Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107020100/ga3050sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270107020100/ga3050Isup2.hkl |
CCDC reference: 628998
An aqueous solution (5 ml) of SrCl2·6H2O (0.2666 g, 1 mmol) was added dropwise to a hot aqueous solution (3 ml) of NO2—H2BDC (0.2210 g, 1 mmol). After mixing for 5 min, an aqueous solution (2 ml) of NaN3 was slowly added. The resulting mixture was stirred for 10 min at room temperature and then filtered. Colourless block-shaped crystals of (I) were obtained from the filtrate at room temperature after four weeks. See the archived CIF for a warning and IR data.
H atoms attached to C atoms were placed in calculated positions, with C—H = 0.93 Å, and allowed to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C). H atoms attached to O atoms were located in a difference map and refined as riding from their as-found positions, with O—H = 0.85–0.87 Å, with Uiso(H) = 1.2Ueq(O).
Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: SHELXTL.
[Sr(C8H3NO6)(H2O)] | F(000) = 1232 |
Mr = 314.75 | Dx = 2.100 Mg m−3 |
Orthorhombic, Pccn | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ab 2ac | Cell parameters from 3159 reflections |
a = 11.0883 (19) Å | θ = 3.0–26.4° |
b = 26.405 (5) Å | µ = 5.44 mm−1 |
c = 6.8010 (12) Å | T = 294 K |
V = 1991.2 (6) Å3 | Block, colourless |
Z = 8 | 0.28 × 0.18 × 0.16 mm |
Bruker SMART CCD area-detector diffractometer | 1747 independent reflections |
Radiation source: fine-focus sealed tube | 1387 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.076 |
ϕ and ω scans | θmax = 25.0°, θmin = 1.5° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −12→13 |
Tmin = 0.311, Tmax = 0.416 | k = −31→28 |
9126 measured reflections | l = −8→6 |
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)] = 0.036 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.081 | H-atom parameters constrained |
S = 1.15 | w = 1/[σ2(Fo2) + (0.0264P)2 + 2.9895P] where P = (Fo2 + 2Fc2)/3 |
1747 reflections | (Δ/σ)max < 0.001 |
154 parameters | Δρmax = 0.74 e Å−3 |
3 restraints | Δρmin = −0.77 e Å−3 |
[Sr(C8H3NO6)(H2O)] | V = 1991.2 (6) Å3 |
Mr = 314.75 | Z = 8 |
Orthorhombic, Pccn | Mo Kα radiation |
a = 11.0883 (19) Å | µ = 5.44 mm−1 |
b = 26.405 (5) Å | T = 294 K |
c = 6.8010 (12) Å | 0.28 × 0.18 × 0.16 mm |
Bruker SMART CCD area-detector diffractometer | 1747 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1387 reflections with I > 2σ(I) |
Tmin = 0.311, Tmax = 0.416 | Rint = 0.076 |
9126 measured reflections |
R[F2 > 2σ(F2)] = 0.036 | 3 restraints |
wR(F2) = 0.081 | H-atom parameters constrained |
