metal-organic compounds
Diaquabis[4-(1H-imidazol-2-yl)pyridine-κN]bis(nitrato-κO)cadmium
aHubei Key Laboratory of Pollutant Analysis & Reuse Technology, College of Chemistry and Environmental Engineering, Hubei Normal University, Huangshi 435002, People's Republic of China
*Correspondence e-mail: jincm1999@yahoo.com
In the title compound, [Cd(NO3)2(C8H7N3)2(H2O)2], the CdII cation is situated on an inversion center and is coordinated by the O atoms of two nitrate anions, by the N atoms of two 4-(imidazol-2-yl)pyridine ligands and by two water O atoms in a slightly distorted N2O4 octahedral geometry. The dihedral angle between the imidazole and pyridine rings is 1.6 (2)°. In the crystal, molecules are linked by N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds, forming a three-dimensional network.
Related literature
For background to compounds with metal-organic framework (MOF) structures, see: Batten & Robson (1998); Burrows (2011); Jin et al. (2010); Tanabe & Cohen (2011). For the use of N,N′-type ligands in MOFs, see: Custelcean (2010); Pschirer et al. (2002). For the structural analysis of an imidazole closely related to the ligand, see: Voss et al. (2008).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2004); cell SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus; 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.
Supporting information
https://doi.org/10.1107/S1600536812050908/im2415sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812050908/im2415Isup2.hkl
The organic ligand 4-(1H-imidazol-2-yl)-pyridine was prepared according to the previously reported literature methods (Voss et al., 2008). Cd(NO3)2 (24 mg, 0.1 mmol) dissolved in 5 ml ethanol and a solution of 4-(1H-imidazol-2-yl)-pyridine (29 mg, 0.2 mmol) in another 5 ml of ethanol were mixed, refluxed for 5 h and filtered. The filtrate was left at room temperature. Suitable single crystals for a X-ray diffraction study were obtained after a few days (yield: 73% based on Cd(II) salts).
H atoms were positioned geometrically at distances of 0.93 (CH), and 0.86 (NH) from the respective parent atoms, a riding model was used during the
process. Uiso values were constrained to be 1.2 times Ueq of the carrier atom.The construction of functional metal-organic frameworks is of great interest due to their intriguing network topologies and their potential applications as microporous, magnetism, catalysis, nonlinear optics, molecular separation, toxic materials adsorption and molecular sensors (Batten & Robson, 1998; Burrows, 2011; Jin et al., 2010; Tanabe & Cohen, 2011). The molecular geometry and flexibility of multidentate ligands play key roles in the field of supramolecular self-assemble on metal-organic frameworks. For example, 4, 4'-bipyridine, 1, 2- bis(4-pyridyl)ethane and trans-bis(4-pyridyl)ethene as ligands can form a lot of coordination polymers with different structure features (Custelcean, 2010; Pschirer et al., 2002). Our interest is to exploit the coordination chemistry of 2-pyridinyl-imidazole and its derivatives together with their potential application in material science.
In the report, the mono-nuclear cadmium(II) complex, [Cd(C8H7N3)2(NO3)2(H2O)2], was obtained via the reaction of 4-(1H-imidazol-2-yl)-pyridine and cadmium(II) nitrate. Single crystal X-ray
reveals that the cadmium(II) atom is six-coordinated in a slightly distorted octahedral geometry by two pyridine nitrogen atoms, two nitrate anions oxygen atoms and two aqua oxygen atoms forming N2O4 donor set (Figure 1). The cadmium atom is situated on an inversion center. Bond distances of Cd(1)—N(1), Cd(1)—O(1) and Cd(1)—O(4) are 2.276 (2), 2.503 (3) and 2.310 (2) Å, respectivity. The dihedral angle between the imidazole and pyridine rings is 1.6 (2)°. In the crystal, molecules are linked by N—H······O, O—H······N and O—H······O hydrogen bonds, forming a three-dimensional network (Figure 2).For background to metal-organic framework structures (MOFs), see: Batten & Robson (1998); Burrows (2011); Jin et al. (2010); Tanabe & Cohen (2011). For the use of N,N'-type ligands in MOFs, see: Custelcean (2010); Pschirer et al. (2002). For the structural analysis of an imidazole closely related to the ligand, see: Voss et al. (2008).
