Efficient Synthesis and Properties of Isomeric Photochromic Diarylethenes Having a Pyrrole Unit

Two new isomeric photochromic diarylethenes with a pyrrole unit have been developed. Their properties, including photochromic behavior,
crystal structures, and fluorescent properties, have been investigated. The two isomeric compounds show distinctly different photochromism,
both in solution and in the single-crystalline phase:  one turns red upon photocyclization whereas the other turns blue, which may be attributed
to the different substituent effects.