Construction,Structure And Assembly Process Of 3D Transition Metal Ligand Clusters Based On Benzimidazole Alcohol Ligands

3d transition metal coordination clusters have become a hot spot in inorganic coordination chemistry research because of their diverse structural features and potential physical and chemical properties.It is one of the challenges in the field of solution coordination chemistry to elucidate the mechanism of their assembly process and to realize their directed design and functional regulation.Our group has used X-ray,mass spectrometry,spectroscopy and other characterization techniques to track the composition of the time-dependent reaction process solid-liquid hybrid system,orderly capture key structural fragments and intermediates,relying on the correlation of solid-liquid structural information and then reveal the assembly process of coordination clusters of the research method provides theoretical guidance for the construction of ligand clusters in a directional manner.Based on this approach,I have studied five cases of multinuclear coordination clusters from the design of ligands to the synthesis of high-nuclear coordination clusters,and from structure to properties.The first chapter is an introduction,which outlines the development and research progress of complexes,mainly focusing on the design synthesis and structural characteristics of highly nucleated clusters,and suggests that ligands are essential for the construction of highly nucleated clusters.The application of electrospray mass spectrometry in coordination chemistry and the research methods carried out are also introduced,from the development and advantages of electrospray to the progress of research on cluster assembly based on electrospray mass spectrometry at home and abroad.Finally,the progress of our group’s work in this area is introduced,which provides theoretical guidance for the study of this work.The significance of the selection of this topic and the content of the research are described.The second chapter investigates the design and synthesis of a new benzimidazole alcohol ligand（2-（N-methyl-benzimidazol-2-yl）-2-methylpropane-1,3-diol,H₂mmbp）based on the structural characteristics of the ligand of the coordination compound,and the reaction with Fe（Cl O₄）₃·6H₂O under solvothermal conditions to synthesize an example of discoidal hentriacontanuclear Fe ligand cluster based on the chelating and bridging properties of this ligand.Combined with X-ray single crystal diffraction,thermogravimetric analysis and elemental analysis,the structure was determined to have the chemical structure formula[Fe₃₁（O）₁₈（mmbp）₁₂（OCH₃）₁₈（HCOO）₆（H₂O）₆]·（Cl O₄）₂·2CH₃OH.The ligand cluster has a novel structure and is the highest 3d transition metal discoidal ligand cluster with the highest nucleation number so far.The solution behavior of the coordination cluster was carefully characterized by electrospray mass spectrometry,and the structure was found to undergo cascade substitution of short-bridge ligands in solution.The structure framework is maintained at 60 e V under pressurized conditions by electrospray mass spectrometry,indicating that the structure has good stability.Based on the solid-liquid structural information correlation,a possible assembly process-internal growth mechanism is proposed based on this structure.It provides theoretical support and research examples for the assembly of highly nucleated disc-like coordination clusters.The positive Weiss constantθ=155.55 K in the magnetic test indicates that the structure as a whole is dominated by ferromagnetic interactions.The third Chapter describes the synthesis of an example of a nanonuclear Mn cluster（[Mn₉（L）₆（HCOO）₆（CH₃O）₃（OH）]·3CH₃OH·2H₂O）by selecting a benzimidazole alcohol（1H-benzimidazol-2-yl）-2-methylpropane-1,3-diol,H₂L)ligand with Mn（Cl O₄）₂·6H₂O under solvothermal conditions.The core skeleton of Mn₉ is a ship-shaped structure consisting of a Mn metal center connected to two cubane Mn₄O₄ core units.The assembly of Mn₉from the reactants through[Mn₄L₃]and[Mn₅L₃]was confirmed by the solid and solution information provided by powder X-ray diffraction and electrospray mass spectrometry,respectively.The magnetic behavior of the Mn₉ structure shows the dominance of antiferromagnetic interactions between its Mn metal ions.On this basis,an example of octanucleare Mn cluster（[Mn₈（L）₄（HCOO）₆（CH₃O）₂（O）₂（OH）₂]·5CH₃OH）was synthesized by changing the solvent conditions,and the core skeleton of this structure consisted of two parallel cubane Mn₄O₄cores.It is noteworthy that the fragment[Mn₄L₃]is also seen in the single crystal mass spectrum of Mn₈ in Mn₉ solution,suggesting that both cases of Mn clusters may be derived from the combination of this unit.And then the author used H₂L with Co Cl₂·6H₂O and Ni（Cl O₄）₂·6H₂O to synthesize two examples of cubane structures Co₄ and Ni₄.The chemical structure formula of the structure was determined by X-ray single crystal diffraction and TG-MS as[Co₄/Ni₄（L）₄（HCOO）₂][2HCOO].The two structures remain in stable frame under mass spectrometric conditions.The magnetic data show that Co₄ and Ni₄ magnetic behaviors are opposite,with antiferromagnetic interactions dominating the magnetic interactions between Co₄ metal ions and ferromagnetic interactions dominating the magnetic interactions between Ni₄ metal ions.