Data collection: APEX2 (Bruker, 2004); cell
SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus (Bruker, 2004); 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).[Cd(NO3)2(C8H7N3)2(H2O)2] | F(000) = 564 |
Mr = 562.78 | Dx = 1.760 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 4257 reflections |
a = 7.2508 (7) Å | θ = 2.4–28.3° |
b = 12.1372 (12) Å | µ = 1.09 mm−1 |
c = 12.3509 (12) Å | T = 298 K |
β = 102.278 (2)° | Block, colorless |
V = 1062.07 (18) Å3 | 0.16 × 0.12 × 0.10 mm |
Z = 2 |
Bruker APEXII CCD area-detector diffractometer | 2462 independent reflections |
Radiation source: fine-focus sealed tube | 2272 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.046 |
phi and ω scans | θmax = 28.0°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −7→9 |
Tmin = 0.845, Tmax = 0.899 | k = −15→15 |
6543 measured reflections | l = −14→16 |
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)] = 0.035 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.084 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0252P)2 + 1.0694P] where P = (Fo2 + 2Fc2)/3 |
2462 reflections | (Δ/σ)max = 0.001 |
157 parameters | Δρmax = 0.73 e Å−3 |
3 restraints | Δρmin = −0.47 e Å−3 |
[Cd(NO3)2(C8H7N3)2(H2O)2] | V = 1062.07 (18) Å3 |
Mr = 562.78 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 7.2508 (7) Å | µ = 1.09 mm−1 |
b = 12.1372 (12) Å | T = 298 K |
c = 12.3509 (12) Å | 0.16 × 0.12 × 0.10 mm |
β = 102.278 (2)° |
Bruker APEXII CCD area-detector diffractometer | 2462 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2272 reflections with I > 2σ(I) |
Tmin = 0.845, Tmax = 0.899 | Rint = 0.046 |
6543 measured reflections |
R[F2 > 2σ(F2)] = 0.035 | 3 restraints |
wR(F2) = 0.084 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | Δρmax = 0.73 e Å−3 |
2462 reflections | Δρmin = −0.47 e Å−3 |
157 parameters |
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 | ||
Cd1 | 1.0000 | 0.5000 | 0.5000 | 0.03811 (11) | |
C1 | 0.8396 (5) | 0.6142 (2) | 0.2671 (2) | 0.0466 (7) | |
H1 | 0.8465 | 0.6754 | 0.3131 | 0.056* | |
C2 | 0.7823 (5) | 0.6301 (2) | 0.1550 (2) | 0.0456 (7) | |
H2 | 0.7498 | 0.7002 | 0.1269 | 0.055* | |
C3 | 0.7732 (4) | 0.5408 (2) | 0.0842 (2) | 0.0341 (5) | |
C4 | 0.8205 (5) | 0.4390 (2) | 0.1325 (2) | 0.0499 (8) | |
H4 | 0.8146 | 0.3764 | 0.0885 | 0.060* | |
C5 | 0.8761 (5) | 0.4304 (3) | 0.2458 (2) | 0.0497 (7) | |
H5 | 0.9086 | 0.3612 | 0.2762 | 0.060* | |
C6 | 0.7176 (4) | 0.5554 (2) | −0.0359 (2) | 0.0337 (5) | |
C7 | 0.6323 (5) | 0.6241 (3) | −0.1984 (2) | 0.0502 (7) | |
H7 | 0.5950 | 0.6748 | −0.2552 | 0.060* | |
C8 | 0.6534 (5) | 0.5154 (3) | −0.2132 (3) | 0.0506 (8) | |
H8 | 0.6350 | 0.4779 | −0.2803 | 0.061* | |
N1 | 0.8860 (4) | 0.51635 (18) | 0.3142 (2) | 0.0396 (5) | |
N2 | 0.6733 (4) | 0.6497 (2) | −0.08794 (19) | 0.0426 (5) | |
