Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270112023153/sf3171sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270112023153/sf3171Isup2.hkl |
CCDC reference: 893479
For related literature, see: Alkordi et al. (2009); Bruker (2007); Cai et al. (2012); Gryz et al. (2006); Gu et al. (2011); Li et al. (2010); Liu et al. (2008); Sheldrick (2008); Starosta & Leciejewicz (2006); Sun & Yang (2007); Sun et al. (2010); Wang et al. (2011); Yin et al. (2009); Zheng et al. (2011).
CdC2O4.3H2O (25.5 mg, 0.10 mmol) and H2imc (22.4 mg, 0.20 mmol) were mixed into H2O–C2H5OH (6 ml, 1:1 v/v) and the pH was adjusted to about 6 using aqueous NaOH (0.20 mol l-1). The mixture was sealed in a 10 ml sample bottle reactor and heated at 373 K under autogenous pressure for 48 h. After the sample had been cooled slowly to room temperature at a rate of 2 K h-1, colourless block-shaped crystals of (I) were obtained in a yield of 68%. Analysis, calculated for C5H5CdN2O5: C 21.03, H 1.77, N 9.81%; found: C 20.97, H 1.82, N 9.88%. IR (KBr pellet, ν, cm-1): 3341 (s), 3152 (m), 2977 (w), 1643 (s), 1589 (s), 1561 (m), 1514 (w), 1398 (s), 1313 (s), 1241 (m), 1083 (w), 997 (m), 930 (w), 809 (s), 793 (m), 652 (m), 613 (w), 564 (w), 501 (w).
The crystal under investigation was found to be nonmerohedrally twinned. The orientation matrices for the two components were identified using the program CELL_NOW (Sheldrick, 2008), with the two components being related by a 180° rotation around the real/reciprocal axis (1 -0.002 -0.999; -0.829 -0.001 1). The two components were integrated using SAINT (Bruker, 2007), resulting in a total of 8238 reflections. 3619 reflections (1506 unique) involved component 1 only (mean I/σ = 13.2), 3602 reflections (1500 unique) involved component 2 only (mean I/σ = 10.2), and 1017 reflections (519 unique) involved both components (mean I/σ = 15.6). The exact twin matrix identified by the integration program was found to be (-0.09207 0.00002 -0.90797; 0.00011 -1 0; -1.09202 -0.00026 0.09207).
The data were corrected for absorption using TWINABS (SHELXL97; Sheldrick, 2008), and the structure was solved using direct methods with only the non-overlapping reflections of component 1. The structure was refined using the HKLF 5 routine with all reflections of component 1 (including the overlapping reflections), resulting in a BASF value of 0.365 (2). The reflections involving component 2 only were omitted from the data set, as this component was somewhat weaker than component 1 and gave a slightly inferior Rint value.
The Rint value given is for all reflections and is based on agreement between observed single and composite intensities and those calculated from refined unique intensities and twin fractions (TWINABS).
The H atoms of water molecule were located in the difference Fourier maps and the other H atoms were placed in calculated positions. They were refined as riding atoms, with C—H = 0.93 Å (imidazole C—H) and N—H = 0.86 Å, and with Uiso(H) = 1.2Ueq(C), 1.2Ueq(N) or 1.5 Ueq(O).
