Search for neutral resonances decaying into a Z boson and a pair of b jets or tau leptons

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C-P bond forming reactivity of N-heteropentacene: isolation and characterization of a phospho-ylide complex of ruthenium(II)

In an unusual reaction of H2L2 (H2L2=N-heteropentacene) with Ru(PPh3)3Cl2 a phospho-ylide ruthenium(II) complex (1) was obtained via unprecedented chemical transformations of the conjugate base [L2]2-. A bidentated phospho-ylide ligand is formed with concomitant aromatic ring hydroxylation and new C-P bond formation reactions. The new ligand, binds to RuII as a neutral N, O-donor. Crystal structure determination by single crystal X-ray diffraction has been used to characterize the compound. The phospho-ylide Ru(II) description of the complex was established based on 13C as well as 31P NMR studies. The complex shows rich spectral and redox properties. UV-Vis-NIR spectrum consisted of multiple low-energy transitions in the visible and near IR regions. Preliminary density functional theory calculations were employed to understand the electronic structure and to assign the spectral transitions. Cyclic voltammogram and EPR-spectrum of the electrogenerated oxidized compound are reported and used to characterize the redox properties

Regioselective fusion of aromatic di-amines to coordinated 2-(phenylazo)pyridine. An approach to the synthesis of new ligands with large denticity

2320-2326Metal mediated oxidative fusion reaction of aromatic di-amines to coordinated 2-(phenylazo)pyridine (pap) ligand in the cationic cobalt complex, [Co(pap)3]2+ affords green complexes of general formula [Co(L)2] (ClO4) [HL = 2-[(N-aryldiamino) phenylazo] pyridine]. In this reaction one of the two amine functions of the di-amine reagent is fused regioselectively to ortho-carbon of the pendant phenyl ring of coordinated pap to yield a bi schelating tridentate ligand while the second amine function remains a pendant and does not take part in the fusion reaction. The crystal structure of one of the representative cobalt complexes, [Co(L2)2] (ClO4) is reported. The structure analysis reveals the presence of two anionic ligands, each of which acts as an N,N,N-tridentate donor. Physicochemical properties of the cobalt complexes are reported. The ligands HL2- HL4 are isolated from the corresponding cobalt complexes by their decomposition. These free ligands showed resolved 1H NMR spectra. The resonance due to -NH and –NH2 in these appeared near 10.5 δ and 4.5 δ, respectively.The ligand HL4 was reacted with salicylaldehyde, which underwent Schiff-base condensation to result an extended ligand H2L5 in a high yield. The 1H NMR spectrum of H2L5 showed the presence of a -CH resonance at 10.6 δ and the -OH resonance at 13.3δ. FAB mass and 1H NMR spectra of the newly synthesized organic ligands indeed confirm their formulations

An unusual (H<SUB>2</SUB>O)<SUB>20</SUB> discrete water cluster in the supramolecular host of a charge transfer platinum(II) complex: cytotoxicity and DNA cleavage activities

The chemical reaction of Pt<SUP>II</SUP>(L<SUP>1</SUP>)Cl<SUB>2</SUB> [L<SUP>1</SUP>=N-4-tolylpyridine-2-aldimine] with a bidentate N,S-donor atom ligand, 2-methylthioaniline, (HL<SUP>2</SUP>) in alkaline methanolic medium yielded a mixed ligand donor-acceptor complex, [Pt<SUP>II</SUP>(L<SUP>1</SUP>)(L<SUP>2</SUP>)]Cl, [1]Cl. The complex has been characterized by different spectroscopic and electrochemical techniques. The complex showed intense interligand charge transfer (ILCT) transition in the long wavelength region of UV-vis spectrum (&gt;600 nm). The single-crystal X-ray structure of complex, [1]Cl·3.3H<SUB>2</SUB>O is reported. The cationic complex upon crystallization from aqueous methanol solvent produces an assembly of discrete, three dimensional (H<SUB>2</SUB>O)<SUB>20</SUB> guest moiety within the reference Pt-complex host lattice. The water assembly showed a unique type of aggregation of a distorted cube encapsulated by hydrogen bonded network of a twelve-water ring. The complex displayed one reversible cathodic response at -0.75 V and two irreversible anodic responses at 0.42 and 0.79 V versus Ag/AgCl reference electrode. The redox processes are characterized by EPR and spectroelectrochemistry. Density-functional theory calculations were employed to confirm the structural features and to support the spectral and redox properties of the complex. The square-planar complex has been found to intercalate DNA. Fluorescence spectroscopy, circular dichroism, cyclic voltammetry, viscosity measurements, together with DNA melting studies have been employed to characterize the binding of [1]Cl with calf thymus DNA. Agarose gel electrophoresis indicates that the complex cleaves supercoiled (SC) pUC19 plasmid DNA to its nicked circular (NC) form via singlet oxygen. As determined by a MTT assay, [1]Cl exhibits significant cytotoxicity with IC<SUB>50</SUB> value 58µM

