Probing the shapes of chiral bis-(o-naphthalimidobenzoyl) systems using X-ray and circular dichroism methods

Abstract

CD (circular dichroism) and X-ray investigations have been carried out in order to identify the prevalent conformations and define the forces that determine the molecular and supramolecular organization of the alkyl-bridged bichromophoric [NAB, ortho-(1,8-naphthalimido)benzoyl] units, each consisting of the benzoyl substituted in the ortho position with the 1,8-naphthalimide group. The results reveal that NAB bichromophores incorporated into the same molecule exist in a variety of conformation/helicity combinations. The molecular structures are largely stabilized by local 1,3-CH/CO dipole–dipole interactions, while the crystal packing besides dispersive H...H interactions is mostly governed by multiple C—H...O(=C) and C—H...π interactions. The relatively small contribution of π...π interactions comes from a pairwise off-face stacking between naphthalimide rings or from pairwise carbonyl...π interactions. All these types of intermolecular interactions have been summarized quantitatively by means of a Hirshfeld surface analysis.