Affiliation: | aInstitute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria bDepartment of Chemistry, Sofia University, 1, James Bourchier ave., 1164 Sofia, Bulgaria |
Abstract: | Chelation with Al(III), Fe(II) or Cu(II) of the open photomerocyanine form obtained under steady irradiation of spiroindolinonaphthooxazines, with a hydroxyl group at the 5′ position in the naphthooxazine moiety, induces a slight hypsochromic shift of its visible absorption band and increases the lifetime of this form, slowing down its thermal bleaching in the dark (rate constant 10−3 s−1). Complexation with Al(III), Fe(II) or Cu(II) allows the spiroindolinonaphthooxazines to isomerize to their open coloured form even under dark conditions giving a complex spectroscopically identical to the photoinduced product. The activation energy of thermal complexation is independent of the metal ion which implies the ring opening as the rate determining step. |