A cation-directed switch of intermolecular spin-spin interaction of guanosine derivatives functionalized with open-shell units.

The guanosine derivative 1 functionalized with the persistent radical unit 4-carbonyl-2,2,6,6-tetramethylpiperidin-1-oxyl in solution has no particular intermolecular spin-spin interactions; however, in the presence of potassium ions this compound can form a D4-symmetric octameric assembly [1(8)K]+ in which the nitroxyl moieties show a weak electron spin-spin exchange interaction. Since the relative geometry of the radicals is the outcome of K+-directed self-assembly, the spin-spin interaction can be suppressed by removing the alkaline ion.