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结构调节对以金属大环为结构特征的配合物性能的影响
The Effect on Properties of Metallamacrocycle-based MOFs Induced by Structure Tuning
【作者】 徐周庆;
【导师】 侯红卫;
【作者基本信息】 郑州大学 , 无机化学, 2014, 博士
【摘要】 金属-有机配位化合物由于其结构的多样性和可调控性以及在催化、磁性、气体分离与吸附、非线性光学等诸多材料领域有着优异的潜在应用前景,已经成为近二十年来无机化学领域发展最为迅速的前沿方向之一。该研究方向当前的主要任务是设计合适的构筑单元并采用相关的晶体工程策略来构筑具有预期结构和特殊性质的晶体材料,并在此基础上深入研究影响晶体材料性能的影响因素,探索晶体结构与性能之间的关系。本论文致力于通过调控溶剂体系及选用不同辅助试剂等手段,以一个刚性不对称三氮唑衍生物5’-(pyridin-2-yl)-2H,4’H-3,3’-bi(1,2,4-triazole)(H2pbt)为有机配体,并选择特定的过渡金属离子来构筑具有结构新颖和优良性能的框架配合物。本论文得到十二个以金属大环为结构特征的功能优异的配位聚合物,并系统地研究了溶剂体系、客体分子及抗衡离子等对这些配位聚合物的磁性及催化性能的影响。本论文主要分为以下四个部分:1)通过调节溶剂体系和反应条件,H2pbt与CuSO4·5H2O自组装形成了三个以十二核铜金属大环为结构特征的三维孔洞化合物。磁性测试结果表明由双三氮唑桥连的双核铜离子之间一般存在较强的反铁磁耦合作用,并且这种耦合作用随着三氮唑桥连的双核铜体系的对称性的提高而增强。这三个配合物的在苯乙炔(1-ethynylbenzene)和2-恶唑烷酮(oxazolidin-2-one)氧化偶联反应体系中的催化效果表明配合物的催化性能不仅与配合物的空腔大小有关系,也与配合物的稳定性有很大关系。2)水热条件下,H2pbt与FeSO4·7H2O在辅助剂硫氰酸钾的作用下自组装形成三个铁的配合物。其中配合物3-1通过失去一个游离的溶剂分子而转变成配合物3-2。57Fe穆斯堡尔谱和XPS证明在转变过程中有7%的中心金属离子有高自旋态转变为了低自旋态,伴随着这个溶剂水分子的脱附,晶体颜色由3-1的金黄色变为3-2的暗红色,同时配合物3-1和3-2的磁性和催化性能也有很大不同。另外,我们还测试并讨论了配合物3-3和3-4的磁性。3)水热条件下,H2pbt和CoCl2·6H2O及Mn(OAC)2·4H2O为得到三个以八核锰金属大环为结构特征的配位化合物。磁性测试结果表明由双三氮唑桥连的双核钴或双核锰之间也存在反铁磁耦合作用。4)同样以H2pbt和CuSO4·5H2O为原料,在5-氨基-间苯二甲酸的辅助作用下得到两个同构的Cu(I)/Cu(II)混价三维笼状化合物。抗衡离子的不同导致两个配合物在所考察的两个催化反应体系中有着不同的催化活性。
【Abstract】 Coordination polymers or metal organic frameworks (MOFs) have been one ofthe most interesting research field in the last two decades, mainly due, on one hand,to the fact that their aesthetically pleasing structures and, on the other hand, to theirpromising potential applications in heterogeneous catalysis, magnetism, gas storageand photochemistry. The main challenge in this field is to design novel building unitand explore advanced crystalline metal-organic materials with more superiorproperties, and theen to determine the influence on the properties of MOFs andunderstand relationship between structure and properties. In this paper, with the aimof preparing novel metal-organic materials with intriguing structures and goodproperties, we select5’-(pyridin-2-yl)-2H,4’H-3,3’-bi(1,2,4-triazole)(H2pbt), anasymmetric triazolate derivative, as a ligand, and obtain12newmetallamacrocycle-based or cages-based metal-organic frameworks with specialproperties under the specific transition metal ions and auxiliary reagents.This work includes the following four parts:1) Combine with H2pbt and CuSO4·5H2O, three dodecamericmetallamacrocycle-based3D frameworks have been synthesized. The magneticmeasurement results reveal that there are strong antiferromagnetic couplingsbetween the dual-copper ions bridged by doubly N1,N2-triazoles, and the higer thesymmetry of the bridged dinuclear, the stronger the antiferromagnetic couplingbetween the dinuclear. The catalytic property measurement results of these MOFs inthe oxidative coupling reaction show that the catalytic activity of the MOFs is notonly associated with the cavity size of MOFs, but have a great relationship with thestability of the MOFs.2) Three Fe-based MOFs have been synthesized by the reactions of H2pbt withFeSO4·7H2O in the presence of KSCN under solvothermal conditions. Interestingly,crystals of3-1allows to stand at160°C for one day undergoing an irreversible lostof one free water molecules to yield {[Fe2(pbt)2(H2O)2]·H2O}n(3-2) accompaniedby a color change from yellow to deep red. Moreover, the dehydration triggers the noticeable changes in catalytic and magnetic properties. These property changes areattributed to the high spin to low spin transition of7.1%center Fe(II), which isdemonstrated by57Fe M ssbauer spectra, XPS, and UV/Vis absorption spectra.3) Reaction of H2pbt with CoCl2·6H2O or Mn(OAC)2·4H2O generates threeoctanuclear metallamacrocycle-based3D MOFs. The magnetic measurement resultsreveal that there are weak antiferromagnetic couplings between the dual-cobalt ordual-manganese ions bridged by double N1,N2-triazoles.4) Under hydrothermal conditions, the ligand H2pbt with CuSO4·5H2O in thepresence of kCl and5-amino-isophthalic acid give rise to two Cu(I)/Cu(II)-based3D metal-organic frameworks. The catalytic property measurement results show thatalthough with identical frame structures these two Cu(I)/Cu(II)-based MOFs exhibitdifferent catalytic activity because the different counterions in the cages.
【Key words】 coordination polymer; metal-organic frameworks; metallamacrocycle; catalytic property; magnetic property; asymmetricazaheterocycles ligand;