Construction And Magnetic Properties Of Fe^?/fe^?N₄O₂ Type Complexs

In this thesis,with the purpose of constructing multi-nuclear spin crossover(SCO)compounds and fluorescence-spin crossover bifunctional complexes,a series of the mononuclear and binuclear Schiff base ligands with NNO donor were designed and synthesized.Series of mononuclear and dinuclear Fe^II/Fe^IIIN₄O₂ complexes were successfully constructed through rational ligand modification and substituent modifications,the crystal structure,spectroscopic properties and magnetic properties of obtained compounds have been systematically studied.The main results are as follows:1.Totally 21 hexacoordinate octahedral compounds with N₄O₂ donor have been synthesized from series binuclear tridentate Schiff base ligands with N,N,O donor sets.The above-mentioned compounds include 18 Fe^IIN₄O₂ type compounds in a high-spin state and 3 Fe^IIIN₄O₂ type compounds by the investigation of magnetic properties.Complex 21 exhibited a gradual incomplete spin crossover phenomenon at room temperature,and complex 11 and 13 exhibited low spin state.Combined with the crystal structure and magnetic properties of the compounds,the effect of substituents and the species of counter anion on the magnetic properties were systematically studied.Meanwhile Schiff base acylhydrazone ligand has keto and enol coordination modes.The keto can exist stably in solution while the enol can exist stably when participating in coordination.The field strength of the ligand is weaker in the keto tautomer than in the enolate form.Therefore we can realize the transition between LS-HS by adjusting the coordination mode of Schiff base acylhydrazone ligand.2.Pyrene is one of the most widely studied organic chromophores with the advantages of high fluorescence efficiency and easy modification,meanwhile the detection of fluorescence signals is relatively sensitive and the means of characterization are relatively simple.Therefore,fluorescence-spin crossover bifunctional compounds have attracted lots of research attention.Based on the design of pyrene pyridyl arohydrazone ligands,7 Fe^IIN₄O₂ type compounds,3 Co^IIN₄O₂ type compounds and 1Zn^IIN₄O₂ type compound were synethesized.Magnetic susceptibility measurements revealed that complex 23 presents a gradual spin crossover and complex 26 exhibits two-step spin crossover behavior.Ligand substituent is one of the effective methods to adjust the magnetic properties of compounds.Comparing their crystal structure and magnetic properties,it is concluded that the substituent effect on the ligand field strength is as follows:-H>-CH₃>-Br.The N ortho-substituent on the amide will also affect the magnetic properties of the complex to a certain extent.When the substituent changes from-H to-CH₃,the ligand field strength increases,causing the complex to exhibit two-step spin-crossing.Therefore,the magnetic properties of the complex can be adjusted by changing the type of the substituent at this place.3.Two flexible phenolamine ligands with N₂O₂ donor were synthesized by Mannich reaction,and imidazole was used as a co-ligand to obtain two Fe^IIIcompounds with N₄O₂ coordination environment.Magnetic susceptibility measurements revealed the compounds are both in the high spin state.