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In the title compound, [CdCl2(C18H12N6)]·3H2O, the Cd atom has a distorted square-pyramidal coordination geometry. The solvent water mol­ecules are hydrogen bonded to each other to form planar cyclic water hexa­mers, which, together with other hydrogen bonds, inter­link the Cd complex mol­ecules to give one-dimensional supra­molecular ribbons that extend along the [111] direction. The chains are assembled into two-dimensional layers parallel to (111) by π–π stacking inter­actions. Furthermore, inter­layer π–π stacking inter­actions and weak C—H...Cl hydrogen bonds complete the formation of a three-dimensional framework.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107015703/ln3046sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107015703/ln3046Isup2.hkl
Contains datablock I

CCDC reference: 649069

Comment top

In recent years, there has been a growing interest in theoretical and experimental research directed at unravelling the structural details of a variety of water clusters in different environments (Atwood et al., 2001; Moorthy et al., 2002; Ghosh & Bharadwaj, 2004). Moreover, it is widely accepted that both water–MOF (metal-organic framework) and water–water interactions are important for the stability of the overall structure (Michaelides et al., 2003). A number of studies of small water clusters have concentrated on the hexamer, which exists in the bulk water founded in some molecular solids (Custelcean et al., 2000). To date, three types of cyclic water hexamers have been detected in host lattices characterized using X-ray crystallographic analysis, and they are denoted as `chair', `boat' and `planar' cyclic water hexamers. In the structure of the title compound, (I), reported here, cyclic water hexamers with the `planar' conformation are present. A similar cyclic planar water hexamer was observed in the structure of bimesityl-3,3-dicarboxylic acid monohydrate (Moorthy et al., 2002). The title compound was obtained during attempts to prepare the Cd analogue of [Co(C2O4)(TPTZ)(H2O)]·4H2O (TPTZ is 2,4,6-tri-2-pyridyl-1,3,5-triazine; Cheng et al., 2006).

The asymmetric unit of the title compound contains one [Cd(C18H12N6)Cl2] complex molecule and three symmetry-independent water molecules. The central CdII ion is five-coordinated by three N atoms from a TPTZ ligand and two chloride ions, which results in a distorted square-pyramidal coordination geometry; a similar coordination geometry is found in the structure of [Cd(C10H15N3)Cl2], which contains the tridentate N,N-dimethyl-N'-pyridin-2-yl-methylene-1,2-diaminoethane ligand (Bian et al., 2003). Atom Cl2 is located at the apex of the pyramid, and atoms N1, N2, N3 and Cl1 lie at the four corners of the base of the square pyramid. Atom Cd1 is displaced by 0.542 (1) Å from the base toward Cl2 (Fig. 1). Selected bond lengths and bond angles involving atom Cd1 are presented in Table 1. As far as is known, five-coordinated CdII complexes only represent about 5% of all known cadmium complexes (Sigel & Martin, 1994; Wang et al., 2003).

Interestingly, the solvent water molecules hydrogen bond to each other to form a cyclic water hexamer, which is centrosymmetric. The main hydrogen bonds are listed in Table 2. The environment of the water hexamer is shown in Fig 2. Within the cluster, the six water molecules are coplanar and each water molecule acts as both a single hydrogen-bond donor and an acceptor. The average O···O distance is 2.84 Å, which is close to the corresponding distance in liquid water (2.85 Å; Narten et al., 1982). In addition, atoms O1, O2 and O3 donate hydrogen bonds to atoms Cl2, N6(1 - x, 2 - y, 1 - z) and Cl1, respectively, of neighbouring Cd-complex molecules. As a consequence of these hydrogen bonds, the water hexamers and Cd-complex molecules are assembled into one-dimensional supramolecular ribbons, which extend along the [111] direction (Fig. 2). Adjacent parallel ribbons are stacked into two-dimensional layers parallel to (111) by intermolecular ππ stacking interactions between the pyridyl ring containing atom N1 and the pyridyl ring containing atom N6 in the centrosymmetrically related molecule at (1 - x, 1 - y, 1 - z). The mean interplanar distance is 3.34 (3) Å and the distance between the respective ring centroids is 3.561 (2) Å. Another strong ππ stacking interaction links adjacent layers; the pyridyl ring containing atom N1 stacks over the pyridyl ring containing atom N3 in the molecule at (x - 1, y, z). The mean interplanar distance is 3.42 (3) Å and the distance between the respective ring centroids is 3.703 (2) Å. The interlayer ππ stacking interactions, together with a weak C1—H1···Cl1 hydrogen bond, lead to the formation of a three-dimensional framework.

