The title compound, N,N,N',N'-tetramethylethylenediammonium diaqua(arsenate)(hydrogen arsenate)dizinc(II), (C6H18N2)0.5[Zn2(AsO4)(HAsO4)(H2O)2], is a new zincoarsenate obtained by hydrothermal synthesis. The structure consists of infinite two-dimensional anionic layers alternating with planes containing centrosymmetric organic diprotonated template N,N,N',N'-tetramethylethylenediammonium cations, [H3NC6H12NH3]2+. The latter are interconnected to the framework through hydrogen bonds.
Supporting information
CCDC reference: 147624
The title compound was synthesized hydrothermally from a 1:2:2:3:100 mixture of ZnO (0.12 g), HCl (38%, 0.29 g), H3AsO4 (80%, 0.51 g), C6H16N2 (0.50 g) and H2O (2.58 g). A thick gel formed which was then heated at 373 K for 7 d. The crystalline obtained product was filtered, washed with distilled water and dried in air at room temperature.
H atoms other than those of the aqua ligands or NH groups were treated as riding with O—H = 0.82 and C—H = 0.96–0.97 Å. The H atoms of NH groups were refined freely and aqua H atoms were refined with DFIX constraints and O—H = 0.90 Å.
Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.
N,
N,
N',
N'-tetramethylethylenediammonium (arsenate)diaqua(hydrogen arsenate)dizinc(II)
top
Crystal data top
(C6H18N2)0.5[Zn2(AsO4)(HAsO4)(H2O)2] | Z = 2 |
Mr = 504.73 | F(000) = 490 |
Triclinic, P1 | Dx = 2.922 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71069 Å |
a = 8.087 (1) Å | Cell parameters from 25 reflections |
b = 11.354 (2) Å | θ = 11.2–13.9° |
c = 6.622 (2) Å | µ = 9.95 mm−1 |
α = 101.15 (2)° | T = 293 K |
β = 96.64 (2)° | Plate, colourless |
γ = 102.79 (1)° | 0.45 × 0.25 × 0.14 mm |
V = 573.7 (2) Å3 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 2284 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.020 |
Graphite monochromator | θmax = 27.0°, θmin = 2.6° |
ω/2θ scans | h = −10→10 |
Absorption correction: ψ scan (North et al., 1968) | k = −14→0 |
Tmin = 0.063, Tmax = 0.248 | l = −8→8 |
2630 measured reflections | 2 standard reflections every 120 min |
2499 independent reflections | intensity decay: 0.7% |
Refinement top
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)] = 0.027 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.077 | Calculated w = 1/[σ2(Fo2) + (0.0505P)2 + 0.775P] where P = (Fo2 + 2Fc2)/3 |
S = 1.12 | (Δ/σ)max < 0.001 |
2499 reflections | Δρmax = 1.45 e Å−3 |
196 parameters | Δρmin = −0.79 e Å−3 |
5 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0095 (10) |
Crystal data top
