【作者】 田菊梅；

【导师】 张景萍；

【作者基本信息】 东北师范大学 ， 高分子化学与物理， 2014， 博士

【摘要】 分子基磁性材料是一个活跃且多学科交叉的研究领域，通常在分子水平上设计、合成并研究其组成、结构与性能间相互关系。分子设计的灵活性赋予了分子磁性材料结构的多样性，从而产生多种不同的磁行为，如自旋翻转、变磁、自旋倾斜、自旋阻挫、自旋玻璃、单分子磁体、单链磁体等。目前对分子基磁性材料研究热点主要如下：（i）具有高临界温度的分子磁体；（ii）多功能磁性材料，如磁电共存、磁手性和用于磁分离的多孔材料等；（iii）非热刺激磁材料，如光诱导、压力诱导磁体和电诱导磁体等。本论文选择三类多齿配体，如二齿的4-甲基-3-硝基苯甲酸(HL)、三齿的亚磷酸和三羟甲基丙烷(H3tmp)以及四齿的西弗碱N, N’-bis(salicylidene)hydrazine (H2salhn)和4-(tris(hydroxylmethyl)methyl)pyridine (4-thmpyH3)为主配体，结合辅助配体与过渡金属离子配位合成出13种配合物，其中有两例为多孔磁性材料。分析了溶剂、温度、pH值及辅助配体等对配合物结构的影响，系统地研究这些化合物的磁性及相应的多孔性质，发现结构与性质之间的相互关系。研究内容主要包括以下五个方面：1．桥连配体对四齿西弗碱H2salhn与钴和铜离子配位的影响：利用叠氮作为桥连配体，使H2salhn与过渡金属钴和铜离子配位得到两个新化合物，[CoIICoIII4(salhn)4(N3)6(MeOH)2(H2O)2]·4MeOH·2H2O (1)和[CuII2(salhn)(N3)2]n(2)。X-射线单晶衍射结果表明，化合物1是一个“之”字型[CoIICoIII4]钴簇，而化合物2是一个结构单元为[CuII2(salhn)(N3)2]的一维配位化合物。两个化合物中叠氮配体均采用end-on (EO,μ-1,1)桥连配位模式。磁性测试结果显示1和2为反铁磁化合物。同时，化合物2具有短程有序，在2K下存在一个0.02T的临界场。与已报道的双核Co2(salhn)3和Cu2(salhn)2(H2O)4体系相比，发现叠氮桥连配体的引入成功实现顺磁离子核数的增加，从而为高核簇化合物的制备提供方案。2．抗衡离子对基于三齿配体（三羟甲基丙烷）的六核铁簇化合物性质的影响：选择三种不同尺寸含氮的抗衡离子（哌嗪、咪唑和三氮唑）与三羟甲基丙烷（H3tmp）和FeCl3采用溶剂热反应合成三例六核Fe(III)化合物：(C5N2H14)[Fe6(μ6-O)Cl6(tmp)4]·2H2O·CH3OH (3)、(C3N2H5)2[Fe6(μ6-O)Cl6(tmp)4](4)和(C4N3H8)3(C2N3H4)[Fe12(μ6-O)2Cl12(tmp)8]·3CH3OH (5)，并对它们的结构和磁学性质进行表征。发现三元醇配体有利于合成高核磁性金属簇。三个化合物具有相同的阴离子簇[Fe6(μ6-O)Cl6(tmp)4]2-，由六个Fe(III)离子、四个tmp3-配体、一个中心O2-离子和六个Cl-离子组成。磁性测试结果表明这三个化合物具有不同的精细磁学性质。化合物3和4表现出自旋翻转行为，化合物5没有明显的自旋翻转行为特征。化合物3显示自旋玻璃行为，化合物4和5为长程有序。利用不同的抗衡阳离子，通过不同的偶极和氢键相互作用，实现调节分子间堆积方式，从而产生不同的精细磁学性质，为精细地调节磁学性质提供实验依据。3．溶剂对基于二齿配体（4-甲基-3-硝基苯甲酸）稀土配合物性能的影响：以4-甲基-3-硝基苯甲酸（HL）为配体通过溶剂热反应合成三例新一维镧系配位聚合物—[Gd(L)3(H2O)(CH3OH)](6)、[Gd(L)3(H2O)2]·(4,4’-bpy)·CH3OH (7)和[Dy(L)3(H2O)(CH3OH)](8)。采用单晶X-射线衍射、红外、粉末XRD、热重和元素分析等手段对这三个化合物进行结构表征。只有混合溶剂条件才可以合成化合物6-8，使用单一的溶剂无法得到任何晶体。除金属离子不同，化合物6和8是同构的。磁性测试表明化合物6和7表现出顺磁行为，而化合物8具有反铁磁行为。化合物8表现出磁化强度的慢驰豫，并观察到频率依赖的虚部信号。然而，在2K零直流场下，并未观察到交流信号最大值。当施加5000Oe的直流场时，观察到频率依赖的交流信号峰值，通过Arrhenius定律拟合，[ln(1/2πf)=lnτ0+Δ/kBT]，得到能垒Δ/kB为39.4K和指前因子τ0为2.12×10-8。4．溶剂挥发速度对基于三齿配体的过渡金属配合物结构与性质的影响：采用亚磷酸配体合成四个新化合物[Ni(HPO3)(4,4’-bpy)(H2O)3]·4H2O (9)、[Co2(HPO3)2(4,4’-bpy)2(H2O)6]·9H2O (10)、[Zn(HPO3)(4,4’-bpy)0.5]·H2O (11)和[Co3(PO3)2(4,4’-bpy)3(H2O)6]·3H2O (12)。化合物9-11均在较快溶剂挥发速度下制得。与化合物10的反应体系相同，通过密封滤液容器，降低滤液挥发速度，从而得到化合物12。对于反应体系9和11，降低溶剂挥发速度并未获得新的晶体。除金属离子和结晶水的数量不同外，化合物9和10是同构的，均为链状结构，亚磷酸的氧原子仅采用单配位方式。化合物11为二维层状结构。化合物12中亚磷酸采取η1:η1:η1:μ3配位模式形成Kagomé结构，具有沿c轴的一维孔道。磁性测试表明化合物9表现出顺磁行为，化合物10为反铁磁行为。化合物12为反铁磁性，并具有显著的场诱导自旋翻转。通过dM/dH曲线得出在2.0K下的临界场为3T。化合物12由于具有kagomé晶格的几何阻挫，因此表现出强的自旋阻挫。去水相12a表现出type-II型氮气吸附等温线。磁性测试表明化合物12a和12的磁学性质略有不同。化合物12a表现出亚铁磁行为，具有0.2T的临界场，自旋阻挫更弱。通过降低溶剂挥发速度使得配体的配位模式发生变化从而得到了具有自旋翻转和自旋阻挫共存的多孔磁性化合物12。当移除晶格溶剂后，体系的氢键消失，从而使得磁学性质发生了变化。在这里的研究结果表明客体分子即主客体氢键相互作用可以对体系的磁学性质起到一定的调控作用。同时较慢的溶剂挥发速度会导致配体配位更完全。5．利用四齿半刚性配体（4-(tris(hydroxylmethyl)methyl)pyridine）与钴离子构建多孔磁性材料：选用半刚性4-(tris(hydroxylmethyl)methyl)pyridine (4-thmpyH3)配体与乙酸钴合成出微孔磁性化合物[Co10O(4-thmpy)4(CH3COO)3(H2O)6(CH3O)3]·8CH3OH (13)。化合物13中，十核钴金属簇作为节点，4-thmpy3-配体作为支架，形成一个NaCl型网络结构。13表现出自旋倾斜的反铁磁性，并具有自旋玻璃行为。客体分子与框架存在氢键相互作用，当移除客体分子后，框架发生了微小变化，从而磁性测试结果表明自发磁化强度移向高温区域。去溶剂样品仍然保持着自旋倾斜和自旋玻璃行为。氮气吸附结果表明该化合物表现出type-I型的吸附曲线，证明其微孔特性。298K下的甲醇和水的吸附测试结果表明该化合物主要表现出疏水特性。GCMC理论模拟得到的氮气吸附结果与实验结果完全吻合。结果显示甲醇的吸附点位于孔内，并与框架中的吡啶环之间形成了强的氢键相互作用(C-H···π=2.879)。使用半刚性的多齿配体为合成多孔磁性材料提供另一个新思路。更多还原

