1,2-Bis[(2,2′:6′,2′′-terpyridin-4′-yl)oxy]ethane

The title compound, C32H24N6O2, has an inversion centre located at the mid-point of the central C—C bond of the diether bridging unit. The terminal pyridine rings are canted relative to the central pyridine ring, with dihedral angles of 12.98 (6) and 26.80 (6)°. The maximum deviation from the eight-atom mean plane, defined by the two bridging O and C atoms and the central pyridine ring, is 0.0383 (10)° for the N atom.

The title compound, C 32 H 24 N 6 O 2 , has an inversion centre located at the mid-point of the central C-C bond of the diether bridging unit. The terminal pyridine rings are canted relative to the central pyridine ring, with dihedral angles of 12.98 (6) and 26.80 (6) . The maximum deviation from the eight-atom mean plane, defined by the two bridging O and C atoms and the central pyridine ring, is 0.0383 (10) for the N atom.
Crystallographically imposed inversion symmetry relates the two halves of the ligand to one another. The inversion centre is located at the mid-point of the diol linkage unit. The three pyridine rings adopt a trans, trans conformation. The same configuration is observed in the other ligands of this series with butyl and hexyl diol linkages (Akerman et al., 2011;Nikolayenko et al., 2012). The parent compound 4′-chloro-2,2′:6′,2′′-terpyridine (Beves et al. 2006), and uncoordinated terpyridine ligands in general show the same configuration.
The central pyridine ring of the terpyridine moeity is in the same plane as the bridging diol chain. The terminal pyridine rings of the terpyridine ligand are, however, canted relative to the central pyridine ring. The C7-C6-C5-N1 torsion angle is 25.9 (2)° while the C9-C10-C11-N3 torsion angle is 11.9 (2)° (refer to Fig. 1 for the atom numbering scheme). The large torsion angle of the pyridine ring containing N1 is seemingly to allow for hydrogen bonding between the pyridine nitrogen atom N1 and the pyridine hydrogen atom H3 of an adjacent molecule. This hydrogen bond links the molecules into an infinite, one-dimensional chain (Fig. 2). The hydrogen bonded chain is co-linear with the a-axis. The hydrogen bond lengths and bond angles are summarized in Table 1. Although the hydrogen bond length does not necessarily correlate linearly with bond strength, due to packing constraints, the interaction is relatively long and it is therefore likely to be a weak interaction. There is no indication of meaningful π-π or C-H···π interactions in the lattice, which are often observed in terpyridine structures (Beves et al. 2006).

Experimental
The title compound was prepared by an adaptation of a previously described method (Van der Schilden, 2006;Constable et al., 2005). Ethanediol (1.13 mmol) was added to a suspension of ground potassium hydroxide (6.69 mmol) in DMSO (30 ml). The solution was heated to reflux for 1 h after which 4′-chloro-2,2′:6′2′′-terpyridine (2.23 mmol) was added. The mixture was again brought to reflux for an additional 24 h. After cooling to room temperature, the brown mixture was added to cold water (100 ml). The resulting off-white precipitate was collected, rinsed with cold ethanol and air dried.
Single crystals were grown by slow liquid diffusion of n-hexane into a chloroform solution of the compound.

Refinement
All non-hydrogen atoms were located in the difference Fourier map and refined anistropically. The positions of all hydrogen atoms were calculated using the standard riding model of SHELX97. with C-H(aromatic) and C-H(methyl-supplementary materials sup-2 Acta Cryst. (2012). E68, o2384-o2385 ene) distances of 0.93 Å and U iso = 1.2U eq .

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at 50% probability level.  A view of packing of the title compound.

1,2-Bis[(2,2′:6′,2′′-terpyridin-4′-yl)oxy]ethane
Crystal data C 32 H 24 N 6 O 2 M r = 524.58 Triclinic, P1 Hall symbol: -P 1 a = 6.2576 (6)  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 > 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.