Synthesis,Circular Dichroism And Magnetic Circular Dichroism Of Chiral Rare Earth-Transition Metal Clusters

Chiral rare earth-transition metal clusters have attracted considerable attention due to their wide applications in asymmetric catalysis,optical materials and enantioselective synthesis.At present,the synthesis of chiral rare earth-transition metal clusters is still a challenging subject in this field,especially rare earth-transition metal clusters with enantiomeric structure.Therefore,the preparation and properties of new chiral rare earth-transition metal clusters have important scientific significance for the development of chiral multi-functional materials.Four chiral rare earth-transition metal clusters R/S-Co₄Ln₃,R/S-Cu₆Ln₃,R/S-Cu₁₂Ln₆ and R/S-Cu₂₄Ln₆ were synthesized by using three chiral Schiff base ligands.Their crystal structures were accurately analyzed and their magnetic,circular and magnetic circular dichroism were preliminarily explored.The details are as follows:1.Synthesis,structure analysis,circular dichroism and magnetic circular dichroism of chiral rare earth-transition metal cluster R/S-Co₄Ln₃.We synthesized a new chiral ligand-?R/S?-N-?2-hydroxy-3-methoxybenzyl?-1,2-propanediol by linking o-vanillin with?R/S?-3-amino-1,2-propanediol,and then refluxed it with metal salts to obtain four chiral rare earth-transition metal clusters.Crystal data show that the system belongs to chiral P3221 space group.The CD data showed that the system had exciton splitting,charge transfer transition and d-d transition of Co²⁺_ions,which confirmed the chiral and chiral transfer of the system.The system also exhibited significant MCD signals confirming the existence of the magnetic-optical effect of the system.2.Synthesis,structure analysis,circular dichroism and magnetic circular dichroism of chiral rare earth-transition metal cluster R/S-Cu₆Ln₃.We synthesized a new chiral ligand-?R/S?-N-?2-hydroxy-4-methoxybenzyl?-1-butanol by linking 2-hydroxy-4-methoxybenzaldehyde with?R/S?-2-amino-1-butanol,and then refluxed it with metal salts to obtain four chiral rare earth-transition metal clusters.Crystal data show that the system belongs to chiral P2₁2₁2₁ space group.The three twisted quadrilateral Cu₂Ln2 units form a Cu₆Ln₃ structure by sharing Ln³⁺ ions.The CD data showed that the system had charge transfer transition and d-d transition of Cu²⁺ ions,which confirmed the chiral and chiral transfer of the system.The system also exhibited significant MCD signals confirming the existence of the magnetic-optical effect of the system.3.Regulated synthesis,structural analysis,circular dichroism and magnetic circular dichroism of chiral rare earth-transition metal clusters R/S-Cu₁₂Ln₆ and R/S-Cu₂₄Ln₆.We selected a single chiral ligand?R/S?-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid to synthesize two kinds of chiral rare earth-transition metal clusters——R/S-Cu₁₂Ln₆ and R/S-Cu₂₄Ln₆ by anionic template method and different metal salts.Crystal data show that both systems belong to R3 space group.For the R/S-Cu12n6 system,six Ln³⁺ are connected together by eight ?₃-OH to form an octahedral unit and are shared by six peripheral Cu₂Ln units to form a Cu₁₂Ln₆ structure.For the R/S-Cu₂₄Ln₆ system,six triangular LnCu₂ cells are connected to the six vertices of the internal octahedral cage by a total of six Ln³⁺ ions to form Cu₂₄Ln₆ structure.Different anions cause different metal core structures in the two systems.The CD data of the two systems showed the ?-?*transition of the ligand benzene ring and the d-d transition of the Cu²⁺_ion,which confirmed the chiral and chiral transfer of the system,and the MCD data of both showed obvious signals confirming the existence of the magnetic-optical effect of two systems.