catena-Poly[[aqua­diimidazole­cadmium(II)]-μ-thio­phene-2,5-dicarboxyl­ato]

The Cd^II atom has distorted pentagonal bipyramidal coord­ination geometry in the coordination polymer [Cd(TDA)(Him)₂(H₂O)]_n [where TDA²⁻ is the thio­phene-2,5-dicarboxyl­ate dianion (C₆H₂O₄S²⁻) and Him is imidazole (C₃H₄N₂)]. The cadmium ion is bound by four carboxylate O atoms from two independent TDA²⁻ groups, two N atoms from two different imidazole ligands, and one water mol­ecule. The carboxyl­ate groups bind in bidentate mode to the Cd center, forming a linear chain structure such that the closest Cd...Cd distance is 10.577 (6) Å. The polymeric chains are connected via hydrogen bonds and π–π stacking inter­actions into a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C) = 0.014 Å
• R factor = 0.041
• wR factor = 0.168
• Data-to-parameter ratio = 16.7

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT213_ALERT_2_C Atom O1      has ADP max/min Ratio .............       3.50 prolat
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        Cd1
PLAT342_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...         14
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.11 Ratio

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

Thiophene-2,5-dicarboxylic acid (H₂TDA) is reported to be a potential anticancer agent (Sahasrabudhe et al., 1960), and additionally an excellent building block for constructing coordination polymers (Chen et al., 1993). In previously studied polymers of this type, the versatile H₂TDA ligand shows a variety of binding modes to metal ions, from mono- to tetradentate (Chen et al., 1998, 1999). In order to further the study of H₂TDA coordination modes, we report here the synthesis and crystal structure of the title Cd^II coordination polymer, [Cd(TDA)(Him)₂(H₂O)]_n, (I). It was obtained by the hydrothermal reaction of cadmium dinitrate tetrahydrate, thiophene-2,5-dicarboxylic acid and imidazole (Him) in an aqueous solution.

As illustrated in Fig. 1, the asymmetric unit of (I) consists of one Cd^II ion, one TDA²⁻ dianion, two imidazole ligands and one coordinated water molecule. Each Cd^II atom is seven-coordinate and bound by four carboxyl O atoms from two independent TDA²⁻ groups, two N atoms from two different imidazole ligands, and one water molecule. The local coordination sphere of the Cd^II atom can be described as distorted pentagonal bipyramidal. The equatorial pentagonal plane is defined by atoms O1, O2, O3ⁱ, O4ⁱ and N1 [symmetry code: (i) x, y − 1, z]. Atom N3 and the water molecule occupy the axial sites. The smallest O—Cd—O angle, 49.1 (3)°, is attributed to the bis-chelate coordination of the TDA²⁻ ligand that forms two four-membered rings. It should be noted that the two C—O bond distances of the carboxyl group (O3/C6/O4) are almost equivalent, and so in agreement with its delocalized state, whereas the O2—C1 distance is longer than the O1—C1 distance, in accordance with the formal double-bond character of the O1—C1 bond. The dihedral angles between the two carboxyl groups and the thiophene ring are 5.3 (4)° (O1/C1/O2) and 6.0 (4)° (O3/C6/O4), respectively, demonstrating that the TDA²⁻ ligand is basically planar.

Each TDA²⁻ group binds in bis-bidentate chelating mode to link neighbouring Cd^II atoms to form a one-dimensional linear chain structure which is propagated parallel to the b axis (Fig. 2), in which the closest Cd···Cd distance is 10.577 (6) Å. Furthermore, the water and imidazole molecules form extensive intermolecular hydrogen bonds with carboxylate O atoms (Table 2). There are π–π stacking interactions between adjacent thiophene rings, the centroid–centroid separation being 3.694 (6) Å. The polymeric chains align in a manner that facilitates both hydrogen-bonding and π–π stacking interactions, leading to a three-dimensional supramolecular network (Fig. 3).

S2. Experimental

Cadmium dinitrate tetrahydrate (3.08 g, 10 mmol) was added to an aqueous solution of thiophene-2,5-dicarboxylic acid (1.72 g, 10 mmol). The pH was adjusted to 6 with 0.1 M sodium hydroxide. Imidazole (1.34 g, 20 mmol) was then added. The mixture was stirred for 1 h and then sealed in a 50 ml Teflon-lined stainless steel bomb and held at 383 K for 3 d. The bomb was cooled naturally to room temperature, and colorless prismatic crystals of (I) were obtained. Analysis calculated for C₁₂H₁₂N₄O₅SCd: C 33.00, H 2.77, N 12.83%; found: C 32.96, H 2.74, N 12.85%.

