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Unprecedented Fluorescent Dinuclear CoII and ZnII Coordination Compounds with a Symmetric Bis(salamo)-Like Tetraoxime.

ABSTRACT: Two unprecedented homometallic CoII and ZnII coordination compounds, [M₂(L)(OCH₃)][M₂(L)(OAc)] (MII = CoII (1) and ZnII (2)), with a novel symmetric bis(salamo)-like tetraoxime ligand H₃L were synthesized and characterized by elemental analyses, infrafred (IR), ultraviolet⁻visible spectroscopy (UV-Vis), fluorescent spectra and single-crystal X-ray diffraction analyses. The unit cell of the two coordination compounds contains two crystallographically and chemically independent dinuclear coordination compounds. In the two coordination compounds, three metal ions are five-coordinated, formed two square pyramidal and a trigonal bipyramidal geometries, and the other metal ion is a hexacoordinate octahedral configuration. In addition, the coordination compound 1 forms a 3D supramolecular structure, and the coordination compound 2 forms a 0D dimer structure by the inter-molecular hydrogen bond interactions. Meanwhile, the fluorescence spectra of the coordination compounds 1 and 2 were also measured and discussed.

SUBMITTER: Zhang LW

PROVIDER: S-EPMC6099918 | biostudies-literature |

REPOSITORIES: biostudies-literature

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A new co-crystal dinuclear/trinuclear ZnII-ZnII/ZnII-SmIII-ZnII complex with a salen-type Schiff base ligand.

Project description:In the penta-nuclear title complex, [SmZn2(C22H18N2O4)2(NCS)2(C3H7NO)2][Zn2(C22H18N2O4)(NCS)3]·C3H7NO·0.32H2O, namely bis-{μ2-6,6'-dimeth-oxy-2,2'-[phenyl-ene-1,2-diylbis(nitrilo-methanylyl-idene)]diphenolato}-1κ4 O,N,N',O':2κ3 O,O',O 6;2κ3 O,O',O 6:3κ4 O,N,N',O'-bis-(di-methyl-formamide-2κO)di-thiocyanato-1κN,3κN-2-samarium(III)-1,3-dizinc(II) {μ2-6,6'-dimeth-oxy-2,2'-[phenyl-ene-1,2-diylbis(nitrilo-methanylyl-idene)]diphenolato-1κ4 O,N,N',O':2κ2 O,O'}trithio-cyan-ato-1κN;2κ2 N,N-dizinc(II) di-methyl-formamide monosolvate 1.32-hydrate, a dinuclear unit and a trinuclear unit co-exist. One of the ZnII centers in the dinuclear unit as well as the two ZnII centers in the trinuclear unit are located in the inner N2O2 cavity of the ligand and are coordinated to the nitro-gen atom of one thio-cyanate moiety, giving rise to a square-pyramidal geometry. The second ZnII center in the dinuclear unit is coordinated to the two phenolate oxygen atoms of the ligand and to two thio-cyanate groups via the nitro-gen atom in a tetra-hedral geometry. The SmIII ion is eight-coordinated by four phenolate O atoms from the two ligand mol-ecules, two meth-oxy O atoms from the two ligand mol-ecules and two O atoms from the DFM solvent mol-ecule. In the dinuclear unit, the two meth-oxy oxygen atoms remain uncoordinated while in the trinuclear unit, for each ligand one meth-oxy oxygen is coordinated and the other one remains uncoordinated. In the crystal, the trinuclear cationic units and dinuclear anionic units are assembled into infinite layers. These layers are held together via electrostatic inter-actions, forming a three-dimensional structure. In the dinuclear unit, the C and S atoms of one of the thio-cyanate groups are disordered over two sets of sites in a 0.680 (4)(4):0.320 (4) ratio.

| S-EPMC6281091 | biostudies-literature

Bonding Analysis of Compounds with Unusual Coordination of Carbon: Proposed Symmetric Systems with Six-Coordinate Carbon.

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Copper(II) 2,2-Bis(Hydroxymethyl)Propionate Coordination Compounds with Hexamethylenetetramine: From Mononuclear Complex to One-Dimensional Coordination Polymer.

Project description:Three new copper coordination compounds derived from 2,2-bis(hydroxymethyl)propionic acid (dmpa) and hexamethylenetetramine (hmta) were obtained and their crystal structures were determined. The stoichiometry of the reagents applied in the syntheses reflects the metal to ligand molar ratio in the formed solid products. Due to the multiple coordination modes of the used ligands, wide structural diversity was achieved among synthesized compounds, i.e., mononuclear [Cu(dmp)2(hmta)2(H2O)] (1), dinuclear [Cu2(dmp)4(hmta)2] (2), and 1D coordination polymer [Cu2(dmp)4(hmta)]n (3). Their supramolecular structures are governed by O-H•••O and O-H•••N hydrogen bonds. The compounds were characterized in terms of absorption (UV-Vis and IR) and thermal properties. The relationships between structural features and properties were discussed in detail. Owing to discrepancies in the coordination mode of a dmp ligand, bidentate chelating in 1, and bidentate bridging in 2 and 3, there is a noticeable change in the position of the bands corresponding to the stretching vibrations of the carboxylate group in the IR spectra. The differences in the structures of the compounds are also reflected in the nature and position of the UV-Vis absorption maxima, which are located at lower wavelengths for 1.

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Modulating the Primary and Secondary Coordination Spheres within a Series of CoII-OH Complexes.

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A Pair of CoII Supramolecular Isomers Based on Flexible Bis-Pyridyl-Bis-Amide and Angular Dicarboxylate Ligands.

