Polyborylation of azulenes

In the presence of an active Ir-based catalyst, azulene underwent stepwise borylation with bis(pinacolato)diboron to produce polyborylated products. The reactivity of the ring atoms toward borylation was found to decrease in the following order: 2-position>1,3-positions>6-position>5,7-positions. Extension of the borylation to some azulenes substituted at the five-membered ring was also examined. Furthermore, the reaction of 2,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)azulene (3a) with an equivalent of hydrogen peroxide revealed that the oxidation proceeds preferentially at the 6-position. This indicates that the reactivity of the boryl group is governed by the π-polarization of the azulenyl skeleton.     

Synthesis of some new pyrimidine selanyl derivatives

The targeted synthesis of 2-(methylsulfanyl)-6-(furan-2-yl)-4(3H)-selenoxo -pyrimidine-5-carbonitrile failed due to the formation 1-methyl-2-methylsulfanyl-6-oxo -4-(furan-2-yl)-1,6-dihydropyrimidine-5-carbonitrile. A new series of 5,6,7,8-tetrahydro-1-benzo thieno[2,3-d]pyrimidine-4-yl substituted selanyl derivatives were prepared by the reaction of sodium diselenide with 4-chloro-5,6,7,8-tetrahydro-1-benzothieno[2,3-d]pyrimidine followed by the reaction with chloroacetic acid derivatives such as ethyl chloroacetate, chloroacetamide or chloroacetonitrile. Hydrazinolysis of ethyl (5,6,7,8-tetrahydro-1-benzothieno[2,3-d]pyrimidine- 4-ylselanyl)acetate with hydrazine hydrate gave the corresponding hydrazino derivative. The latter reacted with ethyl acetoacetate, acetylacetone, diethyl malonate, ethoxymethylenemalononitrile or ethyl 2-cyano-3-ethoxyacetate to afford 5-methyl-2-[2-(5,6,7,8-tetrahydro-1-benzothieno [2,3-d]pyrimidine-4-ylselanyl)acetyl]-2,4-dihydropyrazol-3-one, 1-(3,5-dimethylpyrazol-1-yl)-2- (5,6,7,8-tetrahydro-1-benzothieno[2,3-d]pyrimidin-4-ylselanyl)ethanone, 1-[2-(5,6,7,8-tetrahydro -1-benzothieno[2,3-d]pyrimidine-4-ylselanyl)acetyl]-2,4-dihydropyrazolidine-3,5-dione and 5-Amino-1-[2-(5,6,7,8-tetrahydro-1-benzothieno[2,3-d]pyrimidin-4-ylselanyl)acetyl]-1H-pyrazol -4-yl substituted carbonitrile or ethyl carboxylate, respectively. The structure of the novel compounds was confirmed by spectroscopic tools (IR, ¹H NMR ¹³C NMR and mass spectra) and elemental analysis.     

Crystal structure of the sulfonium salts of natural azulenes

The molecular and crystal structure of dimethyl-(1,4-dimethyl-7-ethylazulyl)-sulfonium perchlorate and dimethyl-(1,4-dimethyl-7-isopropylazulyl)-sulfonium perchlorate was determined by X-ray diffraction analysis. Their crystal structure is mainly determined by C-H...π intermolecular interactions.     

Diastereoselective synthesis of aziridine esters via amino selanyl esters

A synthesis of aziridine esters based on the cyclisation of amino selanyl esters induced by the selanyl group activation was developed with either the Meerwein salt or NBS. Two asymmetric approaches are proposed: the diastereoselective reductions of α-selanyl β-iminoesters derived from α-oxoesters, which lead to cis chiral aziridine esters 6 and 6′; and the diastereoselective conjugate additions of a chiral amide to α,β-unsaturated esters providing trans chiral aziridine esters 6 and 6″.     

The electrochemical behavior of colloidal polypyrrole

 The electrochemical behavior and charge transport of colloidal polypyrrole particles (without stabilizer) modified electrode have been investigated. The voltam-metric results show that the electro-chemical behavior of colloidal polypyrrole is different from that of polypyrrole synthesized electro-chemically. The strong adsorption of the colloidal particles on substrate makes it easy to form a polypyrrole modified electrode. The charge transport of polypyrrole is controlled by the diffusion of counterions. Received: 13 December 1996 Accepted: 24 May 1997     

Effects of heat-treatment on electrochemical behavior

The polyacenic semiconductive (PAS) material is a typical amorphous carbon prepared by pyrolysis of phenolformaldehyde resin, and is actually utilized as anode of high-capacity rechargeable batteries. In this work, change in the discharging amount of Li⁺ before and after heat-treatment of the PAS electrodes at the various doping level was examined in detail. As a result, the doped Li can be classified into two types: (i) heat-resistant Li-dopant (or Li-dopant with high diffusion coefficient) and (ii)heat-fragile Li-dopant (or Li-dopant with low diffusion coefficient). The latter Li-dopants are generated above the doping level of 30% ([Li]/[C]→0.3) and is considered to be the origin of high-capacity of PAS anode compared with that of graphite anode. This aspect is also supported by the ESR, ⁷Li-NMR, and XPS observation results. This revised version was published online in August 2006 with corrections to the Cover Date.     

