| Transition metal Schiff-base complexes had a wide application in the field of catalyticasymmetric synthesis. In particular, the Jacobsen-Katsuki epoxidation system, marked byMnIII（salen*） structure(salen*=N，N’-bis（salicylidene）一（chiral ethylenediamine dianion）,had emerged as a highly reactive and a highly enantioselective catalytic system for theasymmetric epoxidation of unfunctionalized alkenes. Polyoxometalates （POMs）, as one kindof significant metal-oxygen clusters with O-enriched surfaces, had many properties that makethem attractive for applications in catalysis, biology, magnetism, optics, and medicine. In thispaper, nine new compounds based POM and Schiff-base have been synthesized via mixedsolvent methods, and also be characterized by elemental analyses, IR, TG and X-ray singlecrystal diffractions. The electrochemical behavior, electrocatalytic activities, potocatalyticactivities and catalytic asymmetric epoxidation of the compounds have been investigated.1. We have successfully synthesized six compounds based on Schiff-base viaconventional mixed solvent method. Namely，[Mn（salen）（CH3OH）2]3[PMo12O40]（1）[Mn（salen）（CH3OH）2]3[PW12O40]（2）[Mn（salen）（CH3OH）2]4[SiW12O40]（3）[Mn（salen）（H2O）]2[Mn（salen）（H2O）][PW12O40]（4）[NH（CH2CH3）3]2[Mn（salen）（CH3OH）]2[SiW12O40]·2CH3OH （5） and[（Cu（salen））2Cu（H2O）]2[SiW12O40]（6）（H2salen=N,N’-ethylenebis（salicylideneimine））. Wehave investigated the influence of the synthesis condition to the structure. In addition, we alsoinvestigate the electrochemical behavior, electrocatalytic activities, potocatalytic activities ofthe compounds.2. The introduction of chiral Mn-salen obtained through chiral cyclohexanediamine intoPOM systems led to the isolation of7and8.[Mn（salen）（CH3OH）（H2O）]2[Mn（salen）（CH3OH）](PX12O40)]（X=Mo for7and W for8）（H2salen （-）-（R,R）-N,N’-bis（salicylidene）-1,2-cyclohexanediamine）. Compound7and8represent two examples of chiral POM-based materials utilizing enantiopure Schiff baseligands. We discuss the potocatalytic activities and catalytic asymmetric epoxidationproperties of compounds.3. The enantioselectivity is sensitively effected by the3,5-substituents of the the salenrings. In order to improve the enantioselectivity, compound9was obtained by3,5-bis（1,1-dimethylethyl）-2-hydroxy-benzaldehyde instead of salicylaldehyde. Single-crystal X-ray diffraction analyzes reveal that compound9crystallizes in the chiralspace group P21and Flack factoris0.10（7）. |
PDF Full Text Request