Project description:Thermal reactions of cobalt(II) salts with flexible N,N'-bis(pyrid-3-ylmethyl)adipoamide (L) and angular 4,4'-sulfonyldibenzoic acid (H2SDA) in H2O and CH3OH afforded a pair of supramolecular isomers: [Co2(L)(SDA)2], 1, and [Co2(L)(SDA)2]⋅CH3OH⋅H2O, 2. The structure of complex 1 can be simplified as a one-dimensional (1D) looped chain with L ligands penetrating into the middles of squares, forming a new type of self-catenated net with the (42⋅54)(4)2(5)2 topology, whereas complex 2 displays a 2-fold interpenetrated 2D net with the rare (42⋅68⋅8⋅104)(4)2-2,6L1 topology. While both complexes 1 and 2 display antiferromagnetism with strong spin-orbital coupling, the antiferromagnetism of 2 is accompanied by a cross-over behavior and probably a spin canting phenomenon.

| S-EPMC6982743 | biostudies-literature

Symmetric Bis-benzimidazoles Are Potent Anti-Staphylococcal Agents with Dual Inhibitory Mechanisms against DNA Gyrase

Project description:Various bis-benzimidazole derivatives have been reported to possess activity against Gram-positive pathogens. No mechanism of action has been elucidated to fully account for the antibacterial activity of this class of compounds. A group of symmetric bis-benzimidazoles (BBZ) designed as anticancer agents have previously been shown to possess moderate antiproliferative activity. We sought to assess the antibacterial activity and mechanism of action of BBZ compounds against Staphylococcus aureus. Antibacterial activities were assessed by determination of minimal inhibitory concentrations (MICs), time-kill curves, and scanning electron microscopy. Transcriptional responses to BBZ treatment were determined using whole genome microarrays. Activities against bacterial type II topoisomerases were investigated using in vitro supercoiling, decatenation, DNA binding, and DNA cleavage inhibition assays. MICs for EMRSA-16 were between 0.03 and 0.5 μg/mL. The compounds showed concentration-dependent bactericidal activity and induced cell swelling and lysis. Transcriptional responses to BBZ were consistent with topoisomerase inhibition and DNA damage. A subset of BBZ compounds inhibited S. aureus DNA gyrase supercoiling activity with IC50 values in the range of 5−10 μM. This inhibition was subsequently shown to operate through both inhibition of binding of DNA gyrase to DNA and accumulation of single-stranded DNA breaks. We conclude that BBZ compounds are potent antistaphylococcal agents and operate at least in part through DNA gyrase inhibition, leading to the accumulation of single-stranded DNA breaks, and by preventing the binding of gyrase to DNA. [Data is also available from http://bugs.sgul.ac.uk/E-BUGS-106]

2012-10-14 | E-BUGS-106 | biostudies-arrayexpress

A Highly Fluorescent Dinuclear Aluminium Complex with Near-Unity Quantum Yield.

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| S-EPMC9313782 | biostudies-literature

Photophysical and Photobiological Properties of Dinuclear Iridium(III) Bis-tridentate Complexes.

Project description:A series of cationic dinuclear iridium(III) complexes (Ir1-Ir5) bearing terpyridine-capped fluorenyl bridging ligands and different polypyridyl or cyclometalating terminal tridentate ligands were synthesized, characterized, and evaluated for their photophysical and photobiological activities. The influence of the bridging and terminal ligands on the photophysical properties of the complexes was investigated by UV-vis absorption, emission, and transient absorption spectroscopy and simulated by TDDFT calculations. All of the complexes displayed strong bridging-ligand localized visible 1π,π* absorption and red- or near-infrared phosphorescence as well as broad triplet excited-state absorption across both visible and NIR wavelengths. These triplet states were assigned as predominantly 3π,π* for Ir1 (τ = 3.1 μs) and Ir4 (τ = 48 μs) and 3CT (charge transfer) for Ir2, Ir3, and Ir5 (τ = 1.7-2.7 μs). Complexes Ir1-Ir5 acted as in vitro photodynamic therapy (PDT) agents toward human SK-MEL-28 melanoma cells when activated with visible light, with submicromolar photocytotoxicity and phototherapeutic indices ranging from 20 to almost 300. The in vitro PDT effects with visible light did not correlate with singlet oxygen (1O2) quantum yields or DNA photocleaving capacity probed under cell-free conditions. All of the Ir(III) complexes phosphoresced brightly when associated with compromised cells (with or without light treatment) and exhibited photoactivated cellular uptake, highlighting the theranostic potential of this new class of Ir(III) complex photosensitizers.

| S-EPMC6337720 | biostudies-literature

Chelate Coordination Compounds as a New Class of High-Energy Materials: The Case of Nitro-Bis(Acetylacetonato) Complexes.

Project description:The existence of areas of strongly positive electrostatic potential in the central regions of the molecular surface of high-energy molecules is a strong indicator that these compounds are very sensitive towards detonation. Development of high-energy compounds with reduced sensitivity towards detonation and high efficiency is hard to achieve since the energetic molecules with high performance are usually very sensitive. Here we used Density Functional Theory (DFT) calculations to study a series of bis(acetylacetonato) and nitro-bis(acetylacetonato) complexes and to elucidate their potential application as energy compounds with moderate sensitivities. We calculated electrostatic potential maps for these molecules and analyzed values of positive potential in the central portions of molecular surfaces in the context of their sensitivity towards detonation. Results of the analysis of the electrostatic potential demonstrated that nitro-bis(acetylacetonato) complexes of Cu and Zn have similar values of electrostatic potential in the central regions (25.25 and 25.06 kcal/mol, respectively) as conventional explosives like TNT (23.76 kcal/mol). Results of analysis of electrostatic potentials and bond dissociation energies for the C-NO2 bond indicate that nitro-bis(acetylacetonato) complexes could be used as potential energetic compounds with satisfactory sensitivity and performance.

| S-EPMC8470082 | biostudies-literature

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