (4) |
Cd1—N2 | 2.382 (3) | C13—C14 | 1.406 (4) |
Cd1—N1 | 2.383 (3) | C13—C18 | 1.508 (4) |
Cd1—O6ii | 2.449 (2) | C14—C15 | 1.394 (4) |
Cd2—O2 | 2.241 (2) | C14—C19 | 1.520 (4) |
Cd2—O4iii | 2.277 (2) | C15—C16 | 1.404 (4) |
Cd2—O6iv | 2.304 (2) | C15—C20 | 1.522 (4) |
C1—N1 | 1.347 (5) | C16—C17 | 1.408 (4) |
C1—C2 | 1.381 (5) | C16—C21 | 1.503 (4) |
C1—H1 | 0.9300 | C17—C22 | 1.511 (4) |
C2—C3 | 1.379 (6) | C18—H20A | 0.9600 |
C2—H2 | 0.9300 | C18—H20B | 0.9600 |
C3—C4 | 1.385 (6) | C18—H20C | 0.9600 |
C3—H3 | 0.9300 | C19—O4 | 1.238 (4) |
C4—C5 | 1.378 (5) | C19—O3 | 1.263 (4) |
C4—H4 | 0.9300 | C20—H22A | 0.9600 |
C5—N1 | 1.348 (4) | C20—H22B | 0.9600 |
C5—C6 | 1.498 (5) | C20—H22C | 0.9600 |
C6—N2 | 1.331 (4) | C21—O5 | 1.256 (4) |
C6—C7 | 1.404 (5) | C21—O6 | 1.266 (4) |
C7—C8 | 1.376 (6) | C21—Cd1v | 2.755 (3) |
C7—H7 | 0.9300 | C22—H21A | 0.9600 |
C8—C9 | 1.380 (6) | C22—H21B | 0.9600 |
C8—H8 | 0.9300 | C22—H21C | 0.9600 |
C9—C10 | 1.367 (5) | O3—Cd1vi | 2.208 (2) |
C9—H9 | 0.9300 | O4—Cd2vii | 2.277 (2) |
C10—N2 | 1.334 (5) | O5—Cd1v | 2.343 (2) |
C10—H10 | 0.9300 | O6—Cd2v | 2.304 (2) |
C11—O2 | 1.234 (4) | O6—Cd1v | 2.449 (2) |
C11—O1 | 1.258 (4) | ||
O1—Cd1—O3i | 116.07 (10) | C17—C12—C11 | 118.3 (3) |
O1—Cd1—O5ii | 135.11 (10) | C12—C13—C14 | 117.9 (3) |
O3i—Cd1—O5ii | 93.13 (10) | C12—C13—C18 | 120.0 (3) |
O1—Cd1—N2 | 88.34 (10) | C14—C13—C18 | 122.0 (3) |
O3i—Cd1—N2 | 82.60 (10) | C15—C14—C13 | 121.6 (3) |
O5ii—Cd1—N2 | 130.81 (10) | C15—C14—C19 | 120.3 (3) |
O1—Cd1—N1 | 100.40 (10) | C13—C14—C19 | 117.9 (3) |
O3i—Cd1—N1 | 132.35 (10) | C14—C15—C16 | 119.0 (3) |
O5ii—Cd1—N1 | 80.04 (9) | C14—C15—C20 | 120.5 (3) |
N2—Cd1—N1 | 68.25 (10) | C16—C15—C20 | 120.4 (3) |
O1—Cd1—O6ii | 87.28 (9) | C15—C16—C17 | 121.1 (3) |
O3i—Cd1—O6ii | 96.77 (9) | C15—C16—C21 | 119.5 (3) |
O5ii—Cd1—O6ii | 54.36 (8) | C17—C16—C21 | 118.8 (3) |
N2—Cd1—O6ii | 174.77 (9) | C12—C17—C16 | 118.1 (3) |
N1—Cd1—O6ii | 115.40 (9) | C12—C17—C22 | 120.6 (3) |
O2—Cd2—O2viii | 180.0 | C16—C17—C22 | 121.3 (3) |
O2—Cd2—O4i | 95.41 (9) | C13—C18—H20A | 109.5 |
O2viii—Cd2—O4i | 84.59 (9) | C13—C18—H20B | 109.5 |
O2viii—Cd2—O4iii | 95.41 (9) | H20A—C18—H20B | 109.5 |
O2—Cd2—O6iv | 89.30 (8) | C13—C18—H20C | 109.5 |
O2viii—Cd2—O6iv | 90.70 (8) | H20A—C18—H20C | 109.5 |
O4i—Cd2—O6iv | 85.31 (9) | H20B—C18—H20C | 109.5 |
O4iii—Cd2—O6iv | 94.69 (9) | O4—C19—O3 | 126.4 (3) |
N1—C1—C2 | 122.4 (4) | O4—C19—C14 | 118.9 (3) |
N1—C1—H1 | 118.8 | O3—C19—C14 | 114.7 (3) |
