取代基效应调控的芳香羧酸—叠氮铜分子磁性材料的制备、结构和磁性研究
发布时间：2018-08-13 13:19
【摘要】：分子基磁性材料在分子开关、数据存储以及分子水平上的电子设备等方面有潜在的应用,构筑高性能分子基磁性材料已成为材料化学和配位化学的热点课题之一。作为桥连配体,叠氮和羧酸不仅是常用的“化学桥”,而且是优秀的“磁学桥”。本文以叠氮铜体系为研究对象,引入多种氟取代的芳香羧酸作为辅助配体构筑分子基磁性材料,利用取代基效应调控目标物的结构和磁性,为制备高性能分子基磁性材料提供理论及实验指导,具体结果如下:1.采用溶剂热的反应条件,成功构筑了一例叠氮铜磁性配合物:[Cu(3-fba)(N3)(C2H5OH)]n(1)(3-fba为3-氟苯甲酸)。通过X射线结构分析,表明配合物1的最小不对称单元包含一个晶体学独立的Cu(Ⅱ)离子,形成了一个由三重混桥EO-叠氮、syn,syn-羧酸和μ2-乙醇构成的1D铜链。磁性测试表明,目标配合物是由铁磁相互作用的铁磁链组成的,其中Cu-N-Cu键角是105.95°。出现在配合物1相邻铜离子之间明显的磁耦合是由于多重超交换途径的反补偿效应引起的,导致了铁磁有序(Tc=11.0 K)和慢磁驰豫,在大多数叠氮铜配合物中很少被发现。热容测试进一步证明了长程磁有序特征。另外,通过DFT计算对1中铜离子间的铁磁耦合作用进行了深入的研究。2.选取含有不同数量氟原子取代基的苯甲酸衍生物:2-氟苯甲酸和2,6-二氟苯甲酸作为辅助配体,成功合成了两例新颖的叠氮铜配合物:[Cu(2-fba)(N3)(CH3OH)]n(2)和[Cu(2,6-dfba)(N3)(CH3OH)]n(3)(2-Hfba 为 2-氟苯甲酸和 2,6-Hdfba 为 2,6-二氟苯甲酸),对其结构和磁性进行了研究。单晶结构分析表明,两个目标配合物中的金属离子是由交替的三重桥μ-1,1-叠氮,syn,syn-羧酸和μ2-甲醇分子连接起来,构成了相似的线性一维铜链结构,而链内链间的结构参数略有不同。微调的结构导致了两个目标配合物不同的磁性。尽管两个配合物链内相邻的铜离子间强的铁磁耦合均由多重桥的超交换作用导致的反补偿效应产生,然而有趣的磁有序和慢磁弛豫只出现在配合物2中,这种特点在大多数已报道的叠氮铜配合物中很少出现,并且,配合物3表现出由铁磁耦合的铜链构成的反铁磁体的特征。热容测试进一步证明了配合物2的长程磁有序特性和配合物3的反铁磁体行为。此外,DFT计算从理论上定性解释了两个配合物的磁行为。3.基于两种同分异构的氟取代苯乙酸:邻氟苯乙酸和对氟苯乙酸,制备了两例叠氮铜配合物[Cu(o-fpa)(N3)(C2H5OH)]n(4)和[Cu(p-fpa)(N3)(C2H5OH)]n(5)(o-fpa为邻-氟苯乙酸,p-fpa为对-氟苯乙酸)。单晶结构分析表明配合物4和5是由1D链状配位图案组成,其中相邻铜离子是由交替的三重桥μ-1,1-叠氮,syn,syn-羧酸和μ2-乙醇连接起来。在两个配合物中,由两个苯乙酸辅助配体不同的取代基效应造成的羧基上不同的电荷分布导致了链内Cu-Cu距离和Cu-N-Cu键角等结构参数的不同,引起了磁行为的不同。两个配合物相邻铜离子间强的铁磁耦合(J= 87.08 cm-1对于4,J= 66.05 cm-1对于5)是由多重超交换途径的反补偿效应引起的,使两个化合物中出现了铁磁有序(Tc=11.0K对于4,9.5K对于5)和慢磁弛豫行为,这类现象在已报道的叠氮铜配合物中较为罕见。热容测试进一步证明了配合物4和5的长程磁有序。进一步探究了两个化合物的磁构关系。此外,DFT计算对两个配合物中铜离子间的铁磁耦合作用做了进一步的阐明。
[Abstract]:Molecular-based magnetic materials have potential applications in molecular switching, data storage and electronic devices at the molecular level. Building high-performance molecular-based magnetic materials has become one of the hot topics in material chemistry and coordination chemistry. As bridging ligands, azide and carboxylic acids are not only common "chemical bridges" but also excellent "magnetic bridges". In this paper, a variety of fluorine-substituted aromatic carboxylic acids are introduced as auxiliary ligands to construct molecular-based magnetic materials, and the substituent effect is used to control the structure and magnetism of the target compounds, which provides theoretical and experimental guidance for the preparation of high-performance molecular-based magnetic materials. The specific results are as follows: 1. Solvothermal reaction. A magnetic copper azide complex, [Cu (3-fba) (N3) (C2H5OH)] n (1) (3-fba 3-fluorobenzoic acid) was successfully constructed. X-ray structural analysis showed that the smallest asymmetric unit of complex 1 contained a crystallographically independent Cu (II) ion, forming a 1D copper chain consisting of triple mixed bridged EO-azide, syn, syn-carboxylic acid and mu 2-ethanol. Magnetic measurements show that the target complex is composed of ferromagnetic interacting ferromagnetic chains with a Cu-N-Cu bond angle of 105.95 degrees. The apparent magnetic coupling between adjacent copper ions in complex 1 is due to the anti-compensation effect of multiple superexchange pathways, resulting in ferromagnetic ordering (Tc=11.0 K) and slow magnetic relaxation in most copper azide. Ferromagnetic coupling between copper ions in 1 was studied by DFT calculation. 