【Abstract】 Molecule-based magnetism designates an active and interdisciplinary research field thatfocuses on the use of molecular approaches to design, synthesize, and study the composition,structure, properties and structure-property relationships of the magnetic materials. Until now,lots of molecule-based magnetic materials have been reported owing to the flexibility ofmolecular chemistry. The various structures of magnetic materials have demonstrateddifferent magnetic behaviors, such as spin-flop, metamagnetism, spin-canting, spin-frustration,spin-glass, single-molecule magnets (SMM), single-chain magnets (SCM), etc. The trends ofresearch based on the molecule-based magnetic materials can be classified into the followingfour main classes:(i) molecule-based magnets with higher critical temperatures;(ii)multifunctional magnetic materials, such as magneto-electronic coexist, magnetic chiral, andporous material for magnetic separation;(iii) non-thermally stimulated magnetic materials,such as light-induced/stress-induced/electric induced magnet.In order to obtain novel molecule-based magnetic materials and porous magneticmaterials, we have chosen different polydentate ligands Schiff base ligand N,N’-bis(salicylidene)hydrazine (H2salhn),1,1,1-tris(hydroxymethyl)propane (H3tmp),4-methyl-3-nitrobenzoic acid (HL), phosphite, and/or4-(tris(hydroxylmethyl)methyl)pyridine(4-thmpyH3) to react with transition metal ions to obtain thirteen compounds. We haveanalyzed the effects of solvent, temperature, pH, and ancillary ligands on the structures of thecompounds. The structure-property relationships have been summarized by systematicalinvestigation and detailed discussion of the magnetic and porous properties. The outline ofthis dissertation is as follows:1. Two novel complexes,[CoIICoIII4(salhn)4(N3)6(MeOH)2(H2O)2]·4MeOH·2H2O (1) and[CuII2(salhn)(N3)2]n(2)(H2salhn=N, N’-bis(salicylidene)hydrazine), were synthesized andstructurally characterized by X-ray single-crystal diffraction. Complex1is a zigzag-likepentanulear [CoIICoIII4] cobalt cluster, while complex2consists of a1D coordination complexcontaining subunit [CuII2(salhn)(N3)2]. Compounds1and2both possess end-on (EO, μ-1,1)azide bridging. The magnetic measurements indicate that both1and2showantiferromagnetic behaviors. Complex2displays a phase transition with a critical field of0.02T at2.0K. Compared with the previous Co2(salhn)3diamagnetic system