(C6H18N2)0.5[Zn2(AsO4)(HAsO4)(H2O)2] | γ = 102.79 (1)° |
Mr = 504.73 | V = 573.7 (2) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.087 (1) Å | Mo Kα radiation |
b = 11.354 (2) Å | µ = 9.95 mm−1 |
c = 6.622 (2) Å | T = 293 K |
α = 101.15 (2)° | 0.45 × 0.25 × 0.14 mm |
β = 96.64 (2)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 2284 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.020 |
Tmin = 0.063, Tmax = 0.248 | 2 standard reflections every 120 min |
2630 measured reflections | intensity decay: 0.7% |
2499 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.027 | 5 restraints |
wR(F2) = 0.077 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.12 | Δρmax = 1.45 e Å−3 |
2499 reflections | Δρmin = −0.79 e Å−3 |
196 parameters | |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
As1 | 0.45470 (4) | 0.15530 (3) | 0.18012 (5) | 0.0092 (1) | |
As2 | −0.13060 (4) | 0.12917 (3) | −0.31863 (5) | 0.0080 (1) | |
Zn1 | 0.11517 (5) | −0.04617 (4) | −0.15912 (6) | 0.0119 (1) | |
Zn2 | 0.43666 (5) | 0.08903 (4) | −0.33855 (6) | 0.0107 (1) | |
O1 | 0.3695 (3) | 0.2702 (2) | 0.2734 (4) | 0.0184 (5) | |
O2 | 0.4659 (3) | 0.0665 (2) | 0.3523 (3) | 0.0125 (5) | |
O3 | 0.3543 (3) | 0.0721 (2) | −0.0584 (4) | 0.0137 (5) | |
O4 | 0.6634 (3) | 0.2186 (3) | 0.1535 (4) | 0.0240 (6) | |
HO4 | 0.6724 | 0.2048 | 0.0296 | 0.05 (2)* | |
O5 | 0.0273 (3) | 0.2501 (2) | −0.3265 (4) | 0.0157 (5) | |
O6 | −0.1891 (3) | 0.0324 (2) | −0.5578 (3) | 0.0113 (5) | |
O7 | −0.0696 (3) | 0.0499 (2) | −0.1435 (4) | 0.0138 (5) | |
O8 | −0.2938 (3) | 0.1892 (2) | −0.2375 (4) | 0.0122 (5) | |
OW1 | 0.3595 (3) | 0.2523 (2) | −0.3272 (4) | 0.0165 (5) | |
OW2 | −0.0281 (3) | −0.2236 (2) | −0.2659 (4) | 0.0170 (5) | |
N | 0.2025 (4) | 0.5578 (3) | 0.2035 (5) | 0.0192 (6) | |
C1 | 0.2376 (6) | 0.5494 (4) | 0.4263 (6) | 0.0294 (9) | |
H1C1 | 0.1718 | 0.5953 | 0.5071 | 0.05 (2)* | |
H2C1 | 0.3578 | 0.5834 | 0.4800 | 0.07 (2)* | |
H3C1 | 0.2057 | 0.4641 | 0.4349 | 0.03 (1)* | |
C2 | 0.3305 (5) | 0.5121 (4) | 0.0834 (7) | 0.0273 (9) | |
H1C2 | 0.3127 | 0.5257 | −0.0553 | 0.03 (1)* | |
H2C2 | 0.3160 | 0.4251 | 0.0764 | 0.05 (2)* | |
H3C2 | 0.4447 | 0.5563 | 0.1520 | 0.04 (1)* | |
C3 | 0.0206 (5) | 0.4912 (4) | 0.1097 (6) | 0.0196 (7) | |
H1C3 | −0.0567 | 0.5228 | 0.1951 | 0.02 (1)* | |
H2C3 | 0.0035 | 0.4035 | 0.1065 | 0.01 (1)* | |
HN | 0.218 (6) | 0.639 (1) | 0.203 (7) | 0.02 (1)* | |
H1W1 | 0.361 (6) | 0.265 (5) | −0.457 (3) | 0.03 (1)* | |
H2W1 | 0.255 (4) | 0.247 (7) | −0.291 (12) | 0.09 (3)* | |
H1W2 | −0.031 (7) | −0.242 (5) | −0.405 (2) | 0.03 (1)* | |
