Experimental
Crystal data
[Cd(C7H3NO4)(H2O)3] Mr = 331.55 Orthorhombic, P c a 21 a = 16.820 (3) Å b = 6.8076 (14) Å c = 8.6658 (17) Å V = 992.3 (3) Å3 Z = 4 Mo Kα radiation μ = 2.22 mm−1 T = 100 (2) K 0.40 × 0.08 × 0.05 mm
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Data collection
Bruker APEX 1000 CCD area-detector diffractometer Absorption correction: multi-scan (APEX2; Bruker, 2005) Tmin = 0.810, Tmax = 0.901 8990 measured reflections 2255 independent reflections 1848 reflections with I > 2σ(I) Rint = 0.060
|
Refinement
R[F2 > 2σ(F2)] = 0.029 wR(F2) = 0.056 S = 1.01 2255 reflections 151 parameters 7 restraints H atoms treated by a mixture of independent and constrained refinement Δρmax = 0.61 e Å−3 Δρmin = −0.84 e Å−3 Absolute structure: Flack (1983), 1042 Friedel pairs Flack parameter: 0.05 (4)
|
Cd1—O1W | 2.254 (4) | Cd1—O2i | 2.259 (3) | Cd1—O3W | 2.274 (3) | Cd1—O4 | 2.279 (3) | Cd1—N1i | 2.302 (4) | Cd1—O2W | 2.385 (3) | | O3W—Cd1—O4 | 156.89 (12) | O1W—Cd1—N1i | 163.70 (14) | O2i—Cd1—O2W | 171.30 (12) | Symmetry code: (i) . | |
D—H⋯A | D—H | H⋯A | D⋯A | D—H⋯A | O1W—H1⋯O2Wii | 0.85 (2) | 1.99 (2) | 2.782 (5) | 155.61 | O1W—H2⋯O3iii | 0.87 (2) | 1.86 (2) | 2.702 (5) | 163.55 | O2W—H3⋯O1iii | 0.88 (2) | 1.85 (2) | 2.731 (5) | 177.88 | O2W—H4⋯O3iv | 0.87 (2) | 1.84 (2) | 2.687 (5) | 164.45 | O3W—H5⋯O4iii | 0.86 (2) | 1.86 (2) | 2.712 (4) | 171.29 | O3W—H6⋯O1v | 0.87 (2) | 1.89 (2) | 2.735 (8) | 164.32 | C3—H3A⋯O1Wvi | 0.95 (2) | 2.49 (2) | 3.420 (6) | 165 | Symmetry codes: (ii) ; (iii) ; (iv) ; (v) x, y, z-1; (vi) x, y+1, z. | |
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: APEX2; program(s) used to solve structure: SHELXTL (Sheldrick, 1998); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
Supporting information
The proton transfer ion pair was prepared according to the literature (Aghabozorg et al., 2008, in press). A solution of Cd(NO3)2. 6H2O (158 mg, 0.5 mmol) in water (20 ml) was added to a solution of (pipzH2)(py- 2,3-dc) (253 mg, 1.0 mmol) in water (20 ml), in a 1:2 molar ratio. Colorless crystals of the title compound suitable for X-ray characterization were obtained after a few days at room temperature.
All the hydrogen atoms could be located from the difference Fourier syntheses. The water H-atoms were refined isotropically with Uiso(H) = 0.022. The C-bond H-atoms were included in calculated positions and treated as riding atoms: C—H = 0.95 Å with Uiso(H) = 1.2 Ueq(C).
