The use of trans-4-cotininecarboxylate to construct a polymeric copper(II) azido complex: Hydro(solvo)thermal synthesis, structure and magnetic properties

A new pyridyl-carboxylate ligand, the anion of trans-4-cotininecarboxylic acid, HL, 1, has been used to prepare a new polymeric copper(II) complex, [CuLN₃]_2n, 2, based on a [CuLN₃]₂ dimeric building block. The single crystal structures of both 1 and 2 have been determined and 1 has been found to be in its zwitterionic configuration. The structure of 2 is a one-dimensional tape-like polymeric structure based on an end-on azido-bridged binuclear [Cu₂N₃]₂ backbone moiety. Magnetic studies reveal that 2 is close to paramagnetic from 2 to 300 K with a Curie constant of 1.094 emu K/mol, a Weiss temperature of 0.73 K and a corresponding μ_eff of 2.09 μ_B. A fit of χ_MT for 2 with S₁ = S₂ = ½, yields g = 2.441(6), J = −0.49(3) cm⁻¹, zJ = −0.38(2) cm⁻¹ and N(α) = 0.00053(12) emu/mol, a fit that indicates the presence of both very weak intramolecular intrachain antiferromagnetic exchange coupling within the one-dimensional tape-like chains and very weak interchain antiferromagnetic exchange coupling between these chains.     

Synthesis, structure and property of manganese(II) complexes with mixed tetradentate imidazole-containing ligand and benzenedicarboxylate

Three new coordination complexes [Mn(L)(H₂O)₂](1,4-BDC)·2H₂O (1), [Mn(L)_0.5(1,4-BDC)]CH₃OH·H₂O (2) and [Mn(L)(H₂O)₂](1,2-HBDC)₂·2H₂O (3) were synthesized by solvothermal reactions of 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene (L) and 1,4-benzenedicarboxylic acid (1,4-H₂BDC) or 1,2-benzenedicarboxylic acid (1,2-H₂BDC) with Mn(II) salt, and characterized by single crystal X-ray diffraction, IR, thermogravimetric and elemental analyses. In complexes 1 and 3, each ligand L links four Mn(II) atoms to form two-dimensional (2D) cationic network with non-coordinated 1,4-BDC²⁻ and 1,2-HBDC⁻ anions lying in the voids between the two adjacent layers, respectively. The 2D layers are further connected together by hydrogen bonds to give three-dimensional (3D) supramolecular structures. However, the 1,4-BDC²⁻ in 2 acts not only as counteranion, but also as bridging ligand leading to the formation of 2-fold interpenetrated 3D framework with pcu (primitive cubic unit) topology. The Mn(II) atoms bridged by carboxylate groups in 2 show antiferromagnetic interactions.     

A new blue luminescent dichlorido-bridged dinuclear copper(II) complex with DNA binding and cytotoxic activities: Synthesis, structure and DFT studies

A blue luminescent dichlorido-bridged dinuclear copper(II) (S = 1/2) complex, [Cu^II₂(HL)₂(μ-Cl)₂]·2H₂O, 1a was synthesized with the 1:1 reaction of the acyclic tridentate salicylaldehyde 2-pyridyl hydrazone ligand, HL, 1. The complex 1a displays multiple bands in the visible region (400-470 nm). The association constant (K_ass, UV-Vis) was found to be 1.186 × 10⁴ for 1a at 298 K. The copper(II)-copper(III) oxidation potential lies near 0.32 V versus Ag/AgCl electrode. On excitation at 390 nm, the ligand 1 strongly emits at 444 nm due to an intraligand ¹(π-π^∗) transition. Upon complexation with copper(II) the emission peak is slightly red shifted (λ_ex 390 nm, λ_em 450 nm, F/F₀ 0.81) with little quenching. Molecular structure of 1a (Cu···Cu 3.523 Å) has been determined by single crystal X-ray diffraction studies. DFT and TDDFT calculations strongly support the spectral behavior of the ligand and the complex. The complex 1a exhibits a strong interaction towards DNA as revealed from the K_b (intrinsic binding constant) 2.05 × 10⁴ M⁻¹ and K_sv (Stern-Volmer quenching constant) 2.47 values. The complex exhibits cytotoxic effect and the LD₅₀ value for HeLa cells was calculated as 5.44 μM at which the cell cycle was arrested at G₂/M phase.     

Synthesis and characterization of β-diketonato ruthenium(II) complexes with two 4-bromo or protected 4-ethynyl-2,2′-bipyridine ligands

Two new mononuclear mixed-ligand ruthenium(II) complexes with acetylacetonate ion (2,4-pentanedionate, acac) and functionalized bipyridine (bpy) in position 4, [Ru(bpyBr)₂(acac)](PF₆) (2; bpyBr = 4-Bromo-2,2′-bipyridine, acac = 2,4-pentanedionate ion) and [Ru(bpyOH)₂(acac)](PF₆) (3; bpyOH = 4-[2-methyl-3-butyn-2-ol]-2,2′-bipyridine) were prepared as candidates for building blocks. The ¹H NMR, ¹³C NMR, UV-Vis, electrochemistry and FAB mass spectral data of these complexes are presented.     

