| Summary: | 碩士 === 國立臺灣師範大學 === 化學系 === 99 === In order to mimic the Ni-SOD, four nickel complexes, [Ni(H2PPCM P)](ClO4)2 (1), Ni(PPCMP) (2), [Ni(H2IPCMP)](ClO4)2 (3), and Ni(IPC MP) (4), with a bulky ligand , H2PPCMP or H2IPCMP were synthesized and characterized by X-ray diffraction, UV/vis, and 1H-NMR spec- troscopies, and cyclic voltammetry. Such five-coordinate nickel comple- xes containing a mixed thioamide/pyrrolidine ligand were rare in literature.
Complexes 2 and 4 were the deprotonated products of complex 1 and 3, respectively, and expected to form Ni(III) complexes. However, the irreversible redox behavier was observed for complexes 2 and 4 suggestind that both complexes could not form the stable Ni(III) complexes.
Complexes 1 and 3 are only varied by an electron-accepting to an electron-donating ligand, but their chemical properties are quite different. The λmax appears to reflect the donating strength of the ligand. The λmax of 3 is at 362 nm while that of 1 occurs at 353 nm in CH2Cl2. A reversible NiIII/NiII redox couple was observed for complex 3 at 0.836V versus Fc/Fc+ with a ΔEp of 87 mV; whereas, a quasi-reversible NiIII/NiII redox couple was observed for complex 1. This can be easily explained by the fact that the stronger N-H bond of thioamide of 3 results a considerably more reversible oxidation potential and no decomposition was occurred through oxidation process. This result implies that the electron-donaing H2PPCMP better stabilizes the Ni(III) complex after oxidation.
|
|---|