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: APEX2 (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 1998); program(s) used to refine structure: SHELXTL (Sheldrick, 1998); molecular graphics: SHELXTL (Sheldrick, 1998); software used to prepare material for publication: SHELXTL (Sheldrick, 1998).
catena-Poly[[triaquacadmium(II)]-µ-pyridine-2,3-dicarboxylato-
κ3N,
O2:
O3]
top Crystal data top [Cd(C7H3NO4)(H2O)3] | F(000) = 648 |
Mr = 331.55 | Dx = 2.219 Mg m−3 |
Orthorhombic, Pca21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2c -2ac | Cell parameters from 1136 reflections |
a = 16.820 (3) Å | θ = 3.0–24.6° |
b = 6.8076 (14) Å | µ = 2.22 mm−1 |
c = 8.6658 (17) Å | T = 100 K |
V = 992.3 (3) Å3 | Needle, colourless |
Z = 4 | 0.40 × 0.08 × 0.05 mm |
Data collection top Bruker APEX 1000 CCD area-detector diffractometer | 2255 independent reflections |
Radiation source: fine-focus sealed tube | 1848 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.060 |
ω scans | θmax = 27.5°, θmin = 2.4° |
Absorption correction: multi-scan (APEX2; Bruker, 2005) | h = −21→21 |
Tmin = 0.810, Tmax = 0.901 | k = −8→8 |
8990 measured reflections | l = −11→11 |
Refinement top Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.029 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.056 | w = 1/[σ2(Fo2) + (0.02P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.01 | (Δ/σ)max = 0.001 |
2255 reflections | Δρmax = 0.61 e Å−3 |
151 parameters | Δρmin = −0.84 e Å−3 |
7 restraints | Absolute structure: Flack (1983), 1042 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.05 (4) |
Crystal data top [Cd(C7H3NO4)(H2O)3] | V = 992.3 (3) Å3 |
Mr = 331.55 | Z = 4 |
Orthorhombic, Pca21 | Mo Kα radiation |
a = 16.820 (3) Å | µ = 2.22 mm−1 |
b = 6.8076 (14) Å | T = 100 K |
c = 8.6658 (17) Å | 0.40 × 0.08 × 0.05 mm |
Data collection top Bruker APEX 1000 CCD area-detector diffractometer | 2255 independent reflections |
Absorption correction: multi-scan (APEX2; Bruker, 2005) | 1848 reflections with I > 2σ(I) |
Tmin = 0.810, Tmax = 0.901 | Rint = 0.060 |
8990 measured reflections | |
Refinement top R[F2 > 2σ(F2)] = 0.029 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.056 | Δρmax = 0.61 e Å−3 |
S = 1.01 | Δρmin = −0.84 e Å−3 |
2255 reflections | Absolute structure: Flack (1983), 1042 Friedel pairs |
151 parameters | Absolute structure parameter: 0.05 (4) |
7 restraints | |
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 | |
Cd1 | 0.602315 (16) | 0.57263 (4) | 1.12348 (5) | 0.01148 (8) | |
O1 | 0.64375 (15) | 0.5438 (4) | 1.6269 (10) | 0.0146 (4) | |
O2 | 0.77114 (19) | 0.4893 (5) | 1.6812 (4) | 0.0146 (4) | |
O3 | 0.55536 (18) | 0.9159 (5) | 1.5507 (4) | 0.0139 (7) | |
