Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270113010937/mx3099sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270113010937/mx3099Isup2.hkl |
CCDC reference: 950415
The tetrahedral tetradentate linker tpom ligand was synthesized by reacting pentaerythrityl tetrabromide with pyridin-4-ol in N,N'-dimethylformamide (DMF) containing K2CO3 and KI under reflux.
To a solution of tpom (0.022 g, 0.045 mmol) and Zn(NO3)2.6H2O (0.030 g, 0.10 mmol) in DMF (10 ml) were added two drops of aqueous HCl (1:1 v/v) (pH ~5). The mixture was transferred into a vial, which was sealed and heated at 373 K for 3 d. The vial was allowed to cool to room temperature. Colourless octahedral crystals of (I) (yield 0.028 g) were obtained by filtration, and washed with DMF and acetic ether three times each, respectively (final yield 63.6%, based on tpom). Spectroscopic analysis: FT–IR (KBr, cm-1): 3132 (w), 3104 (w), 3052 (w), 1672 (s), 1611 (s), 1567 (s), 1512 (s), 1470 (s), 1439 (s), 1409 (m), 1386 (s), 1334 (w), 1298 (s), 1256 (m), 1209 (s), 1168 (w), 1095 (s), 1060 (s), 1031 (s), 949 (w), 875 (s), 847 (s), 829 (s), 669 (m), 537 (m).
All H atoms were placed in geometrically idealized position and treated as riding, with C—H = 0.96 (methyl), 0.97 (methylene) or 0.93 Å (pyridine), and with Uiso(H) = 1.2Ueq(C) for pyridine and methylene H atoms or 1.5Ueq(C) for methyl H atoms.
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg & Putz, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).
[Zn2Cl4(C25H24N4O4)]·4C6H14NO2 | F(000) = 1044 |
Mr = 1009.41 | Dx = 1.376 Mg m−3 |
Tetragonal, P421c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P -4 2 n | θ = 2.1–28.2° |
a = 12.2905 (14) Å | µ = 1.26 mm−1 |
c = 16.133 (4) Å | T = 291 K |
V = 2437.0 (7) Å3 | Block, colourless |
Z = 2 | 0.20 × 0.19 × 0.18 mm |
Bruker APEXII CCD area-detector diffractometer | 2980 independent reflections |
Radiation source: fine-focus sealed tube | 2149 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.033 |
ϕ and ω scans | θmax = 28.2°, θmin = 2.1° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2008) | h = −16→14 |
Tmin = 0.787, Tmax = 0.806 | k = −16→16 |
14763 measured reflections | l = −21→18 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.031 | H-atom parameters constrained |
wR(F2) = 0.086 | w = 1/[σ2(Fo2) + (0.0446P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max = 0.001 |
2980 reflections | Δρmax = 0.27 e Å−3 |
136 parameters | Δρmin = −0.21 e Å−3 |
