The Molecular Design And Magnetic Research Of The Double Molecular Switch

The research of new functional magnetic materials is too hard to meet the increasing need for application. Researchers’ interest is triggered by the significant magnetic anisotropy and higher spin-reversal barrier(Ueff) of the Dy(Ⅲ) molecular magnet that is crucial in the application of such material in the field of nanoscale electronic devices, sensors and high-density data storage media at the molecular level. The prospect of the application in molecular electronics has been attracting particular concern on researching spin-crossover(SCO) complexes. The coexistence of Dy(Ⅲ) molecular magnet and SCO in a compound simultaneously is still unexploited until work.Herein, we chose two kinds of N-donor ligands and two kinds of O-donor ligands, respectively, preparing four crystals of {[Co][Dy]} system. According to the magnetic determination, these four crystals have spin-crossover phenomenon. Further to demonstrate the occurrence of the SCO phenomenon for this four complex, we prepared four crystals of {[Co][Y]} system using the diamagnetic Y(Ⅲ) ion to replaced the Dy(Ⅲ) ion by the metal-isolated [3d]-[4f] charge-balanced method. The magnetism of them demonstrated the SCO exist in the Dy(Ⅲ) ion complex. And we obtained four double molecular magnetic switches. Further,it disclosed that we can synthesize crystals with different structure and diverse magnetism, when we tuned the ratio of the salt reactant, or adjust the ligand in the same reaction condition. The detailed contents are as follows:(1) We successfully synthesized four complexes by using benzoic acid and 4’-(4-bromophenyl)-2,2’:6’,2’’-terpyridine as bridging ligands. Furthermore, those complexes’ crystal structures were analyzed and their magnetic properties are characterized. The analysis shows that complex 2 are isomorphous compound of 1. Adjusting the salt reactant, we obtained complex 3 and 4, which are isomorphous compounds. Notably, complex 2 and complex 4 are obtained by the diamagnetic ion replaced method, using the Y(III) ion to replace Dy(III) ion in complex 1 and 3, respectively. Complex 1 and 3 show molecular magnetic properties with spin-crossover phenomenon, which is demonstrated by the magnetism of complex 2 and 4, respectively. And 3 show single ion magnetic properties.(2) We obtained complex 5 and 6 with 3-nitrobenzoic acid ligand and 4’-(4-bromophenyl)-2,2’:6’,2’’-terpyridine ligand. Complex 6 was synthesized by the diamagnetic ion replaced method of Y(Ⅲ) ion to replace Dy(Ⅲ) ion in complex 5. Structural features and magnetic properties were studied for them. Complex 6 is isomorphous compound of 5. And complex 5 is molecular magnet with spin-crossover phenomenon demonstrated by the magnetic properties of complex 6.(3) Using the benzoic acid ligand and 2,2’:6’,2’’-terpyridine ligand, we synthesized complex 7 and 8. Complex 8 was synthesized by using Y(Ⅲ) ion to replace Dy(Ⅲ) ion in complex 7. Their structural features and magnetic properties were studied. Complex 7 is typical single molecular magnet with spin-crossover phenomenon demonstrated by the magnetism research of 8.