Light- and Chemical-Stimuli-Induced Isomerization of Donor-Acceptor Stenhouse Adducts

Donor-acceptor Stenhouse adducts (DASAs) are a new class of negative photochromic molecules capable of linear-to-cyclic isomerization. We report three new DASAs that are responsive not only to visible-light irradiation, but also to chemical stimuli including acidity and metal ions. The pendant pyridine group in the donor moiety has been found to play an important role in determining the isomerization process and tuning the relative stability of the isomers. Successful isolation of a new double cyclized isomer requires the pyridine nitrogen atom to be in a suitable position where it is able to form a stable six-membered C4N2 ring. The marked change of color associated with the isomerization has been applied for the visual detection of primary amine vapors and Cu2+ ions.