S = 1.15 | Δρmax = 0.74 e Å−3 |
1747 reflections | Δρmin = −0.77 e Å−3 |
154 parameters |
Experimental. Caution! Metal azide complexes are potentially explosive. Only a small amount of material should be prepared and should be handled with caution. IR (KBr pellet, ν, cm-1): 3620 (w), 1650 (w), 1623 (w), 1591 (s), 1578 (s), 1516 (m), 1434 (m), 1371 (m), 1345 (m), 853 (m), 823 (m), 791 (m), 754 (m), 724 (m). |
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 | ||
Sr1 | 0.16049 (3) | 0.430282 (14) | 0.17910 (6) | 0.01555 (15) | |
O1 | 0.9499 (3) | 0.45920 (12) | 0.1695 (5) | 0.0306 (8) | |
O2 | 0.7891 (3) | 0.50677 (10) | 0.1039 (4) | 0.0200 (7) | |
O3 | 0.3764 (3) | 0.41322 (12) | 0.0371 (5) | 0.0247 (7) | |
O4 | 0.3662 (2) | 0.38796 (11) | 0.3461 (4) | 0.0207 (7) | |
O5 | 0.4329 (3) | 0.29302 (13) | 0.1683 (6) | 0.0450 (10) | |
O6 | 0.5695 (4) | 0.25904 (14) | 0.3488 (7) | 0.0533 (12) | |
O7 | 0.1166 (4) | 0.33264 (14) | 0.2162 (6) | 0.0563 (12) | |
H7A | 0.1215 | 0.3163 | 0.3275 | 0.068* | |
H7B | 0.1372 | 0.3169 | 0.1121 | 0.068* | |
N1 | 0.5311 (4) | 0.29380 (14) | 0.2489 (6) | 0.0288 (10) | |
C1 | 0.8400 (4) | 0.46541 (15) | 0.1469 (6) | 0.0168 (9) | |
C2 | 0.7585 (4) | 0.41996 (14) | 0.1716 (6) | 0.0164 (9) | |
C3 | 0.8065 (4) | 0.37232 (16) | 0.2071 (6) | 0.0193 (10) | |
H3 | 0.8896 | 0.3682 | 0.2142 | 0.023* | |
C4 | 0.7321 (4) | 0.33113 (17) | 0.2320 (7) | 0.0230 (11) | |
H4 | 0.7642 | 0.2991 | 0.2548 | 0.028* | |
C5 | 0.6082 (4) | 0.33818 (16) | 0.2225 (6) | 0.0167 (10) | |
C6 | 0.5567 (4) | 0.38525 (15) | 0.1873 (6) | 0.0153 (9) | |
C7 | 0.6339 (4) | 0.42565 (15) | 0.1598 (6) | 0.0169 (9) | |
H7 | 0.6018 | 0.4574 | 0.1328 | 0.020* | |
C8 | 0.4226 (4) | 0.39555 (15) | 0.1898 (6) | 0.0150 (9) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Sr1 | 0.0106 (2) | 0.0193 (2) | 0.0167 (2) | −0.00074 (18) | −0.00010 (17) | 0.00138 (19) |
O1 | 0.0116 (16) | 0.0316 (19) | 0.049 (2) | 0.0011 (14) | −0.0014 (16) | 0.0068 (17) |
O2 | 0.0182 (15) | 0.0120 (15) | 0.0298 (18) | −0.0005 (13) | 0.0021 (14) | 0.0016 (13) |
O3 | 0.0162 (15) | 0.0410 (19) | 0.0167 (17) | 0.0037 (14) | −0.0054 (14) | 0.0044 (15) |
O4 | 0.0187 (16) | 0.0257 (17) | 0.0178 (18) | 0.0020 (13) | 0.0056 (13) | 0.0001 (14) |
O5 | 0.0249 (19) | 0.029 (2) | 0.081 (3) | −0.0076 (16) | 0.004 (2) | −0.008 (2) |
O6 | 0.049 (2) | 0.025 (2) | 0.085 (3) | 0.0001 (18) | 0.008 (2) | 0.025 (2) |
O7 | 0.082 (3) | 0.033 (2) | 0.054 (3) | −0.010 (2) | 0.000 (2) | 0.005 (2) |
N1 | 0.028 (2) | 0.015 (2) | 0.044 (3) | 0.0013 (18) | 0.011 (2) | −0.0013 (19) |
