Multiple active motifs grafted on cyclotriphosphazene core: a novel catalyst for the chemical activation of carbon dioxide

A novel catalyst having multiple triphenylphosphonium chloride motifs on a single cyclotriphosphazene molecule has been developed for the chemical activation of carbon dioxide for the production of propylene carbonate from carbon dioxide and propylene oxide. The unique structure and multiple catalytic sites on a single framework are the prime factors, resulted in the enhanced catalytic activity and afforded high product yield.     

Synthesis and Crystal Structure of 3,5-Dichloro-N-(2-methoxyphenyl)benzamide

<正>The title compound was synthesized by the direct reaction of 3,5-dichlorobenzoic acid with 2-methoxyaniline in the presence of DCC and HOBT. The structure was supported by the spectroscopic data and unambiguously confirmed by the single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the monoclinic space group P2_1/c with unit cell dimensions of a = 4.9369(16), b = 13.351(5), c = 20.168(7), β = 96.755(8)°, V = 1320.1(8)~3 and Z = 4.     

Cold Pad-Batch dyeing method for cotton fabric dyeing with reactive dyes using ultrasonic energy

Reactive dyes are vastly used in dyeing and printing of cotton fibre. These dyes have a distinctive reactive nature due to active groups which form covalent bonds with -OH groups of cotton through substitution and/or addition mechanism. Among many methods used for dyeing cotton with reactive dyes, the Cold Pad Batch (CPB) method is relatively more environment friendly due to high dye fixation and non requirement of thermal energy. The dyed fabric production rate is low due to requirement of at least twelve hours batching time for dye fixation. The proposed CPB method for dyeing cotton involves ultrasonic energy resulting into a one third decrease in batching time. The dyeing of cotton fibre was carried out with CI reactive red 195 and CI reactive black 5 by conventional and ultrasonic (US) method. The study showed that the use of ultrasonic energy not only shortens the batching time but the alkalis concentrations can considerably be reduced. In this case, the colour strength (K/S) and dye fixation (%F) also enhances without any adverse effect on colour fastness of the dyed fabric. The appearance of dyed fibre surface using scanning electron microscope (SEM) showed relative straightening of fibre convolutions and significant swelling of the fibre upon ultrasonic application. The total colour difference values ΔE (CMC) for the proposed method, were found within close proximity to the conventionally dyed sample.     

Computation using noise-based logic: efficient string verification over a slow communication channel

Utilizing the hyperspace of noise-based logic, we show two string verification methods with low communication complexity. One of them is based on continuum noise-based logic. The other one utilizes noise-based logic with random telegraph signals where a mathematical analysis of the error probability is also given. The last operation can also be interpreted as computing universal hash functions with noise-based logic and using them for string comparison. To find out with 10^-25 error probability that two strings with arbitrary length are different (this value is similar to the error probability of an idealistic gate in today's computer) Alice and Bob need to compare only 83 bits of the noise-based hyperspace.     

Viscoelastic measurements of single molecules on a millisecond time scale by magnetically driven oscillation of an atomic force microscope cantilever

The dynamical nature of biomolecular systems means that knowledge of their viscoelastic behavior is important in fully understanding function. The linear viscoelastic response can be derived from an analysis of Brownian motion. However, this is a slow measurement and technically demanding for many molecular systems of interest. To address this issue, we have developed a simple method for measuring the full linear viscoelastic response of single molecules based on magnetically driven oscillations of an atomic force microscope cantilever. The cantilever oscillation frequency is periodically swept through the system resonance in less than 200 ms allowing the power spectrum to be obtained rapidly and analyzed with a suitable model. The technique has been evaluated using dextran, a polysaccharide commonly used as a test system for single molecule mechanical manipulation experiments. The monomer stiffness and friction constants were compared with those derived from other methods. Excellent agreement is obtained indicating that the new method accurately and, most importantly, rapidly provides the viscoelastic response of a single molecule between the tip and substrate. The method will be a useful tool for studying systems that change their structure and dynamic response on a time scale of 100-200 ms, such as protein folding and unfolding under applied force.     

