A density functional theory mechanistic study of thermal decomposition reactions of nitroethyl carboxylates: undermine of “pericyclic” insight

Quantum chemical study of thermal decomposition reactions of model nitroethyl carboxylates were studied using various density functional theory levels. It was found that conversion esters into nitroalkenes demean according to one‐step mechanism. However, it is not an expected “pericyclic” mechanism but a “one‐step two‐stage” process. Subsequently, nitrous acid extrusion was also analyzed.     

Near-Infrared-III-Absorbing and -Emitting Dyes: Energy-Gap Engineering of Expanded Porphyrinoids via Metallation

The synthesis of organometallic complexes of modified 26π-conjugated hexaphyrins with absorption and emission capabilities in the third near-infrared region (NIR-III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis-Pd^II and bis-Pt^II complexes of hexaphyrin via N-confusion modification led to substantial metal d_π–p_π interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long-wavelength shift of the lowest S₀→S₁ absorption beyond 1700 nm was achieved with the bis-Pt^II complex, t -Pt₂-3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t -Pt₂-3 potentially useful as a NIR-III PA contrast agent. The rigid bis-Pd^II complexes, t -Pd₂-3 and c -Pd₂-3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR-III-emissive and photoacoustic-response capabilities.     

A useful synthetic equivalent of a hydroxyacetone enolate

Indium promoted allylation of carbonyl compounds with 4-(bromomethyl)-1,3-dioxol-2-one diastereoselectively affords anti-α,β-dihydroxyketones, protected as enol carbonates. These initial products can be deprotected to free dihydroxyketones or transformed under mild conditions into the corresponding cyclic carbonates, which constitutes a useful approach to hydroxyacetone aldols.     

The computational methods in the development of a novel multianalyte calibration technique for potentiometric integrated sensors systems

In recent years, integration and miniaturization of ion-selective electrodes (ISEs) have brought many benefits resulting in the possibility of simultaneous determination of the ions concentration in small volume samples. One of the key problems related to the preparation of potentiometric integrated sensors systems (PISSs) is a calibration procedure due to the necessity to calibrate each particular sensor separately. The main aim of the research was to develop a novel calibration method for PISSs fabricated with the use of an all-solid-state technology, which has been compared with other types of sensor calibration technique. The proposed algorithm concerns the method of calibration solutions composition determination for miniature ion-selective sensors before measuring in biological samples especially human saliva samples. This article also compares the parameters of ion-selective sensors for two types of PISSs, including ISEs based on gold (Au) and glassy carbon (GC) electrodes. In addition, a series of measurements was performed using PISS with Au-ISEs in samples of human saliva, which were preceded by different types of sensor calibration and compared with the results obtained with the clinical analyzer. Moreover, the effect of the viscosity of calibration solutions on the ISE parameters and the lifetime of the sensors were investigated.

     

Hydrogen Production via Synthetic Biogas Reforming in Atmospheric-Pressure Microwave (915 MHz) Plasma at High Gas-Flow Output

Plasma Chemistry and Plasma Processing - This paper is a contribution to the development of microwave plasma-based technology for hydrogen (H2) production from a so-called synthetic biogas,...     

Design of the exoskeleton as a rehabilitation system

The presented paper concerns development of a parallel kinematic structure of a palm fingers exoskeleton as a prospective solution for common design difficulties encountered in typical serial-kinematics exoskeletons for the fingers rehabilitation. The performed state of the art review showed that in spite of over 40 years of development of exoskeletons, considered to be particularly useful as programmable medical devices, there is not achieved the acceptable level of safety and usability. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A DFT Study on the Molecular Mechanism of Additions of Electrophilic and Nucleophilic Carbenes to Non-Enolizable Cycloaliphatic Thioketones

The molecular mechanisms of addition of dihalocarbenes and dimethoxycarbene to thioketones derived from 2,2,4,4-tetrmethylcyclobutane-1,3-dione were examined on the basis of the DFT wb97xd/6-311g(d,p)(PCM) calculations. Obtained results demonstrated that the examined processes exhibit polar nature and in the case of electrophilic dichloro-, and dibromocarbenes are initiated by the attack of carbene species onto the sulfur atom of the C=S group. Remarkably, reactions involving more electrophilic carbenes (dichloro-, and dibromocarbene) proceeds via stepwise mechanism involving thiocarbonyl ylide as a transient intermediate. In contrast, analogous reactions with nucleophilic dimethoxycarbene occur via a single step reaction, which can be considered as the [2 + 1] cycloaddition reaction initiated by the attack onto the C=S bond. A computational study showed that difluorocarbene tends to react as a nucleophilic species and resembles rather dimethoxycarbene and not typical dihalocarbene species. Significantly higher reactivity of the thioketone unit in comparison to the ketone group, both present in 3-thioxo-2,2,4,4-tetramthylcyclobutanone molecule, was rationalized in the light of DFT computational study.     

Ion-selective electrodes based on p-tert-butyl-homooxacalixarene di(ethyl)amides

The diethyl amides of p-tert-butyldihomooxacalix[4]arene (1), p-tert-butylhexahomotrioxacalix[3]arene (2) and p-tert-butylcalix[4]arene (3) were used as active materials in ion-selective membrane electrodes to check the detection of different kinds of cations (Na⁺, K⁺, Cs⁺, Mg^2 + , Ca^2 + , Mn^2 + , Cu^2 + , Zn^2 + , Cd^2 + , Pb^2 +  and tetramethylammonium cation). The electrode characteristics and selectivity coefficients were determined and compared. Optimisation of the PVC membrane composition was achieved using three different plasticisers (bis(2-ethylhexyl) adipate, o-nitrophenyl octyl ether and bis(2-butylpentyl) adipate). Amide 3 shows selectivity for Na⁺, whereas compounds 1 and 2 exhibit the highest selectivity for Pb^2 +  among all the studied cations. The X-ray crystal structure of dihomooxacalix[4]arene tetra(diethyl)amide (1) was determined, revealing it to be in the cone conformation.     

Near‐Infrared‐III‐Absorbing and ‐Emitting Dyes: Energy‐Gap Engineering of Expanded Porphyrinoids via Metallation

The synthesis of organometallic complexes of modified 26π‐conjugated hexaphyrins with absorption and emission capabilities in the third near‐infrared region (NIR‐III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis‐Pd^II and bis‐Pt^II complexes of hexaphyrin via N‐confusion modification led to substantial metal d_π–p_π interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long‐wavelength shift of the lowest S₀→S₁ absorption beyond 1700 nm was achieved with the bis‐Pt^II complex, t ‐Pt₂‐3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t ‐Pt₂‐3 potentially useful as a NIR‐III PA contrast agent. The rigid bis‐Pd^II complexes, t ‐Pd₂‐3 and c ‐Pd₂‐3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR‐III‐emissive and photoacoustic‐response capabilities.     

Regioselective free radical phenylsulfenation of a non-activated δ-carbon atom by the photolysis of alkyl benzenesulfenate

A regioselective free radical introduction of a phenylthio group onto a non-activated δ-carbon atom was achieved by photolysis of alkyl benzenesulfenates in the presence of hexabutylditin, and δ-phenylthio alcohols were obtained in 35-91% yields. δ-Phenylsulfenylation of a non-activated carbon atom induced only by irradiation of alkyl benzenesulfenates (without initiation by hexabutylditin) also occurs, however, slower reaction rates were observed and lower yields of δ-phenylthio alcohols were obtained.