C1 | 0.019 (2) | 0.019 (2) | 0.013 (2) | 0.0019 (19) | −0.0003 (19) | 0.0008 (17) |
C2 | 0.019 (2) | 0.016 (2) | 0.014 (2) | 0.0047 (17) | 0.0000 (19) | 0.0028 (19) |
C3 | 0.015 (2) | 0.021 (2) | 0.022 (3) | 0.0030 (18) | −0.0007 (18) | 0.003 (2) |
C4 | 0.020 (2) | 0.016 (2) | 0.032 (3) | 0.0058 (19) | 0.002 (2) | 0.003 (2) |
C5 | 0.018 (2) | 0.015 (2) | 0.018 (2) | 0.0000 (18) | 0.0029 (19) | 0.0002 (18) |
C6 | 0.013 (2) | 0.019 (2) | 0.014 (2) | 0.0028 (17) | 0.0000 (18) | −0.0010 (19) |
C7 | 0.017 (2) | 0.013 (2) | 0.020 (2) | 0.0025 (18) | 0.0005 (18) | −0.0026 (19) |
C8 | 0.015 (2) | 0.009 (2) | 0.021 (2) | −0.0017 (17) | 0.0011 (19) | −0.0063 (19) |
Sr1—O1i | 2.458 (3) | O7—H7A | 0.8729 |
Sr1—O3ii | 2.510 (3) | O7—H7B | 0.8528 |
Sr1—O4iii | 2.543 (3) | N1—C5 | 1.461 (5) |
Sr1—O2iv | 2.604 (3) | C1—C2 | 1.511 (6) |
Sr1—O3 | 2.621 (3) | C2—C3 | 1.387 (5) |
Sr1—O7 | 2.636 (4) | C2—C7 | 1.393 (6) |
Sr1—O2v | 2.641 (3) | C3—C4 | 1.375 (6) |
Sr1—O4 | 2.783 (3) | C3—H3 | 0.9300 |
O1—C1 | 1.239 (5) | C4—C5 | 1.388 (6) |
O2—C1 | 1.263 (5) | C4—H4 | 0.9300 |
O3—C8 | 1.249 (5) | C5—C6 | 1.389 (6) |
O4—C8 | 1.249 (5) | C6—C7 | 1.380 (6) |
O5—N1 | 1.220 (5) | C6—C8 | 1.511 (6) |
O6—N1 | 1.219 (5) | C7—H7 | 0.9300 |
O1i—Sr1—O3ii | 85.79 (10) | Sr1iii—O3—Sr1 | 100.23 (10) |
O1i—Sr1—O4iii | 90.12 (11) | C8—O4—Sr1ii | 138.2 (3) |
O3ii—Sr1—O4iii | 140.01 (10) | C8—O4—Sr1 | 89.9 (2) |
O1i—Sr1—O2iv | 89.19 (10) | Sr1ii—O4—Sr1 | 95.24 (9) |
O3ii—Sr1—O2iv | 150.08 (10) | Sr1—O7—H7A | 123.7 |
O4iii—Sr1—O2iv | 69.34 (9) | Sr1—O7—H7B | 110.4 |
O1i—Sr1—O3 | 155.74 (11) | H7A—O7—H7B | 117.4 |
O3ii—Sr1—O3 | 118.40 (9) | O6—N1—O5 | 123.4 (4) |
O4iii—Sr1—O3 | 72.70 (9) | O6—N1—C5 | 117.9 (4) |
O2iv—Sr1—O3 | 68.98 (9) | O1—C1—O2 | 125.6 (4) |
O1i—Sr1—O7 | 97.51 (12) | O1—C1—C2 | 118.0 (4) |
O3ii—Sr1—O7 | 72.63 (12) | O2—C1—C2 | 116.5 (4) |
O4iii—Sr1—O7 | 68.52 (11) | C3—C2—C7 | 119.2 (4) |
O2iv—Sr1—O7 | 137.29 (11) | C3—C2—C1 | 120.7 (4) |
O3—Sr1—O7 | 92.06 (12) | C7—C2—C1 | 120.1 (4) |
O1i—Sr1—O2v | 109.42 (10) | C4—C3—C2 | 120.6 (4) |
O3ii—Sr1—O2v | 70.06 (10) | C4—C3—H3 | 119.7 |
O4iii—Sr1—O2v | 146.85 (9) | C2—C3—H3 | 119.7 |
O2iv—Sr1—O2v | 84.00 (7) | C3—C4—C5 | 118.8 (4) |
O3—Sr1—O2v | 79.67 (9) | C3—C4—H4 | 120.6 |
O7—Sr1—O2v | 131.44 (11) | C5—C4—H4 | 120.6 |
O1i—Sr1—O4 | 156.15 (10) | C4—C5—C6 | 122.4 (4) |
O3ii—Sr1—O4 | 70.47 (9) | C4—C5—N1 | 117.7 (4) |
O4iii—Sr1—O4 | 106.41 (9) | C6—C5—N1 | 119.9 (4) |
O2iv—Sr1—O4 | 112.46 (9) | C7—C6—C5 | 117.4 (4) |
O3—Sr1—O4 | 48.11 (9) | C7—C6—C8 | 118.2 (4) |
O7—Sr1—O4 | 73.72 (11) | C5—C6—C8 | 124.3 (4) |
O2v—Sr1—O4 | 65.29 (9) | C6—C7—C2 | 121.6 (4) |
