Interactions of Zn(II) Ions with Three His-Containing Peptide Models of Histone H2A

The interactions of Zn(ll) ions with the blocked hexapeptide models -TESHHK-, -TASHHK- and -TEAHHK- of the -ESHH- motif of the C-terminal of historic H2A were studied by using potentiometric and IH-NMR techniques. The first step of these studies was to compare the pKa values of the two His residues inside each hexapeptide calculated by potentiometric or H-NMR titrations. Hereafter, the potentiometric titrations in the pH range 5 11 suggest the formation of several monomeric Zn(ll) complexes. It was found that all hexapeptides bind to Zn(ll) ions initially through both imidazole nitrogens in weakly acidic and neutral solutions forming slightly distorted octahedral complexes. At higher pH values, the combination of potentiometric titrations and one and two dimensional NMR suggested no amide coordination in the coordination sphere of Zn(II) ions. Obviously, these studies support that the -ESHH- sequence of histone H2A is a potential binding site for Zn(II) ions similarly with the Cu(II) and Ni(ll) ions, presented in previous papers

Interactions of Trivalent Lanthanide Cations with a New Hexadentate Di-Schiff Base: New Lanthanide(III) Complexes from (NE,N′E)-2,2′-(ethane-1,2-diylbis(oxy))bis(N-(pyridin-2-ylmethylene)ethanamine)

The novel lanthanide(III) complexes [Ln(NO3)2L](NO3)·3MeOH (Ln = La 1, Pr 2) and [Ln(NO3)3L](NO3)·2MeOH (Ln = Gd 3, Yb 4), where L = (NE,N′E)-2,2′-(ethane-1,2-diylbis(oxy))bis(N-(pyridin-2-ylmethylene)ethanamine), have been obtained by direct reaction of the Schiff base ligand and the corresponding hydrated lanthanide(III) nitrates in methanol. All complexes were characterized spectroscopically and thermogravimetrically. Complex 4 was also characterized with crystallographic studies: orthorhombic P212121, a = 10.6683(14), b = 13.4752(15), c = 19.3320(26) Å. In the molecular structure of 4, Yb(III) is surrounded by all donor atoms of the Schiff base (four nitrogen and two oxygen atoms) and four oxygen atoms belonging to two bidentate chelating nitrato ligands

Supramolecular assemblies involving metal organic ring interactions: Heterometallic Cu(II)-Ln(III) two dimensional coordination polymers

Three isostructural two-dimensional coordination polymers of the general formula [Ln2(CuL)3(H2O)9]$5.5H2O, where Ln is La (1), Nd (2), and Gd (3), have been synthesized and isolated from aqueous solutions and their single-crystal structures determined by X-ray diffraction. The supramolecular interaction between the non-aromatic metallorings plays an important role in stabilizing the structure of these compounds. The thermal stability, reversible solvent uptake, electronic properties and magnetic studies of these compounds are also reported

Bis(2-phenylpyridinato,-C^2′,N)[4,4′-bis(4-Fluorophenyl)-6,6′-dimethyl-2,2′-bipyridine] Iridium(III) Hexafluorophosphate

A new bis cyclometallated Ir(III) phosphor, [Ir(ppy)2L]PF6 (ppy = 2-phenylpyridine, L = 4,4′-bis(4-fluorophenyl)-6,6′-dimethyl-2,2′-bipyridine was prepared and structurally characterized in the solid state (X-ray diffraction) and solution (1 and 2D NMR spectroscopy). The compound exhibited yellow photoluminescence (λem = 562 nm). The quantum yield Φ was solvent-dependent (5% in acetonitrile and 19% in dichloromethane solutions, respectively)

[4,4′-Bis(4-fluorophenyl)-6,6′-dimethyl-2,2′-bipyridine] [bis (2-(diphenylphosphino) phenyl) ether] Silver(I) Hexafluorophosphate