C2—C1—H1 | 118.8 | C15—C20—H22A | 109.5 |
C3—C2—C1 | 119.1 (4) | C15—C20—H22B | 109.5 |
C3—C2—H2 | 120.5 | H22A—C20—H22B | 109.5 |
C1—C2—H2 | 120.5 | C15—C20—H22C | 109.5 |
C2—C3—C4 | 118.7 (4) | H22A—C20—H22C | 109.5 |
C2—C3—H3 | 120.6 | H22B—C20—H22C | 109.5 |
C4—C3—H3 | 120.6 | O5—C21—O6 | 120.6 (3) |
C5—C4—C3 | 119.5 (4) | O5—C21—C16 | 117.3 (3) |
C5—C4—H4 | 120.2 | O6—C21—C16 | 121.9 (3) |
C3—C4—H4 | 120.2 | O5—C21—Cd1v | 57.90 (16) |
N1—C5—C4 | 121.9 (3) | O6—C21—Cd1v | 62.73 (17) |
N1—C5—C6 | 115.7 (3) | C16—C21—Cd1v | 173.3 (2) |
C4—C5—C6 | 122.4 (3) | C17—C22—H21A | 109.5 |
N2—C6—C7 | 121.5 (3) | C17—C22—H21B | 109.5 |
N2—C6—C5 | 116.4 (3) | H21A—C22—H21B | 109.5 |
C7—C6—C5 | 122.1 (3) | C17—C22—H21C | 109.5 |
C8—C7—C6 | 119.0 (4) | H21A—C22—H21C | 109.5 |
C8—C7—H7 | 120.5 | H21B—C22—H21C | 109.5 |
C6—C7—H7 | 120.5 | C1—N1—C5 | 118.3 (3) |
C7—C8—C9 | 119.1 (4) | C1—N1—Cd1 | 122.1 (3) |
C7—C8—H8 | 120.5 | C5—N1—Cd1 | 119.4 (2) |
C9—C8—H8 | 120.5 | C6—N2—C10 | 118.2 (3) |
C10—C9—C8 | 118.2 (4) | C6—N2—Cd1 | 119.8 (2) |
C10—C9—H9 | 120.9 | C10—N2—Cd1 | 122.0 (3) |
C8—C9—H9 | 120.9 | C11—O1—Cd1 | 130.1 (2) |
N2—C10—C9 | 124.0 (4) | C11—O2—Cd2 | 136.0 (2) |
N2—C10—H10 | 118.0 | C19—O3—Cd1vi | 132.2 (2) |
C9—C10—H10 | 118.0 | C19—O4—Cd2vii | 139.7 (2) |
O2—C11—O1 | 127.0 (3) | C21—O5—Cd1v | 95.09 (19) |
O2—C11—C12 | 119.3 (3) | C21—O6—Cd2v | 139.0 (2) |
O1—C11—C12 | 113.8 (3) | C21—O6—Cd1v | 89.91 (19) |
C13—C12—C17 | 122.3 (3) | Cd2v—O6—Cd1v | 102.99 (8) |
C13—C12—C11 | 118.9 (3) |
Symmetry codes: (i) x, −y+3/2, z−1/2; (ii) x, y−1, z; (iii) −x+1, y−1/2, −z+3/2; (iv) −x+1, −y+2, −z+1; (v) x, y+1, z; (vi) x, −y+3/2, z+1/2; (vii) −x+1, y+1/2, −z+3/2; (viii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [Cd3(C12H9O6)2(C10H8N2)2] |
Mr | 1147.95 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 298 |
a, b, c (Å) | 14.178 (4), 9.481 (3), 15.901 (4) |
β (°) | 105.772 (4) |
V (Å3) | 2056.9 (10) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 1.61 |
Crystal size (mm) | 0.10 × 0.08 × 0.06 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.856, 0.910 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10768, 4037, 3371 |
Rint | 0.031 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.068, 1.03 |
No. of reflections | 4037 |
No. of parameters | 289 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.42, −0.44 |
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2008), publCIF (Westrip, 2010).
