Syntheses And Properties Of 2,3-Pyrazinedicarboxylate-based 3d/4d-4f Heterometallic Coordination Polymers

In this paper,by selecting 2,3-pyrazinedicarboxylic acid（2,3-H₂pzdc）as ligand,by self-assembling of 2,3-pzdc,different lanthanide ions,and different transition metal ions under hydrothermal conditions,forty metal-organic coordination polymers（CPs）were obtained.They were characterized by IR,elemental analysis,thermogravimetric analysis,X-ray powder diffraction,and X-ray single-crystal diffraction.The luminescent and magnetic properties of some complexes were studied.1.By the reactions of 2,3-pzdc,rare earth nitrates,and ferrous sulfate under hydrothermal conditions,five isostructural Fe^II-Ln^III heterometallic CPs[Ln₂Fe（2,3-pzdc）₄（H₂O）₆]·2H₂O[Ln=La（1）,Ce（2）,Pr（3）,Nd（4）,Sm（5）]were synthesized.X-ray single-crystal diffraction analysis shows that complexes 1-5 possess a three-dimensional framework with a（4·6²）₂（4²·6²·8²）（6³）₂（6⁵·8）₂ topology.The magnetic properties of complexes1-5 were investigated.2.By the reactions of 2,3-pzdc,rare earth chlorides,and cobalt nitrate under hydrothermal conditions,nine isostructural Co^II-Ln^III heterometallic CPs[Ln₂Co（2,3-pzdc）₄（H₂O）₆]·2H₂O[Ln=La（6）,Pr（7）,Nd（8）,Sm（9）,Eu（10）,Gd（11）,Tb（12）]and[Ln₂Co（2,3-pzdc）₄（H₂O）₄]·4H₂O[Ln=Dy（13）,Er（14）]were synthesized.Complexes 6-14 are basically isostructural with1-5.The magnetic properties of complexes 6-14 were investigated.Complexes 11 and 12 manifest the weak ferromagnetic interactions between Co^II and Ln^III in the low-temperature range.Complex 13 exhibits a field-induced slow magnetic relaxation behavior.3.By the reactions of 2,3-pzdc,rare earth nitrates,and cupric chloride under hydrothermal conditions,eleven isostructural Cu^II-Ln^III heterometallic CPs[Ln₂Cu（2,3-pzdc）₄（H₂O）₆]·2H₂O[Ln=La（15）,Pr（16）,Nd（17）,Sm（18）,Eu（19）,Gd（20）,Tb（21）],[Dy₂Cu（2,3-pzdc）₄（H₂O）₄]·4H₂O（22）,and[Ln₂Cu（2,3-pzdc）₄（H₂O）₄]·2H₂O[Ln=Er（23）,Yb（24）,Lu（25）]were synthesized.Complexes 15-25 are basically isostructural with 1-5.The magnetic properties of complexes 15-25 were investigated.Complex 21shows a magnetic transition between short-range ferromagnetic ordering at 60K and long-range ferromagnetic ordering below 26 K.Complex 22 displays a field-induced single molecule magnet behavior,with a U_eff value of 102.4 K.4.By the reactions of 2,3-pzdc,rare earth nitrates/rare earth chlorides,and zinc nitrate/cadmium nitrate under hydrothermal conditions,fifteen Zn^II/Cd^II-Ln^III/Ln^III CPs[Ln₂Zn（2,3-pzdc）₄（H₂O）₆]·2H₂O[Ln=La（26）,Pr（27）,Nd（28）,Sm（29）,Eu（30）,Tb（31）,Dy（32）],[Ln₂Cd（2,3-pzdc）₄（H₂O）₆]·2H₂O[Ln=La（33）,Pr（34）,Nd（35）],and[Ln₂（2,3-pzdc）₃（H₂O）₅]·3H₂O[Ln=Eu（36）,Tb（37）,Dy（38）,Ho（39）,Er（40）]were synthesized.The Zn^II/Cd^II-Ln^IIIII heterometallic CPs 26-35 are basically isostructural with 1-5.The Ln^III CPs36–40 display isostructural three-dimensional framework with a{4.6.8}{4.6².8³}topology.The luminescent and magnetic properties of complexes 26–40 were investigated.Complexes 36–38 exhibit the characteristic luminescence of the Ln^III ions sensitized by 2,3-pzdc.Complexes 32 and 38 show field-induced slow magnetic relaxation behaviors.