Data collection: APEX2 (Bruker, 2007); cell refinement: APEX2 (Bruker, 2007); data reduction: SAINT (Bruker, 2007); 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(C4H3N2O2)(C2O4)0.5(H2O)] | F(000) = 548 |
Mr = 285.51 | Dx = 2.476 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 1557 reflections |
a = 10.0259 (12) Å | θ = 2.6–27.9° |
b = 6.9271 (8) Å | µ = 2.84 mm−1 |
c = 13.9278 (12) Å | T = 296 K |
β = 127.630 (5)° | Block, colourless |
V = 766.07 (14) Å3 | 0.32 × 0.25 × 0.18 mm |
Z = 4 |
Bruker APEXII CCD area-detector diffractometer | 1393 independent reflections |
Radiation source: fine-focus sealed tube | 1298 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.047 |
ϕ and ω scans | θmax = 25.3°, θmin = 2.6° |
Absorption correction: multi-scan (TWINABS; Sheldrick, 2008) | h = −12→11 |
Tmin = 0.395, Tmax = 0.746 | k = −8→0 |
5542 measured reflections | l = −16→10 |
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)] = 0.032 | H-atom parameters constrained |
wR(F2) = 0.089 | w = 1/[σ2(Fo2) + (0.0409P)2 + 1.2027P] where P = (Fo2 + 2Fc2)/3 |
S = 1.10 | (Δ/σ)max < 0.001 |
1393 reflections | Δρmax = 0.96 e Å−3 |
120 parameters | Δρmin = −1.06 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0102 (15) |
[Cd(C4H3N2O2)(C2O4)0.5(H2O)] | V = 766.07 (14) Å3 |
Mr = 285.51 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 10.0259 (12) Å | µ = 2.84 mm−1 |
b = 6.9271 (8) Å | T = 296 K |
c = 13.9278 (12) Å | 0.32 × 0.25 × 0.18 mm |
β = 127.630 (5)° |
Bruker APEXII CCD area-detector diffractometer | 1393 independent reflections |
Absorption correction: multi-scan (TWINABS; Sheldrick, 2008) | 1298 reflections with I > 2σ(I) |
Tmin = 0.395, Tmax = 0.746 | Rint = 0.047 |
5542 measured reflections |
R[F2 > 2σ(F2)] = 0.032 | 0 restraints |
wR(F2) = 0.089 | H-atom parameters constrained |
S = 1.10 | Δρmax = 0.96 e Å−3 |
1393 reflections | Δρmin = −1.06 e Å−3 |
120 parameters |
Experimental. The crystal under investigation was found to be non-merohedrally twinned. The orientation matrices for the two components were identified using the program CELL_NOW, with the two components being related by a 180° rotation around the real/reciprocal axis (1.000 -0.002 -0.999; -0.829 -0.001 1.000). The two components were integrated using SAINT, resulting in a total of 8270 reflections. 3624 reflections (1506 unique) involved component 1 only (mean I/σ = 13.2), 3624 reflections (1500 unique) involved component 2 only (mean I/σ = 10.2), and 1022 reflections (519 unique) involved both components (mean I/σ = 15.6). The exact twin matrix identified by the integration program was found to be (-0.09207 0.00002 -0.90797; 0.00011 -1.00000 -0.00000; -1.09202 -0.00026 0.09207). The data were corrected for absorption using TWINABS, and the structure was solved using direct methods with only the non-overlapping reflections of component 1. The structure was refined using the HKLF 5 routine with all reflections of component 1 (including the overlapping ones), resulting in a BASF value of 0.36437. The Rint value given is for all reflections and is based on agreement between observed single and composite intensities and those calculated from refined unique intensities and twin fractions [TWINABS (Sheldrick, 2007)]. |
