Hydrogen-Bonded Switchable Dielectric Material Showing the Bistability of Second-Order Nonlinear Optical Properties

Physical properties of phase transition materials are directly linked to the transformation of structural moieties. Here, we report a new hydrogen-bonded binary crystal of cyclohexylatninium chlorodifluoroacetate (1), consisting of two distinct types of the anion cationic structural moieties, which shows an order disorder phase transition around 153 K (phase transition point, T-c).Thermal analyses, dielectric, and second-order nonlinear optical (NLO) measurements solidly confirm the symmetry transformation from the point group mmm to mm2. It is noteworthy that 1 exhibits a coexistence Of switchable dielectric behaviors and bistable NLO effects. In detail, it is NLO-active below T-c, while its quadratic NLO effects completely disappear above TTc Such a change reveals the bistable feature of its quadratic NLO properties. Further, variable-temperature structure analyses reveal that the emergence of NLO effects below TT is ascribed to partial ordering of anions and small-angle reorientation of cations. This mechanism is different from that of the precedent NLO-sWitching materials, which affords a potential avenue to design new electric-ordered molecular compounds as multifunctional materials.