andCu2(salhn)2(H2O)4system, we have successfully obtained two extended networks withantiferromagnetism by employing the azide ligand, which play a guiding role for the future ofexperimental research.2. Solvothermal reactions of1,1,1-tris(hydroxymethyl)propane (H3tmp) and FeCl3using different counterions resulted in three hexanuclear iron(III) clusters(C5N2H14)[Fe6(μ6-O)Cl6(tmp)4]·2H2O·CH3OH (3),(C3N2H5)2[Fe6(μ6-O)Cl6(tmp)4](4), and(C4N3H8)3(C2N3H4)[Fe12(μ6-O)2Cl12(tmp)8]·3(CH3OH)(5), then their structures andmagnetic properties were characterized. The tripodal alcohols ligands are very useful inconstructing magnetically high-nuclearity metal clusters. In all cases, similar anionic cluster[Fe6(μ6-O)Cl6(tmp)4]2-is formed by six Fe(III) ions, four tmp3-ligands, one center O2-ion,and six Cl-ions. Magnetic studies indicate that these three compounds show slightly differentmagnetic data, despite they display similar magnetic features. The dipolar interactions and thehydrogen-bond interactions may be responsible for such differences.3. Three novel one-dimensional (1D) lanthanide coordination complexes involving the4-methyl-3-nitrobenzoic acid (HL) ligand, with the general formula [Gd(L)3(H2O)(CH3OH)](6),[Gd(L)3(H2O)2]·(4,4’-bpy)·CH3OH (7),[Dy(L)3(H2O)(CH3OH)](8), have beensynthesized by the solvothermal reactions. These complexes have been structurallycharacterized by single-crystal X-ray diffraction, IR, PXRD, TGA, and elemental analyses.Compounds6-8were obtained under the condition of the mixed solvent. We want to employpure solvent conditions to investigate whether the mono-solvent coordinated complex can beassembled or not. Unfortunately, single crystals could not be obtained when the reactionsolvent was employed pure water or methanol. Complexes6and8are isostructural except thedistinction of metal ion. Magnetic measurements indicate that complexes6and7both showparamagnetic behaviors, but complex8shows antiferromagnetic behavior. Complex8behaves slow relaxation of the magnetization, where the frequency-dependent out-of-phasesignals are noticed. However, the characteristic maxima were not reached above2K underzero direct current (DC) fields. When a DC field of5000Oe was employed, the frequencydependent peaks of alternating current (AC) signals were obtained.4. Four new compounds,[Ni(HPO3)(4,4’-bpy)(H2O)3]·4H2O (9),[Co2(HPO3)2(4,4’-bpy)2(H2O)6]·9H2O (10),[Zn(HPO3)(4,4’-bpy)0.5]·H2O (11), and[Co3(PO3)2(4,4’-bpy)3(H2O)6]·3H2O (12), have been synthesized. Compounds9-11wereformed under the condition of the unsealed filtrated solution leading to the fast evaporationrate. we change the process of our experiment, i.e., seal the filtrated solution for each, toreduce the rate of the evaporation of the filtrated solution. As expected, new crystal, i.e.,complex12, has been formed with