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 | 0.21993 (5) | 1.19201 (5) | 0.67889 (3) | 0.0306 (2) | |
O1 | 0.2679 (5) | 0.9359 (6) | 0.6062 (4) | 0.0439 (10) | |
O1W | 0.0460 (6) | 0.9916 (7) | 0.6959 (4) | 0.0565 (13) | |
H1W | −0.0109 | 0.9214 | 0.6330 | 0.085* | |
H2W | 0.0007 | 0.9804 | 0.7308 | 0.085* | |
O2 | 0.5273 (5) | 0.8519 (6) | 0.7661 (3) | 0.0388 (9) | |
O3 | −0.0584 (5) | 1.5365 (6) | 0.3544 (3) | 0.0457 (11) | |
O4 | 0.0871 (5) | 1.2964 (5) | 0.4834 (3) | 0.0356 (9) | |
N1 | 0.6074 (6) | 0.7293 (6) | 0.6212 (4) | 0.0295 (10) | |
N2 | 0.4569 (7) | 0.7345 (7) | 0.4244 (4) | 0.0412 (12) | |
H2 | 0.4299 | 0.7203 | 0.3532 | 0.049* | |
C1 | 0.4116 (7) | 0.8666 (7) | 0.6536 (5) | 0.0295 (11) | |
C2 | 0.4506 (7) | 0.8010 (6) | 0.5725 (5) | 0.0266 (11) | |
C3 | 0.3547 (8) | 0.8032 (7) | 0.4492 (5) | 0.0358 (13) | |
H3 | 0.2433 | 0.8431 | 0.3942 | 0.043* | |
C4 | 0.6049 (8) | 0.6929 (7) | 0.5275 (6) | 0.0362 (13) | |
H4 | 0.6958 | 0.6439 | 0.5331 | 0.043* | |
C5 | 0.0078 (6) | 1.4519 (8) | 0.4531 (4) | 0.0314 (11) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cd1 | 0.0281 (3) | 0.0337 (3) | 0.0269 (3) | 0.00464 (15) | 0.0152 (2) | −0.00168 (15) |
O1 | 0.035 (2) | 0.049 (2) | 0.049 (2) | 0.0032 (19) | 0.0262 (19) | −0.015 (2) |
O1W | 0.057 (3) | 0.066 (3) | 0.061 (3) | −0.026 (2) | 0.044 (3) | −0.026 (2) |
O2 | 0.046 (2) | 0.050 (2) | 0.031 (2) | 0.0083 (19) | 0.029 (2) | 0.0018 (17) |
O3 | 0.058 (3) | 0.048 (2) | 0.035 (2) | 0.026 (2) | 0.030 (2) | 0.0099 (18) |
O4 | 0.036 (2) | 0.037 (2) | 0.033 (2) | 0.0107 (16) | 0.0204 (18) | −0.0021 (16) |
N1 | 0.031 (2) | 0.027 (2) | 0.037 (2) | 0.0032 (19) | 0.024 (2) | −0.0019 (19) |
N2 | 0.067 (4) | 0.036 (3) | 0.030 (3) | −0.007 (2) | 0.034 (3) | −0.004 (2) |
C1 | 0.036 (3) | 0.023 (2) | 0.036 (3) | −0.001 (2) | 0.025 (3) | −0.004 (2) |
C2 | 0.029 (3) | 0.024 (3) | 0.028 (3) | −0.002 (2) | 0.018 (2) | −0.0022 (19) |
C3 | 0.039 (3) | 0.033 (3) | 0.028 (3) | 0.003 (2) | 0.017 (3) | 0.000 (2) |
C4 | 0.051 (4) | 0.030 (3) | 0.052 (4) | −0.002 (2) | 0.043 (3) | 0.001 (2) |
C5 | 0.026 (2) | 0.035 (3) | 0.030 (3) | 0.006 (2) | 0.015 (2) | −0.002 (2) |
Cd1—N1i | 2.220 (5) | O4—C5 | 1.249 (6) |
Cd1—O1 | 2.235 (4) | N1—C4 | 1.315 (7) |
Cd1—O4 | 2.298 (4) | N1—C2 | 1.370 (7) |
Cd1—O3ii | 2.336 (4) | N1—Cd1iii | 2.220 (5) |
Cd1—O1W | 2.351 (4) | N2—C4 | 1.321 (8) |
Cd1—O2i | 2.422 (4) | N2—C3 | 1.352 (8) |
O1—C1 | 1.258 (6) | N2—H2 | 0.8600 |
O1W—H1W | 0.8475 | C1—C2 | 1.474 (7) |