Related literature top

For related literature, see: Atwood et al. (2001); Bian et al. (2003); Cheng et al. (2006); Custelcean et al. (2000); Ghosh & Bharadwaj (2004); Michaelides et al. (2003); Moorthy et al. (2002); Narten et al. (1982); Sigel & Martin (1994); Wang et al. (2003).

Experimental top

TPTZ (0.312 g, 1.0 mmol) and oxalic acid were disolved with stirring in 30 ml of aqueous methanol (1:1 v/v). CdCl2·2.5H2O (0.228 g, 1.0 mmol) was added to the above solution to obtain a yellow solution (pH = 0.74), which was filtered. The resulting yellow filtrate was maintained at room temperature and afforded pale-yellow crystals one week later by slow evaporation (yield 5% based on the initial CdCl2·2.5H2O input).

Refinement top

H atoms bonded to C atoms were placed in geometrically calulated positons and were refined using a riding moldel, with Uiso(H) set at 1.2Ueq(C). H atoms attached to O atoms were found in a difference Fourier synthesis and were refined using a riding model with the O—H distances fixed as initially found and with Uiso(H) set at 1.2Ueq(O). The highest peak in the residual electron-density map is located 0.85 Å from atom Cd1 and the deepest hole is located 0.65 Å from atom Cd1.