Helix reversals as bad neighbors to liquid crystal organizations in cholesteric states and thermally reversible gels of poly(ALKYL isocyanates)

While the temperature dependence of the lyotropic cholesteric pitch of the single helical sense poly ((R)-2,6-dimethylheptyl isocyanate) is in line with theory, comparable data on this state produced by chiral doping of the lyotropic nematic state of poly(n-hexyl isocyanate) could suggest an interplay between the supramolecular chirality of the liquid crystal and the dynamic equilibrium of the left and right hand helical blocks in this otherwise racemic polyisocyanate. The exclusion of helix reversals, as undersireable kinks in the liquid crystal organization, could play a role in this effect. Such helix reversal exclusions can also explain the peculiar chiral optical changes associated with the thermally reversible gelation of poly(n-hexyl isocyanate) copolymers in hydrocarbon solvents. These gels likely arise by entering the broad biphasic region of the Flory phase diagram leading to the formation of liquid crystal aggregates.     

Synthesis of 8‐Desoxythunberginol A and (±)‐8‐Desoxy‐3,4‐Dihydrothunberginol A

A two step synthesis of title isocoumarin isolated from Homalium longifolium and its conversion into corresponding 3,4‐dihydroisocoumarin has been described. 3,4‐Dimethoxybenzoyl chloride on condensation with homophthalic acid afforded 3‐(3′,4′‐dimethoxyphenyl)isocoumarin which was demethylated to furnish the 8‐desoxythunberginol A, whereas its sequential saponification, reduction and demethylation yielded the (±)‐8‐desoxy‐3,4‐dihydrothunberginol A. The synthesized compounds were examined in vitro for antibacterial activity.     

Viscoelastic properties of single polysaccharide molecules determined by analysis of thermally driven oscillations of an atomic force microscope cantilever

We report on single molecule measurements of the viscoelastic properties of the polysaccharide dextran using a new approach which involves acquiring the power spectral density of the thermal noise of an atomic force microscope cantilever while holding the single molecule of interest under force-clamp conditions. The attractiveness of this approach when compared with techniques which use forced oscillations under constant loading rate conditions is that it is a near-equilibrium measure of mechanical response which provides a more relevant probe of thermally driven biomolecular dynamics. Using a simple harmonic oscillator model of the cantilever-molecule system and by subtracting the response of the free cantilever taking into account hydrodynamic effects, the effective damping zetamol and elastic constant kmol of a single molecule are obtained. The molecular elasticity measured by this new technique shows a dependence on applied force that reflects the chair-boat conformational transition of the pyranose rings of the dextran molecule which is in good agreement with values obtained directly from the gradient of a conventional constant loading rate force-extension curve. The molecular damping is also seen to follow a nontrivial dependence on loading which we suggest indicates that it is internal friction and not work done on the solvent that is the dominant dissipative process.     

Expeditious and efficient synthesis of Strecker’s α-aminonitriles catalyzed by sulfated polyborate

A straightforward, mild, efficient, and environmentally benign protocol for a three-component Strecker reaction of aldehydes or ketones, amines, and trimethylsilyl cyanide catalyzed by sulfated polyborate has been described to afford α-aminonitriles under solvent-free reaction conditions. The major advantages of the present method are excellent yields, shorter reaction time, simple experimental procedure, easy workup procedure, recyclability of the catalyst, solvent-free reaction conditions and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards.     

An efficient synthesis of 3,5‐dimethoxyhomophthalic acid,a key intermediate for synthesis of natural isocoumarins

3,5‐Dimethoxyhomophthalic acid was prepared efficiently in three steps, from 3,5‐dimethoxybenzyl bromide via rhodium‐catalyzed direct carbonylation to 3,5‐dimethoxyphenylacetic acid followed by successive o‐formylation and oxidation. Isocoumarins related to agrimonolide and achlisocoumarin 1 were prepared in single step by condensation of the homophthalic acid with appropriate acid chlorides.