Crystal structure of tetraaquabis(8-chloro-9,10-dioxo-9,10-dihydroanthracene-1-carboxylato-κO 1)cobalt(II) dihydrate

In the title complex, [Co(C15H6ClO4)2(H2O)4]·2H2O, the CoII ion is bound by two carboxylate O atoms of two 5-chloro-9,10-anthraquinone-1-carboxylate anions and four water O atoms in a trans conformation, forming an irregular octahedral coordination geometry. This arrangement is stabilized by intramolecular O—H⋯O hydrogen bonds between water and carboxylate. Further O—H⋯O hydrogen bonds between coordinating and non-coordinating water and carboxylate produce layers of molecules that extend parallel to (001). The organic ligands project above and below the plane. Those ligands of adjacent planes are interdigitated and there are π–π interactions between them with centroid–centroid distances of 3.552 (2) and 3.767 (2) Å that generate a three-dimensional supramolecular structure.


Related literature
For the synthesis of the title complex, see: George et al. (2006). The major advantage of metal-based over organic-based drugs is the ability to vary coordination number, geometry and redox states, and metals can also change the pharmacological properties of organic-based drugs by forming coordination complexes with them, see: Hambley (2007). Anthraquinones are highly effective chemotherapeutic agents with a wide spectrum of antitumor activity, see: Unverferth et al. (1983); Kantrowitz & Bristow (1984); Stuart et al. (1984); Arcamone (1987). For related compounds, see: Bruijnincx & Sadler (2008); Gruber et al. (2010); Neufeind et al. (2011 Table 1 Hydrogen-bond geometry (Å , ).

data reports
Crystal structure of tetraaquabis(8-chloro-9,10-dioxo-9,10-dihydroanthracene-1-carboxylato-κO 1 )cobalt(II) dihydrate Wen-Juan Cai, Bo Liu, Feng-Yi Liu and Jun-Feng Kou S1. Comment The major advantage of metal-based over organic-based drugs is the ability to vary coordination number, geometry, and redox states and metals can also change the pharmacological properties of organic-based drugs by forming coordination complexes with them. (Hambley et al. 2007) Medicinal inorganic chemistry, covering applications of metals in therapeutics and diagnostics, is a field of increasing prominence (Bruijnincx et al. 2008) after the discovery and successful clinical applications of the Pt-based anticancer drug cisplatin. Anthraquinones are highly effective chemotherapeutic agents with a wide spectrum of antitumor activity. (Unverferth et al. 1983;Kantrowitz et al. 1984;Stuart et al. 1984;Arcamone et al. 1987;). Herein we report the synthesis and structure of the title cobalt(II) anthraquione complex.
The structure of the title complex is shown in Fig. 1, Fig. 2 and hydrogen-bond geometry is given in Table 1. The complex crystallizes in the triclinic space group P1 and the asymmetric unit consists of one crystallographically independent co(II) cation, one 5-cyclo-9,10-anthraquinone-1-carboxylate anion, two coordination water molecules and one free water molecule. As shown in Fig.1

S3. Refinement
H atoms attached to carbons were geometrically fixed and allowed to ride on the corresponding non-H atom with C-H = 0.96 Å, and U iso (H) = 1.2U eq (C) for other H atoms. For the water molecules, all O-H distances were constrained to be equal within a standard deviation of 0.03Å. Similar H···H distance restraints were applied to restrain the bond angle, but with a larger standard deviation. H atoms of bound water were refined with a single isotropic displacement parameter.
Similarly, those of free water were refined with a single, different, U iso .  The molecular structure of the title compound, with atom labels and 30 % probability displacement ellipsoids. Symmetry equivalent atoms labelled with an A (eg O1A) are generated by the symmetry operator 1-x, -y, 1-z.

Figure 2
A view of the crystal packing. Hydrogen bonds are shown as brown dashed lines.
Tetraaquabis(8-chloro-9,10-dioxo-9,10-dihydroanthracene-1-carboxylato-κO 1 )cobalt(II) dihydrate  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )
x y z U iso */U eq