Study On Synthesis,Structure,Theoretical Calculation And Properties Of Salamo-type And Salamo-Salen-Salamo-type Metal(Ⅱ) Complexes

Salen-type ligands are a typical class of Schiff base compounds,which have been studied by scientists due to their existence of a N₂O₂cavity and excellent coordination ability.Salen-type N₂O₂ligands are typically prepared by Schiff base condensation reaction under heating conditions by diamine and salicylaldehyde derivatives.Methods of modifying the carbon chain,such as fixing the C=N double bond in a five-membered ring,extending the carbon chain,or fixing the carbon chain as Saloph,are all modifications to the Salen-type ligands.Recently,by introducing oxygen atoms with high electronegativity into the structure of Salen-type ligand,a new class of oxime-type compound,called Salamo-type ligand,has been formed.Salamo-type ligands are more stable and have better flexibilities than traditional Salen-type ligands.In recent years,the practice of hybridizing two or more classical ligand structures into a single ligand has been welcomed by many chemists.Studies of hybridizing Salen structures with Salamo structures into a single ligand have also made good progress.First,1,2-bis（aminooxy）ethane and 2-hydroxy-1-naphthonaldehyde were used to obtain a half-Salamo-type compound;Then it was reacted with p-methyldialdehyde to synthesize a symmetric bis（salamo）-type ligand H₃L¹.H₃L¹reacted respectively with Co（OAc）₂·4H₂O and Ni（OAc）₂·4H₂O,to synthesize dinuclear metal（II）complexes 1and 2 with similar structures of acetate and phenol-oxygen bridges.The binding ratio of the ligand and metal（II）atoms in the solid-liquid state was determined by UV-Vis titration method,and Bond Valence calculation（BVS）was used to prove that the volatile valence cobalt（II）ions were not oxidized.The ligand molecules were modified with em=gd3（bj）dispersion correction on the basis of B3LYP density functional,6-31G（d）group to optimize the structure of the ligand H₃L¹.The single-point energy of complexes 1 and 2 was calculated using the pseudopotential base group Lanl2DZ and 6-31G（d）combined.Based on this series of theoretical chemical calculations,the interaction force in the ligand and the complexes,the movable region of the complexes in the crystal lattice and other information were further studied.Finally,the fluorescence properties of ligands and complexes were studied.1,2-Bis（aminooxy）ethane and 3-methoxysalarynaldehyde were reacted to obtain a half-Salamo-type compound,Then this half-Salamo-type compound is used to react in 1:1 with p-methyldialdehyde to obtain a ligand H₂L².H₂L²reacted with Zn Cl₂·4H₂O to obtain a dicnuclear zinc（II）complex 3.H₂L²was dissolved in acetone at 55°C and mixed with a methanol/ethanol mixed solution of Ni Cl₂·6H₂O,and the complex 4 was obtained by continuing to heat and stirring and adding triethylamine dropwise.Single crystal X-ray diffraction analysis showed that zinc（II）ions occupy the N₂O₂cavity and the O₄cavity below Salamo,respectively.The consistency of the ratio of ions to the ligand in the liquid and solid phases was demonstrated by ultraviolet titration.Under the condition of heating and adding triethylamine,as the catalytic reaction occurs,the exposed formyl group undergoes an aldol condensation reaction,and the O₄environment was destroyed.Nickel（II）ions belong to metal（II）ions with high coordination numbers,which promotes the occurrence of self-assembly,forming a tetranuclear nickel（II）complex with two molecular ligands and four nickel（II）ions.Through DFT calculations of the ligand H₂L²and complexes 3 and 4,it was found that complex 4 has a large number of weak interactions within it,which promotes its stability.A deeper understanding of this feature can provide ideas for self-assembly.Finally,the zinc（II）ion complex was fluorescence titrated and it was found that chelated fluorescence quench occurred with the addition of zinc ions.On the basis of H₂L²,ethylenediamine was reacted with H₂L²to obtain a Salamo-Salen-Salamo-type hybrid ligand H₄L³,H₄L³was dissolved in dichloromethane and acetone solutions,respectively,the ethanol solution of copper（II）acetylacetonate reacted with the dichloromethane and acetone solutions of H₄L³and stood still,single crystals of complexes 5 and 7 were obtained one day later,and the ethanol solution of nickel acetylacetonate（II）was mixed with the dichloromethane solution of H₄L³and stirred,and stood after the reaction.Single crystals of complex 6are obtained after 2 weeks.The structure of complexes 5,6 and 7 was determined by X single crystal diffraction method,and both copper（II）ions and nickel（II）ions formed a planar quadrilateral coordination mode with Salen’s N₂O₂cavity,and could not coordinate with Salamo’s N₂O₂,but due to the inconsistency of metal（II）ions,the two Salamo long chains of complexes 5,6 and 7 in the thermodynamically stable state showed different extension orientations,which demonstrated that the coordination reaction process was affected by metal（II）ions and solvents.At the same time,through DFT calculations of ligand H₄L³and complexes 5,6 and 7,the configuration of ligand H₄L³under the lowest energy condition was deeply understood,and the huge torsional force required for coordination reaction at Salamo position was demonstrated,and the weak interaction force and HOMO-LUMO gap within complexes 5,6 and 7 molecules were also deeply understood.