A photo- and halochromic multicolor switching system consisting of diarylethene and malachite green moieties

A diarylethene with an attached malachite green moiety was synthesized. The diarylethene moiety undergoes reversible cyclization and cycloreversion reactions upon alternate irradiation with UV (313 nm) and visible (435 nm) light, while the malachite green moiety reversibly changes between neutral, monocationic, and dicationic states up to the proton concentration. The photochromic and halochromic reactions could be controlled, and this provided a multi-reversible system with six states. The cyclization and cycloreversion quantum yields of the diarylethene moiety were dependent on the states of the malachite green moiety.