O4 | 0.56140 (18) | 0.7169 (5) | 1.3472 (4) | 0.0131 (8) | |
C1 | 0.7384 (3) | 0.7512 (7) | 1.5083 (6) | 0.0114 (10) | |
C2 | 0.6813 (3) | 0.8656 (7) | 1.4333 (6) | 0.0120 (11) | |
C3 | 0.7065 (3) | 1.0220 (8) | 1.3431 (7) | 0.0110 (11) | |
H3A | 0.6685 | 1.1023 | 1.2920 | 0.013* | |
C4 | 0.7868 (3) | 1.0616 (8) | 1.3272 (7) | 0.0149 (11) | |
H4A | 0.8050 | 1.1660 | 1.2636 | 0.018* | |
C5 | 0.8403 (3) | 0.9424 (8) | 1.4080 (6) | 0.0168 (11) | |
H5A | 0.8956 | 0.9694 | 1.4001 | 0.020* | |
C6 | 0.7166 (2) | 0.5813 (6) | 1.6146 (9) | 0.0146 (4) | |
C7 | 0.5934 (3) | 0.8271 (7) | 1.4475 (5) | 0.0113 (10) | |
N1 | 0.8168 (2) | 0.7919 (6) | 1.4961 (5) | 0.0125 (9) | |
O1W | 0.5482 (2) | 0.2964 (6) | 1.2211 (4) | 0.0145 (8) | |
H1 | 0.526 (3) | 0.302 (9) | 1.309 (4) | 0.022* | |
H2 | 0.509 (2) | 0.227 (7) | 1.183 (5) | 0.022* | |
O2W | 0.47743 (19) | 0.6981 (5) | 1.0383 (4) | 0.0134 (7) | |
H3 | 0.439 (2) | 0.618 (6) | 1.065 (6) | 0.020* | |
H4 | 0.464 (3) | 0.818 (4) | 1.060 (6) | 0.020* | |
O3W | 0.59058 (19) | 0.3963 (5) | 0.9018 (4) | 0.0147 (8) | |
H5 | 0.5445 (19) | 0.350 (8) | 0.879 (7) | 0.022* | |
H6 | 0.609 (3) | 0.420 (8) | 0.811 (3) | 0.022* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.00902 (12) | 0.01505 (14) | 0.01036 (13) | −0.00047 (13) | 0.0004 (3) | 0.0018 (3) |
O1 | 0.0109 (8) | 0.0186 (11) | 0.0144 (10) | 0.0005 (8) | 0.0029 (11) | 0.0048 (12) |
O2 | 0.0109 (8) | 0.0186 (11) | 0.0144 (10) | 0.0005 (8) | 0.0029 (11) | 0.0048 (12) |
O3 | 0.0112 (16) | 0.0158 (18) | 0.0146 (16) | −0.0006 (14) | 0.0041 (13) | −0.0032 (16) |
O4 | 0.0077 (16) | 0.023 (2) | 0.0084 (17) | −0.0019 (14) | 0.0004 (14) | −0.0031 (16) |
C1 | 0.011 (2) | 0.012 (3) | 0.011 (2) | −0.0042 (19) | −0.0063 (19) | −0.001 (2) |
C2 | 0.010 (2) | 0.014 (3) | 0.012 (3) | −0.0018 (19) | 0.000 (2) | −0.005 (2) |
C3 | 0.009 (3) | 0.013 (3) | 0.011 (3) | 0.004 (2) | 0.000 (2) | −0.002 (2) |
C4 | 0.014 (3) | 0.016 (3) | 0.014 (3) | −0.002 (2) | −0.001 (2) | 0.005 (3) |
C5 | 0.012 (3) | 0.020 (3) | 0.017 (3) | −0.004 (2) | 0.000 (2) | −0.004 (3) |
C6 | 0.0109 (8) | 0.0186 (11) | 0.0144 (10) | 0.0005 (8) | 0.0029 (11) | 0.0048 (12) |
C7 | 0.013 (2) | 0.011 (3) | 0.010 (2) | −0.001 (2) | −0.003 (2) | 0.0057 (19) |
N1 | 0.011 (2) | 0.016 (2) | 0.010 (2) | −0.0057 (17) | 0.0018 (16) | −0.0007 (18) |
O1W | 0.0142 (18) | 0.022 (2) | 0.0070 (17) | −0.0081 (15) | 0.0020 (14) | −0.0012 (16) |
O2W | 0.0127 (17) | 0.0119 (19) | 0.0156 (19) | 0.0014 (14) | −0.0030 (14) | −0.0008 (17) |
O3W | 0.0113 (18) | 0.023 (2) | 0.0093 (16) | −0.0033 (15) | 0.0003 (14) | −0.0040 (16) |
Geometric parameters (Å, º) top Cd1—O1W | 2.254 (4) | C2—C7 | 1.506 (6) |