2. Benzoic acid derivatives containing different amounts of fluorine atom substituents, 2-fluorobenzoic acid and 2,6-difluorobenzoic acid, were selected as auxiliary ligands. Two novel copper azide complexes, [Cu (2-fba) (N3) (CH3OH)] n (2) and [Cu (2,6-dfba) (N3) (CH3OH)] n (3) (2-Hfba is 2-fluorobenzoic acid and 2,6-Hdfba is 2,6-difluorobenzoic acid) have been synthesized and their structures and magnetic properties have been studied. The single crystal structure analysis shows that the metal ions in the two target complexes are triple-bridged mu-1,1-superimposed. Nitrogen, syn, syn-carboxylic acid and mu 2-methanol molecules are linked to form a similar linear one-dimensional copper chain structure with slightly different structural parameters between the inner chains. The fine-tuned structure results in different magnetic properties of the two target complexes. Although the strong ferromagnetic coupling between adjacent copper ions in the two complex chains is conducted by the superexchange of multiple bridges. However, interesting magnetic ordering and slow magnetic relaxation occur only in complex 2, which is rarely seen in most reported copper azide complexes, and complex 3 exhibits the characteristics of an antiferromagnet consisting of ferromagnetic coupling copper chains. In addition, DFT calculations qualitatively explain the magnetic behavior of the two complexes. 3. Two copper azide complexes [Cu (o-fpa) (N3) (C2H5OH)] n (4) and [Cu (p-fpa) (N3) (C2H5OH)] n (5) (o-fpa) were prepared based o n two isomeric fluorophenylacetic acids: o-fluorophenylacetic acid and p-fluorophenylacetic acid. Fluorophenylacetic acid, p-fpa, p-fluorophenylacetic acid). Single crystal structure analysis shows that complexes 4 and 5 are composed of 1D chain-like coordination patterns, in which adjacent copper ions are linked by alternating triple bridges of mu-1,1-azide, syn, syn-carboxylic acid and mu 2-ethanol. In the two complexes, carboxylic acid is caused by the different substituent effects of two phenylacetic acid auxiliary ligands. The strong ferromagnetic coupling (J = 87.08 cm-1 to 4, J = 66.05 cm-1 to 5) between the adjacent copper ions of the two complexes is caused by the inverse compensation effect of multiple super-exchange pathways. Ferromagnetic ordering (Tc = 11.0K for 4,9.5K for 5) and slow magnetic relaxation behavior have been investigated. These phenomena are rare in reported copper azide complexes. The long-range magnetic ordering of complexes 4 and 5 has been further confirmed by heat capacity measurements. The magnetic structure relationship between the two complexes has been further explored. In addition, the ferromagnetism between copper ions in the two complexes has been calculated by DFT. The coupling effect is further elucidated.
