Chemistry of Phenalenyl-based Delocalized Singlet Biradicals

Intramolecular Pancake Bonding in Helical Structures

We show that diradicaloid helical conjugated molecules can display strong through-space bonding interactions. These interactions are analogous to π-stacking pancake bonding widely observed for dimers and other aggregates of stable π-conjugated radicals. We show that these multicenter interactions can have a significant stabilizing effect, but they depend in subtle ways on the specific overlap and relative orientations of the radical carrying subunits. The specific through-space interactions between the radicaloid units occur at specific size ranges of the helical molecules.