Photoisomerization of indolinespirobenzopyran in anionic clay matrices of layered double hydroxides

Abstract

Sulfonated indolinespirobenzopyran (SP–SO₃^–) was intercalated into the Mg/Al or Zn/Al layered double hydroxides (LDHs) in the presence of toluene-p-sulfonic acid (PTS). The new intercalates exhibited reversible photoisomerization between SP–SO₃^– and merocyanine (MC). The presence of PTS was critical for the reversible photoisomerization. MC was very stable and the rate constant of decolorization was <9 × 10^–7S^–1. SP interacted with non-polar portions between the layers although MC interacted with the polar interior surface of the LDH.