0 restraints | Absolute structure: Flack (1983), with 1291 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.006 (18) |
[Zn2Cl4(C25H24N4O4)]·4C6H14NO2 | Z = 2 |
Mr = 1009.41 | Mo Kα radiation |
Tetragonal, P421c | µ = 1.26 mm−1 |
a = 12.2905 (14) Å | T = 291 K |
c = 16.133 (4) Å | 0.20 × 0.19 × 0.18 mm |
V = 2437.0 (7) Å3 |
Bruker APEXII CCD area-detector diffractometer | 2980 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2008) | 2149 reflections with I > 2σ(I) |
Tmin = 0.787, Tmax = 0.806 | Rint = 0.033 |
14763 measured reflections |
R[F2 > 2σ(F2)] = 0.031 | H-atom parameters constrained |
wR(F2) = 0.086 | Δρmax = 0.27 e Å−3 |
S = 1.07 | Δρmin = −0.21 e Å−3 |
2980 reflections | Absolute structure: Flack (1983), with 1291 Friedel pairs |
136 parameters | Absolute structure parameter: 0.006 (18) |
0 restraints |
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 | 0.5000 | 1.0000 | 0.85678 (2) | 0.05180 (12) | |
Cl1 | 0.34442 (8) | 0.97835 (7) | 0.92316 (6) | 0.1075 (3) | |
O1 | 0.54728 (13) | 0.62201 (13) | 0.60884 (9) | 0.0569 (4) | |
O2 | 0.7769 (3) | 1.0492 (4) | 0.6489 (3) | 0.198 (2) | |
N1 | 0.51928 (16) | 0.87304 (14) | 0.77596 (11) | 0.0528 (5) | |
N2 | 0.7964 (2) | 0.8929 (2) | 0.5793 (2) | 0.0926 (8) | |
C1 | 0.6057 (2) | 0.8061 (2) | 0.77321 (17) | 0.0626 (6) | |
H1 | 0.6623 | 0.8177 | 0.8105 | 0.075* | |
C2 | 0.61440 (19) | 0.7234 (2) | 0.71932 (17) | 0.0618 (7) | |
H2 | 0.6750 | 0.6782 | 0.7205 | 0.074* | |
C3 | 0.53285 (18) | 0.70591 (18) | 0.66208 (14) | 0.0487 (5) | |
C4 | 0.44309 (19) | 0.7715 (2) | 0.66406 (16) | 0.0569 (6) | |
H4 | 0.3857 | 0.7603 | 0.6274 | 0.068* | |
C5 | 0.43936 (18) | 0.8540 (2) | 0.72117 (17) | 0.0606 (7) | |
H5 | 0.3785 | 0.8989 | 0.7220 | 0.073* | |
C6 | 0.46106 (17) | 0.59462 (17) | 0.55325 (13) | 0.0469 (5) | |
H6A | 0.4431 | 0.6566 | 0.5186 | 0.056* | |
H6B | 0.3966 | 0.5739 | 0.5841 | 0.056* | |
C7 | 0.5000 | 0.5000 | 0.5000 | 0.0429 (8) | |
C8 | 0.8988 (5) | 0.8688 (6) | 0.6135 (3) | 0.199 (3) | |
H8A | 0.9539 | 0.8772 | 0.5718 | 0.298* | |
H8B | 0.8991 | 0.7952 | 0.6334 | 0.298* | |
H8C | 0.9134 | 0.9175 | 0.6587 | 0.298* | |
C9 | 0.7535 (4) | 0.8170 (4) | 0.5198 (4) | 0.1611 (19) | |
H9A | 0.7640 | 0.7441 | 0.5397 | 0.242* | |
H9B | 0.7907 | 0.8259 | 0.4679 | 0.242* | |
H9C | 0.6772 | 0.8303 | 0.5121 | 0.242* | |
C10 | 0.7416 (4) | 0.9791 (6) | 0.5987 (3) | 0.1448 (19) | |
H10 | 0.6737 | 0.9897 | 0.5746 | 0.174* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Zn1 | 0.0626 (2) | 0.0476 (2) | 0.0452 (2) | −0.0026 (2) | 0.000 | 0.000 |
