| In recent years,d-f heteropolynuclear metal clusters not only have complex and novel structures,but also exhibit unique properties and application prospects in the fields of catalysis,fluorescence,magnetism,biological properties and functional materials.However,the directional synthesis of d-f heteropolynuclear metal clusters is still a huge challenge.Polyhydroxy Schiff bases have multiple phenolic hydroxyl and alkyl hydroxyl coordination sites at the same time,which is the best ligand for constructing this kind of cluster,therefore,it is of great significance to study the synthesis and properties of polyhydroxy Schiff base d-f heteropolynuclear metal clusters.This thesis firstly designs and synthesizes a new type of polyhydroxy Schiff base ligand2-((3-ethoxy-2-hydroxybenzylidene)amino)-2-(hydroxymethyl)propane-1,3-dialcohol(H4L),and use this ligand to prepare homotetranuclear polynuclear metal clusters,and then add zinc salt to construct heterotetranuclear polynuclear metal clusters,on this basis,add nicotinic acid(HNA)to prepare heterohexanuclear polynuclear metal clusters.Finally,cadmium was used to replace zinc to prepare hetero-pentanuclear polynuclear metal clusters.The structure and fluorescence of these clusters was characterized,and the properties of anti-oxygen free radicals were studied.Nine polynuclear metal clusters the molecular formula is as follows:homotetranuclear clusters:[Ln4(?4-O)(HL)4CH4OH4](NO3)2{Ln=Sm(1),Eu(2)}heterotetranuclear clusters:[Ln2Zn2(H2L)4(NO32)](CH3OH)3{Ln=Sm(3),Eu(4),(Pr) (Nd(6)}heterohexanuclear clusters:[Ln4Zn2(HL)2(H2L)2(O)2(H3-Tris)2(NA)2](CH3OH)2(NO3)2 {Ln=Sm(7),Eu(8),Tris(Trometamol)}hetero-pentanuclear cluster:[Ln8Cd7(HL)6(H2L)4(NA)6(NO3)6]{Ln=Sm(9)}.Structural analysis showed that cluster compounds 1,2 were Ln4 homotetranuclear polynuclear structures,3-6 were Ln2Zn2 heterotetranuclear polynuclear structures,7,8 were Ln4Zn2 heterohexanuclear polynuclear structures,and 9 had Ln8Cd7 heteropentanuclear polynuclear structures.The rare earth metal ions in clusters 1-8 are all single-capped quadrangular prisms with nine-coordination twisted configuration,and the rare-earth metal ions of 9 have single-capped quadrangular prisms with nine-coordination twisted and ten-coordinate deformed tridecahedron configuration.The zinc ions are all five-coordinate twisted triangular bipyramid,each zinc ion has different degrees of twisting.The ligand in the multinuclear cluster has two aproton modes:HL3-and H2L2-,four bridging chelation modes:?1:?2:?1:?1:?2:?3,?1:?3:?1:?1:?3,?1:?1:?2:?1:?2,?1:?1:?2:?1:?2.The analysis of the above results shows that the structures of d-f polynuclear metal clusters can be controlled through the selection of transition metals and auxiliary ligands.The study of solid-state fluorescence properties showed that the characteristic fluorescence peaks of ligands appeared in the multinuclear clusters 1-9,which were assigned to?*??.Compared with the ligands,these characteristic fluorescence peaks of 1-9 has a significant blue shift(range:45-92nm)and enhanced,which is due to the coordination of the metal ions with the ligands,and the framework of the organic ligands are fixed by the metal ions,reducing the energy loss caused by the thermal vibration of the molecules.In the DMF solution,the characteristic fluorescence peaks of the ligands have slightly shifted,because of the solvent effect,these fluorescence peaks of 1-9 have been greatly weakened,and the fluorescence of the heteropolynuclear cluster 9 has been quenched.The multinuclear cluster 1-9 scavenged hydroxyl radicals with IC50 ranging from 2.72 to7.98?M,and 1-7 scavenged superoxide radicals with IC50 ranging from 12.4 to 16.9?M.The results show that 1-9 has excellent hydroxyl radical scavenging activity,and 1-7 has good SOD activity.Compared with the ligand(hydroxyl IC50=7.53,superoxide IC50=35.3?M),the scavenging activity of multinuclear clusters has been significantly enhanced,indicating that the addition of rare earth metals,transition metals,zinc,and cadmium is beneficial to enhance the scavenging activity of superoxide radicals,the scavenging activity intensity follows the order of heterohexanucleus>heterotetranucleus>same tetranucleus,indicating that the higher the number of nuclei,the stronger the scavenging activity. |
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