不對稱三核混金屬串與萘啶二胺配基之系列錯合物之合成、結構與物理性質研究

Abstract

Our group was devoted to the research of metal string complexes. We believe that the thinnest metal wire may be applied to practical applications in the future. The dipyridylamide ligand (Hdpa) has been used to stabilize homo-trinuclear metal string complexes. A series of homo-trinuclear M3(dpa)4X2 complexes have been studied in detail in past decades. A new type of heterometallic framework, combining in a linear arrangement with a ruthenium dimer and a third metal atom, either Cu or Ni has been synthesized and studied thoroughly. The metal frameworks of Ru2Cu(dpa)4Cl2, of its mono-oxidized counterpart [Ru2Cu(dpa)4Cl2]PF6, and of their nickel homologues, Ru2Ni(dpa)4Cl2 and [Ru2Ni(dpa)4Cl2]PF6 are nonsymmetric, in spite of a severe disorder affecting the metal positions. This nonsymmetric structure was further confirmed by NMR spectroscopy. The [Ru2M]6+ framework of Ru2Cu(dpa)4Cl2 and Ru2Ni(dpa)4Cl2 was shown from spectroelectrochemical analysis and DFT calculations to exist in the form of a mixed-valent [Ru2]5+ moiety coupled to a formally M+ hetero-metal. The magnetism and redox chemistry were also studied in this work. The study of naphthyridyl modified polypyridylamide analogues is a new direction in our group. Many interesting properties have been unveiled in our recent research. Naphthyridyldiamide ligand is one of the analogues. Studying the metal complexes formed with this ligand helps us to understand more about the characterizations of these series ligands. Ni4(DAniDANy)4 and [Ni4(DAniDANy)4]PF6 has been synthesized. Structure analysis of [Ni4(DAniDANy)4]PF6 shows the decreasing of metal-metal bond lengths which corresponds to oxidation of the metal-based sigma anti-bonding. The strong IVCT band in UV-VIS spectrum was assigned to the one electron excitation from the occupied σ* to the unoccupied σ* orbital. EPR spectrum and magnetic susceptibility study shows that this complex has one unpaired electron and located on metal ions. DFT study on both complex Ni4(DAniDANy)4 and [Ni4(DAniDANy)4]PF6 is consistent with the experimental result. Hetero asymmetric tetranuclear Ru2Ni2(DAniDANy)3(OAc)2Cl was successfully synthesized. The UV-VIS spectrum of Ru2Ni2(DAniDANy)3(OAc)2Cl shows IVCT band at 890nm which is similar with [Ru2]5+. Magnetic and DFT studies show that the three unpaired electrons delocalized over the ruthenium ions. OTTLE study shows that the IVCT band does not disappear in both oxidation and reduction process. The reduction and oxidation processes occur on the Ni2 moiety. We also synthesized the [Ru2Ni2(DAniDANy)3(OAc)2]PF6. Structural analysis shows that the removal of axial ligand results the contraction of Ni-Ni, Ni-Ru and Ru-Ru distances. This can be explained by the fact that the d orbital energy of Ru2 and Ni2 is different. The coordinated chloride will raise the energy of Ru2 and causes the poor overlap between dimers. When the axial chloride was removed, the overlap of σ orbitals becomes better and the bonding interaction enhances. The cluster compounds, ferromagnetic Co3(DAniDANy)3 and antiferromagnetic Ru2(Hdphdany)2(dphdany)2, were studied due to its interesting magnetic ehavior. The magnetic orbitals of Co3(DAniDANy)3 and Ru2(dphdany)2(Hdphdany)2 consist of metal-ligand antibonding. In both complexes, the ligand directs the antiferromagnetic coupling via superexchange between neighboring nitrogen atoms. The origin of the observed ferromagnetism in Co3(DAniDANy)3 is due to the orthogonal magnetic orbitals of central and terminal Co ions.