Synthesis,structure,hirshfeld Analyses And Catalytic Activity Of Salamo-based Cobalt(Ⅱ),nickel(Ⅱ)and Copper(Ⅱ)complexes

As we all know,in recent years,both transition metal complexes and rare earth metal complexes have been studied more and more widely,and have been favored by many researchers in the fields of modern coordination chemistry and organic metal chemistry.Nowadays,with the rapid development of coordination chemistry,the research on the synthesis route,properties and applications of different metal complexes has become one of the hot topics of many research groups.Salamo-based complexes are derived from salen compounds.As a new derivative in the field of modern coordination chemistry,Salamo-based complexes have attracted more and more attention and research.Compared with previous salen-based complexes,Salamo-based complexes have many characteristics,such as stronger stability,better flexibility and more coordination modes.Two salicylaldehydes are linked by alkoxy bridging units,forming a new ligand configuration(-CH=N-O-(CH)n-O-N=CH-).Most transition metal and rare earth metal(Ⅱ/Ⅲ)ions can coordinate with the N2O2 cavity to obtain metal complexes with various structures.There are many hydrogen bonds in these complexes,such as C-H… and π…π interactions.Supramolecular structures can be formed by hydrogen bonding self-assembly.Metal complexes have a wide range of applications,especially in optical properties,magnetic materials,cell imaging,catalytic oxidation and other fields.In addition,on the basis of extensive research,the potential applications of Salamo-based complexes have been gradually recognized.New materials can be produced by using these complexes,which seems to be suitable candidates for further chemical modification.In this paper,according to the previous method,we first synthesized a diamine derivative:1,2-diaminoxyethane;Using 3-bromo-5-chlorosalicylaldehyde as reaction material,the best reaction temperature and solvent type and proportion were selected.The single Salamo-based ligand H2L1 was obtained.Furthermore,1,2-diaminoxy ethane was reacted with 3-bromo-5-chlorosalicylaldehyde to give the intermediate product(methoxy compound)and 4-tert-butyl-2,6-diformylphenol to give the bis(Salamo)-based ligand H3L2.In order to investigate the influence of halogen group on the structure,the reaction conditions were optimized to further select 5-bromo-3-tert-butyl-salicylaldehyde to react with 1,2-diaminoxy ethane to obtain the single Salamo-based ligand H2L3.Two metal complexes[Cu(L1)](1)and[Co(L1)(H2O)2](2)were synthesized by the reaction of ligand H2L1 with transition metal salts(copper acetate monohydrate and cobalt acetate tetrahydrate).The crystal structures of the two complexes were determined by X-ray single crystal diffractometer and characterized by elemental analysis,IR,UV-Vis absorption spectra and Hirshfeld surface analyses.Single crystal X-ray crystallography analyses showed that there were intramolecular hydrogen bonds and intermolecular hydrogen bond interactions in the complexes 1 and 2.Subsequently,the proportions of O…H/H…O,C…H/H…C,and H…H in transition metal complexes 1 and 2 can be clearly observed by Hirshfeld surface analyses and two-dimensional fingerprints.There can be shown that transition metal complexes[Cu(L1)]and[Co(L1)(H2O)2]can exist stably.Finally,the fluorescence spectra show that the ligand H2L1 has relatively strong fluorescence intensity,while the complexes 1 and 2 show fluorescence quenching.Two polynuclear transition metal complexes,[{Co2(L2)(μ2-OH)} {Co2(L2)(OAc)(CH3OH)} {Co2(L2)(u2-OCH3)} {Co2(L2)(u2-OAc)}]-4CH3 OH(3)and[Ni2(L2)(μ2-OAc)(CH3OH)]·CH2Cl2·3CH3OH(4)were synthesized by the reaction of bis(Salamo)-based ligand H3L2 with transition metal salts(cobalt acetate tetrahydrate and nickel acetate tetrahydrate),respectively.Their crystal structures were also determined by X-ray single crystal diffractometer.Through X-ray crystallography,we can clearly see the coordination environment of transition metal atoms in complexes 3 and 4 and the crystal structure of the complexes.Through research,we found that the crystal structures of transition metal atoms in complexes 3 and 4 are different,and the molecular unit of complex 3 contains four crystallographically independent and chemically different heterotrinuclear complexes(molecules molecules A,B,C and D).,while complex 4 has a binuclear structure.In addition,a series of properties of complexes 3 and 4 were characterized by elemental analysis,IR and UV spectra.According to Hirshfeld surface analyses and two-dimensional fingerprints,the proportions of O…H/H…O,C…H/H…C,and H…H of complexes 3 and 4 were observed.The ligand H2L3 binds with transition metal salts(copper acetate monohydrate,cobalt acetate tetrahydrate and nickel acetate tetrahydrate)in the presence of auxiliary ligand 4,4-bipyridine,and three complexes with different structures are obtained.Complex 5 has a mononuclear structure with the molecular formula of[Cu(L3)].Complex 6 has a dimer structure with the molecular formula of[Co2(L3)2(4,4’-bipy)].Complex 7 is a one-dimensional coordination polymer with the molecular formula of[Ni(L3(4,4‘-bipy)]n·nEtOH·n CH3COCH3.Through intermolecular interaction,a three-dimensional supramolecular structure is formed.The spectroscopic properties of the three complexes were studied in detail.The coordination ratio of metal ions to ligand H2L3 was verified by UV-Vis titration.Hirshfeld surface analyses show that when metal ions are added to the ligand H2L3,the short-range interaction will change,and H…H interaction is always the main short-range interaction.By calculating the molecular orbital energy levels of ligand H2L3 and complexes 5-7,the arrangement of electron cloud and the difficulty of electron transition were determined.The results show that the complexes 5-7 have good stability.