Cd1—O2i | 2.259 (3) | C3—C4 | 1.385 (6) |
Cd1—O3W | 2.274 (3) | C3—H3A | 0.9500 |
Cd1—O4 | 2.279 (3) | C4—C5 | 1.400 (7) |
Cd1—N1i | 2.302 (4) | C4—H4A | 0.9500 |
Cd1—O2W | 2.385 (3) | C5—N1 | 1.338 (7) |
O1—C6 | 1.256 (4) | C5—H5A | 0.9500 |
O2—C6 | 1.252 (6) | N1—Cd1ii | 2.302 (4) |
O2—Cd1ii | 2.259 (3) | O1W—H1 | 0.850 (19) |
O3—C7 | 1.255 (6) | O1W—H2 | 0.869 (19) |
O4—C7 | 1.268 (6) | O2W—H3 | 0.88 (2) |
C1—N1 | 1.351 (6) | O2W—H4 | 0.866 (19) |
C1—C2 | 1.397 (7) | O3W—H5 | 0.858 (19) |
C1—C6 | 1.523 (7) | O3W—H6 | 0.87 (2) |
C2—C3 | 1.387 (7) | | |
| | | |
O1W—Cd1—O2i | 95.06 (13) | C2—C3—H3A | 119.9 |
O1W—Cd1—O3W | 80.89 (13) | C3—C4—C5 | 117.7 (5) |
O2i—Cd1—O3W | 97.84 (12) | C3—C4—H4A | 121.1 |
O1W—Cd1—O4 | 85.31 (13) | C5—C4—H4A | 121.1 |
O2i—Cd1—O4 | 101.79 (12) | N1—C5—C4 | 122.6 (5) |
O3W—Cd1—O4 | 156.89 (12) | N1—C5—H5A | 118.7 |
O1W—Cd1—N1i | 163.70 (14) | C4—C5—H5A | 118.7 |
O2i—Cd1—N1i | 73.25 (13) | O2—C6—O1 | 125.0 (6) |
O3W—Cd1—N1i | 89.34 (14) | O2—C6—C1 | 118.8 (4) |
O4—Cd1—N1i | 107.87 (14) | O1—C6—C1 | 116.2 (5) |
O1W—Cd1—O2W | 93.38 (13) | O3—C7—O4 | 123.9 (4) |
O2i—Cd1—O2W | 171.30 (12) | O3—C7—C2 | 118.3 (4) |
O3W—Cd1—O2W | 81.44 (12) | O4—C7—C2 | 117.6 (4) |
O4—Cd1—O2W | 80.96 (12) | C5—N1—C1 | 119.4 (4) |
N1i—Cd1—O2W | 98.06 (13) | C5—N1—Cd1ii | 126.5 (3) |
C6—O2—Cd1ii | 117.6 (3) | C1—N1—Cd1ii | 114.0 (3) |
C7—O4—Cd1 | 135.2 (3) | Cd1—O1W—H1 | 118 (4) |
N1—C1—C2 | 121.3 (5) | Cd1—O1W—H2 | 128 (3) |
N1—C1—C6 | 116.0 (4) | H1—O1W—H2 | 92 (5) |
C2—C1—C6 | 122.6 (4) | Cd1—O2W—H3 | 110 (3) |
C3—C2—C1 | 118.7 (4) | Cd1—O2W—H4 | 120 (4) |
C3—C2—C7 | 118.6 (4) | H3—O2W—H4 | 110 (5) |
C1—C2—C7 | 122.7 (4) | Cd1—O3W—H5 | 118 (4) |
C4—C3—C2 | 120.2 (5) | Cd1—O3W—H6 | 130 (4) |
C4—C3—H3A | 119.9 | H5—O3W—H6 | 101 (5) |
| | | |
O1W—Cd1—O4—C7 | 131.6 (5) | C2—C1—C6—O2 | −177.9 (5) |
O2i—Cd1—O4—C7 | 37.4 (5) | N1—C1—C6—O1 | 179.6 (6) |
O3W—Cd1—O4—C7 | −175.1 (4) | C2—C1—C6—O1 | 2.7 (9) |
N1i—Cd1—O4—C7 | −38.6 (5) | Cd1—O4—C7—O3 | 168.0 (3) |
O2W—Cd1—O4—C7 | −134.3 (5) | Cd1—O4—C7—C2 | −7.0 (7) |
N1—C1—C2—C3 | 0.9 (7) | C3—C2—C7—O3 | −87.1 (6) |
C6—C1—C2—C3 | 177.6 (5) | C1—C2—C7—O3 | 92.4 (6) |
N1—C1—C2—C7 | −178.5 (4) | C3—C2—C7—O4 | 88.2 (6) |
C6—C1—C2—C7 | −1.8 (8) | C1—C2—C7—O4 | −92.3 (6) |
C1—C2—C3—C4 | 0.6 (9) | C4—C5—N1—C1 | 0.2 (8) |
C7—C2—C3—C4 | −179.9 (5) | C4—C5—N1—Cd1ii | 176.0 (4) |
C2—C3—C4—C5 | −1.7 (9) | C2—C1—N1—C5 | −1.3 (7) |
C3—C4—C5—N1 | 1.3 (9) | C6—C1—N1—C5 | −178.3 (5) |
Cd1ii—O2—C6—O1 | 175.2 (6) | C2—C1—N1—Cd1ii | −177.7 (4) |
Cd1ii—O2—C6—C1 | −4.1 (7) | C6—C1—N1—Cd1ii | 5.4 (6) |
N1—C1—C6—O2 | −1.0 (8) | | |
Symmetry codes: (i) −x+3/2, y, z−1/2; (ii) −x+3/2, y, z+1/2. |
