Study On The Synthesis And Modification Of Mn₁₂-Ac Clusters

Different from general mangnetic materials,single molecule magnets(SMMs)is a new kind of magnetic material,whose magnetism is not due to the effect of long range order of multiple magnetic units,but from relatively independent units.Under external magnetic fields,it shows the phenomenon of hysteresis loop.SMMs have heen considered as promising matrtials for future application field of data storage and quantum computing because of its large coereive filed,quantum tunneling of magnetization(QTM)and quantum phaseinterference,At present,it pay more attentation on SMMs associated with Mn,Fe,V Cr and other metal elements cluster,such as Mn4,Mn12,Fe8,Fe12,[Mn12O12(O2CR)14(H2O)4]is aCluster formed by tweleve Mn ions(abbreviated to Mn12-Ac),which get more attention by its high working temperature(blocking temperature Tb)and easy-modifed properties.This paper improved the traditional synthesis of the Mn12-Ac first.After that,also do some research about the modification of Mn12-Ac.We used the monoacid(Phenpxyacetic acid),the dicarboxylic acid(p-phthalic acid,or PTA)and the m-methyl red with the azo functional group(m-Methyl red)to modify Mn12-Ac.Optimized the reaction conditions,then characterized the products,discussed the photosensitive properties and magnetism of the modified.Findings are as folloes.1.The traditional synthesis method of Mn12-Ac is complex,and strict with temperature.So,we disigned method to improve.With the improvements,at room temperature,the appearance of crystal were some black square prisms,and their sizes were around 2.0×2.0×5.0mm3.The crystal were stabile.Then we used the FT-IR,XRD,E.A.TG to characterize it.2.Selected the monacid(Phenoxyacctic acid)and the diearboxylie acid(p-Phthalic acid,PTA)to modify the Mn12-Ac.then explored the synthesis process,optimized the synthesis reaction.Then we used the FT-IR,XRD,E.A.TG to characterize it.3.Choosed the m-Menthyl red with the azo functional group to modify the Mn12-Ac,discussed the influence of reaction conditions(solbents,Mn12-Ac/m-Methl rd ratio,concentration of Mn22-Ac)on the produce.Found that the reaction solvent is acctonitrik.replaced 8 carboxylic acid,the yield is 82%.Optimized the reaction conditions,then characterized the products.4.After that,study on photosensitive properties and magnetism of the modified.The result showed that the introduction of the photoisomerization of groups,to a certain extent,had an effect on the magnetic properties of Mn12-Ac.(1)Uv 10min,the structure begins to change.Uv 60min,the structure of the modified is cis,place it in invisible light after about 360min,the structure changed from cis to trans.Isomerization of cis-trans for once.(2)Curve of χMNT-T is obtained by magnetic testing,and found that uv 20min,value of χMT of modified product MA8-4 higher than the value of χMT that without illumination,probably because of uv irradiation,the azobenzene has some isomerization,leading to magnetic change a bit(value of χM-T increase).