Homochiral ferroelectric three-dimensional cadmium(II) frameworks from racemic camphoric acid and 3,5-di(imidazol-1-yl)benzoic acid

Two three-dimensional (3D) chiral frameworks, [Cd6(L)4(d-Cam)4(H2O)4]·2H2O (1D) and [Cd6(L)4(l-Cam)4(H2O)4]·2H2O (1L) [HL = 3,5-di(imidazol-1-yl)benzoic acid, d-H2Cam = d-camphoric acid, l-H2Cam = l-camphoric acid], have been synthesized under hydrothermal conditions, which represent a nice example of enantioselectivity of organic racemic ligands (dl-camphorates) during the self-assembly process and formation of the metal complexes. Compounds 1D and 1L feature 3D framework with chiral chains constructed by Cd(II) cations and camphorate anions. Solid-state circular dichroism (CD) spectra of 1D and 1L revealed that they are enantiomers. Furthermore, the complex with chiral C2 space group displays ferroelectric behavior with a remnant electric polarization (Pr) of ~ 0.140 μC/cm2 and an electric coercive field (Ec) of ~ 17.11 kV/cm.

Racemic camphorates (dl-Cam2 −) were resolved into two homochiral enantomers in the formation of three-dimensional Cd(II) frameworks with 3,5-di(imidazol-1-yl)benzoate, which provide a nice example of resolution of dl-H2Cam without chiral template.Figure optionsDownload as PowerPoint slideHighlights
► Homochiral three-dimensional cadmium(II) framework.
► Complex with camphoric acid and 3,5-di(imidazol-1-yl)benzoic acid.
► SHG and ferroelectric property of the complex.