Double-stranded helicates of Ni(II), Co(II), Fe(II) and Zn(II) with oligo-α-naphthyridylamino ligand: Synthesis, structure and properties

• Published in: Polyhedron Vol. 144; pp. 75 - 81
• Main Authors: Ismayilov, Rayyat Huseyn, Valiyev, Fuad Famil, Song, You, Wang, Wen-Zhen, Lee, Gene-Hsiang, Peng, Shie-Ming, Suleimanov, Baghir A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-04-2018
• Subjects: Dinuclear complexes; Helical structures; Iron; Naphthyridine-modulated oligo-a-pyridylamino ligand; π–π interactions; π–π interactions; Iron; Helical structures; Naphthyridine-modulated oligo-a-pyridylamino ligand; Dinuclear complexes
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2017.12.034

Using tetranaphthyridyltriamine ligand, N2-(2-(1,8-naphthyridin-7-ylamino)-1,8-naphthyridin-7-yl)-N7-(1,8-naphthyridin-2-yl)-1,8-naphthyridine-2,7-diamine (H3tentra), double-stranded dinuclear helical compounds [M2(H3tentra)2(ClO4)4] [M = NiII (1), CoII (2), FeII (3), ZnII (4)] have been synthesized and structurally characterized. The geometry about the metal (II) ions was described as distorted tetrahedral, with both ligands acting as bisbidentate N4 donors. Strong π–π interactions were observed for all synthesized double stranded helicates of H3tentra ligand.
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By using tetranaphthyridyl-triamine ligand, N2-(2-(1,8-naphthyridin-7-ylamino)-1,8-naphthyridin-7-yl)-N7-(1,8-naphthyridin-2-yl)-1,8-naphthyridine-2,7-diamine (H3tentra), double-stranded dinuclear helical compounds [M2(H3tentra)2(ClO4)4] [M = NiII (1), CoII (2), FeII (3), ZnII (4)] were synthesized and structurally characterized. The single X-ray crystal structure of iron(II) complex showed that both of H3tentra ligands wrap around the metal–metal axis giving rise to a double-stranded dinuclear helical compound with Fe–Fe separation of ca. 5.326 Å. Each ligand uses two nitrogen atoms from two different napthyridine rings, to coordinate one metal centre (Fe or Fe(A)) and therefore, the geometry about the metal ions was described as distorted tetrahedral, with both ligands acting as bisbidentate N4 donors. This distortion is shown by the angles between nitrogen and iron atoms, which range from 80.45(15) to 143.32(14)°. Distorted tetrahedral environment was also proposed for the other complexes on the basis of the magnetic measurements and X-ray results. Strong π–π interactions were observed for all synthesized double stranded helicates of H3tentra ligand. The measured χMT values at 300 K for complexes 2 and 3 found larger than the expected values for two high-spin Co(II) with S = 3/2 and for Fe(II) ions with S = 2 and g = 2, which attributed to the unquenched orbital coupling.