Investigation Of The Magneto-structural Correlation Within Molecule-based Magnets And Multifuncitonal Magnets Based On Carboxylate Groups, Dicyanamido Groups, Or Cyano Groups

Molecule-based magnets have becomed one of the most studied fields in recent years,which have widespread applications in molecular electronics, information storage or sensing.The current trends in this research field can be classified into three main classes of molecularmaterials:（1） molecule-based magnets possessing higher critical temperatures;（2）multifunc tional magnetic materials;（3） molecular nanomagnets and nanos tructured magneticmaterials.In this work, nineteen compounds were prepared by changing the bridging ligands（carboxylate, dicyanamido and cynaide） and transition metal ions. We systematically studythe correlations be tween structure and property in these compounds. The outline of my workis as follows:1. Four novel CuIIcomplexes Cu^II{Na[Cu₄（hmp）₄（CHOO）₃]（ClO₄）₂·H₂O}n （1）,[Cu₈（hmp）₈（CH₃COO）₆]（ClO₄）₂（2）,[Cu₄（hmp）₄（CH₃CN）₂（ClO₄）₂（H₂O）₂]（ClO₄）₂（3）,å'Œ[Cu₄（hmp）₄（CH₃COO）₂（H₂O）₄]（ClO₄）₂·2H₂O （4） with Hhmp=2-（hydroxymethyl）pyridinewere prepared by structural modulation at room temperature. Taking advantage of sterichindrances of the ancillary ligands, the1D coppe r chain （1） is successfully cut down into theocta-nuclear copper cluster （2） with the unchanged antiferromagnetic [Cu4O4] open-cubanethat is further separated into weak antiferromagnetic [Cu4O4]（3） and then modulated to be theferromagnetic tetra-nuclear [Cu4O4] cluster （4）. The obtained four complexes allow us tosystematically investigate their magnetic prope rties and find the rules for further magneticinvestigations. The results showed that there exist antiferromagnetic interactions betweenCu（II） ions in1-3; while4displays a ferromagnetic behaviour. The best fitting results to theexperimental magnetic susceptibilities gave J1=J2=J3=2.26cm1, g=2.11for3and J1=37.05cm1, J2=0.62cm1, J3=0.62cm1, g=2.13for4.2. A new tetranuclear copper（II） complex [Cu4（H2L）4]·H2O （5） and one mononuclearcomplex [Ni（H₃L）₂]·H2O （6） with H4L=[（OH）C₆H₄CH=N-C（CH₂OH）₃] were prepared.Magneto-structural correlations in hydroxide （alkoxide）-bridged coppe r（II） complexes havebeen widely studied and show that the major factor controlling magnetic coupling constants（2J） is the Cu-O-Cu angle. Herein, we report the magnetic behavior and magneto-structuralcorrelation of the tetranuclear copper complexes. The result showed that there existsferromagnetic interaction between Cu（II） ions in5.3. Self-assembly of MX₂（M=Cu, Co or Ni; X=OAc or Cl） with2-hydroxymethylpyridine （Hhmp） results in five new complexes [Cu₄（hmp）₄（CH₃COO）₄]·2H₂O （7）， [Co₄（hmp）₄（CH₃COO）₄（H₂O）₂]·3CH₃OH·CH₃CN （8）， Ni₈（hmp）₈（CH₃COO）₈（H₂O）₄（9），Ni（Hhmp）₂（CH₃COO）₂（10），[Ni₄（hmp）₄（H₂O）₄Cl₄]·CH₃CN （11）。 All complexes consist ofan expected cuba ne [M4O4] core except that complex10is a dinuclear cluster. Magneticstudies show that there exist antiferromagnetic interactions between metal ions in7and8;while complex11displays a ferromagnetic behaviour.4. We describe for the first time the designing and synthesis process of a series ofcompounds12-14based on achiral building blocks from achirality to chirality by molecularmanipulation （12=Cu[N（CN）2]2（Hhmp）,13={Cu[N（CN）2]2（Hhmp）}∞, and14={Cu4[N（CN）2]2（Hhmp）4（CH3COO）2·CH3CN}∞）. Compound12is a mesomer, and compound13is a racemic mixture. While compound14features DNA-type right-hand double-helicalCuIIchain structure. The solid-state circular dichroism （CD） spectrum of14indicates thecrystals are optical activity. The magnetic properties of12-14have also be en studied.5. With the use of [M（CN）₆]₃-（M=FeIIIor CoIII） as building blocks, five newcyano-bridged heterometallic compounds,[Mn(C₄H₁₀ON)（H₂O）][M（CN）₆]（M: FeIII,15; CoIII:16）,[Mn(C₄H₁₁N₂)（H₂O）][Co（CN）₆]（17），[Mn₃（4,4’-bpy）₃（H₂O）₄]-[Co（CN）₆]₂·2（4,4’-bpy）·4H₂O （18）å'ŒMn[Co（CN）₆]·2H₂O （19）(C₄H₁₀ONwere rationally prepared by a facile approach,adjusting the organic connectors, and characterized （C4H10ON: morpholine; C4H11N2:piperazine;4,4’-bpy：4,4’-pyridine）. Compound15-17are isomorphous structures with a2Dnetwork, whereas compound18and19exhibit an intriguing metal–organic framework.Compound19exhibits a volumetric storage capacity of139.075cm3g-1at750mmHg and77K. Magnetic studies show that there exist ferrimagnetic interactions between metal ions in15and18; while no significant magnetic interactions were found between the MnII/MnIIIand theCo（III） ions in compounds16,17and19.