O1W—H2W | 0.8483 | C2—C3 | 1.363 (8) |
O2—C1 | 1.261 (7) | C3—H3 | 0.9300 |
O2—Cd1iii | 2.422 (4) | C4—H4 | 0.9300 |
O3—C5 | 1.248 (6) | C5—C5ii | 1.559 (9) |
O3—Cd1ii | 2.336 (4) | ||
N1i—Cd1—O1 | 116.20 (16) | C4—N1—C2 | 104.9 (5) |
N1i—Cd1—O4 | 153.27 (15) | C4—N1—Cd1iii | 138.6 (4) |
O1—Cd1—O4 | 80.94 (14) | C2—N1—Cd1iii | 116.3 (3) |
N1i—Cd1—O3ii | 94.05 (15) | C4—N2—C3 | 108.8 (5) |
O1—Cd1—O3ii | 149.72 (14) | C4—N2—H2 | 125.6 |
O4—Cd1—O3ii | 71.41 (12) | C3—N2—H2 | 125.6 |
N1i—Cd1—O1W | 90.06 (15) | O1—C1—O2 | 125.0 (5) |
O1—Cd1—O1W | 87.40 (16) | O1—C1—C2 | 118.0 (5) |
O4—Cd1—O1W | 112.09 (16) | O2—C1—C2 | 117.0 (5) |
O3ii—Cd1—O1W | 91.65 (17) | C3—C2—N1 | 109.9 (5) |
N1i—Cd1—O2i | 71.69 (14) | C3—C2—C1 | 130.5 (5) |
O1—Cd1—O2i | 91.91 (15) | N1—C2—C1 | 119.6 (5) |
O4—Cd1—O2i | 88.19 (13) | N2—C3—C2 | 104.9 (5) |
O3ii—Cd1—O2i | 99.17 (15) | N2—C3—H3 | 127.6 |
O1W—Cd1—O2i | 159.28 (15) | C2—C3—H3 | 127.6 |
C1—O1—Cd1 | 124.0 (3) | N1—C4—N2 | 111.4 (5) |
Cd1—O1W—H1W | 107.9 | N1—C4—H4 | 124.3 |
Cd1—O1W—H2W | 143.3 | N2—C4—H4 | 124.3 |
H1W—O1W—H2W | 106.4 | O3—C5—O4 | 125.3 (5) |
C1—O2—Cd1iii | 114.9 (3) | O3—C5—C5ii | 117.7 (6) |
C5—O3—Cd1ii | 115.8 (3) | O4—C5—C5ii | 117.0 (6) |
C5—O4—Cd1 | 117.5 (3) | ||
N1i—Cd1—O1—C1 | −32.5 (5) | C4—N1—C2—C1 | −177.1 (4) |
O4—Cd1—O1—C1 | 125.9 (4) | Cd1iii—N1—C2—C1 | 6.1 (6) |
O3ii—Cd1—O1—C1 | 149.9 (4) | O1—C1—C2—C3 | 0.6 (8) |
O1W—Cd1—O1—C1 | −121.2 (4) | O2—C1—C2—C3 | −178.2 (5) |
O2i—Cd1—O1—C1 | 38.0 (4) | O1—C1—C2—N1 | 178.4 (5) |
N1i—Cd1—O4—C5 | −53.1 (5) | O2—C1—C2—N1 | −0.4 (7) |
O1—Cd1—O4—C5 | 174.3 (4) | C4—N2—C3—C2 | 0.4 (6) |
O3ii—Cd1—O4—C5 | 6.8 (4) | N1—C2—C3—N2 | −0.9 (6) |
O1W—Cd1—O4—C5 | 90.9 (4) | C1—C2—C3—N2 | 177.0 (5) |
O2i—Cd1—O4—C5 | −93.5 (4) | C2—N1—C4—N2 | −0.9 (6) |
Cd1—O1—C1—O2 | 38.7 (8) | Cd1iii—N1—C4—N2 | 174.8 (4) |
Cd1—O1—C1—C2 | −139.9 (4) | C3—N2—C4—N1 | 0.3 (6) |
Cd1iii—O2—C1—O1 | 176.3 (4) | Cd1ii—O3—C5—O4 | 174.0 (4) |
Cd1iii—O2—C1—C2 | −5.1 (6) | Cd1ii—O3—C5—C5ii | −6.5 (8) |
C4—N1—C2—C3 | 1.1 (6) | Cd1—O4—C5—O3 | 173.4 (4) |
Cd1iii—N1—C2—C3 | −175.7 (3) | Cd1—O4—C5—C5ii | −6.0 (7) |
Symmetry codes: (i) −x+1, y+1/2, −z+3/2; (ii) −x, −y+3, −z+1; (iii) −x+1, y−1/2, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O4iv | 0.85 | 1.99 | 2.815 (6) | 163 |
O1W—H2W···O3v | 0.85 | 2.14 | 2.972 (5) | 167 |
N2—H2···O2vi | 0.86 | 2.03 | 2.760 (6) | 142 |
Symmetry codes: (iv) −x, −y+2, −z+1; (v) x, −y+5/2, z+1/2; (vi) x, −y+3/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | [Cd(C4H3N2O2)(C2O4)0.5(H2O)] |
Mr | 285.51 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 296 |
a, b, c (Å) | 10.0259 (12), 6.9271 (8), 13.9278 (12) |
β (°) | 127.630 (5) |
V (Å3) | 766.07 (14) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 2.84 |
Crystal size (mm) | 0.32 × 0.25 × 0.18 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (TWINABS; Sheldrick, 2008) |