Hydrogen-bond geometry (Å, º) top D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1···O2Wiii | 0.85 (2) | 1.99 (2) | 2.782 (5) | 156 |
O1W—H2···O3iv | 0.87 (2) | 1.86 (2) | 2.702 (5) | 164 |
O2W—H3···O1iv | 0.88 (2) | 1.85 (2) | 2.731 (5) | 178 |
O2W—H4···O3v | 0.87 (2) | 1.84 (2) | 2.687 (5) | 165 |
O3W—H5···O4iv | 0.86 (2) | 1.86 (2) | 2.712 (4) | 171 |
O3W—H6···O1vi | 0.87 (2) | 1.89 (2) | 2.735 (8) | 164 |
C3—H3A···O1Wvii | 0.95 (2) | 2.49 (2) | 3.420 (6) | 165 |
Symmetry codes: (iii) −x+1, −y+1, z+1/2; (iv) −x+1, −y+1, z−1/2; (v) −x+1, −y+2, z−1/2; (vi) x, y, z−1; (vii) x, y+1, z. |
Experimental details
Crystal data |
Chemical formula | [Cd(C7H3NO4)(H2O)3] |
Mr | 331.55 |
Crystal system, space group | Orthorhombic, Pca21 |
Temperature (K) | 100 |
a, b, c (Å) | 16.820 (3), 6.8076 (14), 8.6658 (17) |
V (Å3) | 992.3 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 2.22 |
Crystal size (mm) | 0.40 × 0.08 × 0.05 |
|
Data collection |
Diffractometer | Bruker APEX 1000 CCD area-detector diffractometer |
Absorption correction | Multi-scan (APEX2; Bruker, 2005) |
Tmin, Tmax | 0.810, 0.901 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8990, 2255, 1848 |
Rint | 0.060 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.056, 1.01 |
No. of reflections | 2255 |
No. of parameters | 151 |
No. of restraints | 7 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.61, −0.84 |
Absolute structure | Flack (1983), 1042 Friedel pairs |
Absolute structure parameter | 0.05 (4) |
Selected geometric parameters (Å, º) topCd1—O1W | 2.254 (4) | Cd1—O4 | 2.279 (3) |
Cd1—O2i | 2.259 (3) | Cd1—N1i | 2.302 (4) |
Cd1—O3W | 2.274 (3) | Cd1—O2W | 2.385 (3) |
| | | |
O3W—Cd1—O4 | 156.89 (12) | O2i—Cd1—O2W | 171.30 (12) |
O1W—Cd1—N1i | 163.70 (14) | | |
| | | |
N1—C1—C6—O2 | −1.0 (8) | C3—C2—C7—O4 | 88.2 (6) |
N1—C1—C6—O1 | 179.6 (6) | C1—C2—C7—O4 | −92.3 (6) |
Symmetry code: (i) −x+3/2, y, z−1/2. |
Hydrogen-bond geometry (Å, º) top D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1···O2Wii | 0.85 (2) | 1.99 (2) | 2.782 (5) | 155.61 |
O1W—H2···O3iii | 0.87 (2) | 1.86 (2) | 2.702 (5) | 163.55 |
O2W—H3···O1iii | 0.88 (2) | 1.85 (2) | 2.731 (5) | 177.88 |
O2W—H4···O3iv | 0.87 (2) | 1.84 (2) | 2.687 (5) | 164.45 |
O3W—H5···O4iii | 0.86 (2) | 1.86 (2) | 2.712 (4) | 171.29 |
O3W—H6···O1v | 0.87 (2) | 1.89 (2) | 2.735 (8) | 164.32 |
C3—H3A···O1Wvi | 0.95 (2) | 2.49 (2) | 3.420 (6) | 165 |
Symmetry codes: (ii) −x+1, −y+1, z+1/2; (iii) −x+1, −y+1, z−1/2; (iv) −x+1, −y+2, z−1/2; (v) x, y, z−1; (vi) x, y+1, z. |
References
Aghabozorg, H., Daneshvar, S., Motyeian, E., Ghadermazi, M. & Attar Gharamaleki, J. (2007). Acta Cryst. E63, m2468–m2469. Web of Science CSD CrossRef IUCr Journals Google Scholar
