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Updated: Jan 5, 2026
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Ligand Structure Effects on Molecular Assembly and Magnetic Properties of Copper(II) Complexes with
Tatiana Sherstobitova1, Kseniya Maryunina1,1,2, Svyatoslav Tolstikov2
1Department of Chemistry, Graduate School of Science, Chirality Research Center (CResCent), and Institute for Advanced Materials Research, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
Abstract:
Reaction of Cu(hfac)2 with methyl- and bromo-3-pyridyl-substituted nitronyl nitroxides (L ) leads to assemble a diverse set of coordination complexes: mononuclear [Cu(hfac)2L ], binuclear [{Cu(hfac)2}2(H2O)L ], trinuclear [{Cu(hfac)2}3(L )2], pentanuclear [{Cu(hfac)2}5(L )2], and [{Cu(hfac)2}5(L )4], cocrystals [Cu(hfac)2(L )2]·[Cu(hfac)2(H2O)2] and [Cu(hfac)2(L )2]·2[Cu(hfac)2H2O], one-dimensional polymers [Cu(hfac)2L ] and [Cu(hfac)2L ] , and cyclic dimers [Cu(hfac)2L ]2, [Cu(hfac)2L ]2, and [Cu(hfac)2L ]2. The molecular structures of the obtained complexes are strongly affected by the substituent type and its location in the pyridine heterocycle. Occupation of the second position of the pyridine ring increases the steric hindrance of both imine and nitroxide coordination sites of L , which is favorable for the formation of various conformers and precipitation of complexes with different molecular structures. The pentanuclear [{Cu(hfac)2}5(L )2] and [{Cu(hfac)2}5(L )4] complexes do not have prior analogues and are valuable model objects for investigation of the mechanism of formation of various coordination polymers. The arrangement of long Cu-ONO bonds in {CuO6} square bipyramids due to the weakening nitroxide donor site in complexes, based on L , L , and L ligands, results in ferromagnetic exchange interactions between spins of Cu2+ ions and nitroxides. Complexes with substituents that do not considerably affect the coordination ability of ligands (L , L , and L ) exhibit strong antiferromagnetic exchange interactions between spins of Cu2+ ions and nitroxides.
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