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|標題:||Novel multi-spin-state linear hexanickel complexes Ni-6(11+) and their singly oxidized products Ni-6(12+) with 1,8-naphthyridine-based ligands: Tuning the redox properties of the metal string||作者:||Tsao, T.B.
|關鍵字:||metal-metal interactions;multiple bond;N ligands;nickel;electrochemistry;magnetic properties;di(2-pyridyl)amide dpa ligands;ray crystal-structure;magnetic-properties;molecular wires;2,7-bis(2-pyridyl)-1,8-naphthyridine bpnp;tripyridyldiamido dianion;compound co-3(dpa)(4)cl-2;trichromium complexes;electronic-properties;bonding interaction||Project:||Polyhedron||期刊/報告no：:||Polyhedron, Volume 26, Issue 14, Page(s) 3833-3841.||摘要:||
The new ligand, 2,7-bis(alpha-pyrimidylamino)- 1,8-naphthyridine (H(2)bpmany), was prepared by the reaction of 2,7-dichloro-1,8-naphthyridine with 2-aminopyrimidine in the presence of sodium tert-butoxide under palladium-catalyzed conditions. The linear hexanickel Ni-6(11+) complexes [Ni-6(mu(6)-bpmany)(4)X-2]Cl (X = Cl (1); X = NCS (2)) and their singly oxidized products [Ni-6(P-6-bpmany)(4)X-2](BF4)(2) (X = Cl (3); X = NCS (4)) have been synthesized, and compounds 1, 2 and 4 have been crystallographically characterized. The crystal structures of the Ni-6(11+) complexes show remarkably short Ni-Ni distances (ca. 2.22 angstrom), clearly indicative of partial metal-metal bonding in the mixed-valence Ni-2(3+) unit. This is also verified by the axial X-band EPR spectra of the complexes in solution. Magnetic susceptibility measurements reveal that the Ni-6(11+) complexes exhibit anti ferromagnetic interactions (J = -47 cm(-1)) between the terminal Ni2+ ion and the central Ni-2(3+) unit, and the Ni-6(12+) complexes exhibit weak antiferromagnetic interactions (J = -5 cm(-1)) between the two terminal Ni2+ ions. The cyclic voltammograms display three reversible redox waves at E-1/2((1)) = +0.87, E-1/2((2)) = -0.02 and E-1/2((3)) = -0.46 V for 1, and E-1/2((1)) = +0.96, E-1/2((2)) = -0.01, and E-1/2((3)) = -0.41 V for 2. The relatively low potentials of E-1/2((2)) suggest that the Ni-6(11+) complexes can be easily converted to their Ni-6(12+) forms. (c) 2007 Elsevier Ltd. All rights reserved.
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