Copper(II) complexes with new polypodal ligands presenting axial-equatorial phenoxo bridges {2-[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol, 2-[(bis(2-pyridylmethyl)amino)methyl]-4-methyl-6-(methylthio)phenol}: examples of ferromagnetically coupled bi- and trinuclear copper(II) complexes

Two new ligands, 2-[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol (HL) and 2-[(bis(2-pyridylmethyl)amino)methyl]-4-methyl-6-(methylthio)phenol (HSL), were synthesized and were used to prepare the trinuclear copper(II) complex {[CuSL(Cl)]2Cu}(PF6)2.H2O (1) and the corresponding binuclear complexes [Cu2(SL)2](PF6)2 (2) and [Cu2L2](PF6)2 (3). The crystal structure of 1 shows two different coordination environments: two square base pyramidal centers (Cu1 and Cu1a, related by a C2 axes), acting as ligands of a distorted square planar copper center (Cu2) by means of the sulfur atom of the SCH3 substituent and the bridging phenoxo oxygen atom of the ligand (Cu2-S = 2.294 A). Compounds 2 and 3 show two equivalent distorted square base pyramidal copper(II) centers, bridged in an axial-equatorial fashion by two phenoxo groups, thus defining an asymmetric Cu2O2 core. A long copper-sulfur distance measured in 2 (2.9261(18) A) suggests a weak bonding interaction. This interaction induces a torsion angle between the methylthio group and the phenoxo plane resulting in a dihedral angle of 41.4(5) degrees. A still larger distortion is observed in 1 with a dihedral angle of 74.0(6) degrees. DFT calculations for 1 gave a ferromagnetic exchange between first neighbors interaction, the calculated J value for this interaction being +11.7 cm-1. In addition, an antiferromagnetic exchange for 1 was obtained for the second neighbor interaction with a J value of -0.05 cm-1. The Bleaney-Bowers equation was used to fit the experimental magnetic susceptibility data for 2 and 3; the best fit was obtained with J values of +3.4 and -16.7 cm-1, respectively. DFT calculations for 2 and 3 confirm the nature and the values of the J constants obtained by the fit of the experimental data. ESR and magnetic studies on the reported compounds show a weak exchange interaction between the copper(II) centers. The low values obtained for the coupling constants can be explained in terms of a poor overlap between the magnetic orbitals, due to the axial-equatorial phenoxo bridging mode observed in these complexes.     

MULTIGRID METHOD FOR FLUID DYNAMIC PROBLEMS

This paper covers the dynamics problems. The review and some aspects of main development stages of using Multigrid method for fluid multigrid technics are presented. Some approaches for solving Navier-Stokes equations and convection- diffusion problems are considered.     

Comprehensive Analysis of LC/MS Data Using Pseudocolor Plots

We have developed new applications of the pseudocolor plot for the analysis of LC/MS data. These applications include spectral averaging, analysis of variance, differential comparison of spectra, and qualitative filtering by compound class. These applications have been motivated by the need to better understand LC/MS data generated from analysis of human biofluids. The examples presented use data generated to profile steroid hormones in urine extracts from a Cushing’s disease patient relative to a healthy control, but are general to any discovery-based scanning mass spectrometry technique. In addition to new visualization techniques, we introduce a new metric of variance: the relative maximum difference from the mean. We also introduce the concept of substructure-dependent analysis of steroid hormones using precursor ion scans. These new analytical techniques provide an alternative approach to traditional untargeted metabolomics workflow. We present an approach to discovery using MS that essentially eliminates alignment or preprocessing of spectra. Moreover, we demonstrate the concept that untargeted metabolomics can be achieved using low mass resolution instrumentation.      

Flow‐through immobilized enzyme reactors based on monoliths: II. Kinetics study and application

In the last decade, the application of monolithic materials has rapidly expanded to the realization of flow‐through bioconversion processes. Up to these days, different classes of enzymes such as hydrolases, lyases, and oxidoreductases have been immobilized on organic, inorganic, or hybrid monolithic materials to prepare the effective flow‐through enzymes reactors for application in proteomics, biotechnology, pharmaceutics, organic synthesis, and biosensoring. Current review describes the results of kinetic study and specialties of flow‐through immobilized enzyme reactors based on the existing monolithic materials.     

