稀土分子基多铁性材料合成及性能研究

The multiferroics have attracted a great deal of attention because of their potential applications in the aspects of high-density information recording and storage, magnetic induction, quantum control and computation, sensing, and so on. Thereinto molecular multiferroics have become a new research direction of this field in recently years, due to their flexible molecular structures, low density, and convenience in modification, tailoring and regulation. However, due to the restriction of the crystal symmetry and electronic structures, the reported cases of molecular multiferroics are still less at present. The multiferroic critical temperatures of the materials are still very low, and the magnetoelectric couplings are very weak. Thus that how to develop effective synthesis strategies and to improve multiferroic properties of the molecular multiferroics have become the crucial problems needed to be resolved in the research of this area. This project intends to synthesize series of lanthanide complexes crystallizing in non-centrosymmetrical polar space group, and thus to construct the molecule-based systems of multiferroics based on lanthanide, through the systematic designs and applications of chiral acylhydrazone ligands. The assembly methods, rules and multiferroic properties of the complexes will be systematically investigated, and the generation mechanism of magnetism and ferroelectricity, the affect factors to the magnetic and ferroelectric behavior, as well as the relationships of the structure-multiferroic properties will also be explored. The research of the project will extend and deepen the study of the molecular multiferroics, enrich the related knowledge about multiferroics, construct new types of molecule-based multiferroics, and find new members with excellent multiferroic performance, and thus is of great theoretical and practical significance.

多铁性材料由于在高密度信息记录与储存、磁感应、量子调控与计算、传感等方面的潜在应用而备受关注。其中，分子基多铁性材料由于具有柔性的分子结构、密度小、便于修饰和剪裁、易于调控等特点，成为近年来多铁性材料研究的一个新方向。由于结晶对称性及电子结构方面的限制，目前，报道的分子基多铁性材料还很少，多铁性临界温度低，磁电耦合作用弱。如何构建有效的合成策略，提高材料的多铁性能等成为分子基多铁性材料研究急需解决的关键问题。本项目拟通过手性酰腙配体的系统设计和应用，合成系列结晶于非中心对称极性空间群的稀土配合物，构建基于稀土的分子基多铁性材料体系，系统研究配合物的组装方法、规律及其多铁性能，揭示磁电产生机制及其影响因素、结构-多铁性能构效关系。项目工作对于拓展和深化分子基多铁性材料研究，丰富分子基多铁性材料知识，构建新型分子基多铁性材料体系，发现性能优良的稀土基分子多铁性材料，具有重要的理论和实际意义。

根据以手性配体诱导稀土配合物结晶于手性极性空间群的研究思想，项目设计合成了在分子骨架、配位基团与空间位阻等方面具备系统性变化的酰腙、醇胺席夫碱、环己二胺席夫碱与氨基酸席夫碱等系列手性配体，及用于组装规律研究的非手性配体。在多种辅助配体的协同下，合成了包含多例结晶于P1与P21等手性极性空间群的目标体系在内的共计120例新型配合物。所得配合物在核数、桥连因素及拓扑网络等方面均呈现较强的新颖性与多样性，如沙漏状{Dy9}、基于双{Dy5}单元的{Dy10}、碟状{Dy16}以及风车状{Dy18}等。在此基础上，项目通过稀土中心与配体结构的丰富变化，构建了所得体系在稀土中心配位几何构型与偶极矩等方面的结构系统性；并根据合成影响因素与空间结构的关联与对比，提炼了此类配合物的合成规律。.项目对所得配合物的磁性进行了研究。多数体系表现出优良的单分子磁体行为，如有效能垒分别达到68.59与131.5 K的基于环己二胺席夫碱的{Dy4}与Dy链等。项目针对性地对结晶于手性极性空间群的体系进行了铁电性能研究，筛选并获得了以“基于手性醇胺席夫碱配体的系列{Dy2}”为代表的兼具单分子磁体行为与铁电性能的多铁性体系。最高有效能垒、极化强度、剩余极化强度、矫顽电场等多铁性能参数分别达到141.62 K、0.16 μC cm-2、0.6 μC cm-2及47 kV cm-1。通过配体与辅助配体的结构变化，项目对所得多铁性体系的空间群、单离子磁各向异性、磁交换、分子偶极距等与多铁性能相关结构实施了针对性的调控，并深入剖析了相关构效关系。如在基于手性醇胺席夫碱的系列{Dy2}分子中，发现了配体取代基的供吸电子效应对该体系多铁性能的影响规律。.综上，项目在多铁性稀土配合物的设计合成、合成规律、多铁性能与构效关系研究等方面均取得有效进展。迄今，已在Chem. Eur. J.、Commun. Chem.、Inorg. Chem.与Inorg. Chem. Front.等期刊发表标注SCI论文33篇，其中II区及以上24篇；培养博士2名，硕士8名。项目完成了既定研究目标，在稀土分子基多铁性配合物研究领域形成了本项目组的特色。