Study On Solid-state/solution Structure Information Correlation And Assembly Process Of3d Metal Coordination Compounds Based On Benzimidazole Derivatives

3d transition metal coordination compounds have attracted much attention of researchers not only for their varied and interesting structures,also for their high potential applications in magnetism,catalysis,luminescence and gas adsorption and separation.The novel and interesting functions of coordination compounds are due to the diversity and specificity of their structures.Therefore,the synthesis and regulation of coordination compounds structures are still the research hotspot and goal of researchers.Understanding the assembly process and growth mechanism of coordination compounds is the basis for controlling synthesis.And the study of the low-dimensional coordination compounds system is conducive to understanding the construction and assembly mechanism of compounds high-nuclear and high-dimensional coordination compounds.However,chemical reactions are often affected by many factors,which make the study of assembly process extremely difficult.This prompts people to seek appropriate means and methods to explore.Although difficult,it is not impossible to study.Under the exploration of experts and researchers at home and abroad,ESI-MS has been proved to be a good means to study the assembly mechanism of coordination compounds at this stage.In this paper,a series of low-dimensional coordination compounds were constructed based on benzimidazole derivative ligands by acetonitrile solvothermal method.The solid-state/solution structure information was studied in detail by means of Single-crystal x-ray diffraction technique,ESI-MS,density functional theory calculation(DFT)and fluorescence test.The solution behavior of compound crystals under different mass spectra of ion sources was discussed in depth.The full text is divided into four chapters:In the first chapter,the background and application of low-dimensional metal coordination compounds(one-dimensional coordination polymers and transition metal clusters)are introduced.The research progress and application of ESI-MS in the assembly of and solution behavior of metal coordination compounds are mainly introduced,which provides some ideas and methods for the work of this paper.In the second chapter,four compounds,Zn1D-Cl(1),Zn1D-Br(2),Mn₂(3)and Mn₅(4)were successfully synthesized by the reaction of5-(1-methyl-1H-benzimidazole)-3H-1,2,3-triazole-4-carboxylic acid(Hbitc)with different metal salts(Zn Cl₂/Zn Br₂/Mn Br₂·4H₂O)under solvothermal conditions in acetonitrile.The four compounds were characterized by single crystal X-ray diffraction,thermogravimetry(TG),Powder x-ray diffraction(PXRD),IR and ESI-MS.Compound 1 and 2 were constructed by ligands Hbitc and Zn Cl₂/Zn Br₂,respectively.The former was a novel zig-zag one-dimensional coordination polymer and the latter was a helical one,indicating that the effects of Br and Cl with different atomic sizes on the construction of clusters were different.Compound 1 and 2 are poorly soluble in common solvents,and their structure-related fragments have not been captured in ESI-MS,but they are soluble in DMSO under the assistance of ultrasound and can be observed in ESI-MS.And when the ion source energy is 0 e V,compound 1 and 2 mainly exist in the form of[Zn(bit)]⁺/[Zn(bit)Cl₂]^-and[Zn(bit)]⁺/[Zn(bit)Br₂]^-,respectively.That is to say,they exist mainly in the form of mononuclear species.Taking compound 1 as an example,the solution behavior of 1 under different ion source energies was explored.The results show that with the increase of ion source energies,the species gradually change from low-nucleus fragments to high-nucleus fragments or reassemble,and the theoretical calculation verifies that the guess is very possible,which illustrates the step-by-step assembly of polymers from the side.The time-dependent mass spectrometry study of compound 1 showed that the ligand Hbitc chelated with zinc before decarboxylation.At 2 h,the ligand Hbitc had all decarboxylated into Hbit and formed its smallest construction unit{Zn(Hbit)Cl₂},but no higher nucleus fragments were captured,indicating the dissolution of high nucleus species.The study of luminescence properties of compound 1 shows that its luminescence originates from the properties of ligand Hbit itself;compound 3 is a dinuclear manganese compound Mn₂ with centrosymmetric structure constructed by Hbitc and Mn Br₂ in the solvothermal reaction of acetonitrile.The pentanuclear species fragments of[Mn₅^II(bit)₆Br₃]⁺were captured in its single crystal mass spectrometry,which