H2W2 | −0.139 (3) | −0.238 (6) | −0.250 (10) | 0.06 (2)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
As1 | 0.0090 (2) | 0.0121 (2) | 0.0062 (2) | 0.0021 (1) | 0.0003 (1) | 0.0026 (1) |
As2 | 0.0074 (2) | 0.0109 (2) | 0.0059 (2) | 0.0034 (1) | 0.0005 (1) | 0.0017 (1) |
Zn1 | 0.0106 (2) | 0.0157 (2) | 0.0088 (2) | 0.0020 (1) | 0.0013 (1) | 0.0027 (1) |
Zn2 | 0.0112 (2) | 0.0137 (2) | 0.0078 (2) | 0.0045 (1) | 0.0017 (1) | 0.0025 (1) |
O1 | 0.023 (1) | 0.016 (1) | 0.018 (1) | 0.009 (1) | 0.003 (1) | 0.003 (1) |
O2 | 0.016 (1) | 0.017 (1) | 0.008 (1) | 0.008 (1) | 0.003 (1) | 0.005 (1) |
O3 | 0.011 (1) | 0.020 (1) | 0.007 (1) | 0.001 (1) | 0.000 (1) | 0.002 (1) |
O4 | 0.013 (1) | 0.039 (2) | 0.012 (1) | −0.008 (1) | 0.001 (1) | 0.005 (1) |
O5 | 0.011 (1) | 0.015 (1) | 0.018 (1) | 0.000 (1) | 0.003 (1) | 0.002 (1) |
O6 | 0.010 (1) | 0.015 (1) | 0.007 (1) | 0.002 (1) | 0.000 (1) | 0.000 (1) |
O7 | 0.014 (1) | 0.024 (1) | 0.009 (1) | 0.009 (1) | 0.003 (1) | 0.008 (1) |
O8 | 0.010 (1) | 0.014 (1) | 0.014 (1) | 0.004 (1) | 0.004 (1) | 0.003 (1) |
OW1 | 0.015 (1) | 0.019 (1) | 0.016 (1) | 0.006 (1) | 0.002 (1) | 0.004 (1) |
OW2 | 0.017 (1) | 0.019 (1) | 0.016 (1) | 0.004 (1) | 0.004 (1) | 0.005 (1) |
N | 0.021 (2) | 0.012 (1) | 0.023 (2) | 0.003 (1) | 0.000 (1) | 0.003 (1) |
C1 | 0.030 (2) | 0.028 (2) | 0.023 (2) | 0.000 (2) | −0.005 (2) | 0.003 (2) |
C2 | 0.021 (2) | 0.025 (2) | 0.033 (2) | 0.007 (2) | 0.001 (2) | −0.001 (2) |
C3 | 0.019 (2) | 0.017 (2) | 0.021 (2) | 0.003 (1) | 0.000 (1) | 0.004 (1) |
Geometric parameters (Å, º) top
As1—O1 | 1.656 (2) | O4—HO4 | 0.8200 |
As1—O2 | 1.669 (2) | O6—Zn1i | 2.056 (2) |
As1—O3 | 1.683 (2) | O6—Zn2i | 2.116 (2) |
As1—O4 | 1.725 (2) | O7—Zn1ii | 2.086 (2) |
As2—O5 | 1.669 (2) | O8—Zn2viii | 2.182 (2) |
As2—O6 | 1.692 (2) | OW1—H1W1 | 0.896 (10) |
As2—O7 | 1.693 (2) | OW1—H2W1 | 0.898 (10) |
As2—O8 | 1.707 (2) | OW2—H1W2 | 0.900 (10) |
Zn1—OW2 | 2.032 (3) | OW2—H2W2 | 0.900 (10) |
Zn1—O7 | 2.036 (2) | N—C1 | 1.495 (5) |
Zn1—O3 | 2.048 (2) | N—C3 | 1.496 (5) |
Zn1—O6i | 2.056 (2) | N—C2 | 1.497 (5) |
Zn1—O7ii | 2.086 (2) | N—HN | 0.901 (10) |
Zn1—Zn1ii | 3.1508 (10) | C1—H1C1 | 0.9600 |
Zn2—O2iii | 2.061 (2) | C1—H2C1 | 0.9600 |
Zn2—O3 | 2.071 (2) | C1—H3C1 | 0.9600 |
Zn2—OW1 | 2.074 (3) | C2—H1C2 | 0.9600 |
Zn2—O2iv | 2.078 (2) | C2—H2C2 | 0.9600 |
Zn2—O6i | 2.116 (2) | C2—H3C2 | 0.9600 |
Zn2—O8v | 2.182 (2) | C3—C3ix | 1.514 (7) |
Zn2—Zn2vi | 3.0757 (10) | C3—H1C3 | 0.9700 |
O2—Zn2vii | 2.061 (2) | C3—H2C3 | 0.9700 |