Tmin, Tmax | 0.395, 0.746 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5542, 1393, 1298 |
Rint | 0.047 |
(sin θ/λ)max (Å−1) | 0.600 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.032, 0.089, 1.10 |
No. of reflections | 1393 |
No. of parameters | 120 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.96, −1.06 |
Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
Cd1—N1i | 2.220 (5) | Cd1—O3ii | 2.336 (4) |
Cd1—O1 | 2.235 (4) | Cd1—O1W | 2.351 (4) |
Cd1—O4 | 2.298 (4) | Cd1—O2i | 2.422 (4) |
Symmetry codes: (i) −x+1, y+1/2, −z+3/2; (ii) −x, −y+3, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O4iii | 0.85 | 1.99 | 2.815 (6) | 162.9 |
O1W—H2W···O3iv | 0.85 | 2.14 | 2.972 (5) | 167.3 |
N2—H2···O2v | 0.86 | 2.03 | 2.760 (6) | 142.2 |
Symmetry codes: (iii) −x, −y+2, −z+1; (iv) x, −y+5/2, z+1/2; (v) x, −y+3/2, z−1/2. |
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Coordination polymers with multicarboxylate imidazole ligands are of great current interest due to their intriguing architectures and topologies, as well as their many promising applications as functional materials, including optics, magnetism and porosity (Alkordi et al., 2009; Gu et al., 2011; Liu et al., 2008). Many imidazole-based dicarboxylate ligands have been developed and widely applied in the construction of metal–organic frameworks (MOFs) over recent years (Li et al., 2010; Wang et al., 2011; Zheng et al., 2011). However, the coordination chemistry of the simple imidazole-based carboxylate ligand 1H-imidazole-4-carboxylic acid (H2imc) has been less well explored. Similar to imidazole-based dicarboxylate ligands, H2imc can be partially or fully deprotonated to generate Himc- or imc2- anions at different pH values, and it can bind to metal ions through the N atoms of the imidazole ring and the carboxylate O atoms. In addition, it may take part in the formation of noncovalent interactions, such as hydrogen bonds and π–π stacking interactions, thereby contributing greatly to the formation of a wide variety of supramolecular frameworks. To date, the few complexes with the H2imc ligand reported in the literature exhibit mononuclear (Gryz et al., 2006; Sun et al., 2010; Yin et al., 2009) or low-dimensional structures (Starosta & Leciejewicz, 2006; Sun & Yang, 2007). In our previous studies, we introduced different anions (such as acetate, NO3-, ClO4-, Cl-, Br-, I- and SO42-) to investigate their effect (Cai et al., 2012). Positive results indicated that the anions play crucial roles in the structure topologies and transformations. Herein, we selected oxalate for further study. The synthesis, structure and photoluminescence properties of the title new two-dimensional cadmium coordination polymer, (I), which was obtained by hydrothermal reaction of CdC2O4.3H2O with the H2imc ligand, are presented.
