The role of anionic design in modulating material properties: from SHG switching to ferroelastic switching

Abstract

Crystallographic engineering and chemical synthesis modification play crucial roles in modulating material properties and designing multifunctional materials, such as those with second-harmonic generation (SHG) switching and ferroelastic behaviors. Herein, we present the role of anion-based design in crystalline materials through anion H/F substitution. Specifically, the material [NMe₄][CH₃SO₃] exhibits a high phase transition temperature (T_c = 462 K) and excellent SHG switching performance. The introduction of polyfluorinated substitutions results in a new organic ferroelastic material, [NMe₄][CF₃SO₃], which exhibits ferroelastic phase transition at 309 K. The transition from the non-centrosymmetric [NMe₄][CH₃SO₃] to the centrosymmetric [NMe₄][CF₃SO₃] leads to a shift in material properties, transitioning from SHG switching to ferroelastic switching. Our findings underscore the importance of anion-based design in the development of advanced multifunctional phase-transition materials.