O2—Zn2iv | 2.078 (2) | | |
| | | |
O1—As1—O2 | 109.78 (12) | O6i—Zn2—Zn2vi | 86.76 (7) |
O1—As1—O3 | 113.58 (12) | O8v—Zn2—Zn2vi | 86.47 (7) |
O2—As1—O3 | 112.19 (12) | As1—O2—Zn2vii | 133.09 (14) |
O1—As1—O4 | 108.11 (14) | As1—O2—Zn2iv | 129.96 (13) |
O2—As1—O4 | 106.62 (13) | Zn2vii—O2—Zn2iv | 95.98 (10) |
O3—As1—O4 | 106.18 (12) | As1—O3—Zn1 | 131.82 (13) |
O5—As2—O6 | 109.33 (12) | As1—O3—Zn2 | 126.01 (13) |
O5—As2—O7 | 111.73 (12) | Zn1—O3—Zn2 | 101.54 (10) |
O6—As2—O7 | 108.98 (12) | As1—O4—HO4 | 109.5 |
O5—As2—O8 | 106.16 (12) | As2—O6—Zn1i | 132.13 (13) |
O6—As2—O8 | 112.70 (11) | As2—O6—Zn2i | 122.90 (12) |
O7—As2—O8 | 107.97 (11) | Zn1i—O6—Zn2i | 99.79 (10) |
OW2—Zn1—O7 | 101.80 (10) | As2—O7—Zn1 | 126.44 (13) |
OW2—Zn1—O3 | 147.79 (10) | As2—O7—Zn1ii | 132.93 (14) |
O7—Zn1—O3 | 110.39 (10) | Zn1—O7—Zn1ii | 99.70 (10) |
OW2—Zn1—O6i | 93.94 (10) | As2—O8—Zn2viii | 122.08 (13) |
O7—Zn1—O6i | 103.08 (9) | Zn2—OW1—H1W1 | 104 (3) |
O3—Zn1—O6i | 80.28 (9) | Zn2—OW1—H2W1 | 112 (5) |
OW2—Zn1—O7ii | 90.88 (10) | H1W1—OW1—H2W1 | 112 (6) |
O7—Zn1—O7ii | 80.30 (10) | Zn1—OW2—H1W2 | 107 (3) |
O3—Zn1—O7ii | 93.23 (10) | Zn1—OW2—H2W2 | 116 (4) |
O6i—Zn1—O7ii | 173.39 (9) | H1W2—OW2—H2W2 | 105 (5) |
OW2—Zn1—Zn1ii | 98.18 (7) | C1—N—C3 | 110.1 (3) |
O7—Zn1—Zn1ii | 40.73 (6) | C1—N—C2 | 110.8 (3) |
O3—Zn1—Zn1ii | 105.22 (7) | C3—N—C2 | 112.9 (3) |
O6i—Zn1—Zn1ii | 143.50 (7) | C1—N—HN | 107 (3) |
O7ii—Zn1—Zn1ii | 39.57 (7) | C3—N—HN | 109 (3) |
O2iii—Zn2—O3 | 165.18 (10) | C2—N—HN | 107 (3) |
O2iii—Zn2—OW1 | 94.28 (10) | N—C1—H1C1 | 109.5 |
O3—Zn2—OW1 | 91.03 (10) | N—C1—H2C1 | 109.5 |
O2iii—Zn2—O2iv | 84.02 (10) | H1C1—C1—H2C1 | 109.5 |
O3—Zn2—O2iv | 91.70 (9) | N—C1—H3C1 | 109.5 |
OW1—Zn2—O2iv | 175.24 (10) | H1C1—C1—H3C1 | 109.5 |
O2iii—Zn2—O6i | 87.27 (9) | H2C1—C1—H3C1 | 109.5 |
O3—Zn2—O6i | 78.38 (9) | N—C2—H1C2 | 109.5 |
OW1—Zn2—O6i | 96.46 (10) | N—C2—H2C2 | 109.5 |
O2iv—Zn2—O6i | 87.91 (10) | H1C2—C2—H2C2 | 109.5 |
O2iii—Zn2—O8v | 91.28 (9) | N—C2—H3C2 | 109.5 |
O3—Zn2—O8v | 102.36 (9) | H1C2—C2—H3C2 | 109.5 |
OW1—Zn2—O8v | 92.10 (9) | H2C2—C2—H3C2 | 109.5 |
O2iv—Zn2—O8v | 83.50 (9) | N—C3—C3ix | 110.4 (4) |
O6i—Zn2—O8v | 171.40 (9) | N—C3—H1C3 | 109.6 |
O2iii—Zn2—Zn2vi | 42.22 (7) | C3ix—C3—H1C3 | 109.6 |
O3—Zn2—Zn2vi | 131.90 (7) | N—C3—H2C3 | 109.6 |
OW1—Zn2—Zn2vi | 136.34 (7) | C3ix—C3—H2C3 | 109.6 |
O2iv—Zn2—Zn2vi | 41.80 (6) | H1C3—C3—H2C3 | 108.1 |
Symmetry codes: (i) −x, −y, −z−1; (ii) −x, −y, −z; (iii) x, y, z−1; (iv) −x+1, −y, −z; (v) x+1, y, z; (vi) −x+1, −y, −z−1; (vii) x, y, z+1; (viii) x−1, y, z; (ix) −x, −y+1, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N—HN···O8ix | 0.90 (1) | 1.87 (1) | 2.760 (4) | 168 (4) |
