Synthesis And Characterization Of Anionic Spin Crossover Molecule Magnetic Materials

Spin crossover complexes have ideal molecular bistability,and the spin state of the transition metal can switch between high spin(HS)and low spin(LS)by external disturbances(eg temperature,pressure,magnetic field,illumination,etc.),which have a potential application in the thermal display,optical switches,pressure sensors and information storage.Therefore,it has been one of the hot spots for chemical and physical workers to design and synthesis new magnetic bistable materials.At present,the vast majority of spin crossover compounds are cationic compounds,its properties can be controlled by different counter anions.,while the anionic SCO compounds that are regulated by cations are less studied.The introduction of sulfonates into ligands has the following advantages:1)Sulfonate has a higher negative valence state after deprotonation;2)it can form abundant hydrogen bond interactions with counter cations;3)The modification of the sulfonate is far from the coordination atom and does not directly affect the formation of NO-Fe(?)nucleus and its six coordination configuration;4)The benzene ring contains multiple functional modification sites,we can control its properties through the structure,so it has a good research value.Therefore,we get a series of anionic SCO compounds by introducing sulfonic acid groups into the Schiff base ligands and study the crystal structure and magnetic properties.The main achievements of this paper are listed as below:1:Sulfonated anionic spin crossover-compounds.In this paper,8 sulfonated anionic salicylaldehyde Schiff base-Fe? spin crossover complexes were synthesized based on two kinds of ligands:sodium salicylate(HsalSO3Na)and 8-aminoquinoline-5-sulfonic acid(8-aqSO3H).Compounds 1-4:[Fe(qsalSO3)2]·X(X=8-aminoquinoline,Imid,Na),compounds 1,2,3 exhibit mutant spin crossover properties,and compound 2 has 11K Hysteresis width,compound 3 has a hysteresis width of 3K.But because of the differences of counter-cation and solvent molecules different,the show a different magnetic behavior.The size and volume of a counter cation type determines the distance between the cation and the central metal ion;Hydrogen bonds interactns between solvent molecules and the compound can affect the spin transition,due to the presence of hydrogen,compounds are more likely to spin crossover behavior of mutations.Compound 5-8:[Fe(X-qsalSO3)2]Y(X=Br,Cl,Cl2,Y=TEA,Pyridine),exhibited a gradual spin crossover properties.Because the different spatial arrangement of the different substituent atoms,the different electron-withdrawing ability and the different repulsion of the ligand to the metal atom,compounds 6-8 exhibit different spin-crossing properties.2:Sulfonated spin crossover compounds with electric neutrality.In the process of exploring the effect of sulfonate groups on the compounds,we also obtained 3 cases of electrically neutralized sulfonated salicylaldehyde Schiff base-Fe? spin cross-compounds 9-11.Compound 9 is quadratic and exhibits incomplete gradual spin-crossing behavior.Compound 10 is binuclear and exhibits a high spin state over the entire temperature range due to coordination of central ions and water molecules in a weak ligand field,,and no spin crossover phenomenon was observed.Compounds 11 were Fe ? spin crossver compounds,which showed incomplete morphological spins.3:Heteronuclear multi-step spin crossover compounds.We synthesized one case of heteronuclear spin crossover Compound 12:[Fe(sapaSO3)2]2.It consisted of the addition of negatively charged[Fe(sapaSO3)2]-and the positive charge[Fe(dpa)2]+,and compound 12 exhibits an incomplete gradual spin transition behavior over the entire temperature range.