【学位授予单位】：宁夏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O641.4
本文编号：2181119
[Abstract]:Molecular-based magnetic materials have potential applications in molecular switching, data storage and electronic devices at the molecular level. Building high-performance molecular-based magnetic materials has become one of the hot topics in material chemistry and coordination chemistry. As bridging ligands, azide and carboxylic acids are not only common "chemical bridges" but also excellent "magnetic bridges". In this paper, a variety of fluorine-substituted aromatic carboxylic acids are introduced as auxiliary ligands to construct molecular-based magnetic materials, and the substituent effect is used to control the structure and magnetism of the target compounds, which provides theoretical and experimental guidance for the preparation of high-performance molecular-based magnetic materials. The specific results are as follows: 1. Solvothermal reaction. A magnetic copper azide complex, [Cu (3-fba) (N3) (C2H5OH)] n (1) (3-fba 3-fluorobenzoic acid) was successfully constructed. X-ray structural analysis showed that the smallest asymmetric unit of complex 1 contained a crystallographically independent Cu (II) ion, forming a 1D copper chain consisting of triple mixed bridged EO-azide, syn, syn-carboxylic acid and mu 2-ethanol. Magnetic measurements show that the target complex is composed of ferromagnetic interacting ferromagnetic chains with a Cu-N-Cu bond angle of 105.95 degrees. The apparent magnetic coupling between adjacent copper ions in complex 1 is due to the anti-compensation effect of multiple superexchange pathways, resulting in ferromagnetic ordering (Tc=11.0 K) and slow magnetic relaxation in most copper azide. Ferromagnetic coupling between copper ions in 1 was studied by DFT calculation. 2. Benzoic acid derivatives containing different amounts of fluorine atom substituents, 2-fluorobenzoic acid and 2,6-difluorobenzoic acid, were selected as auxiliary ligands. Two novel copper azide complexes, [Cu (2-fba) (N3) (CH3OH)] n (2) and [Cu (2,6-dfba) (N3) (CH3OH)] n (3) (2-Hfba is 2-fluorobenzoic acid and 2,6-Hdfba is 2,6-difluorobenzoic acid) have been synthesized and their structures and magnetic properties have been studied. The single crystal structure analysis shows that the metal ions in the two target complexes are triple-bridged mu-1,1-superimposed. Nitrogen, syn, syn-carboxylic acid and mu 2-methanol molecules are linked to form a similar linear one-dimensional copper chain structure with slightly different structural parameters between the inner chains. The fine-tuned structure results in different magnetic properties of the two target complexes. Although the strong ferromagnetic coupling between adjacent copper ions in the two complex chains is conducted by the superexchange of multiple bridges. However, interesting magnetic ordering and slow magnetic relaxation occur only in complex 2, which is rarely seen in most reported copper azide complexes, and complex 3 exhibits the characteristics of an antiferromagnet consisting of ferromagnetic coupling copper chains. In addition, DFT calculations qualitatively explain the magnetic behavior of the two complexes. 3. Two copper azide complexes [Cu (o-fpa) (N3) (C2H5OH)] n (4) and [Cu (p-fpa) (N3) (C2H5OH)] n (5) (o-fpa) were prepared based o n two isomeric fluorophenylacetic acids: o-fluorophenylacetic acid and p-fluorophenylacetic acid. Fluorophenylacetic acid, p-fpa, p-fluorophenylacetic acid). Single crystal structure analysis shows that complexes 4 and 5 are composed of 1D chain-like coordination patterns, in which adjacent copper ions are linked by alternating triple bridges of mu-1,1-azide, syn, syn-carboxylic acid and mu 2-ethanol. In the two complexes, carboxylic acid is caused by the different substituent effects of two phenylacetic acid auxiliary ligands. The strong ferromagnetic coupling (J = 87.08 cm-1 to 4, J = 66.05 cm-1 to 5) between the adjacent copper ions of the two complexes is caused by the inverse compensation effect of multiple super-exchange pathways. Ferromagnetic ordering (Tc = 11.0K for 4,9.5K for 5) and slow magnetic relaxation behavior have been investigated. These phenomena are rare in reported copper azide complexes. The long-range magnetic ordering of complexes 4 and 5 has been further confirmed by heat capacity measurements. The magnetic structure relationship between the two complexes has been further explored. In addition, the ferromagnetism between copper ions in the two complexes has been calculated by DFT. The coupling effect is further elucidated.
【学位授予单位】：宁夏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O641.4
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