| Metal coordination catalyzed and mediated hydro(solvo)thermal in situ ligand reactions have been widely viewed as important research field of coordination chemistry and organic synthetic chemistry.They are commonly used to discover new types of organic reactions,elucidate the reaction mechanisms and synthesize new compounds that cannot be obtained directly by traditional synthesis methods,it's a new bridge between coordination chemistry and organic synthetic chemistry.One of the primary goals in chemistry is to understand bonding and the way reactions progress.Combinations of crystallography and electrospray ionization mass spectrometry(ESI-MS)provide new ideas and new methods for studying the reaction process and mechanism of complicated systems.Discovering new hydro(solvo)thermal in situ metal/ligand reactions,tracking and studying their assembly processes and reaction mechanisms will help us to understand the essence of chemical reactions.In this paper,a series of N-rich heterocycles compounds are realized by 3d transition metal(Mn(II),Fe(III),Co(II),Cu(II)etc.)coordination catalyzed and mediated in situ ligand reactions of(1-methyl-1H-benzo[d]imidazo-2-yl)methylamine(L1)as precursor under solvothermal condition in acetonitrile.These reaction processes are tracked and studied by combining crystallography and ESI-MS technology,and the reasonable reaction mechanisms are proposed.The full text is divided into three chapters:The first chapter is the introduction.Firstly,introduces the research background and current status of in situ reaction;then,introduces the developments and applications of ESI-MS;finally,explains the significance of topic and the research content.In the second chapter,{[Co2(L4)Cl4]·2CH3CN}(Compound 1)and{[Co1.5(L2O)Cl2]n}(Compound 2)are obtained by using the organic precursor L1 assisted by Co Cl2?6H2O under solvothermal condition at 120?in acetonitrile.[Co(L1)2(H2O)Co Cl4](Compound 3)is obtained by volatilization of mother solution at room temperature,and the intermediate[Co(L1)2(H2O)Co Cl4](Compound 4)is obtained in time-dependent reaction process tracking.It is worth noting,L4 is 2,3,5,6-tetrakis(1-methyl-1H-benzo[d]imidazol-2-yl)pyrazine,HL2O is1-methyl-N-(1-methyl-1H-benzo[d]imidazole-2-carbonyl)-1H-benzo[d]imidazole-2-carboxamid-e,H2L1O is 1-methyl-1H-benzo[d]imidazo-2-formamide.The two reaction processes of starting raw material to product and intermediate to product under solvothermal condition are tracked and studied by using crystallography and ESI-MS,key mass spectrometry fragments[Co(L1)2]2+(190.56),[Co(L1-2H)2(H2O)]2+(197.55),[H(L1O)]+(176.08),[Co(L4)(H2O)2]+(695.20)and[Co(L2O)]+(723.16)are observed,according to the solid/solution structure information relevance,the possible reaction processes and mechanisms are put forward:[Co(II)+L1]?[Co(L1)2]?[Co(L1-2H)2]?[Co(L2)]?[Co(L4)]and[Co(L2O)],L2 is(E)-1-(1-methyl-1H-benzo[d]imidazol-2-yl)-N-((1-methyl-1H-benzo[d]imidazol-2-yl)methylene)methanamine.[Co(L2O)]may come from[Co(II)+L1]?[Co(L1)2]?[Co(L1O)2]?[Co(L2O)].The process tracking of the reaction of raw materials at room temperature and the control experiments of Co(II)show that the conversion of[Co(L1)2]?[Co(L1-2H)2]is not possible at room temperature,only when metal ion involved and given a certain amount of heat energy can be driven.On this basis,in order to further verify the rationality and universality of the mechanism,{[Co2(L4')Cl4](Compound 5)is obtained by using the similar ligand(1,5-dimethyl-1H-benzo[d]imidazol-2-yl)methanamine(L1'),the structure of compound 5 is similar to compound 1,L4'is 2,3,5,6-tetrakis(1,5-dimethyl-1H-benzo[d]imidazol-2-yl)pyrazine.By comparing the two processes of Co(II)coordination catalyzed in situ ligand reaction,it is find that the assembly process is consistent,which proves that the reaction mechanism proposed above is reasonable.Further,Compounds 1 and 5 can remove Co Cl2under the stimulation of water,releasing N-rich organic heterocycles compounds L4 and L4'.Preliminary exploration shows that such N-rich heterocyclic compounds may have potential applications in luminescence.In the third chapter,3d transition metal ions Mn(II),Fe(III)and Cu(II)coordination catalyzed in situ ligand reactions of L1 are described.Under solvothermal condition,[Mn2(L1)2Cl4](Compound 6),[Mn2(L3)2Cl2](Compound 7)and{[Mn2(L4)Br4]·2CH3CN}(Compound 8)are obtained by catalysis of Mn(II);{[Fe2(L4)Cl4]·2CH3CN}(Compound 9)and[Fe2(L3)2Cl2](Compound 10)are obtained by catalysis of Fe(III);{[Cu2(L4)Cl4]n}(Compound 11)and{[Cu3(L3)2Cl4]·CH3CN}(Compound 12)are obtained by catalysis of Cu(II),HL3 is2,2',2''-(1H-imidazole-2,4,5-triyl)tris(1-methyl-1H-benzo[d]imidazole).It is find that[M2(L4)]compounds can be obtained under the catalysis of Mn(II),Fe(III),Co(II)and Cu(II)respectively.Therefore,the catalytic difference and catalytic activity of different 3d transition metal ions for the same type of in situ reaction are studied by combining crystallography and ESI-MS technology in this chapter.Because of the intense reaction under solvothermal condition,it is not easy to stay in a certain intermediate state,and the catalytic activity of different metal ions can not be well distinguished.For this reason,the control experiments at room temperature are designed reasonably,the mass spectrum fragment peaks of L4 are focused by ESI-MS.Firstly,the fragment of[Mn(L4)(H2O)2]+(691.21)appear in Mn(II)system;then,the fragment of[H(L4)]+(619.27)appear in Fe(III)system;finally,the fragments of[H(L4)]+(619.27)and[Cu(L4)]+(681.19)appear in Cu(II)system;but similar fragment is not found in Co(II)system.Therefore,the activity of different 3d transition metal ions for in situ ligand reactions of the same type is Mn(II)>Fe(III)>Cu(II)>Co(II).In addition,some key intermediate fragments are obtained from the mother solution of each reaction at room temperature,such as[M(L1)2],[M(L1-2H)2],[M(L2)],[M(L3)]and[M(L4)].By comparing the single crystals and MS fragments obtained under solvothermal conditions,the reasons for the catalytic differences are analyzed.For Mn(II),Cu(II)and Co(II),the rational reaction processes are proposed:[M(II)+L1]?[M(L1)2]?[M(L1-2H)2]?[M(L2)]?[M(L4)].For Fe(III)system,firstly,L1 is oxidized by Fe(III)to aldehyde LO,then,react with L1 to form Schiff base L2 of bibenzimidazole,finally,form L4 through carbon-carbon coupling,the rational process is[Fe(III)+L1]?[Fe(L1)2]?[Fe(LO)2]?[Fe(L2)]?[Fe(L4)].Of course,there are also differences in the by-products obtained from these reactions,such as{[Co1.5(L2O)Cl2]n},[Mn2(L3)2Cl2],[Fe2(L3)2Cl2]and{[Cu3(L3)2Cl4]·CH3CN},their formations proves the path of the reaction from the side,it is helpful to put forward reasonable reaction mechanisms. |
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