Electron Delocalization in a Rigid Cofacial Naphthalene‐1,8:4,5‐bis(dicarboximide) Dimer

Abstract Investigating through‐space electronic communication between discrete cofacially oriented aromatic π‐systems is fundamental to understanding assemblies as diverse as double‐stranded DNA, organic photovoltaics and thin‐film transistors. A detailed understanding of the electronic interactions involved rests on making the appropriate molecular compounds with rigid covalent scaffolds and π–π distances in the range of ca. 3.5 Å. Reported herein is an enantiomeric pair of doubly‐bridged naphthalene‐1,8:4,5‐bis(dicarboximide) (NDI) cyclophanes and the characterization of four of their electronic states, namely 1) the ground state, 2) the exciton coupled singlet excited state, 3) the radical anion with strong through‐space interactions between the redox‐active NDI molecules, and 4) the diamagnetic diradical dianion using UV/Vis/NIR, EPR and ENDOR spectroscopies in addition to X‐ray crystallography. Despite the unfavorable Coulombic repulsion, the singlet diradical dianion dimer of NDI shows a more pronounced intramolecular π–π stacking interaction when compared with its neutral analog.