| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 94 === The new unsymmetrical ligand, 2-phenylamino-7-( -pyridylamino)-1,8-naphthyridine(H2phapany) has been synthesized by palladium-catalyzed cross-coupling of 2,7-dichloro-1,8-naphthyridine with aniline and 2-aminopyridine. The H2phapany ligands are deprotonated and wrap around the metal ions to form a linear pentanickel complex. The complex may exist as four isomeric forms with different arrangements of the orientation of the phenyl
group of the unsymmetrical ligand, i.e. the (4,0), (3,1), (2,2)-cis and (2,2)-trans forms. By using different metal salt precursors and methods of synthesis, (3,1) form and (4,0) form of pentanickel complexes could be synthesized
successfully.
X-ray structural studies for the (4,0) form reveal the absence of axial ligand of one terminal nickel atom. In compared the bond distances of Ni(4)-Ni(5) and Ni(5)-Namido with those of the (3,1) form, both of them in the (4,0) form are ca. 0.09 Å and 0.14 Å shorter than those in the (3,1) form. The magnetic measurements show that the (4,0) form has only one high spin nickel(II) atom (S=1), on the other hand, there are two high spin nickel(II) atoms, which are antiferromagnetically coupled in the (3,1) form. In the study of electrochemistry, we expected that the metal strings which are geometrical isomers may have different oxidative and reductive peaks. However, the CV spectra of the pentanickel complexes which are (3,1) and (4,0) forms show no significant difference.
In order to study the origin of these isomers, several hypotheses have been described in this research. However, the evidences are not enough, it still need more effort to solve this problem in the future.
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