Bis{N 2,N 6-bis[(pyridin-3-yl)methyl]pyridine-2,6-dicarboxamide-κN}bis(methanol-κO)bis(thiocyanato-κN)cobalt(II)

In the title compound, [Co(NCS)2(C19H17N5O2)2(CH3OH)2], the CoII atom lies on an inversion center and is coordinated by two isothiocyanate N atoms, two O atoms of methanol molecules and two pyridine N atoms in a slightly distorted octahedral environment. Intermolecular O—H⋯O and N—H⋯N hydrogen bonds join the complex molecules into layers parallel to the bc plane.

In the title compound, [Co(NCS) 2 (C 19 H 17 N 5 O 2 ) 2 (CH 3 OH) 2 ], the Co II atom lies on an inversion center and is coordinated by two isothiocyanate N atoms, two O atoms of methanol molecules and two pyridine N atoms in a slightly distorted octahedral environment. Intermolecular O-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds join the complex molecules into layers parallel to the bc plane.
The title compound is a mononuclear complex, where the Co 2+ ion lies at the inversion center, thus the asymmetric unit consists of Co atom, one BPDA, one methanol molecule, and one SCNanion ( Fig. 1). In (1) the coordination center is ligated by two isothiocyanato N atoms, two methanol O atoms, and two BPDA acting as monodentate ligands through their pyridyl N atoms. The octahedral coordination environment is slightly distorted, the largest deviation of coordination angles from idealized values are 1.59 (9) °.
Further aggregation of complex molecules is formed by the multiple hydrogen-bonding between the dicarboxamide groups of BPDA (as donors) and the uncoordinated pyridyl groups of other BPDA (as acceptors) as well as between the coordination methanol molecules (as donors) and the dicarboxamide groups of BPDA (as acceptors) (Table 2).
Consequently, monomers are linked by O-H···O and N-H···N hydrogen bonds into a two-dimensional network parallel to the bc plane (Fig. 2). The layer structure is stabilized by face-to-face π···π stacking interactions between adjacent central pyridine rings of BPDA with a centroid to centroid distance of 3.793 (2) Å. Notably, that the ligand BPDA in (1) have pseudo-C 2 symmetry and adopts helical conformation with the dihedral angles of the pendant pyridyl groups with the central pyridine ring of 76.1 (3) and 75.6 (3) °, respectively.

Experimental
Synthesis of BPDA ligand. A mixture of 2,6-pyridinedicarboxylic acid (10 g, 60 mmol) and thionyl chloride (75 ml) was heated with reflux for 6 h under anhydrous condition, and then excess thionyl chloride was removed by rotary evaporation. The resulting white solid pyridine-2,6-dicarboyl dichloride was dissolved in dry CH 2 Cl 2 (50 ml), to which a solution of 3-(aminomethyl)pyridine (13 g, 120 mmol) and triethylamine (24 ml) in dry CH 2 Cl 2 (70 ml) was added dropwise with continuous stirring in an ice-bath. Stirred at room temperature for another hour, the mixture was washed with water (500 ml). The separated organic phase was dried with magnesium sulfate, and the solvent was removed by rotary evaporation. After recrystallization from alcohol/water (2:1), white crystals of BPDA were obtained (Yield: 70%). The title compound (1) was prepared according to the following process. A solution of BPDA (69.4 mg, 0.2 mmol) in DMF (5 ml) was dropwise added into a solution of CoSO 4 .6H 2 O (28.1 mg, 0.1 mmol) in methanol (5 ml), and then a solution of KSCN (19.4 mg, 0.2 mmol) in methanol (5 ml) was dropwise added into the above mixture. With stirring for 30 minutes, the resulting mixture was filtered. The filtrate was allowed to evaporate at room temperature for two days, and pink crystals were obtain in 48% yield. Selected IR (

Refinement
Two very strong reflections, (2 1 1) and (-1 4 1), were omitted because of intensity overflow. All H atoms attached to the C and N atoms were positioned geometrically at distances 0.98 Å (CH 3 ), 0.99 Å (CH 2 ), 0.95 Å (CH) and 0.88 Å (NH) and refined using a riding model with U iso (H) = 1.2U eq (C,N) and U iso (H) = 1.5U eq (C methyl ). The positional parameters of the H atom attached to oxygen were refined freely, and at the last stage of the refinement they were restrained with the H-O = 0.82 (3) Å and with U iso (H) = 1.2U eq (O).

Figure 1
Diagram of the title compound with atom numbering scheme. Thermal ellipsoids are drawn at the 30% probability level.
Symmetry code: (i) -x, -y, -z + 1.  View of the two-dimensional network in the title compound formed by O-H···O and N-H···N hydrogen bonds.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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.