C1—O1—Sr1vi | 168.2 (3) | C6—C7—H7 | 119.2 |
C1—O2—Sr1iv | 128.9 (3) | C2—C7—H7 | 119.2 |
C1—O2—Sr1vii | 131.0 (3) | O3—C8—O4 | 124.2 (4) |
Sr1iv—O2—Sr1vii | 97.31 (9) | O3—C8—C6 | 117.5 (4) |
C8—O3—Sr1iii | 160.2 (3) | O4—C8—C6 | 118.2 (4) |
C8—O3—Sr1 | 97.6 (2) | ||
O1i—Sr1—O3—C8 | 178.7 (3) | O1—C1—C2—C3 | −3.6 (6) |
O3ii—Sr1—O3—C8 | 3.5 (3) | O2—C1—C2—C3 | 176.1 (4) |
O4iii—Sr1—O3—C8 | −134.5 (3) | O1—C1—C2—C7 | 176.0 (4) |
O2iv—Sr1—O3—C8 | 151.5 (3) | O2—C1—C2—C7 | −4.3 (6) |
O7—Sr1—O3—C8 | −67.8 (3) | C7—C2—C3—C4 | −0.5 (7) |
O2v—Sr1—O3—C8 | 64.0 (2) | C1—C2—C3—C4 | 179.2 (4) |
O4—Sr1—O3—C8 | −2.0 (2) | C2—C3—C4—C5 | −0.5 (7) |
O1i—Sr1—O3—Sr1iii | −9.8 (3) | C3—C4—C5—C6 | 0.5 (7) |
O3ii—Sr1—O3—Sr1iii | 174.97 (4) | C3—C4—C5—N1 | 179.9 (4) |
O4iii—Sr1—O3—Sr1iii | 36.90 (10) | O6—N1—C5—C4 | 27.9 (6) |
O2iv—Sr1—O3—Sr1iii | −37.06 (10) | O5—N1—C5—C4 | −151.0 (4) |
O7—Sr1—O3—Sr1iii | 103.64 (12) | O6—N1—C5—C6 | −152.7 (4) |
O2v—Sr1—O3—Sr1iii | −124.55 (11) | O5—N1—C5—C6 | 28.4 (6) |
O4—Sr1—O3—Sr1iii | 169.49 (16) | C4—C5—C6—C7 | 0.5 (6) |
O1i—Sr1—O4—C8 | −178.7 (3) | N1—C5—C6—C7 | −178.8 (4) |
O3ii—Sr1—O4—C8 | −172.9 (2) | C4—C5—C6—C8 | −175.5 (4) |
O4iii—Sr1—O4—C8 | 49.1 (3) | N1—C5—C6—C8 | 5.2 (7) |
O2iv—Sr1—O4—C8 | −24.9 (2) | C5—C6—C7—C2 | −1.6 (6) |
O3—Sr1—O4—C8 | 1.9 (2) | C8—C6—C7—C2 | 174.7 (4) |
O7—Sr1—O4—C8 | 110.1 (2) | C3—C2—C7—C6 | 1.5 (7) |
O2v—Sr1—O4—C8 | −96.5 (2) | C1—C2—C7—C6 | −178.1 (4) |
O1i—Sr1—O4—Sr1ii | −40.3 (3) | Sr1iii—O3—C8—O4 | −150.5 (6) |
O3ii—Sr1—O4—Sr1ii | −34.48 (9) | Sr1—O3—C8—O4 | 3.9 (4) |
O4iii—Sr1—O4—Sr1ii | −172.47 (7) | Sr1iii—O3—C8—C6 | 32.7 (10) |
O2iv—Sr1—O4—Sr1ii | 113.57 (9) | Sr1—O3—C8—C6 | −172.9 (3) |
O3—Sr1—O4—Sr1ii | 140.40 (15) | Sr1ii—O4—C8—O3 | −101.5 (5) |
O7—Sr1—O4—Sr1ii | −111.40 (13) | Sr1—O4—C8—O3 | −3.7 (4) |
O2v—Sr1—O4—Sr1ii | 41.92 (9) | Sr1ii—O4—C8—C6 | 75.3 (5) |
Sr1vi—O1—C1—O2 | −140.8 (13) | Sr1—O4—C8—C6 | 173.1 (3) |
Sr1vi—O1—C1—C2 | 38.9 (17) | C7—C6—C8—O3 | 62.2 (5) |
Sr1iv—O2—C1—O1 | 50.9 (6) | C5—C6—C8—O3 | −121.8 (5) |
Sr1vii—O2—C1—O1 | −105.5 (5) | C7—C6—C8—O4 | −114.8 (4) |
Sr1iv—O2—C1—C2 | −128.9 (3) | C5—C6—C8—O4 | 61.2 (6) |
Sr1vii—O2—C1—C2 | 74.8 (4) |
Symmetry codes: (i) x−1, y, z; (ii) −x+1/2, y, z+1/2; (iii) −x+1/2, y, z−1/2; (iv) −x+1, −y+1, −z; (v) x−1/2, −y+1, −z+1/2; (vi) x+1, y, z; (vii) x+1/2, −y+1, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7A···O5ii | 0.87 | 2.47 | 3.294 (6) | 157 |
C4—H4···O6viii | 0.93 | 2.48 | 3.335 (6) | 153 |
Symmetry codes: (ii) −x+1/2, y, z+1/2; (viii) −x+3/2, −y+1/2, z. |
Experimental details
Crystal data | |
Chemical formula | [Sr(C8H3NO6)(H2O)] |
Mr | 314.75 |