Computing details top

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 top
[Figure 1] Fig. 1. The molecular structure of (I). Displacement ellipsoids are drawn at the 45% probability level. H atoms have been omitted.
[Figure 2] Fig. 2. The one-dimensional supramolecular chain assembled by hydrogen bonds in (I). Hydrogen bonds are indicated by dashed lines.
dichlorido(2,4,6-tri-2-pyridyl-1,3,5-triazine)cadmium(II) trihydrate top
Crystal data top
[CdCl2(C18H12N6)]·3H2OZ = 2
Mr = 549.68F(000) = 548
Triclinic, P1Dx = 1.714 Mg m3
Hall symbol: -P1Mo Kα radiation, λ = 0.71073 Å
a = 8.9567 (18) ÅCell parameters from 9394 reflections
b = 11.118 (2) Åθ = 3.1–27.5°
c = 11.568 (2) ŵ = 1.31 mm1
α = 106.71 (3)°T = 298 K
β = 98.67 (3)°Block, yellow
γ = 99.21 (3)°0.29 × 0.25 × 0.22 mm
V = 1065.3 (4) Å3
Data collection top
Rigaku R-AXIS RAPID
diffractometer
4829 independent reflections
Radiation source: fine-focus sealed tube4035 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.038
ω scansθmax = 27.5°, θmin = 3.1°
Absorption correction: multi-scan
(ABSCOR; Higashi,1995)
h = 1111
Tmin = 0.506, Tmax = 1.000k = 1413
10540 measured reflectionsl = 1414
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.039Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.114H-atom parameters constrained
S = 1.08 w = 1/[σ2(Fo2) + (0.0651P)2]
where P = (Fo2 + 2Fc2)/3
4829 reflections(Δ/σ)max = 0.001
271 parametersΔρmax = 1.17 e Å3
0 restraintsΔρmin = 0.83 e Å3
Crystal data top
[CdCl2(C18H12N6)]·3H2Oγ = 99.21 (3)°
Mr = 549.68V = 1065.3 (4) Å3
Triclinic, P1Z = 2
a = 8.9567 (18) ÅMo Kα radiation
b = 11.118 (2) ŵ = 1.31 mm1
c = 11.568 (2) ÅT = 298 K
α = 106.71 (3)°0.29 × 0.25 × 0.22 mm
β = 98.67 (3)°
Data collection top
Rigaku R-AXIS RAPID
diffractometer
4829 independent reflections
Absorption correction: multi-scan
(ABSCOR; Higashi,1995)
4035 reflections with I > 2σ(I)
Tmin = 0.506, Tmax = 1.000Rint = 0.038
10540 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0390 restraints
wR(F2) = 0.114H-atom parameters constrained
S = 1.08Δρmax = 1.17 e Å3
4829 reflectionsΔρmin = 0.83 e Å3
271 parameters
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
xyzUiso*/Ueq
Cd10.68260 (3)0.94785 (2)0.74380 (2)0.04167 (11)
Cl10.76603 (14)1.00000 (12)0.96329 (9)0.0663 (3)
Cl20.59244 (11)1.12108 (9)0.67872 (9)0.0534 (2)
N10.4416 (3)0.7979 (3)0.6987 (2)0.0373 (6)
N20.6562 (3)0.7794 (3)0.5663 (2)0.0365 (6)
N30.9248 (3)0.9437 (3)0.6761 (2)0.0394 (6)
N40.4959 (3)0.6061 (3)0.4047 (2)0.0379 (6)
N50.7536 (3)0.6859 (3)0.3925 (2)0.0404 (6)
N60.4607 (4)0.4251 (3)0.1799 (3)0.0461 (7)
C10.3401 (4)0.8058 (3)0.7724 (3)0.0427 (7)
H10.36680.87000.84870.051*
C20.1982 (4)0.7236 (4)0.7406 (3)0.0476 (8)
H20.13040.73210.79450.057*
C30.1578 (4)0.6290 (4)0.6285 (3)0.0467 (8)
H30.06210.57230.60550.056*
C40.2605 (4)0.6183 (3)0.5493 (3)0.0426 (7)
H40.23500.55560.47210.051*
C50.4012 (4)0.7034 (3)0.5888 (3)0.0351 (6)
C60.5231 (4)0.6948 (3)0.5143 (3)0.0357 (6)
C70.7697 (4)0.7700 (3)0.5038 (3)0.0357 (6)
C80.9202 (4)0.8593 (3)0.5651 (3)0.0360 (6)
C91.0470 (4)0.8557 (3)0.5107 (3)0.0409 (7)
H91.04050.79620.43390.049*
C101.1847 (4)0.9430 (4)0.5734 (3)0.0455 (8)
H101.27180.94390.53870.055*
C111.1900 (4)1.0280 (4)0.6875 (4)0.0478 (8)
H111.28131.08660.73150.057*
C121.0576 (4)1.0257 (4)0.7364 (3)0.0467 (8)
H121.06191.08330.81380.056*
C130.6148 (4)0.6072 (3)0.3459 (3)0.0364 (7)
C140.5920 (4)0.5129 (3)0.2205 (3)0.0413 (7)
C150.7066 (5)0.5198 (4)0.1525 (3)0.0503 (9)
H150.79610.58410.18360.060*
C160.6843 (6)0.4295 (5)0.0382 (3)0.0614 (11)
H160.75890.43170.00950.074*
C170.5516 (6)0.3366 (4)0.0045 (3)0.0618 (12)
H170.53500.27370.08100.074*
C180.4414 (6)0.3377 (4)0.0686 (4)0.0579 (10)
H180.35030.27500.03880.069*
O10.9015 (4)1.3381 (4)0.7872 (4)0.0961 (12)
H1A0.89031.41370.79170.115*
H1B0.81221.28860.75220.115*
O20.8419 (4)1.5734 (4)0.7579 (3)0.1016 (15)
H2A0.74371.56280.75630.122*
H2B0.86891.64100.82210.122*
O31.0127 (5)1.2728 (4)1.0018 (4)0.0965 (12)
H3A0.96741.19390.95860.116*
H3B0.99181.30130.93910.116*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cd10.04181 (16)0.04290 (16)0.03342 (15)0.00872 (11)0.01224 (10)0.00034 (11)
Cl10.0762 (7)0.0751 (7)0.0341 (4)0.0064 (6)0.0096 (4)0.0031 (5)
Cl20.0516 (5)0.0511 (5)0.0594 (6)0.0155 (4)0.0159 (4)0.0157 (4)
