Design and Synthesis of Ni, Co Coordinations Based on Controlling Coordinated Water, and the Investigation of Their Magnetic Interactions

Abstract: In this thesis, two reaction systems (S1 and S2) were designed. Four SBUs(Secondary Building Units), containing controllable coordinated water molecules, and eleven coordinations were synthesized. X-ray crystallography, element analysis and IR et al were used to characterize these compounds.The magnetic properties were investigated, and the relationship between structures and magnetic properties were also discussed. The results were shown as follows:In S1.Four SBUs containing controllable coordinated water molecules were synthesized, and they are isostructural and racemism. SBUs(1):[Ni2(bipy)2(5-npa)2(H2O)2]n SBUs(2):[Ni(bipy)(5-npa)(H2O)]n SBUs(3):[Co2(bipy)2(5-npa)2(H2O)2]n SBUs(4):[Ni0.84Co1.16(bipy)2(5-npa)2(H20)2]n Five coordinations were obtained from the four SBUs by three kinds of reactions.1.Substituent reaction. Compound(1),[Ni2(bipy)2(5-npa)2(4,4'-bipy)](H2O), was synthesized by the replacement of coordinated water of SBUs(2) with 4,4'-bipy. The magnetic properties of SBUs(2) and(1) were ferromagnetism and antiferromagnetism respectively.2.Dehydration process.Compound (2), Co2(phen)2 (5-npa)2, was prepared by dehydration reaction of SBUs(3)at 200℃.Magnetic property of (2)indicates an antiferromagnetic interaction between the Co2+ ions.For SBUs(3),it shows an ferromagnetic interaction between the Co2+ ions.3.Dehydration and rehydration process.The interesting reversible phase transformations on dehydration-rehydration between the SBUs and the following discrete compounds were observed. compound (3):[Ni(bipy)(5-npa)(H2O)3]H2O compound (4):[Co(bipy)(5-npa)(H2O)3]H2O compound (5):[Nio.4Coo.6(bipy)(5-npa)(H20)3]H20This phase transforms markedly influence on their magnetic behaviours.Magnetic properties of SBUs(1),SBUs(2) and SBUs(3) indicate an ferromagnetic interaction between the Ni2+ or Co2+ ions.For SBUs(4), it shows an antiferromagnetic interaction. The similar magnetic phenomenons were also observed in the five discrete compounds, they are isostructural.In S2.Six compounds were obtained from diphenic acid, M(NO3)2, bipy and phen(M=Ni,Co). compound (6):[Ni(2,2'-dpa)(H2O)4]n compound (7):[Ni(bipy)(2,2'-dpa)(H2O)2]n compound (8):Ni(phen)2(2,2'-dpa) compound (9):[Co(2,2'-dpa)(H2O)4]n compound (10):[Co(bipy)(2,2'-dpa)(H2O)2]n compound (11):Co(phen)2(2,2'-dpa)The structural analysis and fluorescence properties indicated that the LMCT ability order was:(8)>(7)>(6);(11)>(10)>(9).For (6), (7) and (8)[Ni],the LMCT induced high spin to low spin. For (9),(10) and(11), the origin of magnetic feature at low temperature for some Co compounds was obtained by the analysis of the magnetic properties. [where bipy=2,2'-bipyridine,5-npa=5-nitroisophthalic acid,phen=phena nthroline; dpa=diphenic acid]…
Key words: coordinated water molecule; control; polystep reaction; magnetic interaction; structure-magnetism relationship

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