Structural and theoretical characterization of a new twisted 4′-substituted terpyridine compound: 4′-(isoquinolin-4-yl)-2,2′:6′,2′′-terpyridine

Abstract

4′-Substituted derivatives of 2,2′:6′,2′′-terpyridine with N-containing heteroaromatic substituents, such as pyridyl groups, might be able to coordinate metal centres through the extra N-donor atom, in addition to the chelating terpyridine N atoms. The incorporation of these peripheral N-donor sites would also allow for the diversification of the types of noncovalent interactions present, such as hydrogen bonding and π-π stacking. The title compound, C24H16N4, consists of a 2,2′:6′,2′′-terpyridine nucleus (tpy), with a pendant isoquinoline group (isq) bound at the central pyridine (py) ring. The tpy nucleus deviates slightly from planarity, with interplanar angles between the lateral and central py rings in the range 2.24(7)-7.90(7)°, while the isq group is rotated significantly [by 46.57(6)°] out of this planar scheme, associated with a short Htpy⋯Hisq contact of 2.32Å. There are no strong noncovalent interactions in the structure, the main ones being of the π-π and C - H⋯π types, giving rise to columnar arrays along [001], further linked by C - H⋯N hydrogen bonds into a three-dimensional supramolecular structure. An Atoms In Molecules (AIM) analysis of the noncovalent interactions provided illuminating results, and while confirming the bonding character for all those interactions unquestionable from a geometrical point of view, it also provided answers for some cases where geometric parameters are not informative, in particular, the short Htpy⋯Hisq contact of 2.32Å to which AIM ascribed an attractive character.