Switchable Room-Temperature Ferroelectric Behavior, Selective Sorption and Solvent-Exchange Studies of [H3 O][Co2 (dat)(sdba)2 ]⋅H2 sdba⋅5 H2 O.

A newly synthesized compound, [H3 O][Co2 (dat)(sdba)2 ]⋅H2 sdba⋅5 H2 O (I, dat=3,5-diamino-1,2,4-triazole; H2 sdba=4,4'-sulfonyldibenzoic acid), has Co2 "paddlewheel" units connected by sdba ligands to form one-dimensional chains, which are connected by dat to form an anionic three-dimensional structure with cds topology. The one-dimensional channels in the structure contain water molecules, hydronium ions and H2 sdba. The water molecules could be reversibly exchanged with D2 O, CH3 OH and C2 H5 OH molecules; these exchanges were performed in a single-crystal-to-single-crystal manner. Gas sorption studies on the dehydrated compound showed the selective adsorption of CO2 over methane at 195 K. Nonlinear optical measurements indicated that I exhibits a second harmonic generation signal that is approximately one-third that of urea. Studies of polarization versus electric field demonstrated compound I as a potential room-temperature ferroelectric material with a saturation polarization of 0.23 μC cm-2 and remnant polarization of 0.14 μC cm-2 . The dehydrated compound exhibited a simple paraelectric behavior.