Abstract
Various spirobenzopyrans bearing crown ether moieties, namely, crowned spirobenzopyrans, were synthesized and their photochromism was examined in the presence of metal ions. The crowned spirobenzopyrans show facilitated photoisomerization reflecting not only the metal-ion binding ability of the crown ether moiety but also the metal-ion affinity of the phenolate anion moiety in the merocyanine form. When the interaction of metal-ion with the phenolate anion moiety is strong enough, thermal isomerization is observed. Furthermore, this interaction can induce negative photochromism upon UV irradiation. Thus, positive and negative photochromism switching of crowned spirobenzopyrans is possible through the interaction control of metal-ion with the phenolate anion and crown ether moiety.
