Synthesis,luminescence And Scavenging Free Radical Activity Of D-f Heteronuclear Complexes With Linear Ether Schiff Base

Transition-rare earth?d-f?heteronuclear complexes have excellent properties in magnetic,luminescence and so on,which makes them of great application value in single-molecule magnet,light-emitting diodes,fluorescence sensing and other fields.However,it is still a huge challenge to reasonably control the synthesis of new structures of d-f heteronuclear complexes and the discovery of new properties that.According to the theory of soft-hard acid-base,nitrogen atoms are easy to coordinate with transition cations,while oxygen atoms are easy to coordinate with rare earth ions.Organic ligands containing mixed donor atoms can achieve the preparation of d-f heteronuclear complexes and linear ether Schiff base can play this role well.Meanwhile,rare earth complexes based on Schiff base also show good biological activity in scavenging oxygen free radicals.In this thesis,the linear ether Schiff base?H₂L?selected as the main ligand,bis?5-bromo-2-hydroxy-3-methoxy?-3-oxopentane-1,5-diamine,and nicotinic acid?HNA?or isonicotinic acid?HIN?used as the secondary ligand were reacted with zinc/cadmium salt and rare earth salt in methanol-dichloromethane system to obtain twelve d-f heteronuclear complexes containing trinuclear clusters,coordination polymers and ten-nuclear clusters by n-hexane interfacial diffusion,the molecular formula as follows:?1?d-f hetero trinuclear clusters:[Zn₂LnL₂?OAc??IN?]?NO₃??1 Ln=Sm,2 Ln=Eu,3Ln=Tb,4 Ln=Dy?and[Zn₂TbL₂?OAc??NA?]?NO₃??5?,?2?d-f heteronuclear coordination polymers:[CdLnL?IN??OAc??NO₃??CH₃OH?]_n?6 Ln=Sm,7 Ln=Eu,8 Ln=Tb,9 Ln=Dy?,?3?d-f hetero ten-nuclear clusters:[Cd₆Ln₄L₅?OAc?₅?NA?₅?CH₃OH?₅]?NO₃?₄?10 Ln=Sm,11 Ln=Eu,12 Ln=Tb?.The d-f heteronuclear complexes were characterized by elemental analysis,UV-Vis spectra,IR spectra and X-ray single crystal diffraction.1-5 are trinuclear clusters formed by rare earth ions bridging two[ZnL]secondary units,in which all zinc ions are five-coordinated distorted triangle-bipyramidal configuration,all rare earth ions are ten-coordinated distorted bicapped square antiprism.6-9 are 1D chain coordination polymers formed by the isonicotinic acid bridging[CdLnL?OAc??NO₃??CH₃OH?]secondary unit and 10-12 are ten-nuclear cluster containing six cadmium ions and four rare earth ions,in which all cadmium ions are seven-coordinated pentagonal bipyramidal geometry,all rare earth ions are nine-coordinated distorted capped square antiprism.For the Zn-Ln system,the trinuclear clusters are obtained regardless of whether the secondary ligand is nicotinic acid or isonicotinic acid.Then Cd salt replacing Zn salt,the Cd-Ln-HIN system with isonicotinic acid as the secondary ligand yielded heteronuclear coordination polymers.In addition,after replacing isonicotinic acid with nicotinic acid,the Cd-Ln-HNA system yielded hetero ten-nuclear clusters.The difference in the structure of Zn/Cd-Ln complexes is caused by the different radii of zinc and cadmium ions,and the difference in structure of Cd-Ln complexes is caused by the different secondary ligand.Solid-state fluorescence studies show that the emission peaks of?*??transition of[ML]coordination units?M=Zn/Cd?appeared in the range of 400?530nm in 1-12.Emission peaks of ⁴G_5/2?⁶H_5/2,⁴G_5/2?⁶H_7/2,⁴G_5/2?⁶H_9/2 transition of samarium ions appeared in complexes1,6 and 10.Emission peak of ⁴G_5/2?⁶H_7/2/2 transition showed the highest intensity,the corresponding fluorescence lifetime?quantum yield?was 32.29?s?0.29%??1?,21.82?s?0.02%??6?,8.55?s?10?.The fluorescence spectra of 1-12 in DMF solution only appeared emission peaks of?*??transition of[ML]coordination units,but characteristic emission peaks of rare earth ions not appeared.It is possible that the DMF molecule impeded the energy transfer from[ML]coordination units to the rare earth ions.[ML]coordination units can only sensitize samarium ion luminescence,and the heavy atom effect causes the solid fluorescent property of Cd-Sm complexes to be weaker than that of Zn-Sm complex.In summary,controlling the structure and fluorescent properties of the linear ether Schiff base d-f heteronuclear complexes have been realized by the transition metal zinc/cadmium ion and secondary ligands,nicotinic acid or isonicotinic acid.The IC₅₀ values of scavenging superoxide radical of the H₂L and 1-12 were in the range of 5.6?21.2?M and the IC₅₀ values of scavenging hydroxyl radical of the H₂L,1-5 and 10-12were in the range of 7.7?23.1?M,indicating that the H₂L and 1-12 have good biological activity in scavenging oxygen free radicals.