Very High Cyclization Quantum Yields of Diarylethene Having Two N-Methylpyridinium Ions

Dithienylethenes having a pyridinium cation at one and both thiophene rings were synthesized. The derivatives with two pyridinium cation showed the cyclization quantum yield as high as 0.71, which is much larger than the values of the monocation derivative and the neutral form. This can be explained by the conformation of the open-ring isomer of the diarylethenes.