Crystal system, space group | Orthorhombic, Pccn |
Temperature (K) | 294 |
a, b, c (Å) | 11.0883 (19), 26.405 (5), 6.8010 (12) |
V (Å3) | 1991.2 (6) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 5.44 |
Crystal size (mm) | 0.28 × 0.18 × 0.16 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.311, 0.416 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9126, 1747, 1387 |
Rint | 0.076 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.036, 0.081, 1.15 |
No. of reflections | 1747 |
No. of parameters | 154 |
No. of restraints | 3 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.74, −0.77 |
Computer programs: SMART (Bruker, 1997), SMART, SAINT (Bruker, 1997), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1998), SHELXTL.
Sr1—O1i | 2.458 (3) | Sr1—O2v | 2.641 (3) |
Sr1—O3ii | 2.510 (3) | Sr1—O4 | 2.783 (3) |
Sr1—O4iii | 2.543 (3) | O1—C1 | 1.239 (5) |
Sr1—O2iv | 2.604 (3) | O2—C1 | 1.263 (5) |
Sr1—O3 | 2.621 (3) | O3—C8 | 1.249 (5) |
Sr1—O7 | 2.636 (4) | O4—C8 | 1.249 (5) |
O4iii—Sr1—O2iv | 69.34 (9) | O2iv—Sr1—O3 | 68.98 (9) |
O4iii—Sr1—O3 | 72.70 (9) |
Symmetry codes: (i) x−1, y, z; (ii) −x+1/2, y, z+1/2; (iii) −x+1/2, y, z−1/2; (iv) −x+1, −y+1, −z; (v) x−1/2, −y+1, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7A···O5ii | 0.87 | 2.47 | 3.294 (6) | 157 |
C4—H4···O6vi | 0.93 | 2.48 | 3.335 (6) | 153 |
Symmetry codes: (ii) −x+1/2, y, z+1/2; (vi) −x+3/2, −y+1/2, z. |
In recent years, great interest has been focused on the design and synthesis of coordination polymers due to their intriguing architectures and favourable properties (Biradha & Fujita, 2002; Lee & Lin, 2002; Lin et al., 2000; Moulton & Zaworotko, 2001; Sun et al., 2002; Tominaga et al., 2002). The selected ligand is an important factor that greatly influences the structure of the coordination polymer and the functionality of the complex formed. 4-Nitro-1,3-benzenedicarboxylic acid can act as a multifunctional organic ligand via various coordination modes to metal ions utilizing completely or partially deprotonated sites, and can provide suitable hydrogen-bond acceptors and donors. In addition, the noncoordinated –NO2 functional group may assist in the creation of supramolecular assemblies through the simultaneous formation of dative and noncovalent bonds (Pedireddi & Varughese, 2004; Luo et al.,2003). The structures of alkali earth metal complexes have been explored less than the extensively investigated transition metal complexes. Here, we report a novel SrII coordination polymer, the title compound, [Sr(NO2—BDC)(H2O)]n, (I) [NO2—H2BDC is 4-nitro-1,3-benzenedicarboxylic acid].