Cl1 | 0.1149 (7) | 0.0881 (6) | 0.1196 (6) | −0.0043 (5) | 0.0668 (6) | 0.0056 (5) |
O1 | 0.0504 (8) | 0.0615 (10) | 0.0589 (10) | 0.0118 (8) | −0.0075 (8) | −0.0171 (8) |
O2 | 0.146 (3) | 0.217 (5) | 0.231 (4) | −0.008 (3) | 0.030 (3) | −0.142 (4) |
N1 | 0.0574 (12) | 0.0519 (10) | 0.0491 (10) | 0.0001 (9) | −0.0049 (9) | −0.0035 (9) |
N2 | 0.0869 (19) | 0.0880 (18) | 0.103 (2) | 0.0136 (16) | −0.0005 (18) | 0.0050 (18) |
C1 | 0.0522 (13) | 0.0759 (17) | 0.0596 (16) | 0.0093 (13) | −0.0146 (12) | −0.0102 (14) |
C2 | 0.0460 (13) | 0.0692 (16) | 0.0703 (17) | 0.0154 (11) | −0.0118 (12) | −0.0165 (14) |
C3 | 0.0504 (12) | 0.0487 (12) | 0.0470 (13) | 0.0037 (10) | −0.0014 (10) | −0.0029 (10) |
C4 | 0.0562 (14) | 0.0581 (14) | 0.0564 (16) | 0.0098 (12) | −0.0157 (12) | −0.0109 (12) |
C5 | 0.0559 (14) | 0.0600 (14) | 0.0660 (16) | 0.0113 (12) | −0.0111 (13) | −0.0116 (13) |
C6 | 0.0461 (11) | 0.0470 (12) | 0.0477 (13) | 0.0028 (10) | −0.0038 (10) | −0.0028 (10) |
C7 | 0.0419 (12) | 0.0419 (12) | 0.045 (2) | 0.000 | 0.000 | 0.000 |
C8 | 0.171 (5) | 0.194 (6) | 0.231 (6) | 0.035 (5) | −0.089 (5) | −0.011 (5) |
C9 | 0.188 (5) | 0.147 (4) | 0.148 (5) | −0.030 (4) | −0.005 (4) | −0.018 (4) |
C10 | 0.089 (3) | 0.194 (5) | 0.151 (5) | 0.026 (4) | 0.020 (3) | 0.005 (4) |
Zn1—N1 | 2.0472 (18) | C4—C5 | 1.371 (4) |
Zn1—N1i | 2.0472 (18) | C4—H4 | 0.9300 |
Zn1—Cl1i | 2.2077 (8) | C5—H5 | 0.9300 |
Zn1—Cl1 | 2.2077 (8) | C6—C7 | 1.523 (2) |
O1—C3 | 1.354 (3) | C6—H6A | 0.9700 |
O1—C6 | 1.428 (2) | C6—H6B | 0.9700 |
O2—C10 | 1.260 (6) | C7—C6ii | 1.523 (2) |
N1—C5 | 1.342 (3) | C7—C6iii | 1.523 (2) |
N1—C1 | 1.344 (3) | C7—C6iv | 1.523 (2) |
N2—C10 | 1.293 (6) | C8—H8A | 0.9600 |
N2—C8 | 1.407 (6) | C8—H8B | 0.9600 |
N2—C9 | 1.439 (5) | C8—H8C | 0.9600 |
C1—C2 | 1.342 (3) | C9—H9A | 0.9600 |
C1—H1 | 0.9300 | C9—H9B | 0.9600 |
C2—C3 | 1.380 (3) | C9—H9C | 0.9600 |
C2—H2 | 0.9300 | C10—H10 | 0.9300 |
C3—C4 | 1.366 (3) | ||
N1—Zn1—N1i | 100.88 (10) | O1—C6—C7 | 107.52 (15) |
N1—Zn1—Cl1i | 107.49 (6) | O1—C6—H6A | 110.2 |
N1i—Zn1—Cl1i | 108.50 (6) | C7—C6—H6A | 110.2 |
N1—Zn1—Cl1 | 108.50 (6) | O1—C6—H6B | 110.2 |
N1i—Zn1—Cl1 | 107.49 (6) | C7—C6—H6B | 110.2 |
Cl1i—Zn1—Cl1 | 121.96 (6) | H6A—C6—H6B | 108.5 |
C3—O1—C6 | 118.73 (17) | C6ii—C7—C6 | 108.55 (8) |
C5—N1—C1 | 116.74 (19) | C6ii—C7—C6iii | 111.32 (16) |
C5—N1—Zn1 | 117.89 (15) | C6—C7—C6iii | 108.55 (8) |
C1—N1—Zn1 | 125.37 (16) | C6ii—C7—C6iv | 108.55 (8) |
C10—N2—C8 | 123.0 (5) | C6—C7—C6iv | 111.32 (16) |
C10—N2—C9 | 120.1 (4) | C6iii—C7—C6iv | 108.55 (8) |
C8—N2—C9 | 116.9 (4) | N2—C8—H8A | 109.5 |
