Chemosensitive properties of poly-4,4′-dialkoxy-2,2′-bipyrroles

Chemosensitive properties of 4,4′-dimethoxy-2,2′-bipyrrole and 4,4′-dibuthoxy-2,2′-bipyrrole were investigated. These new conductive polymers were polymerized by cyclic voltammetry on the platinum and gold interdigitated electrodes designed for 2- and 4-point measurement of lateral conductivity. Thus, obtained polymers demonstrated high sensitivity to HCl in the parts per million concentration range. Kinetics of the gaseous HCl influence on the ratios of conductivities measured by 2- and 4-point techniques was analyzed. Some response of the polymers conductance towards NH₃, NO and oxygen was also observed, but with much lower sensitivity than towards HCl. In aqueous solutions, the polymer conductivity was pH dependent; in comparison with 4,4′-dibuthoxy-2,2′-bipyrrole, the conductivity range of the methoxy derivative was shifted to acidic range for about two pH units. A possibility to use the pH dependence for the development of enzymatic biosensors with pH transducing was demonstrated.     

Tris(thianthrene)(2+) bis(dodecamethylcarba‐closo‐dodecaborate) dichloromethane tetrasolvate: a crossed triple‐decker π‐trimer dication

The title compound, (3C₁₂H₈S₂)²⁺·2C₁₃H₃₆B₁₁⁻·4CH₂Cl₂, contains an unusual cation–radical association comprising a π‐trimer dication of crossed thianthrenes. The thianthrene molecular planes are essentially cofacial, but the S...S axes of adjacent molecules are orthogonal to each other. The outer thianthrenes (both located on mirror planes bisecting the units at the S atoms) are bent slightly towards the inner and planar thianthrene (residing on a 2/m symmetry element with the S atoms on the twofold rotation axis), with close noncovalent separations of 3.1 Å indicating strong interplanar interactions within the trimeric dication. Bond‐length analysis indicates that the 2+ charge is delocalized over the three stacked thianthrenes with the maximum charge on the central unit. The crossed monomer arrangement is attributed to the frontier‐orbital symmetry that allows various π‐bonding orientations between thianthrene molecules. The CB₁₁(CH₃)₁₂⁻ counter‐ion resides on a mirror plane. One of the CH₂Cl₂ solvent molecules resides on a twofold rotation axis, whereas the other is located on a mirror plane.     

About some new integral inequalities of Wendroff type for discontinuous functions

In this article, we obtain some new nonlinear integral inequalities for discontinuous functions of two independent variables (Wendroff type) by including also inequalities with delay. We deduce new generalizations of earlier results given by R.P. Agarwal, R. Bellman, I. Bihari, B.K. Bondge, V. Lakshmikantham, S. Leela, B.G. Pachpatte for continuous and discrete functions. Furthermore, generalizations of some results for integro-sum inequalities are obtained as well.     

Halogen Bonding Between Anions: Association of Anion Radicals of Tetraiodo‐p‐benzoquinone with Iodide Anions

Halogen bonding between two negatively charged species, tetraiodo‐p‐benzoquinone anion radicals (I₄Q^?.) and iodide anions, was observed and characterized for the first time. X‐ray structural and EPR/UV–Vis spectral studies revealed that the anion–anion bonding led to the formation of crystals comprising 2D layers of I₄Q^?. anion radicals linked by iodides and separated by Et₄N⁺ counter‐ions. Computational analysis suggested that the seemingly antielectrostatic halogen bonds in these systems were formed via a combination of several factors. First, an attenuation of the interionic repulsion by the solvent facilitated close approach of the anions leading to their mutual polarization. This resulted in the appearance of positively charged areas (σ‐holes) on the surface of the iodine substituents in I₄Q^?. responsible for the attractive interaction. Finally, the solid‐state associations were also stabilized by multicenter (4:4) halogen bonding between I₄Q^?. and iodide.     

Enantioselective total synthesis of (+)-salvileucalin B

An enantioselective total synthesis of the diterpenoid natural product (+)-salvileucalin B is reported. Key findings include a copper-catalyzed arene cyclopropanation reaction to provide the unusual norcaradiene core and a reversible retro-Claisen rearrangement of a highly functionalized norcaradiene intermediate.     

An optimal multivariate spline method of recovery of twice differentiable functions

A continuous quadratic polynomial spline of several variables is constructed. It solves the optimal recovery problem studied by V.F. Babenko, S.V. Borodachov, and D.S. Skorokhodov for the class of functions defined on a convex polytope in R ^d , whose second derivatives in any direction are uniformly bounded, and for a periodic analogue of this class. The information consists of the values and gradients of the function at some finite set of nodes in R ^d .     

Refinement of the experimental energy levels of higher 2D Rydberg states of the lithium atom with very accurate quantum mechanical calculations

Very accurate variational non-relativistic calculations are performed for four higher Rydberg (2)D states (1s(2)nd(1), n = 8,..., 11) of the lithium atom ((7)Li). The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions and finite nuclear mass is used. The exponential parameters of the Gaussians are optimized using the variational method with the aid of the analytical energy gradient determined with respect to those parameters. The results of the calculations allow for refining the experimental energy levels determined with respect to the (2)S 1s(2)2s(1) ground state.     

Oxidative transformations of 6-trifluoromethyl-2H-thiopyran as a route to fluoro-containing thiopyranosides

The synthesis of cis- and trans-6-(trifluoromethyl)-3,4-dihydro-2H-thiopyran-3,4-diols from 6-(trifluoromethyl)-2H-thiopyran via an OsO₄-catalysed dihydroxylation and bromohydroxylation-alkaline hydrolysis sequence is described. Acetylation of the diols followed by S-oxidation affords the corresponding cis- and trans-3,4-diacetoxy-6-(trifluoromethyl)-3,4-dihydro-2H-thiopyran S-oxides which reacted with acetic anhydride and boron trifluoride diethyl ether complex by an additive Pummerer pathway giving tetraacetyl derivatives of trifluoromethyl-containing thiopyranoses.     

Vibrational transitions of the 7LiH+ ion calculated without the Born-Oppenheimer approximation and with leading relativistic corrections

We recently presented very accurate calculations of the fundamental vibrational frequency of the (7)LiH(+) and (3)He(4)He(+) ions [Stanke et al. Phys. Rev. A 79, 060501(R) (2009)] performed without the Born-Oppenheimer approximation and included leading relativistic corrections. The accuracy of those calculations was estimated to be of the order of 0.06 cm(-1). In the present work we extend the calculations to the remaining pure vibrational states of (7)LiH(+) and similarly accurate results are generated. They may lead to the experimental search for still unidentified lines corresponding to those transitions.