N10.0422 (15)0.0393 (14)0.0291 (12)0.0118 (12)0.0120 (11)0.0051 (11)
N20.0372 (14)0.0363 (13)0.0329 (13)0.0098 (11)0.0121 (11)0.0029 (11)
N30.0388 (14)0.0431 (15)0.0346 (13)0.0118 (12)0.0109 (11)0.0066 (12)
N40.0422 (15)0.0380 (14)0.0318 (13)0.0100 (12)0.0117 (11)0.0058 (11)
N50.0447 (15)0.0415 (15)0.0345 (13)0.0121 (12)0.0158 (12)0.0061 (12)
N60.0612 (19)0.0394 (15)0.0317 (14)0.0119 (14)0.0097 (13)0.0013 (12)
C10.0460 (19)0.0477 (19)0.0321 (15)0.0138 (15)0.0139 (14)0.0040 (14)
C20.0474 (19)0.058 (2)0.0430 (18)0.0158 (17)0.0245 (15)0.0144 (17)
C30.0386 (18)0.051 (2)0.0460 (19)0.0032 (15)0.0134 (15)0.0104 (17)
C40.0432 (18)0.0439 (18)0.0377 (17)0.0081 (15)0.0110 (14)0.0077 (15)
C50.0408 (16)0.0392 (16)0.0299 (14)0.0151 (13)0.0140 (12)0.0111 (13)
C60.0402 (16)0.0351 (15)0.0348 (15)0.0129 (13)0.0135 (13)0.0104 (13)
C70.0392 (16)0.0385 (16)0.0331 (15)0.0150 (13)0.0126 (12)0.0106 (13)
C80.0390 (16)0.0387 (16)0.0327 (15)0.0148 (13)0.0107 (12)0.0101 (13)
C90.0405 (17)0.0485 (19)0.0409 (17)0.0197 (15)0.0162 (14)0.0157 (15)
C100.0383 (17)0.056 (2)0.053 (2)0.0182 (16)0.0191 (15)0.0240 (18)
C110.0361 (17)0.053 (2)0.050 (2)0.0076 (15)0.0071 (15)0.0129 (17)
C120.0428 (19)0.050 (2)0.0407 (18)0.0085 (16)0.0084 (15)0.0060 (16)
C130.0441 (17)0.0375 (16)0.0295 (14)0.0151 (14)0.0119 (13)0.0080 (13)
C140.054 (2)0.0425 (17)0.0292 (15)0.0198 (16)0.0116 (14)0.0074 (14)
C150.058 (2)0.057 (2)0.0360 (17)0.0200 (18)0.0177 (16)0.0066 (17)
C160.077 (3)0.076 (3)0.0372 (19)0.035 (3)0.0264 (19)0.009 (2)
C170.092 (3)0.061 (3)0.0333 (18)0.037 (3)0.016 (2)0.0039 (18)
C180.077 (3)0.046 (2)0.0389 (19)0.013 (2)0.0070 (18)0.0011 (17)
O10.066 (2)0.100 (3)0.100 (3)0.004 (2)0.016 (2)0.010 (2)
O20.071 (2)0.112 (3)0.083 (3)0.018 (2)0.033 (2)0.016 (2)
O30.098 (3)0.079 (3)0.085 (3)0.006 (2)0.019 (2)0.007 (2)
Geometric parameters (Å, º) top
Cd1—N22.298 (3)C5—C61.488 (4)
Cd1—N12.392 (3)C7—C81.478 (5)
Cd1—Cl12.4049 (12)C8—C91.379 (4)
Cd1—N32.418 (3)C9—C101.389 (5)
Cd1—Cl22.4650 (11)C9—H90.9300
N1—C11.333 (4)C10—C111.374 (5)
N1—C51.350 (4)C10—H100.9300
N2—C61.329 (4)C11—C121.388 (5)
N2—C71.334 (4)C11—H110.9300
N3—C121.331 (5)C12—H120.9300
N3—C81.345 (4)C13—C141.487 (4)
N4—C61.323 (4)C14—C151.389 (5)
N4—C131.347 (4)C15—C161.375 (5)
N5—C71.327 (4)C15—H150.9300
N5—C131.334 (5)C16—C171.364 (7)
N6—C141.326 (5)C16—H160.9300
N6—C181.338 (5)C17—C181.392 (6)
C1—C21.371 (5)C17—H170.9300
C1—H10.9300C18—H180.9300
C2—C31.368 (5)O1—H1A0.8503
C2—H20.9300O1—H1B0.8601
C3—C41.388 (5)O2—H2A0.8647
C3—H30.9300O2—H2B0.8605
C4—C51.374 (5)O3—H3A0.8693
C4—H40.9300O3—H3B0.8787
N2—Cd1—N168.19 (10)N5—C7—N2123.6 (3)
N2—Cd1—Cl1139.44 (7)N5—C7—C8119.9 (3)
N1—Cd1—Cl1103.21 (8)N2—C7—C8116.5 (3)
N2—Cd1—N368.61 (10)N3—C8—C9122.7 (3)
N1—Cd1—N3135.15 (9)N3—C8—C7115.8 (3)
Cl1—Cd1—N3101.59 (7)C9—C8—C7121.5 (3)
N2—Cd1—Cl2106.25 (7)C8—C9—C10118.4 (3)
N1—Cd1—Cl299.85 (7)C8—C9—H9120.8
Cl1—Cd1—Cl2114.31 (5)C10—C9—H9120.8
N3—Cd1—Cl2103.11 (7)C11—C10—C9118.9 (3)
C1—N1—C5117.6 (3)C11—C10—H10120.5
C1—N1—Cd1124.1 (2)C9—C10—H10120.5
C5—N1—Cd1118.2 (2)C10—C11—C12119.3 (4)
C6—N2—C7116.7 (3)C10—C11—H11120.4
C6—N2—Cd1122.0 (2)C12—C11—H11120.4
C7—N2—Cd1121.0 (2)N3—C12—C11122.1 (3)
C12—N3—C8118.6 (3)N3—C12—H12118.9
C12—N3—Cd1124.3 (2)C11—C12—H12118.9
C8—N3—Cd1116.9 (2)N5—C13—N4124.8 (3)
C6—N4—C13114.9 (3)N5—C13—C14117.0 (3)
C7—N5—C13115.5 (3)N4—C13—C14118.2 (3)
C14—N6—C18117.3 (3)N6—C14—C15123.4 (3)
N1—C1—C2122.9 (3)N6—C14—C13117.0 (3)
N1—C1—H1118.5C15—C14—C13119.6 (3)
C2—C1—H1118.5C16—C15—C14118.4 (4)
C3—C2—C1119.0 (3)C16—C15—H15120.8
C3—C2—H2120.5C14—C15—H15120.8
C1—C2—H2120.5C17—C16—C15119.2 (4)
C2—C3—C4119.6 (3)C17—C16—H16120.4
C2—C3—H3120.2C15—C16—H16120.4
C4—C3—H3120.2C16—C17—C18118.7 (4)
C5—C4—C3117.8 (3)C16—C17—H17120.6
C5—C4—H4121.1C18—C17—H17120.6
C3—C4—H4121.1N6—C18—C17122.9 (4)
N1—C5—C4123.1 (3)N6—C18—H18118.6
N1—C5—C6114.9 (3)C17—C18—H18118.6
C4—C5—C6121.9 (3)H1A—O1—H1B105.8
N4—C6—N2124.4 (3)H2A—O2—H2B95.9
N4—C6—C5120.1 (3)H3A—O3—H3B93.1
N2—C6—C5115.5 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1A···O20.852.022.854 (4)166
O1—H1B···Cl20.862.343.183 (4)167
O2—H2A···N6i0.872.092.908 (4)159
O2—H2B···O3ii0.862.022.794 (4)149
O3—H3A···Cl10.872.603.325 (4)142
O3—H3B···O10.882.002.864 (6)168
Symmetry codes: (i) x+1, y+2, z+1; (ii) x+2, y+3, z+2.

