4′-[2-(Trifluoromethyl)phenyl]-2,2′:6′,2′′-terpyridine

The title compound, C22H14F3N3, is a versatile tridentate N-donor ligand consisting of a terpyridyl (terpy) molecule substituted in the 4′-position by a phenyl group, itself substituted in an ortho-position by a bulky trifluoromethyl group. The phenyl ring is twisted as a result of steric interactions involving the bulky trifluoromethyl substituent. This is reflected in the dihedral angle between the mean plane through the C atoms of the phenyl ring and the terpyridyl unit being 69.2 (1)°. The crystal structure contains no short van der Waals contacts. However, the terpy units stack in a head-to-tail orientation perpendicular to the c axis. The structure is is loosely stabilized by π–π interactions between the terminal pyridine rings of adjacent molecules along the stack. The perpendicular distance between the mean planes through the terpy moieties of adjacent molecules is 3.4 (1) Å.

The title compound, C 22 H 14 F 3 N 3 , is a versatile tridentate Ndonor ligand consisting of a terpyridyl (terpy) molecule substituted in the 4 0 -position by a phenyl group, itself substituted in an ortho-position by a bulky trifluoromethyl group. The phenyl ring is twisted as a result of steric interactions involving the bulky trifluoromethyl substituent. This is reflected in the dihedral angle between the mean plane through the C atoms of the phenyl ring and the terpyridyl unit being 69.2 (1) . The crystal structure contains no short van der Waals contacts. However, the terpy units stack in a head-totail orientation perpendicular to the c axis. The structure is is loosely stabilized byinteractions between the terminal pyridine rings of adjacent molecules along the stack. The perpendicular distance between the mean planes through the terpy moieties of adjacent molecules is 3.4 (1) Å .
The terminal pyridine rings adopt a trans-trans conformation about the interannular bonds C1-C6 and C10-C11.
Several derivatized terpy ligands have been found to adopt this trans-trans geometry by X-ray crystal analysis (Constable et al., 1990) which is more energetically favourable when compared to other conformations as a result of the minimal nitrogen lone pair repulsions (Thummel & Jahng, 1985).
As previously postulated, the o-tolyl moiety is twisted about the interannular bond C8-C16, as reflected in a dihedral angle between the mean plane through the carbon atoms of the 4'-substituted and the terpyridyl moiety of 69.2 (1)°. This angle may be compared with those adopted by terpyridyl ligands containing similar substituents in the 4'-position of the terpy moiety in molecules such as the free 4'-phenyl-terpyridine (10.9°) (Constable et al., 1990), 6,6''-dibromo-4'-phenylterpyridine (35.1°) (Constable et al, 1992) and 4'-(4-anilino)-terpyridine (27.2°) (Storrier et al., 1997). The larger angle witnessed in the title compound is consistent with the bulky nature of the trifluoro group and the fact that it substitutes the ortho-position of the phenyl moiety. Clearly, substitution of a trifluoro group in the ortho-position of the 4'-phenyl group causes a larger rotation about the interannular bond because of steric interactions between the CF 3 group and a hydrogen atom of the central pyridine ring that is also ortho with respect to the interannular bond.

supplementary materials sup-2
There are no short van der Waals contacts less than the sum of the van der Waals radii in this system. However it is worth noting, that the terpy units stack in a head to tail orientation perpendicular to the [c]-axis, presumably as a result of minimizing steric interactions between the bulky trifluoromethyl substituents on adjacent molecules. However it is clear that this arrangement is not entirely successful and that poor packing does result from the presence of these bulky substituents reflected in the large solvent accessible void of 31 Å 3 . This packing orientation allows for π-π interactions between the terminal pyridine rings of adjacent molecules along the stack. The perpendicular distance between the mean planes through the terpy moieties of adjacent molecules is 3.4 (1)Å which is short enough to support π-π interactions being well within the upper distance limit of 3.8 Å for π-π interactions between organic molecules (Hunter & Sanders, 1990).
The stucture of the title compound is shown in Fig. 1. Fig. 2 shows a view perpendicular to the mean plane through the atoms comprising the terpyridyl (terpy) moiety of two adjacent terpy units in the crystals of the 4'-(2'''-trifluoromethylphenyl)-2, 2':6', 2''-terpyridine ligand. Note that the successive molecules are related by a centre of inversion.