Research On Magnetic-Structure Relationship,Track The Changes Of Molecular Fragments And Assembly Processes By Mass Spectrometry Of 3d Metal Complexes Based On Benzimidazole-2-Substituted Derivatives Ligands

Because compounds diversified structure characteristics and potential of physical and chemical properties of 3d transition metal coordination clusters,which has become a hot spot and frontier in the field of inorganic chemistry.There is long-term effort for achieving the rational construction of coordinative compounds with targeted connection,shape,properties and effective modification on their function.For high-nuclear coordination molecular cluster and metal-corrdination and metal-organic frameworks of the design,synthesis,function,and structure-activity relationship of complex structures represented has attracted researchers’great enthusiasm.For simple system understanding the stability,intermolecular interaction,geometry distortion,integration,cleavage of oligomerization species would build crucial basis to the mechanism study of poly-nuclear cluster.In addition,these simple mononuclear system is suitable to theoretical simulation.The resulting supplementary information of bonding,valence state,coordination geometry would help the mechanism building of complex cluster.In this thesis,we choose the key ligands to synthesize a series of compounds with the copper（Ⅰ/Ⅱ）,cobalt（Ⅲ）and zinc（Ⅱ）metal salt by solvothermal or volatilization method.The X-ray diffraction,ESI-MS and DFT were used to study the relationship between the structure and magnetic properties,the solution behavior of compounds under different voltage conditions.The fluorescence properties of zinc-based clusters and assembly process of copper-based clusters were initially explored.The full text is divided into three chapters:The first chapter is the introduction,the research background and hotspot of this thesis.At the same time,We introduced the domestic and foreign research groups using mass spectrometry technology to study the clusters;We also introduce the application of ESI-MS technique in solution chemistry of coordination complexes,which provides new ideas and new methods to explore the solution behavior of clusters.In chapter 2,we report that the ligand of N-methyl-2-hydroxymethylbenzimidazole（Hmbm）with the metal salt Cu Cl₂·2H₂O/Cu Br₂/Co（CH₃COO）·4H₂O in methanol to obtain compound 1[Cu（Hmbm）Cl₂]（Cu1）/2[Cu（mbm）Cl]₂（Cu2Cl）/3[Cu（Hmbm）₂Cu Br₂]（Cu2Br）/4[Co（Hmbco）₃]（Co1）.An mononuclear Cu（Hmbm）Cl₂ molecular chelated by a benzimidazole ligand and two chloride ion attract our interest.A quasi-square coordination geometry of the Cu^Ⅱlocated in a[NOCl₂+Cl]environment was identified by multiple evidence of the bond length,bond angle,coordination geometry comparison,statistical analysis based on CCDC database,as well as computed complexation energies.This example established the method to estimate the weak interaction and coordination bonding of a chloride ion located in the perpendicular axis of a square planar Cu^Ⅱ.DFT calculations reveal bond strength order Cu-Cl>Cu-O/N>>Cu···Cl.Under different ionization,several interesting phenomena including splitting of the benzimidazole ligand,[Cu1]assembly to[Cu2]and to[Cu4],alcohol to aldehyde,Cu^Ⅱ to Cu^Ⅰ were found in the mass spectrum.Such ligand splitting,fragment re-assembling,and redox reaction reveal the great diversity of coordinative cluster in solution.The stability of MS fragments and the reactions between these fragments are combinedly studied for the first time with DFT and MS method,which open new way to more clearly verify the structure information obtained from MS spectra and would be greatly helpful for the study of similar systems.Temperature dependent magnetism,high-field EPR as well as complexation energies analysis of Cu²⁺with its surrounding atoms congruously suggests ferromagnetic behavior between the mononuclear molecules in the solid,which is induced by the intermolecular weak interaction.Presented results provide a vivid example that weak magnetic mediators of H-bonding andπ-πinteraction greatly affect the magnetic behaviors.The magnetic susceptibility was modeled with ferromagnetic coupling J(Cu_a-Cl_2a···Cu)=+0.99（30）cm^-1 and J’（π···π）=+0.35（16）cm^-1 and g=2.38（2）.HF-EPR determined the anisotropic g-values,g_x=2.24,g_y=2.16,and g_z=2.09,and hyperfine constant of A_z=450 G.It is believed the findings will benefit rational design and construction of coordination compounds with targeted magnetic properties in the future.For Cu2Cl at different voltages mass spectrometry data,new findings have been made:First,the fragmentation of Cu2Cl into the active fragment[Cu（mbm）]⁺requires less energy than Cu1（?G=477?384）.Based on this,it is guessed that it is a better precursor for post-synthetic modification.Secondly,the author combines the order of the appearance of fragment peaks under the condition of mass spectrometry with Gibbs free energy to determine the unique structure of the peak of the high nuclear number fragment.For the first time,mass spectrometry was applied to the identification of isomers.For ligands,the authors oxidized the methylol of N-methyl benzimidazole to hydrazine and obtained a hexacoordinated monocobalt compound[Co（Hmbco）₃]（Co1）.The chapter 3,by using the ligand（1H-benzimidazol-2-yl）methanol as the mian ligands obtained a series of cluster,namely Compound 5[Zn₄（Hmbm）₄Cl₄]·2CH₃OH（Zn4L4）,Compound 6/6’[Zn（Hmbm）₂（Cl/Br）₂]（Zn1）,Compound 7[Zn₄（Hmbm）₅Br₃]·CH₃OH（Zn4L5）,compound 8/8’[Zn₄（Hmbm）₆（Cl/Br）₂]·Slov（Zn4L6）.The solution behavior of single-crystal mass spectrometry of a zinc-based cluster compound（5）at different voltages was discussed,and the fragment（6-8）captured under mass spectrometry was successfully constructed.At the same time,the fluorescence properties of this compounds were explored.In addition,using Hmbm as the ligand and Cu SO₄·5H₂O as metal salt,used to solvothermal method compound 10[Cu₂₅（mbm）₁₈（SO₄）₁₄（CO₃）₂（μ₃-H₂O）₂]·Slov（Cu25）was obtained,the assembly process of25-nuclear copper-based clusters was initially explored.Compound 9,11{[2(Cu（Hmbm）₂][Cu₂（mbm）₂（SO₄）₂]}·4CH₃OH（Cu2+2）and 12{[Cu₃（mbm）₂（SO₄）]₂（CH₃OH）]}_n（Cu1D）was successfully captured in the process trace.Relying on powder diffraction,the solid phase transition process of complexes in 25-nuclear copper-based clusters was demonstrated.The compound 9{[Cu₄（mbm）₄（S₂O₇）₂（CH₃OH）₄]·（H₂O）₂}_n（Cu4）is obtained by volatilization at room temperature.Interestingly,literature investigations found that it was the first compound that formed in situ sulfate from pyrophosphate under normal temperature conditions.