Compound (I) exhibits a two-dimensional herringbone-like network, consisting of one CdII ion, one Himc ligand, one half of an oxalate anion and one ligated water molecule, as shown in Fig. 1. The oxalate lies on a centre of inversion. In the structure, the six-coordinated CdII cation lies in a distorted octahedral environment, which is completed by one N atom [N1i; symmetry code: (i) -x + 1, y + 1/2, -z + 3/2] and two carboxylate O atoms (O1 and O2i) from two Himc ligands, two carboxylate O atoms from one bridging oxalate anion [O3ii and O4; symmetry code: (ii) -x, -y + 3, -z + 1], and the water O atom. The water molecule and atom O2i occupy the axial sites and the other donors are located in the equatorial plane. Selected bond lengths for (I) are listed in Table 1. The Cd—O and Cd—N bond lengths are in the normal ranges (Cai et al., 2012; Yin et al., 2009).
In (I), both the Himc anion and the oxalate act as µ2-bridges. The Himc ligands connect the CdII cations to form –Cd–Himc–Cd–Himc–Cd– zigzag chains with a Cd···Cd separation of 5.820 (5) Å along the b direction. These zigzag chains are further linked by tetradentate centrosymmetric oxalate anions to form a two-dimensional herringbone architecture in the ab plane (Fig. 2). Both surfaces of these layers are covered by protruding imidazole rings which interdigitate when adjacent layers come together. They form π–π stacking interactions and the centroid-to-centroid separations between two imidazole rings are 3.485 (5) and 3.544 (5) Å. In addition, there are multiple hydrogen bonds in the structure of (I) of two types. The first type is between the coordinated water molecule and the carboxylate O atoms of the oxalate anions [O···O = 2.815 (6) and 2.972 (5) Å] and the second between the N atom and one carboxylate O atom of the Himc anions [N···O = 2.760 (6) Å]. Thus, the connection of both π–π stacks and hydrogen bonds results in the formation of a three-dimensional supramolecular network (Fig. 3).
As illustrated in Fig. 4, the powder XRD pattern of (I) is in agreement with that simulated based on the single-crystal structure. The diffraction peaks in the experimental and simulated patterns correspond well in their positions, suggesting that the crystal samples are pure.
In our previous work, three CdII coordination polymers with Himc anions exhibited a one-dimensional zigzag chain, a two-dimensional layer and a three-dimensional diamondoid network, respectively (Cai et al., 2012). Although only a sulfate anion took part in the coordination of the last structure, positive results from many synthesis experiments revealed that the anions play crucial roles in the structure topologies of the resulting complexes. In this work, oxalate was selected to construct a new CdII coordination polymer, because it is a commonly used bridging ligand and adopts various coordination modes. In the structure of (I), the oxalate anion adopts a bis-chelating bridging mode connecting two CdII cations. Finally, a two-dimensional herringbone-like network is formed through alternating connections between Himc ligands and oxalate anions, and this is quite different from that in [Cd2(Himc)2(SO4)(H2O)] (Cai et al., 2012), which exhibit a two-dimensional structure with (3,4)-mixed connectivity. This difference can be explained as different coordination modes of the Himc ligand.
The solid-state photoluminescent behaviour of (I) was investigated at room temperature. As shown in Fig. 5, an intense broad emission band at 451 nm is observed after excitation at a wavelength of 369 nm. Compared with the free ligand H2imc (emission at 463 nm with λex = 376 nm), the blue-shifted emission for (I) may be attributed to intraligand transitions (Cai et al., 2012).
In summary, the hydrothermal reaction of CdC2O4 and H2imc results in the formation of a two-dimensional herringbone-like cadmium coordination polymer. Combined with our previous work, it is clear that the anion plays a significant role in the assembly of the metal–anionic ligand system. That is to say, the choice of anion could promote different topological structures. In addition, (I) in the solid state exhibits characteristic emission at room temperature.