Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109000559/ga3114sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109000559/ga3114Isup2.hkl |
CCDC reference: 724189
A mixture of Zn(NO3)2.6H2O (149 mg, 0.5 mmol), H2bdc (83 mg, 0.5 mmol), bib (78 mg, 0.25 mmol), water (6 ml) and ethanol (8 ml) was placed in a Teflon reactor (23 ml). The mixture was heated at 413 K for 3 d, and then it was cooled to room temperature at 5 K h-1. Colorless block-shaped crystals of (I) were obtained (yield 37%, based on Zn). Analysis calculated for C14H9N2O4Zn: C 50.25, H 2.71, N 8.37%; found: C 49.99; H 2.64; N 8.53.
All H atoms were positioned geometrically and refined using a riding model [C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C)].
Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
[Zn2(C8H4O4)2(C12H10N4)] | Z = 2 |
Mr = 334.60 | F(000) = 338 |
Triclinic, P1 | Dx = 1.744 Mg m−3 |
a = 6.9711 (14) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 8.0784 (16) Å | Cell parameters from 6093 reflections |
c = 11.903 (2) Å | θ = 3.2–27.6° |
α = 102.68 (3)° | µ = 1.95 mm−1 |
β = 99.68 (3)° | T = 293 K |
γ = 96.32 (3)° | Prism, colorless |
V = 637.1 (2) Å3 | 0.20 × 0.20 × 0.20 mm |
Bruker SMART 1000 CCD diffractometer | 1952 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.046 |
Graphite monochromator | θmax = 25.0°, θmin = 3.2° |
Detector resolution: 9 pixels mm-1 | h = −8→8 |
ω scans | k = −9→9 |
5445 measured reflections | l = −14→14 |
2244 independent reflections |
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)] = 0.043 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.103 | H-atom parameters constrained |
S = 1.11 | w = 1/[σ2(Fo2) + (0.0461P)2 + 0.183P] where P = (Fo2 + 2Fc2)/3 |
2244 reflections | (Δ/σ)max < 0.001 |
190 parameters | Δρmax = 0.45 e Å−3 |
0 restraints | Δρmin = −0.37 e Å−3 |
[Zn2(C8H4O4)2(C12H10N4)] | γ = 96.32 (3)° |
Mr = 334.60 | V = 637.1 (2) Å3 |
Triclinic, P1 | Z = 2 |
a = 6.9711 (14) Å | Mo Kα radiation |
b = 8.0784 (16) Å | µ = 1.95 mm−1 |
c = 11.903 (2) Å | T = 293 K |
α = 102.68 (3)° | 0.20 × 0.20 × 0.20 mm |
β = 99.68 (3)° |
Bruker SMART 1000 CCD diffractometer | 1952 reflections with I > 2σ(I) |
5445 measured reflections | Rint = 0.046 |
2244 independent reflections |
R[F2 > 2σ(F2)] = 0.043 | 0 restraints |
wR(F2) = 0.103 | H-atom parameters constrained |
S = 1.11 | Δρmax = 0.45 e Å−3 |
2244 reflections | Δρmin = −0.37 e Å−3 |
190 parameters |
Experimental. IR (KBr): 3434(w), 3160(m), 3145(w), 1607(s), 1525(s), 1501(m), 1440(m), 1394(s), 1363(s), 1348(s), 1326(m), 1298(m), 1273(m), 1230(m), 1131(m), 1060(m), 1014(m), 963(m), 948(w), 895(w), 862(w), 835(m), 823(s), 749(s), 653(m), 582(m), 557(m), 524(m), 498(m), 453(w). |