N3 | 0.7075 (4) | 0.4715 (2) | −0.1096 (2) | 0.0427 (6) | |
H3 | 0.7309 | 0.4032 | −0.0939 | 0.051* | |
N4 | 0.7084 (3) | 0.6785 (2) | 0.5340 (2) | 0.0411 (5) | |
O1 | 0.8766 (3) | 0.6853 (3) | 0.5384 (2) | 0.0747 (8) | |
O2 | 0.6297 (5) | 0.5914 (2) | 0.5037 (3) | 0.0965 (11) | |
O3 | 0.6156 (3) | 0.75586 (18) | 0.5590 (2) | 0.0562 (6) | |
O4 | 1.2220 (3) | 0.63059 (19) | 0.4800 (2) | 0.0573 (6) | |
H4B | 1.200 (5) | 0.6945 (15) | 0.461 (4) | 0.086* | |
H4A | 1.334 (2) | 0.617 (3) | 0.490 (4) | 0.086* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cd1 | 0.05052 (19) | 0.03477 (16) | 0.02528 (16) | −0.00965 (11) | −0.00034 (11) | 0.00115 (10) |
C1 | 0.071 (2) | 0.0372 (14) | 0.0297 (13) | −0.0023 (14) | 0.0073 (13) | −0.0033 (11) |
C2 | 0.069 (2) | 0.0356 (14) | 0.0303 (14) | 0.0046 (14) | 0.0079 (13) | 0.0017 (11) |
C3 | 0.0388 (13) | 0.0346 (12) | 0.0279 (12) | −0.0030 (11) | 0.0050 (10) | 0.0008 (10) |
C4 | 0.081 (2) | 0.0318 (14) | 0.0306 (14) | −0.0012 (14) | −0.0011 (14) | −0.0041 (11) |
C5 | 0.074 (2) | 0.0355 (14) | 0.0333 (15) | −0.0032 (14) | −0.0040 (13) | 0.0036 (12) |
C6 | 0.0389 (13) | 0.0332 (13) | 0.0285 (12) | 0.0001 (10) | 0.0059 (10) | −0.0012 (10) |
C7 | 0.065 (2) | 0.0547 (18) | 0.0284 (14) | 0.0112 (15) | 0.0049 (13) | 0.0079 (12) |
C8 | 0.069 (2) | 0.0556 (19) | 0.0252 (14) | 0.0020 (15) | 0.0045 (13) | −0.0020 (12) |
N1 | 0.0523 (14) | 0.0368 (12) | 0.0267 (12) | −0.0080 (10) | 0.0014 (10) | 0.0007 (9) |
N2 | 0.0578 (15) | 0.0393 (12) | 0.0303 (11) | 0.0077 (11) | 0.0083 (10) | 0.0027 (9) |
N3 | 0.0615 (16) | 0.0356 (11) | 0.0293 (12) | 0.0016 (11) | 0.0055 (11) | −0.0029 (9) |
N4 | 0.0460 (13) | 0.0387 (13) | 0.0408 (13) | 0.0056 (10) | 0.0142 (10) | 0.0112 (10) |
O1 | 0.0446 (13) | 0.111 (2) | 0.0681 (17) | 0.0082 (14) | 0.0112 (12) | 0.0077 (16) |
O2 | 0.114 (3) | 0.0367 (14) | 0.151 (3) | −0.0131 (15) | 0.055 (2) | −0.0218 (17) |
O3 | 0.0654 (14) | 0.0389 (11) | 0.0700 (16) | 0.0107 (11) | 0.0271 (12) | 0.0021 (10) |
O4 | 0.0418 (11) | 0.0386 (12) | 0.0886 (18) | −0.0045 (9) | 0.0075 (12) | 0.0101 (12) |
Cd1—N1 | 2.276 (2) | C5—N1 | 1.335 (4) |
Cd1—N1i | 2.276 (2) | C5—H5 | 0.9300 |
Cd1—O4 | 2.310 (2) | C6—N2 | 1.319 (3) |
Cd1—O4i | 2.310 (2) | C6—N3 | 1.357 (3) |
Cd1—O1 | 2.503 (3) | C7—C8 | 1.345 (4) |
Cd1—O1i | 2.503 (3) | C7—N2 | 1.368 (4) |
C1—N1 | 1.333 (4) | C7—H7 | 0.9300 |
C1—C2 | 1.371 (4) | C8—N3 | 1.364 (4) |
C1—H1 | 0.9300 | C8—H8 | 0.9300 |
C2—C3 | 1.386 (4) | N3—H3 | 0.8600 |
C2—H2 | 0.9300 | N4—O1 | 1.211 (3) |
C3—C4 | 1.384 (4) | N4—O2 | 1.222 (4) |
C3—C6 | 1.463 (3) | N4—O3 | 1.232 (3) |
C4—C5 | 1.374 (4) | O4—H4B | 0.816 (10) |
C4—H4 | 0.9300 | O4—H4A | 0.814 (10) |
N1—Cd1—N1i | 180.00 (4) | N1—C5—C4 | 123.4 (3) |
N1—Cd1—O4 | 86.81 (9) | N1—C5—H5 | 118.3 |
N1i—Cd1—O4 | 93.19 (9) | C4—C5—H5 | 118.3 |
