Photochromism of Diarylethene Single Molecules in Polymer
Matrices
Tsuyoshi Fukaminato, Tohru Umemoto, Yasuhide Iwata, Satoshi Yokojima,
Mitsuru Yoneyama, Shinichiro Nakamura, and Masahiro Irie
J. Am. Chem. Soc., 129, 5932-5938 (2007)
Robust fluorescent photoswitching molecules, having perylene bisimide
as the fluorescent unit and diarylethene as the switching unit, were prepared
and their photochromic reactions were measured at the single-molecule level in various polymer matrices. The histograms of the fluorescent on and
off times were found to deviate from normal exponential distribution and
showed a peak when the molecules are embedded in rigid polymer matrices,
such as Zeonex or poly(methyl methacrylate)(PMMA). In soft polymer matrices,
such as poly(n-buthyl methacrylate)(PnBMA), exponential distribution was
observed for the on and off times. The abnormal distribution suggests that
the quantum yields of the photoreactions are not constant and the molecules
undergo the reactions after absorbing a certain number of photons. A multi
local-minima model is proposed to explain the environmental effect.
