Polarity and Dielectric Property Control Triggered by a Coordinated Solvent Molecule Exchange in Luminescent Mononuclear Aluminium(III) Complexes

The development of molecule-based multifunctional switchable materials, exhibiting a switch of polarity and dielectric property, are extremely limited. Herein, we demonstrated solvent-vapour-induced reversible molecular rearrangements between non-polar crystals [Al(sap)(acac)(sol)] (H2sap = 2-salicylideneaminophenol, acac = acetylacetonate, sol = MeOH (1), EtOH (2)) and polar crystal [Al(sap)(acac)(DMSO)] (3). This crystal-to-crystal structural transformation was accompanied by a switch of second harmonic generation (SHG) and dielectric properties, including the formation of ferroelectric domains, reflecting the SHG-active polar Cc space group of 3. This is the first reported example of dielectric properties and polarity switching in luminescent mononuclear aluminium(III) complexes, which exhibit the strong green emission in the solid state.