N1—Cd1—O4i | 93.19 (9) | N2—C6—N3 | 110.6 (2) |
N1i—Cd1—O4i | 86.81 (9) | N2—C6—C3 | 125.8 (2) |
O4—Cd1—O4i | 180.0 | N3—C6—C3 | 123.6 (2) |
N1—Cd1—O1 | 92.58 (9) | C8—C7—N2 | 110.6 (3) |
N1i—Cd1—O1 | 87.42 (9) | C8—C7—H7 | 124.7 |
O4—Cd1—O1 | 71.89 (9) | N2—C7—H7 | 124.7 |
O4i—Cd1—O1 | 108.11 (9) | C7—C8—N3 | 105.9 (3) |
N1—Cd1—O1i | 87.42 (9) | C7—C8—H8 | 127.1 |
N1i—Cd1—O1i | 92.58 (9) | N3—C8—H8 | 127.1 |
O4—Cd1—O1i | 108.11 (9) | C1—N1—C5 | 116.4 (3) |
O4i—Cd1—O1i | 71.89 (9) | C1—N1—Cd1 | 121.42 (18) |
O1—Cd1—O1i | 180.00 (7) | C5—N1—Cd1 | 121.97 (19) |
N1—C1—C2 | 124.1 (3) | C6—N2—C7 | 105.5 (2) |
N1—C1—H1 | 118.0 | C6—N3—C8 | 107.4 (3) |
C2—C1—H1 | 118.0 | C6—N3—H3 | 126.3 |
C1—C2—C3 | 119.4 (3) | C8—N3—H3 | 126.3 |
C1—C2—H2 | 120.3 | O1—N4—O2 | 118.2 (3) |
C3—C2—H2 | 120.3 | O1—N4—O3 | 122.4 (3) |
C4—C3—C2 | 116.9 (2) | O2—N4—O3 | 119.4 (3) |
C4—C3—C6 | 122.3 (3) | N4—O1—Cd1 | 109.1 (2) |
C2—C3—C6 | 120.8 (2) | Cd1—O4—H4B | 126 (3) |
C5—C4—C3 | 119.9 (3) | Cd1—O4—H4A | 123 (3) |
C5—C4—H4 | 120.0 | H4B—O4—H4A | 111 (2) |
C3—C4—H4 | 120.0 | ||
N1—C1—C2—C3 | −0.9 (5) | O1i—Cd1—N1—C1 | −161.4 (3) |
C1—C2—C3—C4 | 1.1 (5) | N1i—Cd1—N1—C5 | −114 (15) |
C1—C2—C3—C6 | −178.3 (3) | O4—Cd1—N1—C5 | 121.5 (3) |
C2—C3—C4—C5 | −1.0 (5) | O4i—Cd1—N1—C5 | −58.5 (3) |
C6—C3—C4—C5 | 178.4 (3) | O1—Cd1—N1—C5 | −166.8 (3) |
C3—C4—C5—N1 | 0.7 (6) | O1i—Cd1—N1—C5 | 13.2 (3) |
C4—C3—C6—N2 | −179.0 (3) | N3—C6—N2—C7 | 0.5 (3) |
C2—C3—C6—N2 | 0.4 (4) | C3—C6—N2—C7 | 179.7 (3) |
C4—C3—C6—N3 | 0.1 (4) | C8—C7—N2—C6 | −0.6 (4) |
C2—C3—C6—N3 | 179.4 (3) | N2—C6—N3—C8 | −0.2 (4) |
N2—C7—C8—N3 | 0.5 (4) | C3—C6—N3—C8 | −179.4 (3) |
C2—C1—N1—C5 | 0.6 (5) | C7—C8—N3—C6 | −0.2 (4) |
C2—C1—N1—Cd1 | 175.5 (3) | O2—N4—O1—Cd1 | −6.3 (4) |
C4—C5—N1—C1 | −0.5 (5) | O3—N4—O1—Cd1 | 173.7 (2) |
C4—C5—N1—Cd1 | −175.3 (3) | N1—Cd1—O1—N4 | 77.8 (2) |
N1i—Cd1—N1—C1 | 72 (15) | N1i—Cd1—O1—N4 | −102.2 (2) |
O4—Cd1—N1—C1 | −53.1 (3) | O4—Cd1—O1—N4 | 163.6 (2) |
O4i—Cd1—N1—C1 | 126.9 (3) | O4i—Cd1—O1—N4 | −16.4 (2) |
O1—Cd1—N1—C1 | 18.6 (3) | O1i—Cd1—O1—N4 | 29 (12) |
Symmetry code: (i) −x+2, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3···O3ii | 0.86 | 2.10 | 2.923 (3) | 160 |
O4—H4B···N2iii | 0.82 (1) | 1.98 (1) | 2.796 (3) | 174 (4) |
O4—H4A···O2iv | 0.81 (1) | 2.14 (1) | 2.946 (4) | 174 (4) |
O4—H4A···O3iv | 0.81 (1) | 2.65 (3) | 3.197 (3) | 126 (3) |
Symmetry codes: (ii) −x+3/2, y−1/2, −z+1/2; (iii) x+1/2, −y+3/2, z+1/2; (iv) x+1, y, z. |
Experimental details
Crystal data | |
Chemical formula | [Cd(NO3)2(C8H7N3)2(H2O)2] |
Mr | 562.78 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 298 |
a, b, c (Å) | 7.2508 (7), 12.1372 (12), 12.3509 (12) |
β (°) | 102.278 (2) |
V (Å3) | 1062.07 (18) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 1.09 |
