Synthesis and photochromic properties of a multiple responsive diarylethene and its selective binding affinity for copper(II) ion

A multiple responsive photochromic diarylethene, 1-[2,5-dimethyl-3-thienyl]-2-[2-methyl-5-(2-pyridyl)-3-thienyl]perfluorocyclopentene (1) with excellent fatigue resistance has been successfully synthesized. Easy and reversible conversion is observed between the two open- and closed-ring isomers of 1 upon irradiation with UV and visible light. Addition of trifluoroacetic acid to these two isomers gives two new protonated products featuring distinctively different color changes. Photochromic diarylethene 1b is found to have selective interaction with copper(II) ion. With increasing amount of copper(II) ion, the absorption maximum of the photostationary state at 563 nm decreases and disappears eventually, and the color of the solution changes from purple to colorless. Upon UV light irradiation, the solution color remains colorless and can no longer be restored. UV vis absorption spectroscopy, fluorescence, and NMR spectroscopy were used to investigate the selective interaction between diarylethene 1b and copper(II) ion with results indicating that diarylethene 1b exhibits selective binding affinity for copper(II) ion. (C) 2011 Elsevier Ltd. All rights reserved.