Self-assembly, Structures and Magnetic Properties of Cobalt (II) Coordination Polymer with 2,3-Dihydroxyquinoxaline Ligand
| Autor: | PO-Hsiang Chuang, 莊博翔 |
|---|---|
| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 In this thesis, 2,3-dihydroxyquinoxaline (H2L) was chosen as a ligand to react with Co2+ metal ion under hydrothermal conditions to prepare metal – organic coordination magnetic materials. Six coordination complexes, [Co(HL)(OAc)]n (1), [Co4(L)2(O2CPh)2(OMe)2(MeOH)2]n (2), [Co(HL)2(O2CPh)] (3), [Co(L’)2(OH2)] (4), [Co3(Btz)2(D-cam)2]n (5), and [Co2(BzIm)4(D-cam)2]n (6) were successfully synthesized. In the first part of this thesis, four Co-based complexes, 1?{4 were synthesized by using 2,3-dihydroxyquinoxaline of various coordination modes. Complex 1 adopted a one-dimensional single-chain structure. Complex 2 represents a 2D layer structure. Complexes 3 and 4 were discrete molecules. In particular, the Co metal center in 3 is trivalent. Furthermore, the structures, thermal stability, and physical properties of complexes 1?{4 were discussed. In the second part of this thesis, two Co(II) based complexes 5?{6 were synthesized by 2,3-dihydroxyquinoxaline and chiral ligand D - camphoric acid under hydrothermal conditions. Interestingly, two different ligands benzotriazole (Bta) and benzimidazole (BzIm) were unexpectedly generated in situ reaction from hydrolysis of 2,3-dihydroxyquinoxaline (H2L). Bta and BzIm coordinate with cobalt to form 5 with 2D architecture and 6 with 1D architecture, respectively, and both of which have chiral space group. Furthermore, the structures, thermal stability, and physical properties of complexes 5?{6 were discussed. Moreover, we focused on the magnetic properties of complexes 1, 2, and 5. In complex 1, results from DC magnetic susceptibility measurement revealed that spin-canted antiferromagnetic interactions within the CoII ions. The susceptibility also showed weak ferromagnetic interaction at low temperature. In addition, the ZFC-FC magnetization and hysteresis loop data confirmed that 1 exhibits single chain magnet of antiferromagnetic spin-canting behavior at low temperature. Complex 2, its DC magnetic susceptibility, ZFC-FC magnetization were also studied. These data indicated the divergence phenomenon of 2 below 12 K. The hysteresis loop of magnetization vs field at 10 K could also be observed. According to the AC magnetic susceptibility and hysteresis loop, we further confirmed that spin-glass behavior of 2 from spin-canting magnetic interaction. In complex 5, results from DC magnetic susceptibility measurement revealed that antiferromagnetic interactions within the CoII ions. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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