C2—C1—N1 | 123.2 (2) | N2—C8—H8B | 109.5 |
C2—C1—H1 | 118.4 | H8A—C8—H8B | 109.5 |
N1—C1—H1 | 118.4 | N2—C8—H8C | 109.5 |
C1—C2—C3 | 119.6 (2) | H8A—C8—H8C | 109.5 |
C1—C2—H2 | 120.2 | H8B—C8—H8C | 109.5 |
C3—C2—H2 | 120.2 | N2—C9—H9A | 109.5 |
O1—C3—C4 | 124.7 (2) | N2—C9—H9B | 109.5 |
O1—C3—C2 | 116.64 (19) | H9A—C9—H9B | 109.5 |
C4—C3—C2 | 118.6 (2) | N2—C9—H9C | 109.5 |
C3—C4—C5 | 118.6 (2) | H9A—C9—H9C | 109.5 |
C3—C4—H4 | 120.7 | H9B—C9—H9C | 109.5 |
C5—C4—H4 | 120.7 | O2—C10—N2 | 122.4 (5) |
N1—C5—C4 | 123.2 (2) | O2—C10—H10 | 118.8 |
N1—C5—H5 | 118.4 | N2—C10—H10 | 118.8 |
C4—C5—H5 | 118.4 | ||
N1i—Zn1—N1—C5 | −58.04 (17) | C1—C2—C3—C4 | −2.4 (4) |
Cl1i—Zn1—N1—C5 | −171.58 (17) | O1—C3—C4—C5 | −179.7 (2) |
Cl1—Zn1—N1—C5 | 54.73 (18) | C2—C3—C4—C5 | 2.0 (4) |
N1i—Zn1—N1—C1 | 122.3 (2) | C1—N1—C5—C4 | −0.3 (4) |
Cl1i—Zn1—N1—C1 | 8.7 (2) | Zn1—N1—C5—C4 | 180.0 (2) |
Cl1—Zn1—N1—C1 | −125.0 (2) | C3—C4—C5—N1 | −0.6 (4) |
C5—N1—C1—C2 | −0.1 (4) | C3—O1—C6—C7 | 178.82 (17) |
Zn1—N1—C1—C2 | 179.6 (2) | O1—C6—C7—C6ii | 173.86 (15) |
N1—C1—C2—C3 | 1.5 (4) | O1—C6—C7—C6iii | −65.00 (8) |
C6—O1—C3—C4 | −3.7 (3) | O1—C6—C7—C6iv | 54.43 (11) |
C6—O1—C3—C2 | 174.6 (2) | C8—N2—C10—O2 | 1.2 (8) |
C1—C2—C3—O1 | 179.2 (2) | C9—N2—C10—O2 | −178.3 (5) |
Symmetry codes: (i) −x+1, −y+2, z; (ii) −y+1, x, −z+1; (iii) y, −x+1, −z+1; (iv) −x+1, −y+1, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C5—H5···O2i | 0.93 | 2.33 | 3.137 (4) | 144 |
C6—H6A···Cl1v | 0.97 | 2.81 | 3.725 (2) | 158 |
Symmetry codes: (i) −x+1, −y+2, z; (v) y−1/2, x+1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | [Zn2Cl4(C25H24N4O4)]·4C6H14NO2 |
Mr | 1009.41 |
Crystal system, space group | Tetragonal, P421c |
Temperature (K) | 291 |
a, c (Å) | 12.2905 (14), 16.133 (4) |
V (Å3) | 2437.0 (7) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 1.26 |
Crystal size (mm) | 0.20 × 0.19 × 0.18 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2008) |
Tmin, Tmax | 0.787, 0.806 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 14763, 2980, 2149 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.665 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.031, 0.086, 1.07 |
No. of reflections | 2980 |
No. of parameters | 136 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.27, −0.21 |
Absolute structure | Flack (1983), with 1291 Friedel pairs |
Absolute structure parameter | 0.006 (18) |
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg & Putz, 2008), SHELXTL (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).