Synthesis and characterization of a new copper(II) amidine complex

630-632A new five coordinate copper(II) complex, [Tp*CuL]ClO4 (Tp* = Hydrotris(3,5-dimethylpyrazolyl)borate and L = 1-methyl-carbaldimino-3,5-dimethylpyrazole) has been synthesised and characterized by IR, UV-Vis, EPR spectroscopies and cyclic voltammetry. The three nitrogen atoms of Tp* and two nitrogen atoms of L are coordinating with copper making a distorted square pyramidal geometry around the metal centre

AFLPs and morphological diversity of Phaseolus lunatus L. in Cuban home gardens : Approaches to recovering the lost ex situ collection

The genetic diversity of 76 accessions of lima bean (Phaseolus lunatus L.), collected mostly from home gardens, was assessed with AFLPs and seed descriptors to evaluate the potential for recovering a lost ex situ collection in Cuba. The sample contained 60 accessions collected from 25 home gardens in the three main geographical regions of Cuba and represented the three cultivated types found on the island. Four more accessions were part of the former ex situ collection and the remaining 12 accessions were selected from the world bean collection held at the International Center for Tropical Agriculture. Some morphological measurements discriminated among cultivated types. The analysis of 62 polymorphic bands obtained with two AFLP primer combinations indicated that the three cultivated bean types were comparable in terms of molecular diversity and that no pattern of variation was associated with geographical distribution. However, a multiple correspondence analysis with the same molecular data detected different genetic groups. Three of these groups included all the cultivated accessions collected from home gardens, but could not be explained by the seed descriptors. The results therefore suggest that a scientifically sound collecting strategy to recover the former Cuban ex situ gene bank should consider combining geographical, morphological, and molecular data. The findings also suggest that any proposed methodologies should be considered before developing a conservation strategy based on an ex situ or combined ex situ and in situ approaches

Two copper complexes from two novel naphthalene-sulfonyl-triazole ligands: Different nuclearity and different DNA binding and cleavage capabilities