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 | ||
Zn1 | 0.84927 (6) | −0.01369 (5) | 0.35343 (4) | 0.03680 (18) | |
O1 | 1.0430 (4) | 0.1996 (3) | 0.4058 (2) | 0.0494 (7) | |
N1 | 0.6388 (4) | 0.0861 (4) | 0.2678 (3) | 0.0372 (7) | |
O2 | 1.2514 (4) | 0.0873 (3) | 0.5188 (2) | 0.0427 (6) | |
N2 | 0.3656 (4) | 0.1063 (4) | 0.1542 (2) | 0.0370 (7) | |
O3 | 0.9684 (4) | −0.1888 (4) | 0.2643 (2) | 0.0545 (7) | |
C12 | 1.3577 (5) | 0.3584 (4) | 0.4867 (3) | 0.0345 (8) | |
O4 | 0.6639 (4) | −0.3220 (4) | 0.1847 (3) | 0.0600 (8) | |
C4 | 0.1782 (5) | 0.0520 (5) | 0.0748 (3) | 0.0356 (8) | |
C14 | 1.3100 (5) | 0.4962 (5) | 0.4413 (3) | 0.0395 (9) | |
H14A | 1.1825 | 0.4936 | 0.4015 | 0.047* | |
C7 | 0.8411 (6) | −0.3024 (5) | 0.1871 (3) | 0.0438 (9) | |
C11 | 1.2067 (5) | 0.2044 (5) | 0.4700 (3) | 0.0367 (8) | |
C8 | 0.9230 (5) | −0.4100 (5) | 0.0924 (3) | 0.0404 (9) | |
C6 | 0.1595 (5) | −0.0783 (5) | −0.0231 (3) | 0.0405 (9) | |
H6A | 0.2676 | −0.1310 | −0.0384 | 0.049* | |
C10 | 1.1244 (6) | −0.4108 (5) | 0.1024 (3) | 0.0432 (9) | |
H10A | 1.2095 | −0.3506 | 0.1717 | 0.052* | |
C13 | 1.5482 (5) | 0.3623 (5) | 0.5450 (3) | 0.0390 (9) | |
H13A | 1.5812 | 0.2700 | 0.5751 | 0.047* | |
C2 | 0.6358 (5) | 0.2556 (5) | 0.2666 (3) | 0.0375 (8) | |
H2A | 0.7342 | 0.3463 | 0.3075 | 0.045* | |
C3 | 0.4682 (5) | 0.2697 (5) | 0.1972 (3) | 0.0412 (9) | |
H3A | 0.4294 | 0.3702 | 0.1814 | 0.049* | |
C5 | 0.0201 (5) | 0.1316 (5) | 0.0992 (3) | 0.0403 (9) | |
H5A | 0.0343 | 0.2203 | 0.1661 | 0.048* | |
C9 | 0.8000 (6) | −0.5012 (5) | −0.0120 (3) | 0.0438 (9) | |
H9A | 0.6647 | −0.5026 | −0.0207 | 0.053* | |
C1 | 0.4740 (5) | 0.0006 (5) | 0.1994 (3) | 0.0433 (9) | |
H1A | 0.4373 | −0.1176 | 0.1843 | 0.052* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Zn1 | 0.0276 (3) | 0.0359 (3) | 0.0423 (3) | −0.00506 (17) | −0.00592 (18) | 0.0146 (2) |
O1 | 0.0329 (15) | 0.0431 (16) | 0.0635 (18) | −0.0123 (11) | −0.0105 (13) | 0.0190 (14) |
N1 | 0.0299 (17) | 0.0373 (17) | 0.0406 (17) | 0.0003 (13) | −0.0041 (13) | 0.0121 (14) |
O2 | 0.0381 (15) | 0.0409 (15) | 0.0504 (15) | −0.0020 (11) | 0.0057 (12) | 0.0200 (13) |
N2 | 0.0263 (16) | 0.0450 (18) | 0.0384 (17) | 0.0036 (13) | −0.0029 (13) | 0.0151 (15) |
O3 | 0.0473 (17) | 0.0528 (18) | 0.0573 (18) | 0.0070 (14) | 0.0024 (14) | 0.0071 (15) |
C12 | 0.032 (2) | 0.036 (2) | 0.0316 (19) | −0.0084 (15) | 0.0023 (15) | 0.0089 (16) |
O4 | 0.0440 (18) | 0.0553 (19) | 0.078 (2) | 0.0051 (14) | 0.0142 (15) | 0.0095 (16) |
