Poly[tris(μ-4,4′-bipyridine-κ2 N:N′)bis(dimethyl sulfoxide-κO)tetrakis(thiocyanato-κN)dicobalt(II)]

The asymmetric unit of the title compound, [Co2(NCS)4(C10H8N2)3(C2H6OS)2]n, consists of one CoII atom, two thiocyanate anions, one dimethyl sulfoxide molecule and one and a half 4,4′-bipyridine molecules. The half-molecule is completed by inversion symmetry. The CoII atom is coordinated in a distorted octahedral geometry by two N atoms from two thiocyanate anions, one O atom from dimethyl sulfoxide as a terminal ligand and three N atoms from three 4,4′-bipyridine molecules as bridging ligands linking the cations, with a Co⋯Co separation of 11.5964 (5) Å. This generates a two-dimensional structure parallel to (-103). A C—H⋯S hydrogen bond links the layers into a three-dimensional supramolecular framework. The layers are stacked in an ABC fashion preventing the occurrence of interlayer void space and hence leading to the absence of lattice solvent and/or organic guest molecules in the structure.

The asymmetric unit of the title compound, [Co 2 (NCS) 4 -(C 10 H 8 N 2 ) 3 (C 2 H 6 OS) 2 ] n , consists of one Co II atom, two thiocyanate anions, one dimethyl sulfoxide molecule and one and a half 4,4 0 -bipyridine molecules. The half-molecule is completed by inversion symmetry. The Co II atom is coordinated in a distorted octahedral geometry by two N atoms from two thiocyanate anions, one O atom from dimethyl sulfoxide as a terminal ligand and three N atoms from three 4,4 0bipyridine molecules as bridging ligands linking the cations, with a CoÁ Á ÁCo separation of 11.5964 (5) Å . This generates a two-dimensional structure parallel to (103). A C-HÁ Á ÁS hydrogen bond links the layers into a three-dimensional supramolecular framework. The layers are stacked in an ABC fashion preventing the occurrence of interlayer void space and hence leading to the absence of lattice solvent and/or organic guest molecules in the structure.

Comment
Metal organic frameworks can be prepared in variety methods and there are many effects influencing their structures. The solvent used in preparing is one of the most important effects on the structures. The influence of the solvent on the structure has been widely studied, for example in the study of iron(II) thiocyanato coordination polymers based on 4,4′bipyridine using methanol as a solvent (Wriedt & Näther, 2010). This finding suggested that if more solvent and higher concentration of N-donor ligand were applied the structure is likely to involve with solvent coordination and the different metal to organic ligand ratio. The solvent has the influence on both metal to organic ligand ratio and the arrangement of the organic linker leading to the variation of the dimension and topology of the network (Yao & Wang, 2009). In addition, the type of N-donor organic linkers also affect the structure (Wriedt & Näther, 2009;. Of interest to us was this effect. A new structure with the different metal to N-donor organic ligand ratio might also be possible by alteration of the solvent, type of N-donor organic ligand, and the metal to N-donor ligand ratio in the preparation. In this contribution, we present synthesis and structural characterization of a two-dimensional framework of poly[µ-tris(4,4′-bipyridine)di(dimethyl sulfoxide)tetrathiocyanato-N-dicobalt(II)] (I) The asymmetric unit of the title compound consists of one Co II centre, two SCNanions, one and a half 4,4′-bpy molecules and one DMSO molecule (Fig. 1). The Co II is surrounded by two N atoms from terminal SCNgroups, one O atom from DMSO and three N atoms from three 4,4′-bpy (Table 1). The 4,4′-bpy acts as a bridge linking metal centres and generates a two-dimensional structure with rectangular spaces (11.60 x 23.25 Å) within layer (Fig. 2). Due to the arrangement of the linker and metal to N-donor organic ligand ratio of 1:1.5, the space within the layer is twice as compared to the related two-dimensional compound {[Fe(4,4′-bpy) 2 (SCN) 2 ](MeOH) 2 } n (Wriedt & Näther, 2010). The layers are stacked in an ABC fashion (Fig. 3). The plane parallel to the layer is (103). The metal atoms in one layer sit above or below the rectangular spaces. As a result, the terminal SCNand DMSO ligands arrange approximately perpendicular to the layer plane and fill up the spaces between adjacent layers. This arrangement of the layers is in the ABC fashion preventing the occurrence of the interlayer spaces along the crystallographic c axis and hence leading to the absence of lattice solvent and/or organic guest molecules in the interlayer spaces (Fig. 3). In addition, the extended structure of I has been illustrated (Fig. 4). The hydrogen bonds between H1 and S1 link the layers with the distance of 2.82 Å ( Table 2). As a result, these layers are assembled into a three-dimensional supramolecular framework.

Refinement
C-bound H atoms were positioned geometrically, with C-H = 0.93 (aromatic) or 0.96 Å (methyl), and included as riding atoms, with U iso (H) = 1.5U eq (C) for methyl groups and 1.2U eq (C) otherwise.

Figure 1
A view of the local coordination of the Co II in the title compound, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.  A partial packing diagram of the title compound, showing that terminal ligands, DMSO and SCNfill up the rectangular space of adjacent layer (a) and ABC arrangement structure layers prevent the occurrence of the channel along C axis (b).

Figure 4
The extended structure of the title compound illustrates the hydrogen bonds (dotted lines) between H1 and S1 (-x + 3/2, y -1/2, -z + 1/2) linking two-dimensional layers leading to a three-dimensional supramolecular framework. The adjacent layers are shown in different colours.

Poly[tris(µ-4,4′-bipyridine-κ 2 N:N′)bis(dimethyl sulfoxide-κO)tetrakis(thiocyanato-κN)dicobalt(II)]
Crystal data [Co 2 (NCS) 4 (C 10 H 8 N 2 ) 3 (C 2 H 6 OS) 2 ] M r = 974.98 Monoclinic, P2 1 /n Hall symbol: -P 2yn a = 11.0772 (3)  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.02 e Å −3 Δρ min = −0.58 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. 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