N,N-Bis(pyridin-2-ylmethyl)cyclohexanamine

The pyridine rings of the title compound, C18H23N3, are in a nearly perpendicular orientation relative to the plane defined by the three amino-bonded C atoms, making dihedral angles of 87.4 (1) ° and 84.2 (1) °. One of the pyridine N atoms acts as an hydrogen-bond acceptor for two pyridine C—H groups. By means of these intermolecular hydrogen bonds, the molecules form a two-dimensional network parallel to the ab plane.

The pyridine rings of the title compound, C 18 H 23 N 3 , are in a nearly perpendicular orientation relative to the plane defined by the three amino-bonded C atoms, making dihedral angles of 87.4 (1) and 84.2 (1) . One of the pyridine N atoms acts as an hydrogen-bond acceptor for two pyridine C-H groups. By means of these intermolecular hydrogen bonds, the molecules form a two-dimensional network parallel to the ab plane.
There are non-classical hydrogen bonds between the pyridine nitrogen atom, N2, and the pyridine hydrogen atoms, H4 and H11 of two separate, adjacent molecules. N2 acts as an acceptor for both hydrogen bonds. These bonds lead to the formation of an infinite two-dimensional hydrogen-bonded network. This network is co-planar with the ab plane. The network consists of one-dimensional chains with adjacent molecules linked by the N2···H4 hydrogen bond. These onedimensional chains are then cross-linked by the N2···H11 hydrogen bond, thus forming an infinite, two-dimensional network. Although hydrogen bond length does not necessarily correlate linearly to bond strength, due to packing constraints in the lattice, these bonds are considerably shorter than the sum of their van der Waals radii and are thus likely to be moderate to high in strength. This also seems likely as the D-H···A bond angle of both bonds, 165.7 (1) ° and 153.1 (1) ° for N2···H4-C4 and N2···H11-C11 respectively, do not show a marked deviation from ideality. The hydrogen bond lengths and angles are summarized in Table 1.

Experimental
The tridentate ligand is formed by reacting two molar equivalents of 2-picolyl chloride hydrochloride under basic aqueous conditions with one molar equivalent of cyclohexylamine, following an improved method of Sato et al., (1992) previously reported by Toftlund & Yde-Andersen (1981) as well as Anderegg & Wenk (1967). Colourless crystals were obtained by slow evaporation of an ethanol solution of the ligand over a period of several days. Yield: 1.276 g (44%).

Refinement
The positions of all C-bonded hydrogen atoms were calculated using the standard riding model of SHELXL97 (Sheldrick, 2008) with C-H(aromatic) distances of 0.95 Å and U iso = 1.2 U eq , C-H(methylene) distances of 0.99 Å and U iso = 1.2 U eq and a C-H(methine) distance of 1.00 Å and U iso = 1.2 U eq . In the absence of significant anamalous scattering, Friedel pairs were merged.

Computing details
Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis CCD (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: WinGX (Farrugia, 1999); software used to prepare material for publication: publCIF (Westrip, 2010  Thermal ellipsoid plot of (1), rendered at 50% probability. Hydrogen atoms are shown as spheres of arbitrary radius.  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 > 2σ(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.