Mono- and dinuclear manganese(II) complexes derived from the cis/trans isomers of 2,4,5-tris(2-pyridyl)-4,5-dihydroimidazole

Two new manganese(II) complexes, [Mn(L1)(L1H)(ClO₄)(H₂O)][ClO₄]₂·0.5CH₃CN·H₂O (1) [L1 = trans-(±)2-(2,5-di(pyridin-2-yl)-4,5-dihydro-1H-imidazol-4-yl)pyridine)] and [Mn₂(μ-L2)₂(H₂O)₃(CH₃CN)₃][ClO₄]₄·2CH₃CN (2) [L2 = cis-(±)2-(2,5-di(pyridin-2-yl)-4,5-dihydro-1H-imidazol-4-yl)pyridine)], have been prepared and examined by single-crystal X-ray diffraction analysis, showing that complex 1 is a mononuclear compound, whereas complex 2 is a dinuclear species. The cis/trans isomers L1 and L2 have similar coordination properties, but behave as bidentate and tridentate chelating ligands, respectively, giving distorted octahedral metal coordination geometries. X-ray diffraction studies revealed that the molecular and crystal structures are stabilized by a series of intra- and intermolecular interactions. In both cases extended supramolecular networks are generated, in compound 1 through O-H···O, O-H···N, N-H···O, N-H···N, C-H···O, C-H···N, C-H···π and π···π interactions, and in compound 2 through O-H···O, O-H···N, C-H···O and π···π interactions. The observed structural differences between the two metal complexes might be a consequence of these stabilizing effects.     

Structure and properties of two polymorphs of tetra-n-butylammonium bis(maleonitriledithiolato)platinate(1−)

Structural determination of tetra-n-butylammonium bis(maleonitriledithiolato)platinate(1−), a polymorphic compound, revealed that one polymorph consists of a columnar arrangement of dimers of the anion and is isomorphous with a corresponding nickelate complex. In contrast to the nickelate complex, the complex exhibited no spin-Peierls transition; strong antiferromagnetic interactions were observed between the anions due to dimerization in the column. The other polymorph consists of a tetramer unit of the anion.     

A new copper(II) complex of unsymmetrical tetradentate ligand generated in situ: synthesis and molecular structure

A new copper(II) complex with tetradentate unsymmetrical ligand was prepared by one-pot condensation of methyl-2-pyrrole carboxylate, diethylenetriamine and copper(II) sulfate. The complex was characterized by elemental analysis, electronic and IR spectral, as well as X-ray crystal structure determination. The X-ray structure of the molecule reveals the copper(II) center is in a square planar environment through coordination by two nitrogen atoms of the amine, one amide nitrogen atom and one nitrogen atom of the pyrrole moieties, respectively. The copper(II) complex is neutral due to deprotonation of the amide and pyrrole groups.     

Isolation and characterisation of the biological repeating unit of cepacian, the exopolysaccharide produced by bacteria of the Burkholderia cepacia complex

The repeating unit of cepacian, the exopolysaccharide produced by the majority of the microorganisms belonging to the Burkholderia cepacia complex, was isolated from inner bacterial membranes and investigated by mass spectrometry, with and without prior derivatisation. Interpretation of the mass spectra led to the determination of the biological repeating unit primary structure, thus disclosing the nature of the oligosaccharide produced in vivo. Moreover, mass spectra recorded on the native sample revealed that acetyl substitution was very variable, producing a mixture of repeating units containing zero to four acyl groups. At the same time, finding acetylated oligosaccharides showed that binding of these substituents occurred in the cellular periplasmic space, before the polymerisation process took place. In the chromatographic peak containing the repeating unit, oligosaccharides shorter than the repeating unit co-eluted. Mass spectrometric analysis showed that they were biosynthetic intermediates of the repeating unit and further investigation revealed the biosynthetic sequence of cepacian building block.     

Differential requirement of lipid rafts for FcγRIIA mediated effector activities

Immunoglobulin G (IgG) dependent activities are important in host defense and autoimmune diseases. Various cell types including macrophages and neutrophils contribute to pathogen destruction and tissue damage through binding of IgG to Fcγ receptors (FcγR). One member of this family, FcγRIIA, is a transmembrane glycoprotein known to mediate binding and internalization of IgG-containing targets. FcγRIIA has been observed to translocate into lipids rafts upon binding IgG-containing targets. We hypothesize that lipid rafts participate to different extents in binding and internalizing targets of different sizes. We demonstrate that disruption of lipid rafts with 8 mM methyl-β-cyclodextrin (MβCD) nearly abolishes binding (91% reduction) and phagocytosis (60% reduction) of large IgG-coated targets. Conversely, binding and internalization of small IgG-complexes is less dependent on lipid rafts (49% and 17% inhibition at 8 mM MβCD, respectively). These observations suggest that differences between phagocytosis and endocytosis may arise as early as the initial stages of ligand recognition.