N-{1,2-Bis(pyridin-3-yl)-2-[(E)-(pyridin-3-yl)methylideneamino]ethyl}nicotinamide

In the title compound, C24H20N6O, the pyridin-3-yl groups on the ethylene fragment are found in a trans conformation with a C(py)—C(e)—C(e)—C(py) (py = pyridine, e = ethylene) torsion angle of 179.2 (3)°. The dihedral angle between the pyridine rings is 3.5 (1)°. In the crystal, N—H⋯N and C—H⋯O=C interactions form a layer arrangement parallel to the bc plane. The compound displays disorder of the ethylene fragment over two positions with an occupancy ratio of 0.676 (7) to 0.324 (7) that extends into the amide section of the nicotinamide moiety.

In the title compound, C 24 H 20 N 6 O, the pyridin-3-yl groups on the ethylene fragment are found in a trans conformation with a C(py)-C(e)-C(e)-C(py) (py = pyridine, e = ethylene) torsion angle of 179.2 (3) . The dihedral angle between the pyridine rings is 3.5 (1) . In the crystal, N-HÁ Á ÁN and C-HÁ Á ÁO C interactions form a layer arrangement parallel to the bc plane. The compound displays disorder of the ethylene fragment over two positions with an occupancy ratio of 0.676 (7) to 0.324 (7) that extends into the amide section of the nicotinamide moiety.
In the title compound I, C 24 H 20 N 6 O, the ethylene fragment presents a trans conformation between the two pyridin-3-yl groups with a torsion angle of 179.2 (3)° [C27-C10-C9-C21], and the nicotinamide groups presents a torsion angle Compound I has an imine group with a C-N distance of 1.329 (4) Å and the crystal structure is stabilized by hydrogen bonds (N-H···N and C-H···O=C). The hydrogen bond between the carboxyl group and the C-H bond produces a centrosymmetric dimer with a H···O distance of 2.25 Å. The dimers are further connected by N-H···N interactions between the imine group and one pyridine N-atom, and these interactions give rise to a layer arrangement parallel to the bc plane. The ethylene group (C9-C10) and the oxygen (O1) atom exhibit a statistical orientational disorder, Figure 3.

Refinement
H atoms were included in calculated positions (C-H = 0.93 Å for aromatic H, C-H = 0.97 Å for methyn H), and refined using a riding model, with U iso (H) = 1.2 U eq of the carrier atom. H atoms on N were located in a Fourier map and refined with U iso (H) = 1.2 U eq (N).
The disorder was modelled by splitting atoms with the highest prolate anisotropic displacement parameters (ADPs) into two components; the naming convention used involved appending a "B" suffix to the index number, such that O1, C9 and C10 became O1B, C9B and C10B. To ensure a sensible geometry for the disordered model, the bond distances and angles along the ethylene and carbonyl moieties were restrained to be similar (instructions SAME and SADI), and the ADPs of the disordered atoms were also restrained to be similar (instruction SIMU), with an s.u. value of 0.01 Å 2 . Subject to these conditions, the refined occupancies for the two major components were 0.676 (7) for the ethylene moiety and 0.61 (6) for the oxygen atom.
The positions and displacement parameters of the rest of the atoms are sufficiently well defined to allow for a refinement without any additional positional or similarity restraints. program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009   The molecular structure of the title compound I with displacement ellipsoids at the 50% probability. The minor fraction of the disorder was omitted.    The major and minor component of the disorder of compound I, dashed lines indicate the minor fraction. The displacement ellipsoids are at the 50% probability. 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 Occ. (