[EN] Two novel naphthalene-sulfonyl-triazole ligands, 5-amino-N1-(naphthalen-3-ylsulfony1)-1,2,4-triazole (anstrz) and 3,5-diamino-N1-(naphthalen-3-ylsulfony1)-1,2,4-triazole (danstrz), purposely designed to interact with DNA, have been prepared for the first time and then fully characterized by H-1, C-13 NMR and IR spectroscopy, mass spectrometry and elemental analysis. The crystal structures of two copper complexes of these derivatives, i.e. [Cu(anstrz)(4)(NO3)(2)]center dot 4CH(3)OH (1), mononuclear, and [Cu(danstrz)(mu-OAc)(2)](2)center dot 2(danstrz) (OAc = acetato) (2), dinuclear, have been determined by single-crystal X-ray diffraction. In both cases the ligand coordinates in a monodentate fashion via the N4 nitrogen atom of the triazole ring. Compound 2, an example of paddle wheel type copper acetate, presents a Cu - Cu' distance of 2.667(1) angstrom. As a result of strong stacking interactions and intense H-bonds, the structure of 2 constitutes a MOF (metal-organic framework). Besides, this dinuclear compound exhibits a very strong antiferromagnetic coupling (J = -324 cm(-1)) and a silent X-band EPR at room temperature. The affinity toward DNA of 1 and 2 has been examined by fluorescence emission spectroscopy, thermal denaturation and viscosimetry assays. The apparent binding constant (K-app) values of 2.2 x 10(7) M-1 for 1 and 2.6 x 10(7) M-1 for 2 suggest important DNA interaction. The dinuclear compound (2) intercalates and produces a high change in the T-m. Both compounds promote DNA scission in the presence of H2O2/ascorbate (1) or ascorbate (2) through oxidative mechanism. The possible reasons for the higher DNA affinity and the more efficient DNA cleavage displayed by compound 2 in relation to compound 1 are discussed.This work was supported by the Ministerio de Educacion y Ciencia (MEC, Spain) (Project CTQ2007-63690/BQU), and by the Ministerio de Ciencia e Innovacion and FEDER-EC (Project MAT2010-15594). JHG acknowledges for a PhD. grantship (Project CTQ2007-63690/BQU, MEC, Spain).Hernandez-Gil, J.; Ferrer, S.; Cabedo Escrig, N.; López Gresa, MP.; Castineiras, A.; Lloret, F. (2013). Two copper complexes from two novel naphthalene-sulfonyl-triazole ligands: Different nuclearity and different DNA binding and cleavage capabilities. Journal of Inorganic Biochemistry. 125:50-63. https://doi.org/10.1016/j.jinorgbio.2013.04.007S506312

Variable coordination modes of benzaldehyde thiosemicarbazones - synthesis, structure, and electrochemical properties of some ruthenium complexes

Reaction of benzaldehyde thiosemicarbazones [H<SUB>2</SUB>LR, where H<SUB>2</SUB> stands for the two protons, the hydrazinic proton, and the phenyl proton at the ortho position, with respect to the imine function and R (R = OCH<SUB>3</SUB>, CH<SUB>3</SUB>, H, Cl, and NO<SUB>2</SUB>) for the para substituent] with [Ru(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)<SUB>2</SUB>Cl<SUB>2</SUB>], carried out in refluxing ethanol, afforded monomeric complexes of type [Ru(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)(HLR)(H)]. The crystal structure of the [Ru(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)(HLNO<SUB>2</SUB>)(H)] complex was determined. The thiosemicarbazone ligand is coordinated to the ruthenium center as a bidentate N,S-donor ligand forming a four-membered chelate ring. When the reaction of the thiosemicarbazones with [Ru(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)<SUB>2</SUB>Cl<SUB>2</SUB>] was carried out in refluxing toluene, a family of dimeric complexes of type [Ru2(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)<SUB>2</SUB>(LR)<SUB>2</SUB>] were obtained. The crystal structure of [Ru2(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)<SUB>2</SUB>(LCl)<SUB>2</SUB>] was determined. Each thiosemicarbazone ligand is coordinated to one ruthenium atom, by dissociation of the two protons, as a dianionic tridentate C,N,S-donor ligand, and at the same time the sulfur atom is also bonded to the second ruthenium center.<SUP> 1</SUP>H NMR spectra of the complexes of both types are in excellent agreement with their compositions. All the dimeric and monomeric complexes are diamagnetic (low-spin d<SUP>6</SUP>, S = 0) and show intense absorptions in the visible and ultraviolet regions. Cyclic voltammetry of the [Ru(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)(HLR)(H)] and [Ru<SUB>2</SUB>(PPh<SUB>3</SUB>)<SUB>2</SUB>(CO)<SUB>2</SUB>(LR)<SUB>2</SUB>] complexes show the ruthenium(II)-ruthenium(III) oxidation within 0.48-0.73 V vs. SCE followed by a ruthenium(III)-ruthenium(IV) oxidation within 1.09-1.47 V vs. SCE. Potentials of both the oxidations are found to correlate linearly with the electron-withdrawing character of the substituent R