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

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The development of molecule‐based multifunctional switchable materials that exhibit a switch of polarity and dielectric property are extremely limited. We have demonstrated solvent‐vapour‐induced reversible molecular rearrangements between nonpolar crystals [Al(sap)(acac)(sol)] (H 2 sap=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, thus 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 strong green emission in the solid state.