Photo-induced isomerization and polymerization of (Z,Z)-muconate anion in the gallery space of [LiAl2(OH)6]+ layers

Abstract

Photoreaction of guest organic anions in layered organic-inorganic hybrid materials was investigated. The layered hybrids were synthesized by an anion-exchange reaction of [LiAl2(OH)6]Cl·yH2O layered double hydroxide with aqueous (Z,Z)- and (E,E)-muconates under inert atmospheric condition, to give new organic-inorganic hybrids of [LiAl2(OH)6]2[(Z,Z)-C6 H4O4]·zH2O and [LiAl2(OH)6]2[(E,E)-C6 H4O4]·zH2O, respectively. The basal spacings calculated by XRPD of intercalates indicate that muconate anions have almost vertical arrangements against the host [LiAl2(OH)6]+ lattices in the interlayer of organic-inorganic hybrid materials. When UV light was irradiated on the suspension of [LiAl2(OH)6]2[(Z,Z)-C6 H4O4]·zH2O, the (Z,Z)-muconate anions of the gallery space of hybrids were polymerized in the aqueous media while it was isomerized into more stable (E,E)-muconate in the methanollic suspension in the presence of catalytic amount of molecular iodine. All the products were characterized using elemental analysis, TGA, XRPD, FT-IR, 1H NMR and 13C CP-MAS NMR.