O4—HO4···O8v | 0.82 | 1.80 | 2.619 (4) | 174 |
OW1—H1W1···O1iii | 0.90 (1) | 1.81 (1) | 2.700 (4) | 173 (5) |
OW1—H2W1···O5 | 0.90 (1) | 1.84 (3) | 2.682 (3) | 156 (7) |
OW2—H1W2···O5i | 0.90 (1) | 1.77 (1) | 2.659 (4) | 170 (5) |
OW2—H2W2···O1ii | 0.90 (1) | 1.80 (2) | 2.686 (4) | 169 (6) |
Symmetry codes: (i) −x, −y, −z−1; (ii) −x, −y, −z; (iii) x, y, z−1; (v) x+1, y, z; (ix) −x, −y+1, −z. |
Experimental details
Crystal data |
Chemical formula | (C6H18N2)0.5[Zn2(AsO4)(HAsO4)(H2O)2] |
Mr | 504.73 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 8.087 (1), 11.354 (2), 6.622 (2) |
α, β, γ (°) | 101.15 (2), 96.64 (2), 102.79 (1) |
V (Å3) | 573.7 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 9.95 |
Crystal size (mm) | 0.45 × 0.25 × 0.14 |
|
Data collection |
Diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.063, 0.248 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2630, 2499, 2284 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.638 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.027, 0.077, 1.12 |
No. of reflections | 2499 |
No. of parameters | 196 |
No. of restraints | 5 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 1.45, −0.79 |
Selected bond lengths (Å) topAs1—O1 | 1.656 (2) | Zn1—O3 | 2.048 (2) |
As1—O2 | 1.669 (2) | Zn1—O6i | 2.056 (2) |
As1—O3 | 1.683 (2) | Zn1—O7ii | 2.086 (2) |
As1—O4 | 1.725 (2) | Zn2—O2iii | 2.061 (2) |
As2—O5 | 1.669 (2) | Zn2—O3 | 2.071 (2) |
As2—O6 | 1.692 (2) | Zn2—OW1 | 2.074 (3) |
As2—O7 | 1.693 (2) | Zn2—O2iv | 2.078 (2) |
As2—O8 | 1.707 (2) | Zn2—O6i | 2.116 (2) |
Zn1—OW2 | 2.032 (3) | Zn2—O8v | 2.182 (2) |
Zn1—O7 | 2.036 (2) | | |
Symmetry codes: (i) −x, −y, −z−1; (ii) −x, −y, −z; (iii) x, y, z−1; (iv) −x+1, −y, −z; (v) x+1, y, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N—HN···O8vi | 0.90 (1) | 1.87 (1) | 2.760 (4) | 168 (4) |
O4—HO4···O8v | 0.82 | 1.80 | 2.619 (4) | 174.41 |
OW1—H1W1···O1iii | 0.90 (1) | 1.81 (1) | 2.700 (4) | 173 (5) |
OW1—H2W1···O5 | 0.90 (1) | 1.84 (3) | 2.682 (3) | 156 (7) |
OW2—H1W2···O5i | 0.90 (1) | 1.77 (1) | 2.659 (4) | 170 (5) |
Symmetry codes: (i) −x, −y, −z−1; (iii) x, y, z−1; (v) x+1, y, z; (vi) −x, −y+1, −z. |
