Two different mechanisms of stabilization of regular ?-stacks of radicals in switchable dithiazolyl-based materials

Materials based on regular ?-stacks of planar organic radicals are intensively pursued by virtue of their technologically relevant properties. Yet, these ?-stacks are commonly unstable against ?-dimerization. In this computational study, we reveal that regular ?-stacks of planar dithiazolyl radicals can be rendered stable, in some range of temperatures,viatwo different mechanisms. When the radicals of a ?-stack are both longitudinally and latitudinally slipped with respect to each other, the corresponding regular ?-stacked configuration is associated with a locally stable minimum in the potential energy surface of the system. Conversely, those regular ?-stacks in which radicals are latitudinally slipped with respect to each other are stable as a result of a dynamic interconversion between two degenerate dimerized configurations. The existence of two stabilization mechanisms, which can be traced back to the bonding properties of isolated ?-dimers, translates into two different ways of exploiting spin-Peierls-like transitions in switchable dithiazolyl-based materials.