1,1′-(Butane-1,4-diyl)bis[2-(pyridin-2-yl)-1H-benzimidazole]

The complete molecule of the title compound, C28H24N6, is generated by inversion symmetry with the inversion centre located at the mid-point of the central C–C bond of the butanediyl unit. The benzimidazole and pyridine rings are almost coplanar, the dihedral angle between their mean planes being 6.86 (11)°.

The complete molecule of the title compound, C 28 H 24 N 6 , is generated by inversion symmetry with the inversion centre located at the mid-point of the central C-C bond of the butanediyl unit. The benzimidazole and pyridine rings are almost coplanar, the dihedral angle between their mean planes being 6.86 (11) .

Shao-Chuan Zhou and Hong-Zhen Xie Comment
The long spacer ligands, particularly the flexible N-bridging donors have been investigated as auxiliary ligands for the construction of novel MOFs [Liu et al., 2010;Barnett et al., 2003;Tong et al., 2009]. As part of our ongoing studies, the title compound was synthesized and characterized by X-ray diffraction.
The complete molecule of the title compound, C 28 H 24 N 6 , is generated by crystallographic inversion symmetry and the central C-C bond of the butanediyl unit is bisected by the inversion symmetry. The dihedral angle between the benzimidazole ring system and the pyridine ring is 6.86 (11)°, which indicates that they are almost coplanar.

Experimental
According to the literature [Liu et al., 2010], 2-(2-pyridyl)benzimidazole (7.80 g) and NaOH (1.68 g) in DMSO (20 ml) were stirred at 60°C for 0.5 h, and then 1,4-dibromobutane (4.32 g) was added. The mixture was stirred at 60°C for 12 h, and then poured into 400 ml of ice water after being cooled to room temperature. The yellow solid was obtained and isolated by filtration after drying in air. The above products were recrystallized in methanol and yellow crystals of the title compounds were obtained.

Refinement
The H atoms bonded to C except for C14 were placed at calculated positions and refined in riding mode with U iso (H)=1.2Ueq(C). The H atoms of C14 were located at difference Fourier maps and refined freely.

Computing details
Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction:  ORTEP view of complex molecule of (I). Displacement ellipsoids are drawn at the 45% probability level. H atoms were omitted for clarity.

1,1′-(butane-1,4-diyl)bis[2-(pyridin-2-yl)-1H-benzimidazole]
Crystal data C 28 H 24 N 6 M r = 444.53 Monoclinic, P2 1 /n Hall symbol: -P 2yn a = 6.5617 (7)  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.