A new emissive heteroleptic Ag(I) complex formulated as [AgL(POP)][PF6] (L = 4,4′-bis (4-Fluorophenyl)-6,6′-dimethyl-2,2′-bipyridine, POP= bis (2-(diphenylphosphino) phenyl) ether) was synthesized and characterized in both the solid state (X-ray crystallography) and the solution. The compound is a yellow-green phosphor (λem = 528 nm), with moderate quantum efficiency (ΦPL = 25% in deaerated dichloromethane)

The first structural determination of a copper (II) complex containing the ligand [1-(4-((1H-benzo[d][1,2,3]triazol-2(3H)-yl)methyl)benzyl)-1H-benzo[d][1, 2,3]triazole]

The reaction of the ligand [1-(4-((1H-benzo[d][1,2,3]triazol-2(3H)-yl)methyl)benzyl)-1H-benzo[d][1, 2,3]triazole] (L) with CuCl2 in acetonitrile yields a dinuclear copper(II) complex [Cu2Cl4L2]center dot 2CH(3)CN (1.2CH3CN), which has been characterized by elemental analysis, powder and single crystal X-ray diffraction, thermal gravimetric analysis as well as IR, UV-Vis and EPR spectroscopy The crystal structure reveals that the metal coordination geometry is best described as square planar. (C) 2011 Elsevier B. V. All rights reserved

[6-(Furan-2-yl)-2,2′-bipyridine]bis(triphenylphosphine) Copper(I) Tetrafluoroborate

A new heteroleptic Cu(I) complex, [Cu(L)(PPh3)2][BF4] (L = 6-(furan-2-yl)-2,2′-bipyridine; PPh3 = triphenylphosphine), was successfully synthesized and characterized. Its molecular structure was determined using X-ray crystallography, and NMR as well as HR-ESI-MS data confirm the compound’s integrity in solution. The complex exhibits emission solely in the solid state (λem = 576 nm) and demonstrates a photoluminescence quantum yield of 2.5%

Supramolecular networks derived from hexacyanoferrates and nitrogen heterocyclic cations

Eight novel supramolecular frameworks (bpyH2)2[Fe(CN)6]·2H2O (1), (bpyH2)(H3O)[Fe(CN)6] (2), (bpeH2)(H3O)[Fe(CN)5(CNH)]·H2O (3), (bpeH2)(H5O2)[Fe(CN)6]·2H2O (4), (dabcoH2)(H3O)[Fe(CN)6]·2H2O (5), (ampyH2)2[Fe(CN)6]·2H2O (6), (tptzH3)2[Fe(CN)4(CNH)2]3·10H2O (7), and (tptzH3)[Fe(CN)6]·3H2O (8) (where bpy = 4,4′-bipyridine, bpe = 1,2-bis(4-pyridyl)ethylene, dabco = 1,4-diazabicyclo[2.2.2]octane, ampy = 4-aminomethylpyridine, tptz = tris(4-pyridyl)triazine) have been synthesized by the reaction of the nitrogen heterocycle with ferrocyanide or ferricyanide salts, under mild conditions. The supramolecular structures are constructed mainly by cooperative hydrogen bonding between the inorganic anions, the organic cations and oxoniums or lattice water molecules. There are some characteristic features that can separate the compounds in groups. Those are (a) increase of H-bonding ability by formation of supramolecular complexes, (b) formation of hydro- and dihydro-hexacyanoferrates and (c) the participation of the cationic heterocycle as constituent of the structure or as a guest. The structures are additionally discussed in terms of topology

[Pr(NO3)3L]: a mononuclear ten-coordinate lanthanide(III) complex with a tetradentate di-Schiff base

The novel praseodymium(III) complex [Pr(NO3)3L] (1), where L=N,N′-bis[1-(pyridin-2-yl)ethylidene]ethane-1,2-diamine, has been obtained by direct reaction of the Schiff base and the metal salt; the gadolinium(III) homologue has also been prepared and so far characterized only spectroscopically. The crystal structure resembles those reported for hexadentate macrocyclic Schiff bases