Zn1—N1 | 2.0472 (18) | Zn1—Cl1i | 2.2077 (8) |
Zn1—N1i | 2.0472 (18) | Zn1—Cl1 | 2.2077 (8) |
N1—Zn1—N1i | 100.88 (10) | N1—Zn1—Cl1 | 108.50 (6) |
N1i—Zn1—Cl1i | 108.50 (6) | Cl1i—Zn1—Cl1 | 121.96 (6) |
Symmetry code: (i) −x+1, −y+2, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C5—H5···O2i | 0.93 | 2.33 | 3.137 (4) | 144.4 |
C6—H6A···Cl1ii | 0.97 | 2.81 | 3.725 (2) | 157.9 |
Symmetry codes: (i) −x+1, −y+2, z; (ii) y−1/2, x+1/2, z−1/2. |
The design and synthesis of coordination polymers containing transition metal cations and organic ligands in a metal–organic framework (MOF) have rapidly developed because of their various unique architectures and potential applications as absorbent, luminescent or nonlinear optical materials (Allendorf et al., 2009; Kuppler et al., 2009; Farrusseng et al., 2009; Maspoch et al., 2007). The creation of designed MOFs using various functional multidentate organic ligands with different lengths, geometries and degrees of rigidity provides a new route to producing novel inorganic–organic hybrid materials (Zhang et al., 2010; Long & Yaghi, 2009). N- and O-donor bridging linkers, such as carboxylic acid and pyridine derivatives, have been widely reported to funtion generally as rigid bridging coordination ligands (Janiak, 2003; Sun & Wang, 2009; Zhang et al., 2009). Among the known N-containing compounds, tetrakis[(pyridin-4-yl)oxymethyl]methane (tpom) is an important flexible tetradentate ligand used to produce diversely structured MOFs with various metal ions (Guo et al., 2011; Kitigawa & Uemura, 2005; Moulton & Zaworotko, 2001; Janiak, 2003; Hu et al., 2012). Tpom-containing crystal structures were not found in the Cambridge Structural Database (CSD, Version 5.32; Allen, 2002) until 2008, when Zhang et al. (2008) reported two metal clusters (MOF-9 and MOF-10) coordinated with tpom ligands (CSD refcode VOMCOQ [One refcode for two structures?]; Zhang et al., 2008). In later studies, tpom was used to produce various coordination assemblies with one-, two- or three-dimensional structures [References?]. Closed-shell d10 metal cations, such as ZnII, CdII and HgII, have attracted much attention because of their coordination adaptability and significant luminescent properties (Zeng et al., 2010; Wang et al., 2009; Wei et al., 2006). Several structures with different three-dimensional frameworks containing tpom and ZnII cations have been reported previously (Zeng et al., 2010; Zhang et al., 2010; Ren et al., 2010). However, to the best of our knowledge, no other studies have reported two-dimensional structures with ZnII and tpom.
We previously synthesized a series of tpom-containing compounds, including porous coordination polymers built from tpom and transition metal sulfides with the three-dimensional PtS topology (Zhang et al., 2010), as well as a photoluminescent triply-interpenetrating diamondoid MOF based on Cu4I4 clusters and tpom (Ren et al., 2009). In this study, the synthesis and crystal structure of a new 4-connected two-dimensional wave-like sheet complex {[Zn2Cl4(tpom)].2DMF}n (DMF is dimethylformamide), (I), is introduced.
