Structural insight into the photoinduced E→Z isomerisation of cinnamate embedded in ZnAl and MgAl layered double hydroxides

Abstract Hybrid E-cinnamate- and Z-cinnamate-intercalated layered double hydroxides (Mg2Al- E- or Z-Cin LDH and Zn2Al- E- or Z-Cin LDH) were prepared by the co-precipitation method, and structurally characterised by powder X-ray diffractometry, UV–Vis, FT-IR and 13C CP MAS solid-state NMR spectroscopies to gain further insights on the arrangement of the organic anions in the interlamellar domain. UV light irradiation induced E–Z isomerisation reaction was subsequently attempted in the solid state and in methanolic suspension. Although reaction was observed in the solid state; however, E–Z isomerisation mainly occurred in the slurry phase. The fact that there was no isomerisation when E-Cin was solely adsorbed on the surfaces of pristine LDHs highlights that the reaction took place in the interlayer region. Similar behaviour was observed for the two LDH compositions proving that the LDH structures acted as nanoreactors confining the photoinduced isomerisation.