Potentially Ferroelectric {CuIIL2}n Based Two-Dimensional Framework Exhibiting High Polarization and Guest-Assisted Dielectric Anomaly

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• 作者：Anant Kumar Srivastava ; Pillutla Divya ; B. Praveenkumar ; Ramamoorthy Boomishankar
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：August 11, 2015
• 年：2015
• 卷：27
• 期：15
• 页码：5222-5229
• 全文大小：598K
• ISSN：1520-5002

文摘

Ferroelectrics in metal鈥搊rganic materials have attracted recent interest owing to their synthetic simplicity and tunable nature. Utilizing isomeric dipodal phosphoramide ligands, L¹ [PhPO(NH⁴Py)₂] and L² [PhPO(NH²Py)₂], two new Cu^IIL₂ derivatives, 1 ({[CuL¹₂(H₂O)₂]路(NO₃)₂路(H₂O)_1.5路(CH₃OH)}_{鈭?/sub>) and 2 ([CuL²2]路(NO3)2), were synthesized. Compound 1 crystallizes in a noncentrosymmetric polar space group Cc as a two-dimensional framework, and 2 is a centrosymmetric complex. Electrical hysteresis (P鈥?i>E loop) measurements on 1 at room temperature gave the remnant (Pr) and saturation (Ps) polarization values of 27.96 and 21.79 渭C路cm^鈥?, respectively, which are the highest among all of the known metal鈥搊rganic ferroelectric materials. Also, the Pr value obtained for 1 is comparable to that of barium titanate and higher than most of the organic, polymeric, and inorganic ferroelectric materials. The permittivity measurements on 1 and 2 result in high dielectric constant values of 186.3 and 53.24, respectively, at 1 Hz frequency at room temperature. Temperature-dependent permittivity measurement on 1 yields a dielectric anomaly peak at 40 掳C due to phase transition assisted by desolvation. The existence of phase transition is further confirmed by differential scanning calorimetry, powder X-ray diffraction, and polarized light microscopy. A comparison of the P鈥?i>E loops of 1, 1desolvated, and 1resolvated suggest that gasification/release of the solvate molecules from the packing structure affects the polarization in 1.}