Reversible “Chiral Memory” in Ruthenium Tris(phenanthroline)–Anionic Porphyrin Complexes

Happy memories: J aggregates (J) of the tetraanionic meso-tetrakis(4-sulfonatophenyl)porphine (H2TPPS4) gain chirality by interaction with Δ- or Λ-[Ru] (see picture, [Ru]=[Ru(1,10-phenanthroline)3]2+). After destroying and reforming the aggregates by changing the pH of the solution, the final species “remember” the initially imprinted chirality, even in the presence of an excess of the ruthenium complex with the opposite chirality to that memorized.