S3. Refinement

The H atoms attached to C atoms and imidazole N atoms were placed in calculated positions, with C—H = 0.93 Å, N—H = 0.86 Å and U_iso(H) = 1.2U_eq(C,N), and were refined with the riding-model approximation. Water H atoms were located in a difference Fourier map and refined with O—H and H···H distance restraints of 0.85 (1) and 1.39 (1) Å, respectively, and with U_iso(H) = 1.5U_eq(O). The largest residual peak is 1.08 Å from the Cd atom and the deepest is hole is ?? Å from ??.

Computing details

Data collection: RAPID-AUTO (Rigaku Corporation, 1998); cell refinement: RAPID-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. ORTEPII plot (Johnson, 1976) of the title complex, with displacement ellipsoids drawn at the 30% probability level. [Symmetry code: (i) x, y − 1, z].
	Fig. 2. The linear chain structure of the title complex. H atoms attached to C atoms have been omitted.
	Fig. 3. Packing diagram of the title complex along the a axis. The hydrogen bonds are shown as dashed lines. H atoms attached to C atoms have been omitted.

catena-Poly[[aquadiimidazolecadmium(II)]-µ-thiophene-2,5-dicarboxylato]

Crystal data

[Cd(C6H2O4S)(C3H4N2)2(H2O)]	Z = 2
Mr = 436.72	F(000) = 432
Triclinic, P1	Dx = 1.838 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.7486 (15) Å	Cell parameters from 7316 reflections
b = 10.577 (2) Å	θ = 3.0–27.5°
c = 10.947 (2) Å	µ = 1.55 mm^−1
α = 103.71 (3)°	T = 295 K
β = 101.57 (3)°	Prism, colorless
γ = 108.43 (3)°	0.36 × 0.24 × 0.18 mm
V = 789.1 (4) Å^3

Data collection

Rigaku R-AXIS RAPID diffractometer	3564 independent reflections
Radiation source: fine-focus sealed tube	2125 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.086
Detector resolution: 10 pixels mm^-1	θmax = 27.5°, θmin = 3.0°
ω scans	h = −9→10
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −13→13
Tmin = 0.641, Tmax = 0.761	l = −14→11
7628 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.168	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0795P)^2] where P = (Fo^2 + 2Fc^2)/3
3564 reflections	(Δ/σ)max < 0.001
214 parameters	Δρmax = 1.78 e Å^−3
3 restraints	Δρmin = −1.65 e Å^−3