Experimental details

Crystal data
Chemical formula[CdCl2(C18H12N6)]·3H2O
Mr549.68
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)8.9567 (18), 11.118 (2), 11.568 (2)
α, β, γ (°)106.71 (3), 98.67 (3), 99.21 (3)
V3)1065.3 (4)
Z2
Radiation typeMo Kα
µ (mm1)1.31
Crystal size (mm)0.29 × 0.25 × 0.22
Data collection
DiffractometerRigaku R-AXIS RAPID
diffractometer
Absorption correctionMulti-scan
(ABSCOR; Higashi,1995)
Tmin, Tmax0.506, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections
10540, 4829, 4035
Rint0.038
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.039, 0.114, 1.08
No. of reflections4829
No. of parameters271
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.17, 0.83

Computer programs: RAPID-AUTO (Rigaku Corporation, 1998), RAPID-AUTO, CrystalStructure (Rigaku/MSC, 2002), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), SHELXL97.

Selected geometric parameters (Å, º) top
Cd1—N22.298 (3)Cd1—N32.418 (3)
Cd1—N12.392 (3)Cd1—Cl22.4650 (11)
Cd1—Cl12.4049 (12)
N2—Cd1—N168.19 (10)Cl1—Cd1—N3101.59 (7)
N2—Cd1—Cl1139.44 (7)N2—Cd1—Cl2106.25 (7)
N1—Cd1—Cl1103.21 (8)N1—Cd1—Cl299.85 (7)
N2—Cd1—N368.61 (10)Cl1—Cd1—Cl2114.31 (5)
N1—Cd1—N3135.15 (9)N3—Cd1—Cl2103.11 (7)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1A···O20.852.022.854 (4)166
O1—H1B···Cl20.862.343.183 (4)167
O2—H2A···N6i0.872.092.908 (4)159
O2—H2B···O3ii0.862.022.794 (4)149
O3—H3A···Cl10.872.603.325 (4)142
O3—H3B···O10.882.002.864 (6)168
Symmetry codes: (i) x+1, y+2, z+1; (ii) x+2, y+3, z+2.
 

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