DFT and local MP2 study of switching process in a pH controllable molecular “shuttle”

A pH controllable molecular “shuttle,” comprising of dibenzo 24 crown‐8 (DB24C8) macroring bound to a “finger” molecule possessing two different recognition sites has been studied at the density functional theory (DFT) and Møller‐Plesset second‐order (MP2) levels of theory. The calculation confirmed experimental results that translational conformer with DB24C8 located around NH station has the lowest energy, while the conformer with DB24C8 located around NH station shows the highest energy. It has been found that Bpym2+ unit consists of two “substations” separated by an energy barrier of 3–17 kcal/mol depending on the state of the NH–NH station. The translational conformers are stabilized by NH…O, ⁺NH…O, ⁺NCH…OH‐bonds, and π–π stacking with different contributions, depending on the conformer type. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem 2007     

Spontaneous Ring‐Opening Polymerization of Macrocyclic Aromatic Thioether Ketones under Transient High‐Temperature Conditions

Summary: Spontaneous ring‐opening polymerization of macrocyclic aromatic thioether ketones [ 1,4‐SC₆H₄COC₆H₄ ]_n (n = 3 and 4), in which the thioether linkages are para to the ketone, occurs during rapid, transient heating to 480 °C, to afford a soluble, semi‐crystalline poly(thioether ketone) of high molar mass (η_inh > 1.0 dL · g⁻¹). Corresponding macrocyclic ether ketones, and a macrocyclic thioether ether ketone in which the thioether linkage is para to the ether rather than to the ketone, show no evidence of polymerization under analogous conditions.

The uncatalysed ring‐opening polymerization of macrocycle 1 , within the pores of an alumina microfiltration membrane, leads to formation of polymer 3 with the microstructure shown in the above scanning electron micrograph.     

A Novel,One‐Pot Synthesis of Novel 3F, 5F,and 8F Aromatic Polymers

A series of novel, linear, soluble, high‐molecular‐weight, fluorinated aromatic polymers has been obtained for the first time using a superacid‐catalyzed polyhydroxyalkylation reaction of fluorinated carbonyl‐containing compounds: 1,1,1,‐trifluoroacetone ( 1 ), 2,2,2‐trifluoroacetophenone ( 2 ), 2,3,4,5,6,‐pentafluorobenzaldehyde ( 3 ), and octafluoroacetophenone ( 4 ) with aromatic hydrocarbons such as biphenyl ( a ), phenyl ether ( b ), terphenyl ( c ), and 4,4′‐diphenoxybenzophenone ( d ). These Friedel‐Crafts‐type aromatic electrophilic substitution reactions are performed at room temperature in trifluoromethane sulfonic acid or in its mixtures with dichloromethane. The polymers obtained are soluble in common organic solvents, and colorless transparent films could be cast from the solutions. ¹H and ¹³C NMR analyses of the polymers synthesized reveal their linear, highly regular structure. The polymers also possess high thermostability.

     

Spin-glass ordering in amorphous Tb-Cr alloys

This paper discusses amorphous TbxCr_100−x alloys (x=16, 28.5, 43, and 59 at.%) obtained by quenching from the vapor phase. It is found that the structure of the alloys is heterogeneous: the coexistence of two amorphous phases, characterized by different short-range order, is observed. The short-range order of these phases qualitatively corresponds to the structure of pure components (Cr or Tb). In the low-temperature region, the alloys transform to the spin-glass state. It is established that the transition temperatures to the spin-glass state depends on the composition linearly, increasing as the terbium concentration increases. It is shown that the magnetic properties of amorphous Tb-Cr alloys are determined by the random magnetic anisotropy associated with the Tb atoms. Fiz. Tverd. Tela (St. Petersburg) 41, 1236–1239 (July 1999)     

Novel Dinuclear Redox‐isomeric Complexes with a Tetrapodal Pyridine‐based Ligand

Tris‐o‐semiquinonato cobalt complexes react with a tetrapodal pyridine‐derived ligand to form dinuclear cobalt compounds of general formula (OMP)[CoQ₂]₂, where OMP = 2,2′‐(pyridine‐2,6‐diyl)bis(N¹,N¹,N³,N³‐tetramethylpropane‐1,3‐diamine), Q = mono‐ or dianion of 3,6‐di‐tert‐butyl‐o‐benzoquinone (complex 1 ) and it derivatives: 3,6‐di‐tert‐butyl‐4,5‐N,N′‐piperazino‐o‐benzoquinone (complex 2 ), and 3,6‐di‐tert‐butyl‐4‐Cl‐o‐benzoquinone (complex 3 ). Single crystal X‐ray crystallography of 1 and 3 indicates two bis‐quinonato cobalt units bound by an OMP ligand, which acts as a bridge. Each central cobalt atom is chelated by one N¹,N¹,N³,N³‐tetramethylpropane‐1,3‐diamine and two o‐quinonato fragments. The nitrogen atom of the pyridine ring is uncoordinated. All complexes were characterized by NIR‐IR and EPR spectroscopy, precise adiabatic vacuum calorimetry, and by variable‐temperature magnetic susceptibility measurements. All data indicate a reversible thermally driven redox‐isomeric (valence tautomeric) transformation in the solid state for all complexes.     

Some Methods for Human Liquid and Solid Waste Utilization in Bioregenerative Life-Support Systems

Bioregenerative life-support systems (BLSS) are studied for developing the technology for a future biological life-support system for long-term manned space missions. Ways to utilize human liquid and solid wastes to increase the closure degree of BLSS were investigated. First, urine and faeces underwent oxidation by Kudenko's physicochemical method. The products were then used for root nutrition of wheat grown by the soil-like substrate culture method. Two means of eliminating sodium chloride, introduced into the irrigation solution together with the products of urine oxidation, were investigated. The first was based on routine electrodialysis of irrigation water at the end of wheat vegetation. Dialysis eliminated about 50% of Na from the solution. This desalinization was performed for nine vegetations. The second method was new: after wheat cultivation, the irrigation solution and the solution obtained by washing the substrate containing mineral elements not absorbed by the plants were used to grow salt-tolerant Salicornia europaea L. plants (saltwort). The above-ground biomass of this plant can be used as a food, and roots can be added to the soil-like substrate. Four consecutive wheat and Salicornia vegetations were cultivated. As a result of this wheat and Salicornia cultivation process, the soil-like substrate salinization by NaCl were considerably decreased.     

Electromagnetic scattering by a homogeneous chiral obstacle in a chiral environment

Time-harmonic electromagnetic waves are scattered by a homogeneouschiral obstacle embedded in a chiral environment. The correspondingtransmission problem is reduced, via Bohren's decomposition,to an integral equation over the interface between the obstacleand the surrounding medium. This integral equation is shownto be uniquely solvable except for a discrete set of electromagneticparameters of the obstacle.     

Fractal structure of fullerite

We have obtained macroscopic fractal aggregates of fullerite ranging in size from 100 to 400 μm. The fractal structure of fullerite is formed by microscopic (30–100 nm) fullerite crystals in the presence of a temperature gradient under conditions of diffusion-limited aggregation. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 684–685 (10 May 1998)