Halogen–Halogen Bonded Donor-Acceptor Stacks Foster Orthogonal Electron and Hole Transport

Abstract

The sophisticated, yet ingenious, supramolecular architectures in nature have often inspired the design of synthetic molecular frameworks mimicking the efficacious emergent properties nurtured by these systems. Herein, the unique crystalline assembly of a dibromonaphthalimide derivative, 1,8-dibromonaphthalene(3,5-dimethoxyphenyl)imide (NIBr2OMe), forming base-pair-like dimers via a stabilizing parallelogram-type Br4 synthon, that further slip-stack to form segregated donor-acceptor arrays, is reported. The peculiar arrangement of the covalently linked donor-acceptor (D-A) moieties with HOMO/LUMO localized on the donor/acceptor part and the peri-peri halogen-halogen interactions imparts higher hole and electron transfer couplings for stacked and halogen–halogen bonded dimers of NIBr2OMe, respectively. The theoretical calculation of anisotropic mobility displayed orthogonal trajectories for maximal hole and electron transport along the slip-stacked and halogen–halogen bonded edge-to-edge directions, respectively. Thus, the unnarrated crucial role of interhalogen interactions in modulating intermolecular electronic couplings and hence the directionality of charge transport is revealed. The study is the first indication for the pre-proposed orthogonal electron and hole transport character in a crystalline organic donor-acceptor system providing novel strategies toward designing archetypical organic materials with charge carrier transport in predetermined trajectories for advanced optoelectronic applications.