Cd1—O1 | 2.184 (2) | Cd1—O6ii | 2.449 (2) |
Cd1—O3i | 2.208 (2) | Cd2—O2 | 2.241 (2) |
Cd1—O5ii | 2.343 (2) | Cd2—O4iii | 2.277 (2) |
Cd1—N2 | 2.382 (3) | Cd2—O6iv | 2.304 (2) |
Cd1—N1 | 2.383 (3) | ||
O1—Cd1—O3i | 116.07 (10) | O3i—Cd1—O6ii | 96.77 (9) |
O1—Cd1—O5ii | 135.11 (10) | O5ii—Cd1—O6ii | 54.36 (8) |
O3i—Cd1—O5ii | 93.13 (10) | N2—Cd1—O6ii | 174.77 (9) |
O1—Cd1—N2 | 88.34 (10) | N1—Cd1—O6ii | 115.40 (9) |
O3i—Cd1—N2 | 82.60 (10) | O2—Cd2—O4i | 95.41 (9) |
O5ii—Cd1—N2 | 130.81 (10) | O2v—Cd2—O4i | 84.59 (9) |
O1—Cd1—N1 | 100.40 (10) | O2v—Cd2—O4iii | 95.41 (9) |
O3i—Cd1—N1 | 132.35 (10) | O2—Cd2—O6iv | 89.30 (8) |
O5ii—Cd1—N1 | 80.04 (9) | O2v—Cd2—O6iv | 90.70 (8) |
N2—Cd1—N1 | 68.25 (10) | O4i—Cd2—O6iv | 85.31 (9) |
O1—Cd1—O6ii | 87.28 (9) | O4iii—Cd2—O6iv | 94.69 (9) |
Symmetry codes: (i) x, −y+3/2, z−1/2; (ii) x, y−1, z; (iii) −x+1, y−1/2, −z+3/2; (iv) −x+1, −y+2, −z+1; (v) −x+1, −y+1, −z+1. |
Recently, the design and synthesis of metal–organic frameworks (MOFs) have attracted much attention due to their interesting topologies and potential applications in fields such as gas adsorption, nonlinear optics, magnetism, molecular recognition etc. (Evans & Lin, 2002; Chen et al., 2010; Leong & Vittal, 2011; Sun et al., 2011). The construction of novel MOFs with desired topologies based on carboxylates is still a huge challenge since many factors, such as the geometry of the ligand, metal ion and solvent, influence the resulting structure of the MOFs (Sun et al., 2010). The widely used carboxylic acids, including aliphatic and aromatic carboxylic acids, often participate in coordination with transition metals, rare earth metal ions or mixed metal ions, exhibiting diverse coordination modes such as monodentate bridging, bidentate chelating or bridging (Ma et al., 2008; Zhang et al., 2008). In these carboxylate-based MOFs, the carboxyl groups and central benzene rings almost are coplanar, which is one of the most important factors in determining the topology of the final structure. Despite the fact that MOFs constructed from 1,3,5-benzenetricarboxylic acid (H3BTC) have been widely reported, to the best of our knowledge, only one MOF based on H3TMBTC (2,4,6-trimethylbenzene-1,3,5-tricarboxylic acid) has been documented to date (He et al., 2010). The introduction of methyl groups on the C atoms between the carboxyl groups may generate novel MOFs different from those constructed from the planar BTC ligand. Based on the above-mentioned points and our previous work (Sun et al., 2009; Dai et al., 2008; Zhao et al., 2009), we describe here the structure of the title compound, (I), obtained using trimethyl-decorated H3BTC and bpy (2,2'-bipyridine) as mixed ligands and CdII ions. The components build an infinite two-dimensional sheet incorporating hourglass-like [Cd3(COO)6] secondary building units (SBUs), which can be simplified to a (3,6)-connected 2-nodal net with the rare kgd (Kagomé dual) topology (O'Keeffe et al., 2007).
