Photochromic Properties Of Perhydro- And Perfluorodithienylcyclopentene Molecular Switches

Various substituted phenylthienyl perhydro- and perfluoro-cyclopentenes have been synthesized in order to compare their spectroscopic and photochromic properties. The differ-ence in the electron densities of the central cyclopentene moieties in the perhydrocyclopentene and perfluorocyclo-pentene molecular switches has only a small effect on the absorption maxima of the electronic spectra, but causes some subtle changes in substituent and solvatochromic effects. The photochromic behaviour is remarkably similar, and both type of switches combine excellent quantum yields (0.6) with high degrees of photoconversion (> 0.85). The main difference is the lower photochemical and thermal stability of the perhy-drocyclopentene molecular switches. It is concluded that in most studies the perhydrocyclopentenes are an excellent al-ternative for the perfluorocyclopentenes, while the perfluoro-cyclopentenes might be better suited for applications such as data storage, which depend critically on fatigue resistance and thermal stability.

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