Kinetic Analysis of the Photochemical Paths in Asymmetric Diarylethene Dimer

An asymmetric diarylethene dimer composed of 2- and 3-thienylethene units linked by m-phenylene developed various colors upon UV irradiation via an independent photochromic reaction on each unit. The change in contents and the other photoresponses of the photogenerated four isomers were analyzed using quantum yield for all the possible photochemical paths, i. e., photoisomerization, fluorescence, energy transfer, and the other non-radiative paths. Almost all the rate constants of photochemical paths were calculated using measurable quantum yields and lifetimes. It was found that a significant contribution on photoresponse was the competition between photoisomerization and intramolecular energy transfer. The clear difference was observed in the photoresponses of the dimer and the 1 : 1 mixture solution of the model compounds. The m-phenylene spacer appropriately regulated the rate of energy transfer in the asymmetric dimer, and the spacer enabled isolation of the excited state of the dimer, making the above quantitative analysis possible.

Automated summary

An asymmetric diarylethene dimer with independent photochromic reactions on each unit exhibited various colors upon UV irradiation. The photogenerated isomers were analyzed for their contents and other photoresponses, including photoisomerization, fluorescence, energy transfer, and non-radiative paths. Rate constants for the photochemical paths were calculated using measurable quantum yields and lifetimes. The competition between photoisomerization and intramolecular energy transfer was found to significantly contribute to the photoresponse.