Controlled Assembly Of 3d Metal Ions Low Dimensional Complexes (polymers) And Structure-decorating, Magnetic Properties

The low magnetical complexes (polymers) (including single molecular magnet and single chain magnet) with the desired structures and functions which are constructed directionally, are the basis to research molecule-based magnetic materials. The studies on low magnetical coordination complexes are in the interface between chemistry, physics, biology and material ology. In this thesis, we selected 3d transition metal ions and organic aromatic ligands containing N, O atoms as the object of our study. Thirteen low-dimensional coordination polymers (including two single molecular magnets) have been synthesized and characterized by elemental analyses, IR, X-ray analyses, variable-temperature and variable-field magnetic measurements. This thesis is divided into four chapters.In the first chapter, the main facets and several recent topics of molecular magnetism are systemically introduced, as well as the research significance and the results of this thesis. In the second chapter, three isolated cubane and five tricubanes clusters with the ligand of Hbm have been described by displacing the auxiliary ligand and metal ions (cobalt or nickel or cobalt/nickel (1:1)). Compounds of 1-3 [M4(bm)4(EtOH)4Cl4] (M = CoII or NiII or CoII:NiII(1:1)), isomorphous and isostructural, are isolated cubane clusters. Magnetic studies on compounds 1-₂ have revealed there exist evidently ferromagnetic interaction in the cubane. And relaxation and long range ording behaviors coexist above 8 K in compound 1. Compounds 4-8 are constructed by three isolated cubanes, which are connected by the template of NO₃- and the auxiliary ligands of Ac-. The compound of [Co'12(O₂CMe)6(EtOH)6](NO₃)5 (Co'12 = Co12(bm)12(NO₃)) (4) is a twelve nuclear supercluster with the diameter of ca. ₂ nm. It is the first time that the anion of NO₃- are linked to six metal ions by theμ6-NO₃- bridging. the structure of 4 is rather unusual for a molecular species, magnetic analyses of 4 have revealed that it is the fourth cobalt-based SMMs, which displays the largest energy barrier of ca. 8₂ K to reorientation of the magnetization for SMMs, and highlights the potential for creating improved SMMs by using Co(II) as metal centers. The results further suggest that other M4O4 cubanes may also find use as starting points for judiciously assembling supercluster with higher nuclearity and higher spin products. The compound of [Co'12(O₂CMe)6(EtOH)3(H₂O)3](NO₃)5·₂H₂O (5) is obtained under the same environment with 4, the trace water replace the portion of coordinated ethanol. The compound of [Ni'12(O2CMe)6(EtOH)3(H₂O)3](NO₃)5·2H₂O (6) is isomorphous and isostructural with 5. TheχmT-T curve of 4 reveals it takes on evidently ferromagnetic interaction in clusters above 27.3 K, and the ac susceptibility curve indicates that it is not a single molecular magnet. The compound of [Co'6Ni'6(O2CMe)6(EtOH)6](NO₃)5 (7) is isomorphous and isostructural with 4. Magnetic studies on 7 have revealed that it is a single molecular magnet and there exist evidently ferromagnetic interaction in clusters. The compound of [Co'12(O2CH)6(EtOH)6](NO₃)5 (8) has the similar structure of 4.In the third chapter, 1D catenarian binuclear carboxylate copper complexes of [Cu2(2,4-dcpa)4(pyz)]n (9), [Cu2(4-cpa)4(pyz)]n (10) and [Cu2(pa)4(pyz)]n (11) have been constructed to investigate the influence on structure and magnetism of the Cl atom at the different place of R in the SBU of Cu2(μ-O2CR)4. The crystal structures have revealed pyz molecules link the Cu2(μ-O2CR)4 units into an infinite one-dimensional chain. In compounds 9 and 10, the 1D chains extend along one direction and stack into three-dimensional structures by the weak interaction of Cl···Cl. However, in compound 11 the 1D chains extend along two different directions to form the ABAB array and stack into three-dimensional structures by the van der Waals interaction. The primary magnetic analysises have revealed there exist strongly antiferromagnetic interaction in two nuclear coppers of 9 - 11, there is no evident differentiation above high temperature among 9 - 11. The results show that halogen-halogen interactions affect the stack between chains, but not the magnetism evidently in compounds of 9 - 11.In the fourth chapter, syntheses and structures of two coordination polymers with Hpa, ina, 4,4′-bipy and cobalt ions are described. The compound of [Co3(OH)2(pa)2(ina)2]n (12) is constructed by linear three nuclear Co(II) SBU to form a two-dimensional layer and take on a novel 2D (4, 63) topology. The compound of {[Co3(pa)4(bipy)4](NO₃)2}n (13) is constructed by different linear three nuclear Co(II) SBU ,which form a two-dimensional sheet, there exists two different of 4,4-grid constructed by Co(II) and 4,4′-bipy and form ABAB array. The self-fillings between adjacent sheets afford a three-dimensional network. Magnetic analyses reveal that in the compound of 12, the antiferromagnetically correlated Co3 clusters leads to a weak ferromagnetic ordering. The presence of the weak anisotropy and the intercluster dipole-dipole interaction also leads to spin-canting and present a spontaneous magnetic moment. In the compound of 13, the antiferromagnetically correlated Co3 clusters doesn't lead to the long range ordering behavior.