Crystal size (mm) | 0.16 × 0.12 × 0.10 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.845, 0.899 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6543, 2462, 2272 |
Rint | 0.046 |
(sin θ/λ)max (Å−1) | 0.661 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.035, 0.084, 1.10 |
No. of reflections | 2462 |
No. of parameters | 157 |
No. of restraints | 3 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.73, −0.47 |
Computer programs: APEX2 (Bruker, 2004), SAINT-Plus (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3···O3i | 0.86 | 2.10 | 2.923 (3) | 159.5 |
O4—H4B···N2ii | 0.816 (10) | 1.982 (12) | 2.796 (3) | 174 (4) |
O4—H4A···O2iii | 0.814 (10) | 2.135 (12) | 2.946 (4) | 174 (4) |
O4—H4A···O3iii | 0.814 (10) | 2.65 (3) | 3.197 (3) | 126 (3) |
Symmetry codes: (i) −x+3/2, y−1/2, −z+1/2; (ii) x+1/2, −y+3/2, z+1/2; (iii) x+1, y, z. |
Acknowledgements
We gratefully acknowledge financial support by the National Natural Science Foundation of China (21171053) and the Science Foundation of Hubei Provincial Department of Education (Z20102501).
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The construction of functional metal-organic frameworks is of great interest due to their intriguing network topologies and their potential applications as microporous, magnetism, catalysis, nonlinear optics, molecular separation, toxic materials adsorption and molecular sensors (Batten & Robson, 1998; Burrows, 2011; Jin et al., 2010; Tanabe & Cohen, 2011). The molecular geometry and flexibility of multidentate ligands play key roles in the field of supramolecular self-assemble on metal-organic frameworks. For example, 4, 4'-bipyridine, 1, 2- bis(4-pyridyl)ethane and trans-bis(4-pyridyl)ethene as ligands can form a lot of coordination polymers with different structure features (Custelcean, 2010; Pschirer et al., 2002). Our interest is to exploit the coordination chemistry of 2-pyridinyl-imidazole and its derivatives together with their potential application in material science.
In the report, the mono-nuclear cadmium(II) complex, [Cd(C8H7N3)2(NO3)2(H2O)2], was obtained via the reaction of 4-(1H-imidazol-2-yl)-pyridine and cadmium(II) nitrate. Single crystal X-ray diffraction analysis reveals that the cadmium(II) atom is six-coordinated in a slightly distorted octahedral geometry by two pyridine nitrogen atoms, two nitrate anions oxygen atoms and two aqua oxygen atoms forming N2O4 donor set (Figure 1). The cadmium atom is situated on an inversion center. Bond distances of Cd(1)—N(1), Cd(1)—O(1) and Cd(1)—O(4) are 2.276 (2), 2.503 (3) and 2.310 (2) Å, respectivity. The dihedral angle between the imidazole and pyridine rings is 1.6 (2)°. In the crystal, molecules are linked by N—H······O, O—H······N and O—H······O hydrogen bonds, forming a three-dimensional network (Figure 2).