Ion-depended photochromism of oxadiazole containing spiropyrans

New 8-(5-(p-tolyl)-1,3,4-oxadiazol-2-yl) substituted spirobenzopyrans appear as polychromogenic molecular system demonstrating both positive photochromism and ionochromic properties. Introduction of electron withdrawing formyl group into 6-position of the pyran part leads to increasing of spiropyran photocoloration reaction efficiency but decreases thermodynamical stability of merocyanine form complexes. Upon irradiation with visible light colored solutions of complexes with Zn 2+ , Cd 2+ ions exhibiting negative photochromism, undergo reversible discoloration as a result of photodissociation characterized by the quantum yields reaching 46%. On one side this allows realizing controlled by light irradiation cation induced isomerizations into complexes of the merocyanine form. On the other hand, a system, in which direction of photochromic transformations can be driven by transition metal ions, can be designed. © 2019 Elsevier B.V.