Design And Synthesis Of POM-based Single Molecule Magnets

Single-molecule magnets （SMMs） have attracted great attention due to the potentialapplication in the area of high-density magnetic memories and quantum computing devices.Nowadays, the design and synthesis of polyoxometalate （POM）-based SMMs is becoming ahot topic in POM chemistry. The aim of this thesis is to design and synthesis of newPOM-based SMMs. Based on various synthetic strategies summarized from the publicationsin recent five years, a series of new POM-based hybrid compounds with SMM or potentialSMM behaviors have been synthesized. The syntheses, structures and magnetic properties ofthese compounds were investigated. In addition, the synthetic strategies and rules were alsostudied.1. Eight new POM-based Shciff-base hybrids have been isolated by the reaction of{TM^IILn^III}（TM=Ni or Cu） Schiff-base complexes and different POM units. In thesestructures, POM can be viewed as structure-directing agents. Magnetic studies reveal thatcompound3and6are the first POM-supported3d-4f heterometallic SMMs.Na₄[CuL¹]₂[Mo₈O₂₆]·6DMF （1）L1=1,3-propanediylbis（2-iminomethylene-6-methoxy-phenol）Na₃[Ni2L2K（H₂O）]2[IMo₆O₂₄]·3H₂O （2）[{CuTbL（H₂O）₃}₂{IMo₆O₂₄}]Cl.2MeOH.8H₂O （3）[{CuDyL（H₂O）₃}₂{IMo₆O₂₄}]Cl·2MeOH·8H₂O （4）Na[{CuGdL（H₂O）₃}₂{IMo₆O₂₄}]Cl₂2MeOH8H₂O （5）[{CuTbL（H₂O）₂}₂{AlMo₆O₁₂（OH）₆}₂]·MeOH·10H₂O （6）[{CuDyL（H₂O）₂}₂{AlMo₆O₁₈（OH）₆}₂]·MeOH·8H₂O （7）[{CuGdL（H₂O）₂}₂{AlMo₆O₁₈（OH）₆}₂] MeOH10H₂O （8）L=N, N’-bis（3-methoxysalicylidene）ethylene-1,2-diamine2. When α-Keggin-type polyanions [PMo₁₂O₄₀]^3-were used as magnetic diluting agentsto disperse the mononuclear lanthanide-pridine-N-O coordination complex units, five newionic crystal compounds based on [Ln（bpyno）₄]3+and [PMo₁₂O₄₀]3-units were prepared.Magnetic measurements indicate that compound10exhibits frequency dependent ac magneticsusceptibilities indicative of slow relaxation of the magnetization and possible SMMbehaviors.[Dy（2,2’-bipyridyl–N-N’-dioxide）₃（H₂O）][PMo₁₂O₄₀]·H₂O·CH₃CN （9）[Dy（bpyno）₄][PMo₁₂O₄₀]·2H₂O （10）[Tb（bpyno）₄][PMo₁₂O₄₀]·2H₂O （11）[Er（bpyno）₄][PMo₁₂O₄₀]·2H₂O （12） [Ho（bpyno）₄][PMo₁₂O₄₀]·2H₂O （13）bpyno=4,4’-dimethyl-2,2’-bipyridyl–N, N’-dioxide3. When [As₂W₁₉O₆₇（H₂O）]^14-were used as multi-dentate inorganic ligands to react withvarious lanthanides cations, three new one-dimensional POM-based lanthanide complexeswere isolated. The magnetic and luminescent properties of compound14and15have beeninvestigated, but no SMM behaviors were found. The possible reason was predicted.Na₁₀[Tb₆（H₂O）₂₂{As₄W₄₄（OH）₂（proline）₂O₁₅₁}]·20H₂O （14）Na₁₀[Dy₆（H₂O）₂₂{As₄W₄₄（OH）₂（proline）₂O₁₅₁}]·25H₂O （15）Na₁₀[Nd₆（H₂O）₂₆{As₄W₄₄（OH）₂（proline）₂O₁₅₁}]·31H₂O （16）...