Aghabozorg, H., Manteghi, F. & Ghadermazi, M. (2008). Acta Cryst. E64. Submitted for publication. CrossRef IUCr Journals Google Scholar
Aghabozorg, H., Sadr-khanlou, E., Soleimannejad, J. & Adams, H. (2007). Acta Cryst. E63, m1769. Web of Science CSD CrossRef IUCr Journals Google Scholar
Bruker (2005). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Li, L. J. & Li, Y. (2004). J. Mol. Struct. 694, 199–203. Web of Science CSD CrossRef CAS Google Scholar
Manteghi, F., Ghadermazi, M. & Aghabozorg, H. (2007). Acta Cryst. E63, o2809. Web of Science CSD CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (1998). SHELXTL. Version. 5.10. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
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Recently, ion pairs or complexes related to the title compound have been reported (Aghabozorg, Daneshvar, Motyeian et al., 2007). Proton transfer from pyridine-2,3-dicarboxylic acid (py-2,3-dcH2) to amines, such as piperazine (pipz) and propane-1,3-diamine (pn), resulted in the formation of novel systems (Aghabozorg, Manteghi et al., 2007 submitted; Manteghi et al., 2007). The resulting compounds, with some remaining sites as electron donors, can coordinate to metallic ions (Aghabozorg, Sadr-khanlou et al., 2007). The molecular structure of the title compound shows that only the anionic fragment of starting proton transfer compound is incorporated into the complex and that the (pipzH2)2+ dication has been lost. Each cadmium(II) atom is coordinated by five O-atoms and one N-atom. The asymmetric unit consists of one cadmium, one bridging (py-2,3-dc)2- and three coordinated water molecules (Fig. 1). The (py-2,3-dc)2- groups bridge two cadmium ions by adopting two different coordination modes, bidentate and monodentate. The existance of both coordination modes is seldom found in pyridine multicarboxylate coordination polymers (Li et al. 2004). The bond lengths and bond angles of the equatorial bonds around the metal center with atoms N1A, O2A, O1W and O2W, and the axial bonds with atoms O4 and O3W, indicate that the geometric arrangement of the six donor atoms around the cadmium(II) atom is distorted octahedral (Table 1). It is noticeable that one of the carboxylate groups is almost coplannar with the pyridine ring and the other is perpendicular to it (Fig. 1). The formation of the polymeric chains along the c axis is illustrated in Fig. 2. There are a number of O—H···O hydrogen bonds (Table 2) involving the coordinated water molecules and other O-atoms, [D···A distances ranging from 2.685 (5) to 2.789 (5) Å], and a C—H···O bond [D···A distance of 3.430 (6) Å], that give rise to the formation of a three-dimensional network (Fig. 3).