Copper-catalyzed 1,2-addition of nucleophilic silicon to aldehydes: mechanistic insight and catalytic systems

Activation of the Si-B inter-element bond with copper(I) alkoxides produces copper-based silicon nucleophiles that react readily with aldehydes to yield α-silyl alcohols (that is, α-hydroxysilanes) after hydrolysis. Two independent protocols were developed, one employing a well-defined NHC-CuOtBu complex and one using the simple CuCN-NaOMe combination without added ligand. The mechanism of the aldehyde addition was investigated in detail by stoichiometric and catalytic experiments as well as NMR spectroscopic measurements. The primary reaction product of the addition of the Si-B reagent and the aldehyde (a boric acid ester of the α-silyl alcohol) and also the "dead-end" intermediate, formed in the competing [1,2]-Brook rearrangement, were characterized crystallographically. Based on these data, a reasonable catalytic cycle is proposed. The NHC-CuOtBu catalytic setup performs nicely at elevated temperature. A more reactive catalytic system is generated from CuCN-NaOMe, showing fast turnover at a significantly lower temperature. Both aromatic and aliphatic aldehydes are transformed into the corresponding α-silyl alcohols in good to very good yields under these mild reaction conditions.     

Studies on the Structure and Properties of Membrane Phospholipase A1 Inclusion Bodies Formed at Low Growth Temperatures Using GFP Fusion Strategy

The effect of cultivation temperatures (37, 26, and 18 °C) on the conformational quality of Yersinia pseudotuberculosis phospholipase A₁ (PldA) in inclusion bodies (IBs) was studied using green fluorescent protein (GFP) as a folding reporter. GFP was fused to the C-terminus of PldA to form the PldA-GFP chimeric protein. It was found that the maximum level of fluorescence and expression of the chimeric protein is observed in cells grown at 18 °C, while at 37 °C no formation of fluorescently active forms of PldA-GFP occurs. The size, stability in denaturant solutions, and enzymatic and biological activity of PldA-GFP IBs expressed at 18 °C, as well as the secondary structure and arrangement of protein molecules inside the IBs, were studied. Solubilization of the chimeric protein from IBs in urea and SDS is accompanied by its denaturation. The obtained data show the structural heterogeneity of PldA-GFP IBs. It can be assumed that compactly packed, properly folded, proteolytic resistant, and structurally less organized, susceptible to proteolysis polypeptides can coexist in PldA-GFP IBs. The use of GFP as a fusion partner improves the conformational quality of PldA, but negatively affects its enzymatic activity. The PldA-GFP IBs are not toxic to eukaryotic cells and have the property to penetrate neuroblastoma cells. Data presented in the work show that the GFP-marker can be useful not only as target protein folding indicator, but also as a tool for studying the molecular organization of IBs, their morphology, and localization in E. coli, as well as for visualization of IBs interactions with eukaryotic cells.     

<Emphasis Type="Italic">fac</Emphasis>-[Re(CO)<Subscript>3</Subscript>L] Complexes Containing Tridentate Monoanionic Ligands (L<Superscript>−</Superscript>) Having a Terminal Amido and Two Amine Ligating Groups

