多酸基磁性材料的设计、合成、结构及磁性研究

Polyoxometalates (POMs), as a unique class of metal oxide clusters, have aroused great research interest because of their intriguing geometrical characteristics (large size, high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties. ① These clusters are good candidates for the encapsulation of polynuclear d- and f-block metaloxo fragments, leading to products with interesting magnetic properties. And the coordination configuration of metal ions can be easily defined owing to the strong rigidty of POM ligands. ②Their oxygen-rich surface with strong coordination abilities qualifies POMs for combination with various paramagnetic metal ions, forming high spin compounds. ③POMs are easily to form crystals to explore their correlation between structures and properties. ④ It was shown that rigid POMs are also ideal ligands for single molecular magnets (SMMs) as they may shield the magnetic core from interaction.with other molecules, creating a discrete magnet..The aim of this project is to design and synthesis of new POM-based SMMs, taking simple materials or polyoxoanions as precusors and then reacting with complexes with SMM properties, lanthanides and transition ions, respectively. Compound would be characterized systemically, and correalations between the magnetic properties and structure parameters of these compounds would be also investigated..Furthermore, the effect of structure parameters on magnetic properties and their SMM properties could be revealed. In addition, the synthetic strategies and rules were also studied..In summary, this project is expected to provide a platform for the systematic development of POM-based SMMs, which not only broaden the research fields of magnetic chemistry, but also could be applied to design and synthesize POM-based magnetic complexes and POM-based SMMs of better quality, in order to get promising POM-based magnetic materials. Therefore, this research has important academic.value as well as far-reaching reality significance.

利用多酸阴离子作为配体表现出的①配体刚性强，易于限定金属离子的配位构型，进而限定金属离子的连接方式和磁性作用；②配体表面配位氧原子多，易于和多个金属原子结合形成高自旋化合物；③易于形成晶体，便于探索化合物结构与性质的相关性；④体积较大且具有抗磁性，和磁性核结合后，易于阻断分子间的磁相互作用，对磁性分子具有很好的稀释作用，利于单分子磁体形成等优点，以简单原料或多酸为前驱体，分别与具有单分子磁体性质的配合物、稀土离子和过渡金属离子反应，设计、制备具有磁性及单分子磁体性质的多酸基化合物，对化合物进行系统表征并研究化合物的磁性与化合物结构参数之间的关系，进一步揭示结构参数对化合物磁性及单分子磁体性质的影响，拓宽磁化学研究内容，设计、合成性质更为优良的多酸基磁性化合物和单分子磁体，以期得到具有应用前景的多酸基磁性材料。

项目在研期间，系统开展了基于多酸前驱体其简单原料和过渡金属、稀土元素及磁性化合物反应设计、合成多酸基单分子磁体的研究。通过多酸前驱体K14[P2W19O69(H2O)]·24H2O、K14[As2W19O67(H2O)]、Dawson结构缺位阴离子Na12[P2W15O56]·24H2O和K12[H2P2W12O48]·24H2O、K7HNb6O19·13H2O、K8Ta6O19·17H2O与过渡金属离子、稀土元素离子及单分子磁体化合物反应，制得了多系列多酸基化合物；通过有机膦酸和钼酸根及过渡金属离子反应，得到了多例有机膦酸构成的多酸，对这些化合物进行了系统的表征和结构分析。结构分析表明，所得化合物中有80余种新多酸基化合物，其中20余种结构类型为首次发现。根据结构分析，对可能具有磁学特性的化合物进行了系统的磁学性质研究，测试了数十种化合物的磁学性质，其中8例为具有单分子磁体特性的化合物。化合物Cs4.5K9Na10.5H9[{(AsW9O33)3Dy2(H2O)4W4O9 (H2O)}2 (NH2(CH2PO3 2)]·23H2O的磁滞回线开口温度达到8 K，调研文献可知，该化合物在零场下的有效能垒和磁滞回线开口温度均创造了多酸单分子磁体领域的新纪录。这些化合物的合成及分子结构的确定，丰富了多酸化学的合成方法和多酸的结构类型，将为新型多酸的设计合成及性质研究提供理论指导和技术支撑；具有单分子磁体性质的多酸化合物的设计合成与性质测定，将对基于多酸设计、合成单分子磁体化合物提供重要参考。.在基金支持下，培养博士研究生3位，硕士研究生5位，发表研究论文40余篇，参加国际学术会议2次，国内学术会议9次，国内外会议均做了主题报告。