Co(III) complexes of Me-salpn and Me-salbn and the ring size effect on the coordination modes and electrochemical properties: The crystal structures of trans-[Co(Me-salpn)(py)2]PF6 and cis-α-[Co(Me-salbn)(4-Mepy)2]BPh4 · 4-Mepy

The synthesis and characterization of a series of cobalt(III) complexes of the general type [Co(N₂O₂)(L₂)]⁺ are described. The N₂O₂ Schiff base ligands used are Me-salpn (H₂Me-salpn = N,N′-bis(methylsalicylidene)-1,3-propylenediamine) (1–3) and Me-salbn (H₂Me-salbn = N,N′-bis(methylsalicylidene)-1,4-butylenediamine) (4–5). The two ancillary ligands L include: pyridine (py) 1, 3-metheylpyridine (3-Mepy) 2, 1-methylimidazole (1-MeIm) 3, 4-methylpyridine (4-Mepy) 4 and pyridine (py) 5. These complexes have been characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structures of trans-[Co^III(Me-salpn)(py)₂]PF₆, 1, and cis-α-[Co^III(Me-salbn)(4-Mepy)₂]BPh₄ · 4-Mepy, 4, have been determined by X-ray diffraction. Examination of the solution and crystalline structures revealed that the outer coordination sphere of the complexes exerts a noticeable influence on the inner coordination sphere of the Co(III) ion. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial (R-py)–cobalt bonds. It has also been observed that the Co(III) state is stabilized with increasing the flexibility of the ligand environment.     

Essential Oil Composition of <Emphasis Type="Italic">Nepeta involucrata</Emphasis> from Iran

The essential oil of Nepeta involucrata (Bunge) Bornm. (Lamiaceae) obtained by hydrodistillation from the aerial parts during the flowering stage was analyzed by GC and GC-MS. Forty-eight compounds representing 97.2% of total oil were identified. The main compounds of the oil were 1,8-cineol (23.1%), germacrene-D (15.1%), and β-pinene (12.2%). No traces of nepetalactone isomers were found as oil constituents. __________ Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 562–564, November–December, 2005.     

Selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles in water at ambient temperature

A highly selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles from the reaction of o-phenylenediamines and aromatic aldehydes in the presence of silica sulfuric acid is reported. The reactions were performed in ethanol or water and the catalyst could be reused for several runs.     

Ionic Liquid Promoted Eco-friendly and Efficient Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones

2,3-Dihydroquinazolin-4(1H)-ones were efficiently synthesised by the reaction of isatoic anhydride, a primary amine or ammonium acetate, and different aromatic aldehydes in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄) without using any acidic catalyst. Also a bis-derivative of the title compound as a polyheterocyclic system was synthesised successfully in high yield.     

Comparative study of nanoscale surface structures of calcite microcrystals using FE-SEM, AFM, and TEM.

The bulk morphology and surface features that developed upon precipitation on micrometer-size calcite powders and millimeter-size cleavage fragments were imaged by three different microscopic techniques: field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) of Pt-C replicas, and atomic force microscopy (AFM). Each technique can resolve some nanoscale surface features, but they offer different ranges of magnification and dimensional resolutions. Because sample preparation and imaging is not constrained by crystal orientation, FE-SEM and TEM of Pt-C replicas are best suited to image the overall morphology of microcrystals. However, owing to the decoration effect of Pt-C on the crystal faces, TEM of Pt-C replicas is superior at resolving nanoscale surface structures, including the development of new faces and the different microtopography among nonequivalent faces in microcrystals, which cannot be revealed by FE-SEM. In conjunction with SEM, Pt-C replica provides the evidence that crystals grow in diverse and face-specific modes. The TEM imaging of Pt-C replicas has nanoscale resolution comparable to AFM. AFM yielded quantitative information (e.g., crystallographic orientation and height of steps) of microtopographic features. In contrast to Pt-C replicas and SEM providing three-dimensional images of the crystals, AFM can only image one individual cleavage or flat surface at a time.     