C4 | 0.030 (2) | 0.044 (2) | 0.036 (2) | 0.0056 (16) | −0.0001 (15) | 0.0195 (18) |
C14 | 0.0294 (19) | 0.042 (2) | 0.041 (2) | −0.0056 (16) | −0.0069 (16) | 0.0121 (18) |
C7 | 0.045 (3) | 0.035 (2) | 0.052 (2) | 0.0036 (18) | 0.004 (2) | 0.0166 (19) |
C11 | 0.034 (2) | 0.038 (2) | 0.0345 (19) | −0.0027 (16) | 0.0016 (16) | 0.0086 (17) |
C8 | 0.036 (2) | 0.038 (2) | 0.049 (2) | 0.0041 (16) | 0.0037 (17) | 0.0201 (19) |
C6 | 0.030 (2) | 0.048 (2) | 0.045 (2) | 0.0107 (16) | 0.0024 (17) | 0.0141 (19) |
C10 | 0.037 (2) | 0.040 (2) | 0.049 (2) | −0.0021 (17) | −0.0017 (18) | 0.0145 (19) |
C13 | 0.034 (2) | 0.035 (2) | 0.042 (2) | −0.0063 (15) | −0.0053 (16) | 0.0141 (17) |
C2 | 0.037 (2) | 0.033 (2) | 0.037 (2) | 0.0027 (15) | 0.0009 (16) | 0.0043 (16) |
C3 | 0.040 (2) | 0.038 (2) | 0.044 (2) | 0.0095 (17) | 0.0011 (17) | 0.0093 (18) |
C5 | 0.036 (2) | 0.046 (2) | 0.036 (2) | 0.0078 (17) | 0.0019 (16) | 0.0072 (18) |
C9 | 0.032 (2) | 0.045 (2) | 0.052 (2) | −0.0008 (17) | 0.0019 (18) | 0.016 (2) |
C1 | 0.029 (2) | 0.043 (2) | 0.055 (2) | −0.0019 (16) | −0.0089 (17) | 0.0230 (19) |
Zn1—O3 | 1.927 (3) | C14—C13ii | 1.387 (5) |
Zn1—O2i | 1.955 (3) | C14—H14A | 0.9300 |
Zn1—O1 | 1.978 (3) | C7—C8 | 1.499 (6) |
Zn1—N1 | 1.990 (3) | C8—C9 | 1.386 (5) |
O1—C11 | 1.253 (4) | C8—C10 | 1.390 (5) |
N1—C1 | 1.313 (4) | C6—C5iii | 1.379 (5) |
N1—C2 | 1.375 (4) | C6—H6A | 0.9300 |
O2—C11 | 1.256 (4) | C10—C9iv | 1.371 (6) |
O2—Zn1i | 1.955 (3) | C10—H10A | 0.9300 |
N2—C1 | 1.340 (4) | C13—C14ii | 1.387 (5) |
N2—C3 | 1.374 (5) | C13—H13A | 0.9300 |
N2—C4 | 1.439 (4) | C2—C3 | 1.344 (5) |
O3—C7 | 1.284 (5) | C2—H2A | 0.9300 |
C12—C13 | 1.385 (5) | C3—H3A | 0.9300 |
C12—C14 | 1.388 (5) | C5—C6iii | 1.379 (5) |
C12—C11 | 1.492 (5) | C5—H5A | 0.9300 |
O4—C7 | 1.223 (4) | C9—C10iv | 1.371 (6) |
C4—C6 | 1.365 (5) | C9—H9A | 0.9300 |
C4—C5 | 1.376 (5) | C1—H1A | 0.9300 |
O3—Zn1—O2i | 112.06 (12) | O2—C11—C12 | 118.6 (3) |
O3—Zn1—O1 | 107.96 (12) | C9—C8—C10 | 118.0 (4) |
O2i—Zn1—O1 | 113.91 (11) | C9—C8—C7 | 120.4 (3) |
O3—Zn1—N1 | 118.46 (12) | C10—C8—C7 | 121.3 (3) |
O2i—Zn1—N1 | 107.67 (11) | C4—C6—C5iii | 119.8 (3) |
O1—Zn1—N1 | 95.96 (11) | C4—C6—H6A | 120.1 |
C11—O1—Zn1 | 120.9 (2) | C5iii—C6—H6A | 120.1 |
C1—N1—C2 | 106.1 (3) | C9iv—C10—C8 | 121.2 (4) |
C1—N1—Zn1 | 126.1 (3) | C9iv—C10—H10A | 119.4 |
C2—N1—Zn1 | 127.7 (2) | C8—C10—H10A | 119.4 |
C11—O2—Zn1i | 129.3 (2) | C12—C13—C14ii | 120.1 (3) |
C1—N2—C3 | 107.2 (3) | C12—C13—H13A | 119.9 |
C1—N2—C4 | 124.6 (3) | C14ii—C13—H13A | 119.9 |
C3—N2—C4 | 128.3 (3) | C3—C2—N1 | 109.3 (3) |
C7—O3—Zn1 | 112.6 (3) | C3—C2—H2A | 125.3 |
C13—C12—C14 | 119.6 (3) | N1—C2—H2A | 125.3 |