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cd1	0.21550 (8)	0.13174 (6)	0.24203 (6)	0.0330 (2)
S1	0.1860 (3)	0.6113 (2)	0.2039 (2)	0.0362 (5)
O1W	−0.1113 (9)	0.0124 (6)	0.1333 (6)	0.0416 (14)
O1	0.2263 (11)	0.2568 (7)	0.0406 (10)	0.083 (3)
O2	0.1526 (9)	0.3269 (7)	0.2207 (9)	0.060 (2)
O3	0.2784 (9)	0.9456 (6)	0.0900 (6)	0.0452 (15)
O4	0.1993 (9)	0.9063 (7)	0.2621 (7)	0.0503 (16)
N1	0.1869 (10)	0.1785 (9)	0.4484 (8)	0.0499 (19)
N2	0.0766 (13)	0.1798 (8)	0.6174 (8)	0.051 (2)
N3	0.5332 (9)	0.2600 (8)	0.3021 (8)	0.0432 (17)
N4	0.8273 (10)	0.3311 (9)	0.2983 (9)	0.054 (2)
C1	0.1985 (12)	0.3449 (10)	0.1212 (14)	0.060 (3)
C10	0.6629 (12)	0.2187 (10)	0.2620 (10)	0.045 (2)
C11	0.6190 (15)	0.4018 (11)	0.3577 (11)	0.064 (3)
C12	0.8015 (14)	0.4472 (11)	0.3620 (11)	0.060 (3)
C2	0.2286 (11)	0.4832 (9)	0.0998 (9)	0.040 (2)
C3	0.2954 (12)	0.5263 (9)	0.0019 (9)	0.044 (2)
C4	0.3111 (12)	0.6694 (8)	0.0178 (8)	0.0352 (18)
C5	0.2550 (10)	0.7282 (8)	0.1211 (7)	0.0293 (16)
C6	0.2438 (11)	0.8691 (8)	0.1598 (8)	0.0332 (17)
C7	0.0363 (13)	0.1639 (10)	0.4944 (10)	0.048 (2)
C8	0.3338 (14)	0.2176 (14)	0.5630 (10)	0.069 (3)
C9	0.2646 (16)	0.2170 (13)	0.6624 (10)	0.063 (3)
H10	0.6433	0.1268	0.2162	0.053*
H11	0.5581	0.4599	0.3889	0.077*
H12	0.8920	0.5387	0.4004	0.072*
H14	−0.0026	0.1686	0.6627	0.061*
H15	0.9317	0.3296	0.2835	0.065*
H1W1	−0.142 (14)	0.049 (8)	0.075 (6)	0.062*
H1W2	−0.132 (14)	−0.073 (3)	0.096 (7)	0.062*
H3	0.3255	0.4714	−0.0639	0.053*
H4	0.3555	0.7179	−0.0374	0.042*
H7	−0.0854	0.1441	0.4419	0.057*
H8	0.4618	0.2406	0.5683	0.082*
H9	0.3344	0.2389	0.7495	0.076*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.0388 (3)	0.0268 (3)	0.0415 (4)	0.0160 (2)	0.0178 (2)	0.0159 (2)
S1	0.0380 (11)	0.0313 (11)	0.0513 (13)	0.0172 (9)	0.0196 (9)	0.0236 (10)
O1W	0.047 (3)	0.034 (3)	0.041 (3)	0.014 (3)	0.011 (3)	0.012 (3)
O1	0.068 (5)	0.021 (4)	0.146 (8)	0.025 (3)	0.014 (5)	0.007 (4)
O2	0.050 (4)	0.040 (4)	0.116 (6)	0.027 (3)	0.036 (4)	0.050 (4)
O3	0.059 (4)	0.028 (3)	0.058 (4)	0.021 (3)	0.018 (3)	0.023 (3)
O4	0.066 (4)	0.042 (4)	0.061 (4)	0.028 (3)	0.035 (3)	0.023 (3)
N1	0.043 (4)	0.061 (5)	0.046 (4)	0.012 (4)	0.020 (3)	0.025 (4)
N2	0.082 (6)	0.042 (5)	0.046 (5)	0.033 (4)	0.041 (4)	0.015 (4)
N3	0.037 (4)	0.034 (4)	0.062 (5)	0.015 (3)	0.019 (3)	0.017 (4)
N4	0.032 (4)	0.061 (6)	0.080 (6)	0.021 (4)	0.018 (4)	0.036 (5)
C1	0.026 (4)	0.026 (5)	0.122 (10)	0.013 (4)	0.000 (5)	0.027 (6)
C2	0.026 (4)	0.033 (5)	0.056 (6)	0.009 (3)	0.004 (4)	0.015 (4)
C3	0.050 (5)	0.036 (5)	0.041 (5)	0.019 (4)	0.011 (4)	0.000 (4)
C4	0.053 (5)	0.025 (4)	0.034 (4)	0.024 (4)	0.016 (4)	0.006 (3)
C5	0.031 (4)	0.023 (4)	0.032 (4)	0.010 (3)	0.006 (3)	0.010 (3)
C6	0.032 (4)	0.026 (4)	0.037 (4)	0.009 (3)	0.006 (3)	0.009 (4)
C7	0.049 (5)	0.036 (5)	0.067 (7)	0.023 (4)	0.020 (5)	0.021 (5)
C8	0.040 (5)	0.094 (9)	0.039 (6)	−0.002 (5)	0.004 (4)	0.008 (6)
C9	0.074 (7)	0.067 (8)	0.032 (5)	0.020 (6)	0.017 (5)	−0.004 (5)
C10	0.042 (5)	0.040 (5)	0.064 (6)	0.025 (4)	0.018 (4)	0.023 (5)
C11	0.072 (7)	0.043 (6)	0.060 (7)	0.010 (5)	0.035 (5)	−0.011 (5)
C12	0.051 (6)	0.041 (6)	0.072 (7)	0.007 (5)	0.014 (5)	0.007 (5)

Geometric parameters (Å, º)

