Chiral imides as potential chiroptical switches: synthesis and optical properties

A series of chiral aromatic imides and diimides were synthesized and their electrochemical, absorption, fluorescent, and chiroptical properties were examined for their potential application as molecular chiroptical switches. These compounds exhibit strong UV–vis absorptions, and can be electrochemically reduced to radical anions that absorb in the near infrared (NIR) region. Further reduction to the dianionic states results in new absorptions in the visible region. The changes in circular dichroism upon redox switching were apparent in the UV–vis region but were absent in the NIR region. 2004 Elsevier Ltd. All rights reserved. There has been considerable interest in recent years in the development of a new class of molecular switch based on changes in the optical properties of a compound. To be useful as a molecular switch, such a molecule must possess bistability, meaning that two different forms of the molecule can be interconverted by application of external stimuli. The major methods used to stimulate molecular switching are by chemical, electrochemical and photochemical means. Electrochemical switches are based on the changes in optical, electrical, chemical, and/or physical properties of a molecule upon application of electric fields to the switching cell or device. Electrochromic compounds are able to change colors when they undergo redox reactions, which can readily be monitored using standard spectroscopic techniques. By introducing chiral elements into an electrochromic molecule, a chiroptical switch can be attained in which its chiroptical property changes upon application of a bias to the electrochemical cell. To be an effec0040-4039/$ see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2004.11.147