C13—C12—C11 | 120.0 (3) | C2—C3—N2 | 106.4 (3) |
C14—C12—C11 | 120.4 (3) | C2—C3—H3A | 126.8 |
C6—C4—C5 | 121.0 (3) | N2—C3—H3A | 126.8 |
C6—C4—N2 | 119.5 (3) | C4—C5—C6iii | 119.2 (4) |
C5—C4—N2 | 119.4 (3) | C4—C5—H5A | 120.4 |
C13ii—C14—C12 | 120.3 (3) | C6iii—C5—H5A | 120.4 |
C13ii—C14—H14A | 119.9 | C10iv—C9—C8 | 120.7 (4) |
C12—C14—H14A | 119.9 | C10iv—C9—H9A | 119.6 |
O4—C7—O3 | 124.8 (4) | C8—C9—H9A | 119.6 |
O4—C7—C8 | 120.1 (4) | N1—C1—N2 | 111.0 (3) |
O3—C7—C8 | 115.1 (3) | N1—C1—H1A | 124.5 |
O1—C11—O2 | 124.1 (3) | N2—C1—H1A | 124.5 |
O1—C11—C12 | 117.3 (3) | ||
O3—Zn1—O1—C11 | −60.1 (3) | C13—C12—C11—O2 | 6.3 (5) |
O2i—Zn1—O1—C11 | 65.0 (3) | C14—C12—C11—O2 | −175.4 (3) |
N1—Zn1—O1—C11 | 177.4 (3) | O4—C7—C8—C9 | 15.7 (5) |
O3—Zn1—N1—C1 | 57.0 (4) | O3—C7—C8—C9 | −161.7 (3) |
O2i—Zn1—N1—C1 | −71.4 (3) | O4—C7—C8—C10 | −169.4 (4) |
O1—Zn1—N1—C1 | 171.2 (3) | O3—C7—C8—C10 | 13.1 (5) |
O3—Zn1—N1—C2 | −122.3 (3) | C5—C4—C6—C5iii | 0.0 (6) |
O2i—Zn1—N1—C2 | 109.4 (3) | N2—C4—C6—C5iii | 179.6 (3) |
O1—Zn1—N1—C2 | −8.1 (3) | C9—C8—C10—C9iv | 0.1 (6) |
O2i—Zn1—O3—C7 | 81.7 (3) | C7—C8—C10—C9iv | −174.9 (3) |
O1—Zn1—O3—C7 | −152.1 (2) | C14—C12—C13—C14ii | 0.5 (6) |
N1—Zn1—O3—C7 | −44.6 (3) | C11—C12—C13—C14ii | 178.8 (3) |
C1—N2—C4—C6 | −50.9 (5) | C1—N1—C2—C3 | 0.0 (4) |
C3—N2—C4—C6 | 128.5 (4) | Zn1—N1—C2—C3 | 179.4 (2) |
C1—N2—C4—C5 | 128.8 (4) | N1—C2—C3—N2 | −0.2 (4) |
C3—N2—C4—C5 | −51.8 (5) | C1—N2—C3—C2 | 0.3 (4) |
C13—C12—C14—C13ii | −0.5 (6) | C4—N2—C3—C2 | −179.2 (3) |
C11—C12—C14—C13ii | −178.8 (3) | C6—C4—C5—C6iii | 0.0 (6) |
Zn1—O3—C7—O4 | −14.7 (5) | N2—C4—C5—C6iii | −179.6 (3) |
Zn1—O3—C7—C8 | 162.6 (2) | C10—C8—C9—C10iv | −0.1 (6) |
Zn1—O1—C11—O2 | −10.0 (5) | C7—C8—C9—C10iv | 174.9 (3) |
Zn1—O1—C11—C12 | 168.7 (2) | C2—N1—C1—N2 | 0.1 (4) |
Zn1i—O2—C11—O1 | −68.7 (5) | Zn1—N1—C1—N2 | −179.3 (2) |
Zn1i—O2—C11—C12 | 112.6 (3) | C3—N2—C1—N1 | −0.3 (4) |
C13—C12—C11—O1 | −172.4 (3) | C4—N2—C1—N1 | 179.2 (3) |
C14—C12—C11—O1 | 5.8 (5) |
Symmetry codes: (i) −x+2, −y, −z+1; (ii) −x+3, −y+1, −z+1; (iii) −x, −y, −z; (iv) −x+2, −y−1, −z. |
Experimental details
Crystal data | |
Chemical formula | [Zn2(C8H4O4)2(C12H10N4)] |
Mr | 334.60 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 6.9711 (14), 8.0784 (16), 11.903 (2) |
α, β, γ (°) | 102.68 (3), 99.68 (3), 96.32 (3) |
V (Å3) | 637.1 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 1.95 |
Crystal size (mm) | 0.20 × 0.20 × 0.20 |
Data collection | |
Diffractometer | Bruker SMART 1000 CCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5445, 2244, 1952 |
Rint | 0.046 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.043, 0.103, 1.11 |
