Study On The Synthesis, Structure And Properties Of Single Ion Magnets Based On Chelating Phosphine-oxygen Ligands

Since the first single-molecule magnet[Mn₁₂O₁₂?O₂CMe?₁₆?H₂O?₄]has been reported,single-molecule magnets have received extensive attention because of their small unit size,easy sythesis,size and quantum effects.With the continuous development of magnetic theory,single-ion magnets have caught much attention because of their simple structure,easy design and improvement,and the replacement of multi-nuclear magnetic complexes.Rare earth ions have great magnetic anisotropy due to their 4f orbital angular momentum.Therefore,rare earth single-ion magnets have attracted the attention of researchers.Since the first report of earth single-ion magnets[Pc₂Ln]^-TBA⁺,the field of rare earth single-ion magnets has achieved rapid breakthrough and development.With the advancement of relevant theories,rare earth single-ion magnets with high energy barrier and high blocking temperature are constantly being reported.The single-ion magnets[Dy?Cpttt?₂][B?C₆F₅?₄]and[?CpiPr₅?Dy?Cp*?][B?C₆F₅?₄],which were reported in 2017 and 2018,respectively,refreshed the record of effective energy barrier and blocking temperature at that time.The Co???ion has a half-integer spin ground state and can effectively suppress the quantum tunneling effect.In addition,the Co???ion has a strong first order spin-orbit coupling effect and therefore has a large magnetic anisotropy.Since the first two Co???single-ion magnets[{ArNdCMe}₂?NPh?]Co?NCS?₂ and[{ArNdCPh}₂?NPh?]Co?NCS?₂ have been reported,Co???single-ion magnets has received wide attention.Therefore,many Co???single-ion magnets have been reported rapidly,which makes that Co???single-ion magnets the most important transition metal single-ion magnets.The properties of phosphine oxide complexes are mainly reported in the field of luminescent and catalytic properties.The magnetic properties are reported very rarely.Especially,the magnetic properties of 9,9-dimethyl-4,5-bis?diphenylphosphino?xanthene oxide complexes,whose ligand was used in this paper,has not been reported before.Herein we describe the syntheses and magnetic properties of five xantpO-based complexes.In Chapter 2,we report the crystal structures of two Co???complexes[CoL?NCE?₂]?E=S?1?and O?2??of xantpO.These two complexes are the first reported d-blocKSIMs supported by a phosphine oxide ligand,who provides different ligand field than the corresponding phosphine ligand.Magnetic property measurements show different slow magnetic relaxation behaviours of the two complexes.Fits to the magnetic data and ab initio CASSCF calculations reveal opposite magnetic anisotropies for the two complexes which arise from the small geometrical changes of the Co ions and the different ligand fields imposed by the two terminal ligands NCS^-and NCO^-.In Chapter 3,we report the crystal structure of three xantpO rare earth complexes[Dy?L?2Cl2]Cl·THF·H2O?Ln=Dy?4?,Er?5?,Yb?6??.Magnetic properties measurements indicate that all three complexes exhibit slow magnetic relaxations at low temperature.While the single-molecule magnet properties of 6 are the best,which possesses both Orbach and Raman relaxation processes under a 600 Oe dc field.