基于咪唑类离子液体构筑非中心对称功能化合物及其光电性能研究

Within the last few years, significant attention has been paid to the application of ionic liquids as neoteric media for the functional materials synthesis due to their prominent advantages, such as negligible vapor pressures, wide liquidus ranges, good thermal stability, tunable solubility for both organic and inorganic molecules, and much synthetic flexibility. In this proposal, the imidazolium-based ion liquids will be utilized as solvent to prepare three series of novel non-centrosymmetric compounds, [RMIm]n[MOFs]，[RMIm]n[MXa] and [RMIm]n[POMs], which can exhibit important nonlinear optical (NLO) properties and ferroelectric behavior. In our opinion, the ion liquids solvent can effectively lead to non-centrosymmetric compounds because (i) the asymmetric imidazolium cations usually act as templates or structure-directing agents (SDA); (ii) the asymmetric ion liquid solvents can transfer the non-centrosymmetric or chiral information to the product more efficiently than the case in situations, for example, where the chirality of the environment is diluted by the presence of symmetric molecular solvents; (iii) the order-disorder phase change of the imidazolium cations can induce the non-centrosymmetric crystallization. All the resulting non-centrosymmetric complexes will be characterized by X-ray single-crystal diffraction, elemental analysis, X-ray powder diffraction (XRPD), FT-IR, raman spectrum, TGA, and so on. Especially, the second-order nonlinear optical effects and ferroelectric or dielectric measurements will be invetigated in detail to choose the non-centrosymmetric compounds with potential application as optical or electrical materials. The development of this proposal can provide fresh opportunities for constructing novel functional non-centrosymmetric materials.

作为新型的绿色可设计溶剂介质, 离子液体在功能材料合成中的应用近年来备受关注；本项目拟选择系列咪唑类离子液体为溶剂，结合其溶液性质研究的结果，以非线性光学效应和铁电性能为功能导向, 利用其不对称阳离子的模板效应或结构导向作用，离子型溶剂传递不对称信息的高效性, 以及无序咪唑阳离子的无序-有序相变等优势来构筑阴离子配位聚合物体系[RMIm]n[MOFs]，过渡金属卤化物杂化体系[RMIm]n[MXa]和多酸基杂化体系[RMIm]n[POMs]等三大系列非中心对称化合物；采用X-射线单晶衍射和各种谱学测试对化合物进行表征，结合材料性能计算结果，筛选获得结构稳定且性能良好的目标功能材料,培养其大尺寸单晶体，挖掘其应用潜力；本项目的实施对于阐明离子液体在功能材料制备过程中作用的规律性，构筑结构新颖、性能优良和用途广泛的非心晶态材料，揭示其合成、结构与性能之间的内在联系具有重要的学术意义和应用价值。

本项目立足于离子液体为溶剂介质的材料制备新方法，以面向能源环境需求的功能晶态材料为目标，成功构筑了多酸基无机-有机复合物，多元混合金属卤化物和新型金属-有机骨架等三大系列共计120余例功能晶态材料，具体进展如下：（1）在离子热条件下，通过调控反应温度、原料配比、反应时间及烷基咪唑离子液体中取代基的长度等条件，制备了12个多酸基无机有机复合物材料，系统考察了不对称烷基咪唑阳离子与高对称性杂多酸阴离子簇的自组装反应。（2）采用离子热合成方法，选择具有d10电子构型的金属Pb、Cu、Ag作为配位金属中心原子，成功合成7个结构新颖的Cu(Ag)-X-Pb-OH多元混合金属卤化物和14个从0-D到3-D的卤氰合亚铜晶态材料，开辟了多元混合金属卤化物光电功能材料设计合成的新思路。（3）以烷基咪唑离子液体或酰胺等有机分子为溶剂，在离子热或常规溶剂热条件下，研究了芳香多羧酸，多氮唑羧酸，吡啶多羧酸和多氮唑/芳香二羧酸混合配体等与Mg, Zn, Cd, In或稀土离子等金属中心的自组装反应，成功合成了90余个从一维到三维结构的新型金属有机骨架材料。对所合成目标化合物进行了单晶结构分析等表征，重点探讨了上述目标材料的光电和气体吸附性能。此外，选择部分金属有机骨架材料为前驱体，通过简单煅烧方法，成功制备了系列介孔NiO和In2O3材料，探讨了其在超级电容器电极材料和甲醛气敏传感材料方面的应用潜力。本项目研究工作的开展为深入了解离子热合成，阐明其反应机理提供了丰富的实例，对推动离子热合成的广泛应用具有积极的意义。项目实施期间，在Inorg. Chem., Dalton Trans., Cryst. Growth. Des., CrystEngComm等国际著名SCI源刊杂志上公开发表研究论文25 篇，获批中国发明专利5项，相关研究结果引起了国内外同行的广泛关注，圆满完成了预期研究计划内容。