Fatigue Resistance of Photochromic Diarylethene in the Presence of Cyclodextrins with Different Pore Sizes

Abstract

Among the various types of photochromic compounds, diarylethenes have good fatigue resistance, but further improvement is required. In this study, we investigated photochromic reaction behavior and fatigue resistance by inclusion in cyclodextrin (CD), which is a cyclic host molecule with three different pore sizes. A water-soluble diarylethene (DE1) synthesized in this work exhibited reversible photochromism in water. Continuous irradiation with UV light resulted in the formation of its byproduct. The addition of αCD showed no improvement of fatigue resistance. However, the addition of βCD and γCD suppressed a side reaction to result in the improvement of fatigue resistance. Especially, the addition of γCD gave a large improvement. To clarify the relationship between fatigue resistance of DE1 and the pore size of CD, the host-guest interaction between DE1 and CD was investigated using NOESY spectra. The results indicate that the depth of DE1 included in CD shows a large effect on suppression of the side reaction of DE1.