title: New ternary ligands consisting of an N4 bridging ligand and two terpyridines, and their Co(II) and Ni(II) dinuclear complexes. Structure, redox properties, and reaction with acid.
abstract: Two ternary ligands consisting of two 2,2′:6′,2′′-terpyridines and one N4-quadridentate μ2,η(2)-bridging ligand were synthesized. The N4 bridge is 1,4-bis(2-pyridyl)phthalazine in ligand 1, and 3,6-bis(2-pyridyl)pyridazine in ligand 2. Two Co(II) dinuclear complexes [(1)Co2(μ-OH)]3+ and [(2)Co2(μ-OH)]3+, and one Ni(II) dinuclear complex [(1)Ni2(μ-Cl)]3+ were obtained. In the crystal structures of [(1)Co2(μ-OH)]3+ and [(1)Ni2(μ-Cl)]3+, two pyridine rings are twisted around the pyridine-phthalazine bonds to avoid steric repulsion between the hydrogen atoms. The pyridine rings also showed a significant tilt from the octahedral coordination plane, which causes the large positive shift of the first reduction potentials. Upon the addition of a proton, the cobalt dinuclear complexes can release one cobalt ion selectively, and the dinuclear complexes can be easily restored by the addition of a tertiary amine.
authors: Research Center for Molecular Scale Nanoscience, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan.
authors: Hiroki
authors: H
authors: Kon
authors: Toshi
authors: T
authors: Nagata