Research Of Nitrogen Radicals Related Single-Molecule Magnets And Chiral Compounds

Radicals are a class of species which contain unpaired electrons.Owing to their intrinsic high reactivity,most radicals are not stable and easily undergo polymerization,dimerization and reactions with other molecules.By careful choosing ligands with suitable electronic and steric properties,more and more stable radicals were isolated,some of which showed significant potential in many frontiers,such as catalysis,lithium ion battery,conductive material.Combining with theoretical calculations,this thesis focuses on the research of nitrogen-based radicals related single-molecule magnets and chiral compounds.The main studies are listed as follow:1.Through the charge transfer approach,the reactions of LM^??tol??L =CH?MeC=NDipp?₂,Dipp = 2,6-iPr₂C₆H₃,tol = toluene,M = Co and Fe?with 2,2'-bipyrimidine?bpym?afforded the dinuclear Co^??1?and Fe^??3?complexes,respectively,in which the bpym moiety is in the dianion state and the transition metal ions are in+2 oxidation state.One-electron oxidation of 1 and 3 with[Cp₂Fe][BPh₄]yielded the cationic complexes 2 and 4,respectively,in which the bpym group was converted to the radical anion state.The presence of the sandwiched bpym radical anion mediates strong magnetic coupling between the transition metal ions,which makes the cobalt complex 2 a single-molecule magnet?SMM?.In contrast,the complex 1 does not have SMM property,suggesting the importance of radicals in tuning the magnetic properties.Moreover,complex 2 can be turned back to 1 by one-electron reduction,which makes them a new example exhibiting a fully reversible 'on-off' switching of SMM property in anodic and neutral states.2.By introducing the chiral binaphthyl group as a bridge,the neutral binaphthyl-diamine 5 was synthesized and its one-and two-electron oxidation reactions with silver salts were investigated.In the one-electron oxidation reaction with AgSbF₆,the monoradical cation 6 was obtained.The radical salt 6 is a mixed-valence compound and the spin density is equally located on two triarylamine groups through intramolecular ?-? interaction,as demonstrated by electron paramagnetic spectroscopy and theoretical calculations.The two-electron oxidation with Ag{Al[OC?CF₃?₃]₄} did not result in the formation of the expected diradical dication salt,but one carbon-carbon coupling occurred to give a spiro single radical 7 in which the unpaired electron is mainly at the one triarylamine group.The CD spectra show that the radicals 6 and 7 have a chiral property.