Abstract Treatment of fac-[Re(CO)₃(H₂O)₃]⁺ with two unsymmetrical tridentate NNN donor ligands (LH) based on a diethylenetriamine (dien) moiety with a 2,4,6-trimethylbenzoyl (tmbCO) group linked to a terminal nitrogen of dien through an amide produced the neutral complexes [Re(CO)₃(tmbCO-N,N-Me₂dien)] and [Re(CO)₃(tmbCO-dien)]. The [Re(CO)₃(tmbCO-N,N-Me₂dien)] complex crystallized in the space group P2₁/c, a = 19.5793 (15), b = 7.4239 (5), c = 14.8071 (10) ?, β = 104.425(5)°, V = 2084.4(3) ?³, and the [Re(CO)₃(tmbCO-dien)] complex crystallized in the space group C2/c, a = 36.861 (7), b = 7.3990 (10), c = 14.933 (3) ?, β = 102.145 (8)°, V = 3981.6(12) ?³. X-ray crystallographic and NMR analyses confirm that in both the solid and solution states the ligands are bound to the fac-Re(CO)₃ core in a tridentate fashion with the amide group being deprotonated. An important property in radiopharmaceuticals is shape, which in turn depends on ring pucker. For [Re(CO)₃(tmbCO-N,N-Me₂dien)], the two chelate rings have different pucker chirality, as is commonly found for a broad range of metal complexes. However, for fac-[Re(CO)₃(tmbCO-dien)], the two chelate rings have the same pucker chirality, a finding attributable to two strong intermolecular hydrogen bonds from the NH₂ to two waters of crystallization. Impeded by methyl group clashes with chelate ring hydrogens, the tmb ring rotation about the C(amido)–C(tmb) bond is slow on the NMR time scale. Index Abstract fac -[Re(CO) ₃ L] Complexes Containing Tridentate Monoanionic Ligands (L ⁻ ) Having a Terminal Amido and Two Amine Ligating Groups Anna Maria Chirstoforou, Patricia A. Marzilli, Frank R. Fronczek, and Luigi G. Marzilli X-ray crystallographic and NMR analyses of fac-Re(CO)₃ complexes containing diethylenetriamine-based, NNN tridentate ligands with a terminal deprotonated amido donor group allow comparison to previously reported analogues with a terminal deprotonated sulfonamido donor group. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Chemical Characterization,Antioxidant and Antimicrobial Properties of Different Types of Tissue of Cedrus brevifolia Henry Extracts

This study aimed to determine the chemical composition of different types of tissue of Cedrus brevifolia Henry (Pinaceae) methanolic extracts, namely needles, twigs, branches, and bark. Cedrus brevifolia is a narrow endemic coniferous tree species of Cyprus, growing in a sole population in the mountainous area of Paphos Forest. Chemical analysis of the extracts was performed using liquid chromatography combined with time-of-flight high-resolution mass spectrometry (LC/Q-TOF/HRMS). The majority of the 36 compounds tentatively identified belonged to the flavonoids family. The extract of needles was the richest extract in terms of secondary metabolites. The extracts were studied for their antioxidant activity using the DPPH free radical scavenging assay. Additionally, the antibacterial activity was evaluated by determining both the minimum inhibitory concentration and the minimum bactericidal concentration against Staphylococcus aureus and Escherichia coli. All extracts demonstrated antioxidant property, while bark gave the highest antioxidant capacity (IC₅₀ value of 0.011 mg/mL) compared to the other tissues. Antibacterial activity was observed against both types of bacteria, with the extract of branches presenting the strongest activity against S. aureus (MIC, 0.097 mg/mL and MBC, 0.195 mg/mL). This is the first time that extracts of needles, twigs, branches, and bark of C. brevifolia are compared regarding their chemical composition as well as their antimicrobial and antioxidant properties.     

Exciton dissociation in conjugated polymers

In conjugated polymers, a majority of photogenerated charges form metastable geminate pairs (GPs), of which only some fraction can dissociate completely. Both the yield of GP photogeneration and the probability of further dissociation of GPs into free charges depend upon an external electric field. In the present article we discuss several experimental methods to detect the existence of geminate pairs such as delayed field collection of charges, field quenching of fluorescence, and field-assisted photoinduced optical absorption. It is shown that the field dependences of the exciton dissociation into GPs and of the free carrier photogeneration yield are rather similar. This is in contrast with the traditional Onsager theory, which assumes field-independent yield of primary photoionization and disregards the field dependence of the initial separations between carriers in GPs.     

Helical Bilayer Nonbenzenoid Nanographene Bearing a [10]Helicene with Two Embedded Heptagons

The precision synthesis of helical bilayer nanographenes (NGs) with new topology is of substantial interest because of their exotic physicochemical properties. However, helical bilayer NGs bearing non-hexagonal rings remain synthetically challenging. Here we present the efficient synthesis of the first helical bilayer nonbenzenoid nanographene ( HBNG1 ) from a tailor-made azulene-embedded precursor, which contains a novel [10]helicene backbone with two embedded heptagons. Single-crystal X-ray analysis reveals its highly twisted bilayer geometry with a record small interlayer distance of 3.2 Å among the reported helical bilayer NGs. Notably, the close interlayer distance between the two layers offers intramolecular through-space conjugation as revealed by in situ spectroelectrochemistry studies together with DFT simulations. Furthermore, the chiroptical properties of the P/M enantiomers of HBNG1 are also evaluated by circular dichroism and circularly polarized luminescence.