Microporous compounds with an anionic framework are of particular interest because of their catalytic properties (Thomas, 1988) and their use as molecular sieves. During the last decade, many aluminophosphates (Chippindale et al., 1992; Yao et al., 1999), gallophosphates (Jones et al., 1991; Chippindale et al., 1998) and zincophosphates (Harrison et al., 1992; Chavez et al., 1999) with open frameworks have been synthesized hydrothermally. Replacement of phosphate by arsenate in the framework leads to a variety of phases (Bu et al., 1998; Harrison et al., 1999), some of which are analogous to zincophosphates (Harrison et al., 1999). In our search for novel framework structures containing zinc in combination with P or As atoms, we have discovered two new zincophosphate materials, namely Zn2(HPO4)2Cl2·2NC6H14 (Trojette et al., 1998) and [H2N2C6H16]0.5[Zn2(PO4)(HPO4)(H2O)]·H2O (Hajem et al., 1999). As part of these studies, we have examined the structure of [H2N2C6H16]0.5[Zn2(AsO4)(HAsO4)(H2O)2], (I) and report here its synthesis and structural characterization.
The title compound contains a layered structure (Fig. 1) consisting of organic sheets corresponding to N,N,N',N'-tetramethylethylenediamine (TMEDA) molecules and inorganic layers alternating along [010].
In the framework structure, the Zn atoms exhibit two types of coordination. The polyhedron around Zn1 is a distorted trigonal bipyramid formed by four O atoms and one terminal water molecule (OW2). The Zn2 atom is surrounded by five O atoms and one terminal water molecule (OW1) resulting in an octahedral coordination. The two As atoms are tetrahedrally coordinated by O atoms. The As1 atom has two As—O bonds bridging to Zn atoms. The remaining As—O bonds consist of an As1—O4H group and an As1═O1 double bond. For the As2 atom, three of the coordinating O atoms are bonded to Zn atoms, while the fourth O atom is terminal (As2═O5).
The two-dimensional framework can be considered as a parallel arrangement (along the [101] direction) of chains built up from ZnO6 and ZnO5 polyhedra interconnected by AsO4 tetrahedra (Fig. 2). Each chain makes –Zn1–Zn1–Zn2–Zn2– linkages (oxygen designation omitted) and every zinc polyhedron shares two edges with its nearest neighbor zinc polyhedron through four trigonally coordinated O atoms. These O atoms have a trigonal coordination because they contain not only Zn—O—Zn linkages, but also Zn—O—As linkages.
The TMEDA molecules are inserted between the inorganic layers and give rise to hydrogen bonds between H atoms of the protonated amine and O atoms of the framework (N—HN···O8; Fig. 1). Finally, the terminal –OH and OH2 groups participate in in-sheet hydrogen bonds, i.e. O4—HO4···O8, OW1—H1W1···O1, OW1—H2W1···O5, OW2—H1W2···O5 and OW2—H2W2···O1.