Elucidation of the electrochemical behavior of phenothiazine-based polyaromatic amines

Polyarlylamines with discrete redox active groups in the polymer backbone represent a promising class of cathode materials for electrical energy storage applications. In this area, our group recently reported a set of phenothiazine-based polymers that exhibit both high capacities and power densities. In order to rationally improve the properties of these electrode materials, a fundamental understanding of their electrochemical properties is indispensable. Herein, we probe the electrochemical behavior of our phenothiazine-based systems by synthesizing small molecule analogs using C–N cross-coupling. Additionally, electropolymerization of a class of these small molecule phenothiazines yields thin films that were then characterized with an electrochemical quartz crystal microbalance. Analysis of these materials provides insights into the number of electrons accessed from each repeat unit in our polymer backbone during electrochemical cycling, as well as counter ion transport dynamics.     

乙撑二氧噻吩在中性水溶液中的电化学聚合及行为研究

本文研究了乙撑二氧噻吩在中性水溶液中的电化学聚合过程以及聚乙撑二氧噻吩膜的电化学行为, 利用光电子能谱和红外光谱等方法对聚合物膜进行了表征, 研究表明在中性水溶液中制成的聚乙撑二氧噻吩膜修饰电极具有较好的电化学行为和稳定性。     

Difference in the electrochemical behavior of three isomeric phthalaldehydes

Polarographic current–voltage curves enabled distinguishing between the degree of covalent hydration of iso-, tere-, and orthophthalaldehydes. Hydration, which is negligible for isophthalaldehyde, strong for terephthalaldehyde and very strong for orthophthalaldehyde, together with acid–base reactions, affect the electrolysis of each of the three isomers differently. In solutions of orthophthalaldehyde polarography enables simultaneous following of concentrations of the unhydrated, acyclic monohydrated, cyclic hemiacetal forms. Each of these forms react with amino acids by a different rate.     

Theoretical approach to the out-of-plane deformation of 1,3-disubstituted azulenes

Computational calculations at B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) levels were employed to analyze the structure and conformation of 1,3-bis(4-bromophenyl)azulene (1), 1,3-bis(2-thienyl)azulene (2), and 1,3-bis(2-pyrrollyl)azulene (3) in order to rationalize the out-of-plane deformation found in the azulene cores of 1 and 2 in the crystalline state, whereas compound 3 shows a totally planar azulene moiety. Our results indicate that 1,3-disubstituted azulenes possess two almost equally stable and easily convertible minimum energy conformers, which differ in the relative orientation of the substituent groups and in the planarity degree of the azulene core. An absolute planarity index (P) is introduced to quantify the out-of-plane distortion found in the azulenes under study. The aromaticity of minimum energy conformers was evaluated by means of geometric (HOMA), magnetic (NICS), and energetic (the frequency of the lowest out-of-plane vibration, ν_min) aromaticity indicators, which suggest that compound 3 possesses the most aromatic azulene core within the group. Calculated molecular dipole moments suggest that the conformation of 1,3-disubstituted azulenes in the crystalline state can be explained in terms of electrostatic intermolecular interactions rather than relative stability of planar and non-planar conformers.     

On the theory of the electrochemical diode

Russian Chemical Bulletin -     

On the corrosion behavior of Al2Cu by local electrochemical impedance spectroscopy using droplet cell microscopy

Journal of Solid State Electrochemistry - In this short communication, we study the electrochemical behavior of an individual Al2Cu intermetallic phase (coexisting with α-Al) in 0.1 M...     

Unexpectedly large binding constants of azulenes with fullerenes

In spite of having small pi-conjugation systems, azulenes show large binding constants (10(4)-10(5)) to C(60) and C(70), which are larger than those of monoporphyrins and alternant aromatic hydrocarbons.     

Adsorptive behavior and electrochemical determination of the anti-fungal agent ketoconazole

The adsorptive properties and electrochemical behavior of ketoconazole, an oral anti-fungal agent, are demonstrated at a glassy carbon electrode. The adsorption of the compound obeys the Frumkin isotherm with an interaction factor (α) of 0.985 and adsorptive coefficient (β) of 1.98 × 10⁶ L mol^–1. The Gibbs energy of adsorption (ΔG) is –3.59 × 10⁴ J mol^–1 at 25?°C. A very sensitive electroanalytical method has been developed for determination of the drug with a detection limit of 4.0 × 10^–11 mol L^–1. Relationships between stripping current and concentration of ketoconazole were linear in the range 10^–6–10^–10 mol L^–1 with different preconcentration periods. The method has been used to measure the ketoconazole content of tablets.     

Adsorptive behavior and electrochemical determination of the anti-fungal agent ketoconazole

The adsorptive properties and electrochemical behavior of ketoconazole, an oral anti-fungal agent, are demonstrated at a glassy carbon electrode. The adsorption of the compound obeys the Frumkin isotherm with an interaction factor (alpha) of 0.985 and adsorptive coefficient (beta) of 1.98 x 10(6) L mol(-1). The Gibbs energy of adsorption (deltaG) is -3.59 x 10(4) J mol(-1) at 25 degrees C. A very sensitive electroanalytical method has been developed for determination of the drug with a detection limit of 4.0 x 10(-11) mol L(-1). Relationships between stripping current and concentration of ketoconazole were linear in the range 10(-6)-10(-10) mol L(-1) with different preconcentration periods. The method has been used to measure the ketoconazole content of tablets.