Schiff Base D/f Single Molecule Magnet Spin Center Coordination Potential Optimization

We used the diamagnetic Zn?II?/Co?III?ions and hexadentate Salen-type Schiff base?H₂L¹ and H₂L²?ligands,?-diketone ligands and hydroximic acid ligand to construct a series of heterobinuclear Zn?II?-Dy?III?and Co?III?-Dy?III?complexes.These complexes have been characterized by X-ray single crystal analysis.Some strategies were performed by changing the accordinate group around transition metal ions,the accordinate environments of Dy?III?centers,charge density distribution and molecule symmetry of spin center to improve the SMM behavior.Meanwhile,the intramolecular exchange interaction was applied to enhance the anisotropy energy barrier of complexes.The alternating-current?ac?susceptibilities and theoretical calculation were performed.The main dissertations are as follows:1.Seven lanthanide binuclear complexes with formula[L¹ZnClDy?acac?₂]?1?,[L¹Zn Br Dy?acac?₂]?2?,[L¹Zn ODy?acac?₂]?PF₆?CH₂Cl₂?3?,[L²Zn ODy?acac?₂]?PF₆?4?,[py Zn L¹Dy?acac?₂]?PF₆?5?,[3-NH₂'-pyZn L¹Dy?acac?₂]?PF₆?6?and[4,4'-bipy-?ZnL¹Dy?acac?₂?₂]?PF₆?7?,?L¹=N,N?-bis?3-methoxysalicylidene?phenylene-1,2-dia mine,L²=N,N?-bis?3-methoxysalicylidene?-1,2-diaminocyclohexane,acac=Diacet one,3-NH₂'-py=Triaminopyridine,4,4'-bipy=4,4'-bipyridyl?were synthesized.The Dy?III?-based derivatives,complex 3 and 7,showed significant single-molecu le magnet behavior under zero dc field.2.Based on above studies,a series of complexes were designed and synthesized by replacing different?-diketone,namely,[L¹ZnClDy?TTA?₂]?8?,[L¹ZnClDy?TFNB?₂]?9?,[L¹ZnClDy?Hfac?₂]?10?,[L¹ZnClDy?DBM?₂][L¹ZnClDy?DBM?₂MeOH]?11?,?DBM=dibenzoylmethane,TTA=Benzoylacetone,Hfac=Hexafluoroacetylacetone,TFNB=Naphthyl trifluoroacetone?.The magnetic measurements also showed that complex 11exhibited slow magnetic relaxation under zero dc fields.3.By replacing Zn?III?by Co?III?ions,a series of Co?III?-Dy?III?complexes were synthesized,[L²CoBr₂Dy?acac?₂]?CH₂Cl₂?12?,[L²CoCl₂Dy?acac?Cl?MeOH?]?13?,[L²CoCl₂Dy?acac?Cl?H₂O?]?14?,[L²CoCl₂Dy?NO₃?₂MeOH]?15?,and their SMMs behaviors were studied.Complexes 12-14 displayed significant slow magnetic relaxation under zero dc field.4.In order to introduce the magnetic exchange interaction into the Zn?II?-Dy?III?system,six complexes:[ZnL¹Dy?CH₃OH?]₂??-R?₂?CF₃SO₃??R=pyzha,?17?;picha,?18?;saliha,?19?;benzha,?20?;acetha,?21??,[ZnL¹Dy?CH₃CH₂OH?]₂??-R?₂?CF₃SO₃??R=quinha,?16??were synthesized with bridged ligand hydroximic acid and their SMMs behaviors were measured.5.To improve the local symmetry,metallacrown complexes 22-26 were synthesized and magnetically characterized:Ln[12-MC_{Zn?II?,quinHA}-4]?Ln=Dy?III?,?22?;Tb?III?,?23?;Er?III?,?24??,Dy[16-MC_{Zn?II?,quinHA}-8]?25?,and Dy[15-MC_{Zn?II?,quinHA}-5]?26?.6.In order to synthesize a SMM with high local symmetry and coupling interaction,the Zn?II?ion was replaced by Dy?III?ion resulted in a Dy?III?₂ complex?27?with D_4dd geometry,in which the acetate anions were employed to form the first coordination environments of the two Dy?III?ions.