The asymmetric unit of (I) contains two crystallographically independent CdII centres, one TMBTC ligand and one bpy ligand. As shown in Fig. 1, atom Cd1 is six-coordinated by two N atoms of the same bipy ligand and four carboxylate O atoms from three different TMBTC ligands, giving a distorted octahedral coordination geometry. Atom Cd2, located on a crystallographic inversion centre, has a CdO6 octahedral environment surrounded by six carboxyl groups from six different TMBTC ligands. The Cd—N bond lengths are identical to within experimental error and the average Cd—O distance is 2.281 (2) Å (Table 1), comparable with values reported for Cd-based MOFs (Liu et al., 2008; Zhang et al., 2003; Zhou et al., 2003). Of the three carboxyl groups, one carboxyl group of the TMBTC ligand adopts a bidentate–chelating/bridging mode, and the other two carboxyl adopt a bidentate-bridging mode. The three CdII atoms are bridged by six carboxyl groups to form a trinuclear hourglass-like [Cd3(COO)6] SBU with a Cd···Cd contact of 3.7205 (12) Å. Because of the steric hindrance between the methyl and carboxyl groups, the three carboxyl groups of the TMBTC ligand are not coplanar with the central benzene ring, with dihedral angles of 88.2 (4), 83.9 (2) and 63.1 (2)°, respectively, much larger than those found in MOFs constructed by BTC (Chui et al., 1999).
The hourglass-like [Cd3(COO)6] SBUs are joined by TMBTC ligands to form an infinite two-dimensional sheet (Fig. 2). The bpy ligand acts as a terminal group to occupy the remaining coordinate sites, which prevents the structure from attaining higher dimensionalities. Adjacent two-dimensional sheets are interdigitated with each other to form a resulting three-dimensional supramolecular framework (Fig. 3). This framework is reinforced by a weak intersheet π–π interaction (Janiak, 2000) between the bpy ligands, with a Cg1···Cg2vi separation of 3.721 (3) Å [Cg1 and Cg2 are the centroids of the N1/C1–C5 and N2/C6–C10 rings, respectively; symmetry code: (vi) -x + 2, -y + 1, -z + 1], and by a C—H···π interaction [C3—H3···Cg3vii = 143°, H3···Cg3vii = 2.63 Å and C3···Cg3vii = 3.418 (5) Å; Cg3 is the centroid of the C12–C17 ring; symmetry code: (vii) -x + 2, y - 1/2, -z + 3/2].
An appealing structural feature of (I) is that the two-dimensional sheet can be seen as a rare kgd network by simplifying the TMBTC ligand as a 3-connecting node and the trinuclear hourglass-like [Cd3(COO)6] SBUs as a 6-connecting node (Figs. 4a and 4b). Therefore, the whole two-dimensional sheet can be represented as a (3,6)-connected 2-nodal net with a kgd topology (Fig. 4c). The ratio of 3-connecting nodes (vertex symbol 43) and 6-connecting nodes (vertex symbol 46.66.83) in this net is 2:1. Therefore, the short Schläfli vertex notation of the net can be represented as {43}2{46.66.83}, as indicated by the TOPOS software (Blatov, 2006). To the best of our knowledge, regular (4,4), (6,3) and (3,6) nets are the three most common topologies observed in two-dimensional coordination networks (Batten & Robson, 1998). The offset overlap of two common (6,3) nets connected together by CdII ions thus yields a kgd net. The TMBTC ligands in this kgd net are non-coplanar and are arranged alternately up and down to form a concavo–convex kgd net. Despite the fact that a kgd net can be constructed theoretically by employing a six-coordinate metal centre and a trigonal tridentate ligand, it is hard to achieve in practice due to the requirement of an approximately planar 6-connecting node, which illustrates why there are few cases known, even though there are various known coordination polymers based on trigonal ligands (Zheng et al., 2008).