The aim of this thesis is to investigate the synthesis, structures and properties of the mixed ligand tri-nickel complexes, where the ligands are dipyridylamine (Hdpa), 2,6-Bis(benzoylamino)pyridine(H2pdaBz2). The mixed ligand tri-nickel complexes, [Ni3(dpa)2(pdaBz2)2], can be synthesized at high temperature by using naphthalene as the solvent. The X-Ray structures show that there are two geometric isomers . They are named [(2,2)-trans-Ni3(dpa)2(pdaBz2)2] (1a) and [(2,2)-cis-Ni3(dpa)2(pdaBz2)2] (1b). One is that two identical ligands(dpa) are ortho, the other is that two identical ligands(dpa) are para. Both two isomers show that the middle Ni(Ⅱ) ion displayed short Ni-N(~1.9Å) bond distances which are consistent with a low spin state of Ni(Ⅱ) ions. The terminal Ni(Ⅱ) ions bonded with axial ligands are in square-pyramidal (NiN4X) environment and exhibit long Ni-N bond distance(~2.1Å) which are consistent with a high spin Ni(Ⅱ) configuration. The magnetic measurements show that the terminal Ni(Ⅱ) ions are high spin configuration, the middle Ni(Ⅱ) ion are low spin configuration. The magnetic susceptibility shows that both two complexes are antiferromagnetic interaction. The μeff value for two complexes are 2.893 B.M. and 2.635 B.M. respectively at 300K. And the coupling constant J13 are -107 cm-1and -100 cm-1 . According to the cycling voltammograms , both two complexs exhibit one reduction waves at-0.9585V (1a) and -0.9685V.