No. of reflections | 2244 |
No. of parameters | 190 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.45, −0.37 |
Computer programs: SMART (Bruker, 1997), SAINT (Bruker, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
Zn1—O3 | 1.927 (3) | Zn1—O1 | 1.978 (3) |
Zn1—O2i | 1.955 (3) | Zn1—N1 | 1.990 (3) |
O3—Zn1—O2i | 112.06 (12) | O3—Zn1—N1 | 118.46 (12) |
O3—Zn1—O1 | 107.96 (12) | O2i—Zn1—N1 | 107.67 (11) |
O2i—Zn1—O1 | 113.91 (11) | O1—Zn1—N1 | 95.96 (11) |
Symmetry code: (i) −x+2, −y, −z+1. |
Metal–organic frameworks (MOFs) are hybrid materials where metal ions or small clusters are bridged by multifunctional organic linkers into one-dimensional chains, two-dimensional layers or three-dimensional nets. During the past decade, the construction of MOFs through crystal engineering has attracted considerable attention owing to their various intriguing architectures and potential applications as functional materials (Kitaura et al., 2003; Eddaoudi et al., 2000; Kepert et al., 2001). As nature abhors a vacuum, mutual interpenetration is a common phenomenon in supramolecular chemistry and provides a unique class of robust framework (Carlucci et al., 2000). Comprehensive reviews of interpenetration, which has been the most investigated type of entanglement, are given by Batten (2001) and Blatov et al. (2004). Much effort has been devoted to the synthesis of novel interpenetrating networks with interesting topologies. The most commonly used synthetic strategy is to select appropriate long-chain ligands, which bridge metal ions to afford infinite networks. Recently, the synthetic strategy utilizing secondary building units (SBUs) has achieved stable, highly porous open frameworks; two efficient SBUs are the tetrameric M4O(COO)6 clusters and the paddle-wheel dimeric M2(COO)4 clusters formed by carboxylate ligands (Chae et al., 2004; Sun et al., 2006; Han et al., 2008; Chen, Che et al., 2007). There are many inorganic–organic hybrid complexes composed of polyoxometalates (POMs) associated with various metal–ligand systems (Tian et al., 2008). A large number of attractive MOFs of ingenious design based on flexible bis(imidazole) ligands have been crystallographically characterized (Jin et al., 2006; Li et al., 2006; Fan et al., 2006). In order to enrich the coordination chemistry of interpenetrating MOFs based on POMs as nodes, we describe the synthesis and crystal structure of a novel threefold-interpenetrating primitive cubic network constructed from terephthalic acid (H2bdc), 1,4-bis(imidazol-1-yl)benzene (bib) and ZnII, namely [Zn2(bdc)2(bib)]∞, (I).
