Xu Wei-Jian, Romanyuk Konstantin, Martinho José M G, Zeng Ying, Zhang Xue-Wen, Ushakov Andrei, Shur Vladimir, Zhang Wei-Xiong, Chen Xiao-Ming, Kholkin Andrei, Rocha João
MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China.
Department of Physics and CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal.
J Am Chem Soc. 2020 Oct 7;142(40):16990-16998. doi: 10.1021/jacs.0c06048. Epub 2020 Sep 23.
Molecular ferroelectrics are becoming an important area of research due to their ability to form a variety of structures exhibiting the desired properties. However, the precise control over the assembly of molecular building blocks for the design and synthesis of photoresponsive molecular ferroelectrics remains a considerable challenge. Here, we report a new hybrid high-temperature ferroelectric, (MeNH)[NaFe(CN)(NO)], by judiciously assembling inorganic photochromic nitroprusside anion, as the framework building block, and polar organic cation MeNH, as the dipole-moment carrier, into the crystal lattice. Ferroelectricity arises through the synergetic ordering of MeNH below 408 K. Piezoresponse force microscopy witnessed the presence of 180° ferroelectric domains and evidenced polarization switching by repeatedly applying an external electric field. Irradiation of the N-bound nitrosyl ligand (ground state) leads to two different conformations: isonitrosyl O-bound (metastable state I) and side-on nitrosyl conformation (metastable state II). Such photoisomerization realized in solid-state molecular ferroelectrics allows for the photoswitching between the ferroelectric ground state and the metastable state. These results pave the way for new design approaches toward developing next-generation photostimulated ferroelectric materials at the molecular level.
分子铁电体因其能够形成具有所需特性的多种结构而成为一个重要的研究领域。然而，对于用于光响应性分子铁电体的设计与合成的分子构建单元的组装进行精确控制仍然是一项巨大的挑战。在此，我们通过将无机光致变色硝普阴离子作为骨架构建单元，以及将极性有机阳离子甲胺作为偶极矩载体，巧妙地组装到晶格中，报道了一种新型杂化高温铁电体（甲胺）[铁氰化钠硝酰]。铁电性通过甲胺在408 K以下的协同有序排列而产生。压电力显微镜证实了180°铁电畴的存在，并通过反复施加外部电场证明了极化切换。对N键合的亚硝酰配体（基态）进行辐照会导致两种不同的构象：异亚硝酰O键合（亚稳态I）和侧基亚硝酰构象（亚稳态II）。在固态分子铁电体中实现的这种光异构化使得能够在铁电基态和亚稳态之间进行光开关切换。这些结果为在分子水平上开发下一代光刺激铁电材料的新设计方法铺平了道路。