different color and shape from10. However, no newcrystals have been obtained from the systems9and11, which indicate that the differentevaporation rate is feeble for the systems9and11. Compounds9and10are linear chains andisostructural except for the distinction of the metal ion and the number of lattice watermolecules. Compound11consists of2D sheet structure. For compound12, phosphite PO33-group acts as η1:η1:η1:μ3mode linking three Co ions forming Kagomé framework with1Dhexagonal channels along the c axis. Magnetic measurements indicate that compound9shows paramagnetic behavior, while compound10displays antiferromagnetic behavior. Compound12exhibits the antiferromagnetism with a pronounced field-induced spin-flop transition. Acritical field of3T at2.0K is determined from the derivative dM/dH curve. Meanwhile,compound12shows a strong spin-frustration arising from the geometric frustration inkagomé lattice. The dehydrated phase12a displays a characteristic of N2-adsorption withtype-II isotherm. We performed detailed magnetic measurements for12a, which exhibits quitedifferent magnetic properties from12. Compound12a displays a ferrimagnetic behavior witha lower transition field of0.2T, and a weaker spin-frustration. The results showed that themagnetic properties of the system can be tuned by the hydrogen bonding interactions betweenthe guest molecules and the host framework. Furthermore, slower evaporation rate of thesolvent may result in more complete of coordination.5. We have synthesized a microporous magnetic framework based on the tripodal alcoholderivative with pyridyl group4-(tris(hydroxymethyl)methyl)pyridine (4-thmpyH3) ligand,[Co10O(4-thmpy)4(CH3COO)3(H2O)6(CH3O)3]·8CH3OH (13), which contains supertetrahedraldeca-metallic cobalt clusters as nodes and4-thmpy3-ligands as linkers to form a NaCl-likenetwork. The complex shows a canted antiferromagnetism with spin-glass behavior. There ishydrogen bonding between the guest methanol molecules and the framework in compound13.The removal of guest molecules might lead to the slight change of the framework, whichbenefits the spontaneous magnetization at higher temperature. Nonetheless, the spin-cantingand spin-glass behaviors are still maintained. The permanent porosity was evaluated by N2adsorption measurement, which exhibits a typical type-I curve. The complex mainly showshydrophobic nature validated by CH3OH and H2O adsorption measurements that is consistentwith the grand canonical Monte Carlo (GCMC) theoretical simulation. It is observed that theCH3OH molecule locates inside the hole and forms short contacts with the pyridine ring(C-H···π=2.879). We have obtained microporous magnetic materials by using semirigidligand, which provide another theoretical and experimental basis for the future synthesis ofporous magnetic.更多还原