Cd1—O1W	2.341 (6)	N2—H14	0.8600
Cd1—O1	2.829 (6)	N3—C10	1.326 (11)
Cd1—O2	2.318 (6)	N3—C11	1.355 (12)
Cd1—O3^i	2.503 (6)	N4—C10	1.346 (12)
Cd1—O4^i	2.413 (6)	N4—C12	1.356 (13)
Cd1—N1	2.267 (8)	N4—H15	0.8600
Cd1—N3	2.269 (7)	C1—C2	1.489 (12)
O1—C1	1.227 (14)	C2—C3	1.390 (13)
O2—C1	1.249 (14)	C3—C4	1.444 (12)
O3—C6	1.244 (9)	C3—H3	0.9300
O4—C6	1.248 (10)	C4—C5	1.374 (11)
S1—C2	1.716 (10)	C4—H4	0.9300
S1—C5	1.716 (7)	C5—C6	1.485 (11)
O1W—H1W1	0.85 (7)	C7—H7	0.9300
O1W—H1W2	0.85 (6)	C8—C9	1.306 (14)
O3—Cd1^ii	2.503 (6)	C8—H8	0.9300
O4—Cd1^ii	2.413 (6)	C9—H9	0.9300
N1—C7	1.340 (11)	C10—H10	0.9300
N1—C8	1.387 (12)	C11—C12	1.329 (14)
N2—C7	1.277 (12)	C11—H11	0.9300
N2—C9	1.333 (13)	C12—H12	0.9300
N3—Cd1—O1	80.4 (3)	N4—C12—H12	127.5
O1W—Cd1—O1	86.1 (3)	C1—C2—S1	120.7 (8)
O2—Cd1—O1	49.1 (3)	C1—O2—Cd1	104.5 (6)
O1—Cd1—O3^i	84.4 (3)	C2—C3—C4	109.7 (8)
O1—Cd1—O4^i	136.0 (2)	C2—C3—H3	125.2
O1—CD1—N1	139.2 (2)	C2—S1—C5	92.8 (4)
N1—Cd1—N3	96.3 (3)	C3—C2—C1	126.7 (9)
N1—Cd1—O2	90.5 (3)	C3—C2—S1	112.6 (6)
N3—Cd1—O2	90.2 (2)	C3—C4—H4	122.7
N1—Cd1—O1W	95.8 (2)	C4—C3—H3	125.2
N3—Cd1—O1W	166.2 (2)	C4—C5—C6	128.1 (7)
O2—Cd1—O1W	83.2 (2)	C4—C5—S1	110.4 (6)
N1—Cd1—O4^i	84.6 (3)	C5—C4—C3	114.6 (8)
N3—Cd1—O4^i	103.5 (2)	C5—C4—H4	122.7
O2—Cd1—O4^i	165.8 (2)	C6—C5—S1	121.4 (6)
O1W—Cd1—O4^i	84.1 (2)	C6—O3—Cd1^ii	90.4 (5)
N1—Cd1—O3^i	136.3 (2)	C6—O4—Cd1^ii	94.5 (5)
N3—Cd1—O3^i	86.4 (2)	C7—N1—C8	101.7 (8)
O2—Cd1—O3^i	133.2 (2)	C7—N1—Cd1	132.8 (7)
O1W—Cd1—O3^i	89.3 (2)	C7—N2—C9	107.0 (8)
O4^i—Cd1—O3^i	52.7 (2)	C7—N2—H14	126.5
Cd1—O1W—H1W1	108 (7)	C8—C9—H9	125.9
Cd1—O1W—H1W2	108 (7)	C8—C9—N2	108.2 (9)
O1—C1—C2	117.1 (12)	C8—N1—Cd1	125.1 (7)
O1—C1—O2	124.2 (9)	C9—C8—H8	125.2
O2—C1—C2	118.7 (10)	C9—C8—N1	109.5 (9)
O3—C6—C5	119.4 (8)	C9—N2—H14	126.5
O3—C6—O4	122.4 (8)	C10—N3—C11	105.6 (8)
O4—C6—C5	118.3 (7)	C10—N3—Cd1	126.6 (7)
N1—C7—H7	123.3	C10—N4—C12	108.8 (8)
N1—C8—H8	125.2	C10—N4—H15	125.6
N2—C7—H7	123.3	C11—C12—H12	127.5
N2—C7—N1	113.4 (9)	C11—C12—N4	105.1 (9)
N2—C9—H9	125.9	C11—N3—Cd1	125.9 (6)