Application of N-halo reagents in organic synthesis

This review article summarizes published data on the application of N-halo reagents (such as N-halo amines, N-halo amides and/or imides, N-halo sulfonamides and/or imides, and etc.) in various organic functional group transformations such as: oxidation reactions, deprotection and protection of different functional groups, halogenation of saturated and unsaturated compounds, acylation of alcohols, phenols, amines or thiols, epoxidation of alkenes, aziridination and etc. The main purpose of writing this review is encouraging of active researchers interested to this field for the synthesis of new N-halo reagents specially with different halogens and applications of these new N-halo reagents in organic reactions or finding more and more applications of existing N-halo reagents in organic synthesis.     

Oxidative Deprotection of Acetals and Trimethylsilylethers by γ‐PCC‐SiO2

Acetals, ketals and trimethylsilyl ethers mildly and selectively underwent oxidative deprotection to carbonyl compounds by silica gel supported γ‐picolinium chlorochromate under non‐aqueous conditions in good to excellent yields.     

General maximal inequalities related to the strong law of large numbers

For any sequence (ξ _n ) of random variables, we obtain maximal inequalities from which we can derive conditions for the a.s. convergence to zero of the normalized differences $$\frac{1}{{2^n }}\left( {\mathop {\max }\limits_{2^n \leqslant k < 2^{n + 1} } \left| {\sum\limits_{i = 2^n }^k {\xi _i } } \right| - \left| {\sum\limits_{i = 2^n }^{2^{n + 1} - 1} {\xi _i } } \right|} \right).$$ The convergence to zero of this sequence leads to the strong law of large numbers (SLLN). In the special case of quasistationary sequences, we obtain a sufficient condition for the SLLN; this condition is an improvement on the well-known Móricz conditions.     

Triiodide PVC Membrane Electrode Based on a Charge‐Transfer Complex of Iodine with Ditertbutyl‐Dicyclohexyl‐18‐Crown‐6

A new triiodide ion‐selective electrode based on a charge‐transfer complex of iodine with ditertbutyl‐dicyclohexyl‐18‐crown‐6 (t‐Bu)₂DC18C6 as membrane carrier was prepared. The electrode has a linear dynamic range from 6.3 × 10^?3‐5 × 10^?6 with a Nernstian response of 58.6 ± 1 mV decade^?1 and a detection limit of 1.3 × 10^?6 M. The response time of the sensor was 25 s. The membrane could be used for two months without any divergence in potentials. The electrode exhibits an anti‐Hofmeistetr selectivity sequence with a preference for triiodide at pH 2.0‐10.0. The response mechanism of the electrode was investigated by Uv‐Vis spectroscopic technique. The electrode can be used for the determination of ascorbic acid in orange juice.     

Analysis of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> PAO1 Biofilm Protein Profile After Exposure to <Emphasis Type="Italic">n</Emphasis>-Butanolic <Emphasis Type="Italic">Cyclamen coum</Emphasis> Extract Alone and in Combination with Ciprofloxacin

Pseudomonas aeruginosa biofilm-related infections are the major cause of premature death in cystic fibrosis patients. Strategies to induce biofilm dispersal are of interest, because of their potential in preventing biofilm-related infections. Our previous work demonstrated that n-butanolic Cyclamen coum extract with ciprofloxacin could eliminate 1- and 3-day-old P. aeruginosa PAO1 biofilms. To gain new insights into the role of C. coum extract and its synergistic effect with ciprofloxacin in eliminating P. aeruginosa PAO1 biofilms, two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry-based protein identification were used. Changes in the bacterial protein expression were analyzed when 3-day-old biofilm cells were exposed to the C. coum extract alone and in combination with ciprofloxacin. Proteins involved in alginate biosynthesis, quorum sensing, adaptation/protection, carbohydrate and amino acid metabolism showed a weaker expression in the C. coum extract-ciprofloxacin-treated biofilm cells compared to those in the untreated cells. Interestingly, the proteome of C. coum extract-ciprofloxacin-treated biofilm revealed more resemblance to the planktonic phenotype than to the biofilm phenotype. It appears that saponin extract in combination with ciprofloxacin causes biofilm disruption due to several mechanisms such as motility induction, cell envelope integrity perturbation, stress protein expression reduction, and more importantly, signal transduction perturbation. In conclusion, exposure to a combination of biofilm dispersal such as saponin extract and antimicrobial agents may offer a novel strategy to control preestablished, persistent P. aeruginosa biofilms and biofilm-related infections.