engleski

Structural and dielectric studies of bis(oxalato)chromium(III) complexes with azabicyclic cations

In ferroelectric materials, spontaneous electric polarization can be reversibly switched under the external electric field. While homochirality provides an important bridging effect between structure and ferroelectric properties, the discovery of new ferroelectrics is often random rather than strategically designed.[1] Here we report on the targeted synthesis of two metal- organic complex salts containing bicyclic amine cations and bis(oxalato)chromium(III) anions: (DABCO)[Cr(phen)(C2O4)2]2·9H2O (DABCO = 1, 4- diazabicyclo[2.2.2]octane ; phen = 1, 10- phenanthroline) and (COOH-OH-ABCO)[Cr(bpy) (C2O4)2]·H2O (COOH-OH-ABCO = 3-hydroxy-1- azabicyclo[2.2.2]octane-3-carboxylic acid ; bpy = 2, 2′-bipyridine). Complex salts were prepared using the mechanochemical synthesis and recrystallized from aqueous solutions to give single crystals. Structural and dielectric properties of these compounds were studied by combination of single-crystal X-ray diffraction, thermal analysis, infrared and impedance spectroscopy, and polarization−voltage measurements. Newly prepared azabicyclic cation COOH-OH-ABCO+ was characterized using 1H and 13C NMR spectroscopy. Interesting optical phenomena of pleochroism was observed in (DABCO)[Cr(phen) (C2O4)2]2·9H2O, where crystals change color from pink to orange if rotated under plane-polarized light.

ferroelectric materials ; azabicyclic cation ; DABCO ; dielectric study

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