Thermal and Photochemical Properties of 4′,7‐Dihydroxyflavylium in Water–Ionic Liquid Biphasic Systems: A Write–Read–Erase Molecular Switch

Switching colors: 4′,7-Dihydroxyflavylium (AH+) in water–ionic liquid biphasic systems can be used as a write–read–erase system. In acid media, the chalcone (Ct) form is soluble in ionic liquids and is thermally metastable, but reacts photochemically (write) to give the yellow flavylium salt, which can be optically read without being erased. The system is prepared for a new cycle by two consecutive pH “jumps”.