N3—C10—H10	125.5	C12—C11—H11	124.4
N3—C10—N4	109.0 (9)	C12—C11—N3	111.2 (9)
N3—C11—H11	124.4	C12—N4—H15	125.6
N4—C10—H10	125.5	H1W1—O1W—H1W2	109 (7)
C1—C2—C3—C4	−177.8 (7)	N1—Cd1—O2—C1	166.5 (6)
C10—N3—C11—C12	−4.8 (13)	N3—C11—C12—N4	4.4 (14)
C10—N4—C12—C11	−2.3 (12)	N3—Cd1—N1—C7	164.2 (9)
C11—N3—C10—N4	3.2 (11)	N3—Cd1—N1—C8	−23.8 (9)
C12—N4—C10—N3	−0.6 (11)	N3—Cd1—O2—C1	70.2 (6)
C2—C3—C4—C5	−1.1 (10)	O1—C1—C2—C3	−3.9 (13)
C2—S1—C5—C4	−0.8 (6)	O1—C1—C2—S1	177.9 (7)
C2—S1—C5—C6	177.1 (6)	O1W—Cd1—N1—C7	−9.2 (9)
C3—C4—C5—C6	−176.5 (7)	O1W—Cd1—N1—C8	162.7 (9)
C3—C4—C5—S1	1.2 (9)	O1W—Cd1—N3—C10	−76.2 (13)
C4—C5—C6—O3	4.1 (12)	O1W—Cd1—N3—C11	86.0 (14)
C4—C5—C6—O4	−176.0 (8)	O1W—Cd1—O2—C1	−97.7 (6)
C5—S1—C2—C1	178.6 (6)	O2—C1—C2—C3	174.1 (8)
C5—S1—C2—C3	0.1 (6)	O2—C1—C2—S1	−4.2 (11)
C7—N1—C8—C9	2.9 (13)	O2—Cd1—N1—C7	74.0 (9)
C7—N2—C9—C8	−2.4 (13)	O2—Cd1—N1—C8	−114.1 (9)
C8—N1—C7—N2	−4.6 (12)	O2—Cd1—N3—C10	−137.3 (8)
C9—N2—C7—N1	4.6 (11)	O2—Cd1—N3—C11	24.9 (9)
Cd1—N1—C7—N2	168.7 (7)	O3^i—Cd1—N1—C7	−104.3 (9)
Cd1—N1—C8—C9	−171.1 (8)	O3^i—Cd1—N1—C8	67.6 (10)
Cd1—N3—C10—N4	168.3 (6)	O3^i—Cd1—N3—C10	−4.0 (8)
Cd1—N3—C11—C12	−170.1 (8)	O3^i—Cd1—N3—C11	158.2 (9)
Cd1—O2—C1—C2	−163.0 (6)	O3^i—Cd1—O2—C1	−15.1 (7)
Cd1—O2—C1—O1	14.8 (11)	O4^i—Cd1—N1—C7	−92.7 (9)
Cd1^ii—O3—C6—C5	179.6 (6)	O4^i—Cd1—N1—C8	79.2 (9)
Cd1^ii—O3—C6—O4	−0.3 (8)	O4^i—Cd1—N3—C10	46.2 (8)
Cd1^ii—O4—C6—C5	−179.6 (6)	O4^i—Cd1—N3—C11	−151.6 (8)
Cd1^ii—O4—C6—O3	0.3 (8)	O4^i—Cd1—O2—C1	−123.9 (10)
N1—C8—C9—N2	−0.4 (14)	S1—C2—C3—C4	0.5 (9)
N1—Cd1—N3—C10	132.2 (8)	S1—C5—C6—O3	−173.4 (6)
N1—Cd1—N3—C11	−65.6 (9)	S1—C5—C6—O4	6.5 (10)

Symmetry codes: (i) x, y−1, z; (ii) x, y+1, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1W1···O3^iii	0.85 (7)	1.93 (4)	2.732 (8)	157 (8)
O1W—H1W2···O1^iv	0.85 (6)	1.96 (3)	2.770 (10)	160 (7)
N2—H14···O4^v	0.86	1.92	2.758 (10)	165
N4—H15···O2^vi	0.86	1.97	2.826 (10)	171

Symmetry codes: (iii) −x, −y+1, −z; (iv) −x, −y, −z; (v) −x, −y+1, −z+1; (vi) x+1, y, z.