reveals the potential of constructing{Mn5}clusters in this reaction system.Compound 4(Mn5)was successfully constructed in DMF solvothermal reaction with the same ratio of raw materials.Through time-dependent mass spectrometry analysis of compound 4,it was also observed that Hbitc decarboxylated completely to Hbit during the reaction period from2 to 4 h.When the reaction lasted for 4 h,the frame peak[Mn₅^II(bit)₆Br₃]⁺of compound 4 was captured and crystallization was observed by macro-photography,but the formation of intermediate species was not captured in the process.The formation of compound 4 is very fast,and the mononuclear species[Mn^II(Hbit)Br]⁺will soon become[Mn₅^II(bit)₆Br₃]⁺.This process also verifies that the molecular formula of compound 4 is{Mn₅^II(bit)₆Br₄}.In Chapter 3,a binuclear supramolecular compound Cu₁₊₁(5)linked by hydrogen bonds and a binuclear copper compound Cu₂(6)with a central symmetric configuration similar to Tetrafolium tetrafolium were successfully constructed by using ligand N-methyl-2-hydroxymethylbenzimidazole(Hmbm)with Cu(Cl O₄)₂·6H₂O under acetonitrile solvothermal/ambient temperature volatilization conditions,respectively.The crystallographic data of compound 5 show that the two copper ions in the structure should be one with+1 valence and one with+2 valence,and XPS tests confirm that there are two valence states of+1 and+2 in the compound 5,while the metal coordination sphere and bond level calculation show that the copper with+1 valence is a two-coordination mode and the copper with+2 valence is a plane four-coordination mode.Through the study of single crystal solution mass spectrometry of compound 5 and 6,it was found that the main existing forms of them in ESI-MS is[Cu₂^II(mbm)₃]⁺,and there is a"bottom-up"reassembly of higher nucleus species fragments,such as tetranuclear species fragments,or even higher nucleus fragments,which indicated that the system have the potential to obtain higher nucleus clusters,which inspired the author to successfully construct a tetranuclear copper cluster Cu₄(7)with vacancy cubic alkane configuration by adjusting the proportion of reactants,and also verifies the hypothesis that the system has compounds with higher nuclear number.Time-dependent ESI-MS of 7 reveals the step-by-step assembly process:[Cu(mbm)]⁺?[Cu₂(mbm)₂]⁺?[Cu₂(mbm)₃]⁺?[Cu₃(mbm)₃]⁺?[Cu₃(mbm)₄]⁺?[Cu₄(mbm)₅]⁺.Compound 5 and 6 are likely to be important fragments in the assembly process of compound 7.Ligand Hmbm showed great potential to construct higher nucleus coordination compounds in Chapter 3,so in Chapter 4 Hmbm is still used as ligand to modify metal salts to successfully construct a hexanuclear zinc cluster(8)with co-absent cubic alkane configuration by reacting with Zn(NO₃)₂·6H₂O under acetonitrile solvothermal conditions.Generally,the addition of bridging ligands is beneficial to the construction of high-core clusters.Therefore,the author added CH₃COONa as a small ligand to the synthesis scheme of compound 8,but unexpectedly obtained a tetranuclear zinc cluster Zn₄(9)with a vacancy cubic alkane.The results of single crystal solution mass spectrometry of compounds 8 and 9 show that the structures of these two compounds are unstable and exist mainly in the form of[Zn₂(mbm)₃]⁺.The solution system of compound 9 is more complex with the participation of acetate,which has a competitive relationship with nitrate and competes to coordinate with zinc.ESI-MS of compound 8 show that the ligand Hmbm and Zn(NO₃)₂ reacted immediately to form[Zn(mbm)(CH₃CN)]⁺once they met,and then assembled step by step with the reaction time to product 8:[Zn(mbm)]⁺?[Zn(Hmbm)(mbm)]⁺?[Zn₂(mbm)₂]⁺?[Zn₂(mbm)₃]⁺?[Zn₃(mbm)₄]⁺?[Zn₄(mbm)₅]⁺?[Zn₄(mbm)₆]⁺?[Zn₅(mbm)₇]⁺?[Zn₆(mbm)₈]⁺.A tetranuclear iron cluster Fe₄(10)with vacancy cubane configuration was successfully constructed when metal salts were modulated to Fe Cl₂·4H₂O.The strongest peak of[Fe^IIIFe₄^II(mbm)₆Cl₄(CH₃OH)]⁺was found in the study of its single crystal MS,which indicated that the system can construct higher clusters.This inspired the author to successfully construct one new iron cluster Fe₇₊₁₊₁(11)with stable disk configuration based on the synthesis scheme of compound 10 by changing the ratio of reactants.The above studies show that the single crystal and mass spectra of compounds at different ion source energies can help us to discover the possible species in the system,and further inspire us to help the construction of higher nucleus compounds or obtain intermediates in the assembly process of some compounds by changing reaction conditions or regulating the reaction process.