The asymmetric unit of (I) consists of one SrII ion, one NO2—BDC ligand molecule and one coordinated water molecule (Fig. 1). Each SrII ion is eight-coordinate via seven O atoms of six symmetry-related NO2—BDC ligands (see the caption to Fig. 1 for the designations of these ligands) and one O atom of a water molecule. The coordination environment of the SrII ion can be described as a distorted bicapped triangular prism. The dihedral angle between the two basal planes (O2D/O3/O4 and O1A/O4C/O7) is 18.38 (15)°, and the vertical distances between the two capping atoms, O2E and O3B, and their side planes O1A/O2D/O3/O4C and O1A/O2D/O4/O7 are 2.061 (3) and 1.847 (3) Å, respectively. The Sr—O bond distances fall in the range 2.458 (3)–2.783 (3) Å (mean 2.600 Å; Table 1) and are all within the range of those observed for other eight-coordinated SrII complexes with O-donor ligands (Davies et al., 2001; Deng et al., 2005; Marchetti et al., 2006; Stahl et al., 2006).
In (I), the O1/C1/O2 group of NO2—BDC adopts a tridentate bridging coordination mode to bind three SrII ions, while the O3/C8/O4 group coordinates to one SrII ion in a bidentate chelate fashion and further bridges another two SrII ions through two three-coordinating O atoms (Fig. 1). The O1/C1/O2 group of NO2—BDC is nearly coplanar with the phenyl ring, with an interplanar angle of 4.3 (5)°, while the O3/C8/O4 group shows a large distortion from planarity with the phenyl ring, with a dihedral angle of 62.5 (5)°. The identical C—O bond distances [1.249 (5) Å] in O3/C8/O4 are different from those in the O1/C1/O2 group (Table 1), as might be expected from the different coordination modes of the two carboxylate groups. However, the average carboxylate C—O bond distance of 1.250 (5) Å is identical to that in the complex [La2(HL)2(L)2(H2O)6]·2H2O [1.256 (4) Å; H2L is 3-nitro-1,2-benzenedicarboxylic acid; Xiong & Qi, 2007] and that in [Mn(NO2—HBDC)2(H2O)4]·2H2O [1.254 (3) Å; Xiong et al., 2007].
Interestingly, the SrII ions are bridged by three O atoms of carboxylic acid groups (O3, O2E and O4C) in a `three-bladed propeller' mode to form a one-dimensional chain with Sr—O—Sr connectivity parallel to the c axis of the unit cell with similar O—Sr—O angles (Table 1). This mode has been reported in the complex strontium bis-N,N-di(isopropyl)aminoethylamino-2-penten-4-onate (Sergej et al., 2005), but there the Sr—O—Sr connectivity is limited to trimer units.
The O1/C1/O2 groups of NO2—BDC, acting as T-shaped units, link the SrII ions to form a one-dimensional chain with Sr—O—C—O—Sr connectivity parallel to the a axis of the unit cell. As a result, a two-dimensional layered architecture is obtained (Fig. 2) which has close contacts between the non-coordinating nitro O atoms [O5···O6i = 2.986 (5) Å; symmetry code: (i) x, 1/2 - y, -1/2 + z]. This kind of O···O contact has been reported in 1,2,3,4,5,7-hexanitrocubane (Gilardi et al., 2002).
In addition, there is an intramolecular O—H···O hydrogen bond between the bound water molecule and one nitro O atom (O5) and an intermolecular C—H···O hydrogen bond utilizing the other nitro O atom (O6) (Table 2). The latter provides a weak link between the two-dimensional layers and has a graph-set motif of R22(10) (Bernstein et al., 1995). A similar layered coordination polymer has been reported in polymeric diaquatetrakis(µ-1,2-benzenedicarboxylato)di-µ-nitrato-pentastrontium(II) (Stein & Ruschewitz, 2005), where the two-dimensional layers are only held together by weak van der Waals forces.