Syntheses,Stuctures And Properties Of Single-molecule Magnets Based On Multidcntate Schiff Base Ligands

In this project,four different multidentate schiff base ligands were designed and obtained.Complexes possessing single-molecule magnet behavior and fluorescence detection properties were successfully synthesized through the solvothermal reactions of these ligands and metal salts.We found that the decrease of the steric hindrance of the ligands can lead to the formation of lanthanide metal clusters with more nuclearities.Besides,two dinuclear dyprosium complexes exhibited dual relaxation processes.We also selected the nonanuclear Tb Ⅲ compound to explore its fluorescence detection performance.The main contents are as follows.1.The utilization of a Schiff base ligand 2-((2-hydroxy-4-methoxy-benzy lideneamino)methyl)phenol(H2L1)afforded five nonanuclear lanthanide(Ⅲ)clusters of formula[H3O][Ln9(Li)8(μ3-OH)8(μ5-O)2(DMF)8]·nH2O(Ln=Eu,n=1(1);Ln=Gd,n=4(2);Ln=Tb,n=3(3);Ln=Dy,n=6(4);Ln=Ho,n=2(5)).These complexes are isomorphic and have a topology similar to diabolo.The intriguing Ln9 core is constructed by two square pyramidal units which share a vertex metal centre.Weak antiferromagnetic interactions for 2-5 were determined by measuring the dc magnetic susceptibility.DyⅢ9 cluster displays slow magnetic relaxation.Fluorescence measurements revealed intense green photoluminescence for TbⅢ9 compound.The luminescent tests showed that TbⅢ9 analogue could perform as a highly sensitive,selective and recyclable luminescence sensing material for Fe3+,CrO42-and Cr2O72-.2.The synthesis,structures and single-molecule magnetic properties are investigated for[Dy2(L3)2(HL3)(NO3)(EtOH)]·0.5EtOH(6)and[Et3NH][Dy2(L3)2(NO3)(CH3COO)2](7)(H2L3=5-chloro-2-(((2-hydroxy-3-methoxybenzyl)imino)methyl)phenol.The syhthesis and structure of tetranuclear complex[Dy4(L3)4(C6H5COO)4](8)were also discussed.The two DyⅢ ions of 6 are inequivalent in which the two kind of ligand sets were shared by two DyⅢ ions.The rationally introduction of CH3COOH in the reaction mixture used for the synthesis 6 induces the competition between CH3COO-and HL-groups,resulting in the formation of 7 with asymmetric structure.Ferromagnetic interactions have been found in both 6 and 7.Complexes 6 and 7 exhibit single-molecule magnet behavior with dual slow relaxation processes due to the possession of inequivalent metal sites.The energy barriers of 69.19 and 45.73 K for 6,and 92.77 and 72.95 K for 7 were determined.The theoretical calculations reveal that the dual relaxation processes both in 6 and 7 are mainly originated from the single-ion magnetism of two distinct DyⅢ ions with inequivalent coordination environments.3.Eight compounds of formulae[Co2Dy(L1)4(DMF)2][NO3]·HtOH(9),[Co2Y(L1)4(DMF)2][NO3]·EtOH(10),[Co3(L2)2(C7H4ClO2)2(CH3COO)2]’MeCN(11),[Co4(L1)4(DMF)2](12),[Cob(L 1)4(CH3 COO)2(MeO)4].2MeOH(13),[Co6(L2)4(CH3COO)2(MeO)4](14)[Cu2(L1)2](15),[Cu2(L2)2](16)were synthesized.The solvothermal reaction of Schiff base ligands 2-(((2-hydroxy-4-methoxybenzyl)imino)methyl)phenol(H2L1)and 2-(((2-hydroxy-4-chlorobenzyl)imino)methyl)phenol(H2L2)with metal salts gave block crystals of them.The crystal structures were discussed and magnetic properties of 13 and 14 were investigated.4.A Schiff base ligand 5-methoxy-2-(((1R,2S)-1-amino-2-indanol)imine)phenol(H2L4)was designed.Four transition metal complexes of compositions[Co2ⅡCo3Ⅲ(L4)3(CH3COO)3(CH3O)4]·3MeOH(17),[Ni2(L4)2](18),[Cu4(L4)4](19),[Zn4(L4)4]MeCN(20)were obtained under solvothermal conditions.Crystal structures of them were collected and discussed.