As shown in Fig. 1, the ZnII centre is four-coordinated by one N atom from the bib ligand and three O atoms from individual bdc anions to form a slightly distorted tetrahedral configuration, in which the Zn—O/N bond lengths are in the range 1.927 (3)–1.990 (3) Å (Table 1), comparable to those observed in related ZnII polymeric structures (Li et al., 2008; Chen, Che et al., 2007; Wang et al., 2006). The bdc and bib ligands lie about centers of symmetry. In the bdc anion, the two carboxylate groups show different bridging modes, viz. monodentate and syn–syn bidentate (Fig. 2). The bib ligand is trans-coordinated to the ZnII centre and keeps its rigid conformation in the self-assembly of the coordination polymer. As depicted in Fig. 2, two crystallographically equivalent ZnII atoms, i.e. Zn1 and Zn1(-x + 2, -y, -z + 1), are bridged by two syn–syn connecting carboxylates with a Zn···Zn distance of 3.706 (1) Å. This arrangement constitutes a relatively rare dinuclear SBU [Zn2(CO2)2N2O2], in which two ZnII centres are encompassed by two syn–syn bridging and two monodentate carboxylates, respectively. Thus, it is quite different from the common paddle-wheel dimeric unit, which is bridged by four syn–syn connecting carboxylates. Some similar zinc-based SBUs linked by this carboxylate bridging mode are found in coordination polymers, but there are minor differences from the present compound in the coordination environments of the ZnII ions (Dietzel et al., 2006; Wang et al., 2006). One closely related structure is reported by Chen, Zhang & Lu (2007), with the dinuclear ZnII unit also connected by two bdc ligands; however, the Zn···Zn distances within this unit are 3.522 (1) and 3.564 (1) Å, respectively, somewhat shorter than here. Furthermore, the Zn···Zn separations in paddle-wheel SBUs are generally around 2.9 Å, and two intra-unit ZnII centres are typically much closer (Ma et al., 2005; Zhou et al., 2000; Li et al., 2004; Chun et al., 2005).
A better insight into this fascinating structure can be achieved by the application of topology analysis. Although each ZnII centre sits in a tetrahedral coordination environment, the dinuclear SBU is octahedrally connected by four bdc anions and two bib molecules (Fig. 2). Each six-connected SBU is linked to four equivalent units through four bdc anions to generate a neutral two-dimensional square-grid (4,4)-layer, [Zn2(bdc)2]∞. As shown in Fig. 3, the two-dimensional layer is further pillared by the long bib ligand to afford an extended three-dimensional framework, [Zn2(bdc)2(bib)]∞, with a cube-like structure, which is also found in the two-dimensional parallel catenation of bilayer [Zn2(bdc)2(bpp)]∞ [bpp is 1,3-bis(4-pyridyl)-propane; Chen, Zhang & Lu, 2007]. If the dinuclear SBU is simplified to a six-connected node and, accordingly, the bdc and bib ligands act as two-connected linkers, the overall topology can be described as an α-polonium framework (Abrahams et al., 2002), which possesses large cubic cavities of approximately 10 × 13 × 17 Å. (Fig. 4). The large voids formed by a single three-dimensional framework allow the incorporation of two identical frameworks, thus giving a threefold-interpenetraing α-polonium-related network, as shown in Fig. 5. The nodes of the second and third nets are located, equally spaced, along the cubic diagonal of the first net, and each square window has a rod from each of the adjacent two nets passing through it, giving a complicated interpenetration. We recognize as did previous workers that, among the currently known examples of α-polonium topology, the majority are twofold (Niel et al., 2002; Jensen et al., 2002; Yang et al., 2002), and only a few threefold-interpenetrated frameworks have been identified (Abrahams et al., 2002; Wang et al., 2006).
In summary, a novel threefold-interpenetrating network with an α-polonium topology has been synthesized and is another interpenetrating MOF based on a POM as the node.