Stereoselective preparation of mono- and bis-derivatives of pentacyclo[6.3.0.02,6.03,10.05,9] undecane (D 3-trishomocubane)

The rearrangement of easily accessible Cookson’s diketone with chlorosulfonic acid in chloroform followed by the acidic hydrolysis gave 6-chloro-7-hydroxy-dichloropentacyclo[6.3.0.0^2,6.0^3,10.0^5,9]undecane-4-one, whose syn-stereochemistry was assigned through the X-ray crystal structure analysis. This key structure was used for the stereoselective synthesis of the D ₃-trishomocubane derivatives as well as for the preparation of potential drugs bearing hydroxy- and amino-functional groups. A new multigram preparative synthesis of D ₃-trishomocubane was developed.      

Electrochemically deposited thiophene-based polymers as protective agents for Prussian Blue thin films

A composite material based on overlapped layers of electrochemically synthesized Prussian Blue (PB) and terthiophene-derived polymer is described, aiming at enhancing the stability of the hexacyanoferrate thanks to the protective action of the polymer. Two bilayer configurations and deposition methods (for the polymer component) were tested. The morphology and electrochemical behavior in organic solvent and in aqueous solutions containing different supporting electrolytes were carried out. The best performances of electrodes modified with films of the composite material as to increased stability of PB were achieved with the potentiostatically deposited polymer covering the PB layer, in acetate buffer at pH 5.5. As for potential cycling stress, the anodic and cathodic peak currents due to PB were not decreased after 20 cycles. Conversely, PB alone displayed the anodic peak currents relevant to PB/Prussian White (PW) and PB/Berlin Green (BG) systems decreased by about 30 %. The stability to local pH increase was assessed by cyclic voltammetry after electrochemical reduction of H₂O₂. For example, the anodic peak currents were decreasing by 15 % and 5 % for the two PB redox systems, while for PB alone the same currents decreased by 35 % and 10 %. The response sensitivity to hydrogen peroxide was improved by 54 %, with respect to PB alone, as evaluated by chronoamperometry.     

Antimicrobial Activities of Plant Extracts against Solanum tuberosum L. Phytopathogens

The purpose of the study was to select an environmentally friendly plant biopesticide to protect seed potatoes against phytopathogens. The scope included the evaluation of the antimicrobial activities of 22 plant water extracts, 22 water-glycol extracts, and 3 subcritical carbon dioxide extracts using the agar diffusion method against 10 potato phytopathogens. For the most effective extracts, minimal inhibitory concentration (MIC), chemical composition analysis by gas chromatography–mass spectrometry and in situ assays on seed potatoes were performed. Garlic water extract was finally selected as the most effective in phytopathogen growth inhibition, both in vitro and in situ, with MIC values ranging between 6.3–25 mg/mL. 5-Hydroxymethylfurfural was determined to be the main component of this extract (33.24%). Garlic water extract was proposed as a potential biopesticide against potato phytopathogens.     

Phase conjugation by reflection gratings in electrooptic crystals

Phase conjugation by reflection gratings in electrooptic crystals in investigated in a nonlinear model proposed by Kukhtarev and Semenets [1] which takes into account not only photoconductivity but also dark conductivity. The coupled-wave equations of the model can be solved analytically. To take the boundary conditions into account, numerical calculations are unavoidable. These can be performed, however, without any approximation. Phase mismatch and self-oscillation effects are dealt with in the undepleted pump approximation.Two of us (KHR and GT) would like to dedicate this paper to Prof. Dr. H. Salecker on the occasion of his 65^th birthday     

1H NMR Study of the HCa2Nb3O10 Photocatalyst with Different Hydration Levels

The photocatalytic activity of layered perovskite-like oxides in water splitting reaction is dependent on the hydration level and species located in the interlayer slab: simple or complex cations as well as hydrogen-bonded or non-hydrogen-bonded H₂O. To study proton localization and dynamics in the HCa₂Nb₃O₁₀·yH₂O photocatalyst with different hydration levels (hydrated—α-form, dehydrated—γ-form, and intermediate—β-form), complementary Nuclear Magnetic Resonance (NMR) techniques were applied. ¹H Magic Angle Spinning NMR evidences the presence of different proton containing species in the interlayer slab depending on the hydration level. For α-form, HCa₂Nb₃O₁₀·1.6H₂O, ¹H MAS NMR spectra reveal H₃O⁺. Its molecular motion parameters were determined from ¹H spin-lattice relaxation time in the rotating frame (T_1ρ) using the Kohlrausch-Williams-Watts (KWW) correlation function with stretching exponent β = 0.28: Ea=0.2102 eV, τ0=9.01 × 10−12 s. For the β-form, HCa₂Nb₃O₁₀·0.8H₂O, the only ¹H NMR line is the result of an exchange between lattice and non-hydrogen-bonded water protons. T_1ρ(1/T) indicates the presence of two characteristic points (224 and 176 K), at which proton dynamics change. The γ-form, HCa₂Nb₃O₁₀·0.1H₂O, contains bulk water and interlayer H⁺ in regular sites. ¹H NMR spectra suggest two inequivalent cation positions. The parameters of the proton motion, found within the KWW model, are as follows: Ea=0.2178 eV, τ0=8.29 × 10−10 s.     

Study of regioselectivity in cyanomethylation of 4-(trifluoromethyl)pyrimidin-2(1Н)-ones

Chemistry of Heterocyclic Compounds - Cyanoacetic acid reacted selectively with 4-(trifluoromethyl)pyrimidin-2(1Н)-ones with the formation of Michael addition–decarboxylation products...     

Models of multicriterial optimization of structuring made of composite materials

Mechanics of Composite Materials -     

Conformational Analysis of N-Alkyl-N-[2-(diphenylphosphoryl)ethyl]amides of Diphenylphosphorylacetic Acid: Dipole Moments,IR Spectroscopy,DFT Study

Experimental and theoretical conformational analysis of N-methyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, N-butyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, and N-octyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide was carried out by the methods of dipole moments, IR spectroscopy, and Density Functional Theory (DFT) B3PW91/6-311++G(df,p) calculations. In solution, these N,N-dialkyl substituted bisphosphorylated acetamides exist as a conformational equilibrium of several forms divided into two groups—with Z- or E-configuration of the carbonyl group and alkyl substituent, and syn or anti arrangement of the phosphoryl-containing fragments relative to the amide plane. The substituents at the phosphorus atoms have eclipsed cis- or staggered gauche-orientation relative to the P=O groups, and cis orientation of the substituents is due to the presence of intramolecular H-contacts P=O...H−C_phenyl or p,π conjugation between the phosphoryl group and the phenyl ring. Preferred conformers of acetamides molecules are additionally stabilized by various intramolecular hydrogen contacts with the participation of oxygen atoms of the P=O or C=O groups and hydrogen atoms of the methylene and ethylene bridges, alkyl substituents, and phenyl rings. However, steric factors, such as a flat amide fragment, the bulky phenyl groups, and the configuration of alkyl bridges, make a significant contribution to the realization of preferred conformers.