Compound (I) crystallizes in the noncentrosymmetric space group P421c and is constructed using two-dimensional polymeric layers, with the four axes directed along the tetragonal c axis. Each layer is a regular tpom array located on the 4 axes, which are bridged by ZnCl2 units on the twofold axes. The asymmetric unit contains half a ZnII cation, one Cl- anion, half a tpom ligand and one solvent DMF molecule. Each ZnII cation (Fig. 1) is tetracoordinated by two terminal Cl atoms (Cl1 and Cl1iv) and two N atoms (N1 and N1iv) of two tpom ligands [symmetry code: (iv) x, y - 1, z]. The coordination environment of ZnII (Fig. 1 and Table 1) is a distorted tetrahedron, with bond angles in the range 101.15 (2)–122.41 (1)°. The Zn—N bond length is similar to those found in related structures (Zeng et al., 2010; Hu et al., 2010). Each tetradentate tpom ligand adopts a distorted tetrahedral geometry and coordinates four ZnCl2 units via its N-donor atoms, thereby forming a two-dimensional framework. The central C atoms of adjacent ligands in this framework are linked to a common ZnCl2 unit. These atoms are separated by a Ccore···Ccore distance of 12.290 (5) Å, whereas the Zn···Zn distances spanned by the tpom ligand are 12.290 (5) and 14.423 (7) Å (Fig. 2). The extended layer in the ab plane is constructed by connecting the quaternary bridges and the ZnCl2 units.
As mentioned above, tpom is a flexible ligand and its various coordination configurations cause the observed structural differences. A previous study reported that the tpom conformation can be assessed from the distortion of the tetrahedral orientation by comparing the N—Ccore—N angles and the Ccore—CH2—O—Cpy torsion angles (py is pyridine; Ryan et al., 2009). Guo et al. (2011) concluded that tpom ligands can bend and rotate freely when coordinated to metal atoms because of the flexible nature of the spacers between the four pyridine rings (Guo et al., 2011). Li & Yu (2012) discussed the effect of the additional rotation of the pyridine rings on the variable conformations (Li & Yu, 2012). The N—Ccore—N angles of the tpom ligand in (I) range from 91.68 (5) to 119.03 (2)° (Fig. 2), whereas the Ccore—CH2—O—Cpy torsion angles are 179.16 (2)°. Therefore, the ligand deviates slightly from tetrahedral geometry and adopts a fully extended configuration. A similar distortion was observed in the three-dimensional tpom complex [Fe(SCN)2(tpom)].2[HN(CH3)2].4H2O (Li & Yu, 2012).
A better understanding of the framework of (I) can be achieved through topological analysis. The tetradentate tpom ligands are considered as four connecting `X' nodes, and the neutral ZnCl2 units are linear linkers that are connected to two tpom ligands. Therefore, (I) can be reduced to the topology of a uninodal 4-connected two-dimensional sql/Shubnikov tetragonal plane net with the Schläfli symbol {44,62}, as calculated by the TOPAS software (Blatov, 2006) (Fig. 3). The two-dimensional interleaved sheets stack on top of each other along the c axis, with a repeat distance of 8.066 (5) Å, such that they block the solvent molecules. The DMF solvent molecules fill the space between two layers of the stable framework structure via weak C—H···O2 hydrogen bonds (Table 2). PLATON (Spek, 2009) calculates that 1.6% of the unit cell is occupied by the solvent. The three-dimensional packing of the structure is governed by classical C—H···Cl1 hydrogen bonds between pyridine groups and terminal chloride ligands (Fig. 4).
In summary, we have synthesized the unprecedented 4-connected two-dimensional metal–organic framework {[Zn2Cl4(tpom)].2DMF}n from the assembly of a semi-rigid tetrahedral tpom ligand, in which hydrogen bonds interweave two-dimensional wave-like sheets into a three-dimensional architecture. Based on both our previous work and the present study, a new route to the diverse assembly of MOF structures is via adjustment of the configurations of flexible ligands. The flexible nature of the tpom ligand allows for changes in its coordination modes. Further studies will involve the synthesis of a new series using this ligand with other functional groups and coordination complexes.