Dioxomolybdenum reagents in organic synthesis: utility of redox capability to design reduction and oxidation

The usefulness of dioxomolybdenum reagents in oxo-transfer reactions have been reviewed. The redox ability of dioxomolybdenum reagent has been utilized in designing several synthetic methods, which are useful in organic synthesis. Several reactions such as oxidation of alcohols, sulfides, amines, azides olefins etc are accomplished by using dioxomolybdenum reagents. Similarly, it is also demonstrated that dioxomolybdenum complex is useful in performing reduction of aldehydes, ketones, esters, azides etc. A fine tuning of reaction conditions provides suitable conditions to perform either oxidation or reduction by using catalytic amount of reagents. The oxidation reactions are further simplified by employing the polymer supported molybdenum reagents.

Nanostructured barbed wire architecturing of organic conducting material blends by electrospinning

In this study, fibers of barbed wire structure were obtained by electrospinning blend of organic conducting crystalline material and polyethylene oxide. Thermal and structural characterization of the blend fibers has been carried out to study the fiber characteristics. An increase in crystallinity in the electrospun fibers was observed and was attributed to both electrospinning process as well as addition of organic conducting crystalline material. A mechanism for the formation of this barbed wire structure has also been proposed. (C) 2012 American Institute of Physics. [doi:10.1063/1.3673620]

Charge transfer complex states in diketopyrrolopyrrole polymers and fullerene blends: Implications for organic solar cell efficiency

The spectral photocurrent characteristics of two donor-acceptor diketopyrrolopyrrole (DPP)-based copolymers (PDPP-BBT and TDPP-BBT) blended with a fullerene derivative [6,6]-phenyl C-61-butyric acid methyl ester (PCBM) were studied using Fourier-transform photocurrent spectroscopy (FTPS) and monochromatic photocurrent (PC) method. PDPP-BBT: PCBM shows the onset of the lowest charge transfer complex (CTC) state at 1.42 eV, whereas TDPP-BBT: PCBM shows no evidence of the formation of a midgap CTC state. The FTPS and PC spectra of P3HT:PCBM are also compared. The larger singlet state energy difference of TDPP-BBT and PCBM compared to PDPP-BBT/P3HT and PCBM obliterates the formation of a midgap CTC state resulting in an enhanced photovoltaic efficiency over PDPP-BBT: PCBM. (C) 2011 American Institute of Physics. [doi:10.1063/1.3670043]

Evaluation of the role of disordered organic fluorine in crystal packing: insights from halogen substituted benzanilides

The determination of the crystal and molecular structures of a large number of compounds containing the C(sp(2))-F bond has been investigated in detail in halogenated benzanilides and also in liquids, namely the fluorinated amines. It has been observed that when the fluorine atom is present in the ortho or meta position with respect to the amide functionality in benzanilides or the amino group in fluorinated amines which are liquids at room temperature, the fluorine atom exhibits positional disorder. This is associated with changes in patterns of intermolecular interactions which affect crystal packing. Furthermore, the presence of a fluorine atom on the benzanilide framework, in the presence of a heavier halogen (chloro, bromo and iodo), meta or ortho to the amide group does not eliminate the disorder associated with these molecules. In this article, we highlight the salient features present in halogenated compounds exhibiting disorder in the position of organic fluorine with concomitant changes in crystal packing. This feature is also compared with related compounds exhibiting similarity in electronic features, namely positional disorder.

Biodegradation of some organic reagents from mineral process effluents

The utility of a soil microbe, namely Bacillus polymyxa, in the removal of organic reagents such as dodecylamine, ether diamine, isopropyl xanthate and sodium oleate from aqueous solutions is demonstrated. Time-bound removal of the above organic reagents from an alkaline solution was investigated under different experimental conditions during bacterial growth and in the presence of metabolites by frequent monitoring of residual concentrations as a function of time, reagent concentration and cell density. The stages and mechanisms in the biodegradation process were monitored through UV-visible and FTIR spectroscopy. Surface chemistry of the bacterial cells as well as the biosorption tendency for various organics were also established through electrokinetic and adsorption density measurements. Both the cationic amines were found to be biosorbed followed by their degradation through bacterial metabolism. The presence of the organic reagents promoted bacterial growth through effective bacterial utilization of nitrogen and carbon from the organics. Under optimal conditions, complete degradation and bioremoval of all the organics could be achieved.

Dithienylcyclopentadienone derivative-co-benzothiadiazole: An alternating copolymer for organic photovoltaics

Alternating copolymer of 7,9-di(thiophen-2-yl)-8H-cyclopenta[a]acenaphthylen-8-one-co-benzothia diazole was synthesized by palladium(0) catalyzed Stille coupling reaction. This solution processable copolymer shows an excellent thermal stability and has a broad absorption range from 300 to 800 nm with a band gap of about 1.51 eV. High LUMO energy level and low band gap of the synthesized copolymers suggest that, this copolymer will be a suitable donor material for use in an organic photovoltaic device. Photovoltaic devices were fabricated from the blend of copolymer and phenyl-C61-butyric acid methyl ester as the active material. (C) 2011 Elsevier By. All rights reserved.

Pulsed plasma treatment of polluted gas using wet/low temperature corona reactors

pplication of pulsed plasma for gas cleaning is gaining prominence in recent years mainly from the energy consideration point of view. Normally, gas treatment is carried out, at or above room temperature, by a conventional dry type corona reactor. However, this treatment is still inadequate in the removal of certain stable gases present in the exhaust/flue gas mixture. The authors report some interesting results of the treatment of such stable gases with pulsed plasma at very low ambient temperature. Also reported in the paper is an improvement in DeNO/DeNOx efficiency using unconventional wet-type reactors, designed and fabricated by the authors, operating at different ambient temperatures. Apart from laboratory tests on simulated gas mixtures, field tests were also carried out on the exhaust gas of a 8 kW diesel engine. Further, an attempt was made to test the feasibility of a helical wire as a corona electrode in place of the conventional straight wire electrode. A comparative analysis of the various tests is presented together with a note on the energy consideration

Pulsed plasma treatment of polluted gas using wet/low temperature corona reactors

Application of pulsed plasma for gas cleaning is gaining prominence in recent years mainly from the energy consideration point of view. Normally, gas treatment is carried out, at or above room temperature, by a conventional dry type corona reactor. However, this treatment is still inadequate in the removal of certain stable gases present in the exhaust/flue gas mixture. The authors report some interesting results of the treatment of such stable gases with pulsed plasma at very low ambient temperature. Also reported in the paper is an improvement in DeNO/DeNOx efficiency using unconventional wet-type reactors, designed and fabricated by the authors, operating at different ambient temperatures. Apart from laboratory tests on simulated gas mixtures, field tests were also carried out on the exhaust gas of a 8 kW diesel engine. Further, an attempt was made to test the feasibility of a helical wire as a corona electrode in place of the conventional straight wire electrode. A comparative analysis of the various tests is presented together with a note on the energy consideration

Performance evaluation of nonthermal plasma reactors for NO oxidation in diesel engine exhaust gas treatment

The discharge plasma-chemical hybrid process for NO/sub x/ removal from the due gas emissions is an extremely effective and economical approach in comparison with the conventional selective catalytic reduction system. In this paper we bring out a relative comparison of several discharge plasma reactors from the point of NO removal efficiency. The reactors were either energized by AC or by repetitive pulses. Ferroelectric pellets were used to study the effect of pellet assisted discharges on gas cleaning. Diesel engine exhaust, at different loads, is used to approximately simulate the due gas composition. Investigations were carried out at room temperature with respect to the variation of reaction products against the discharge power. Main emphasis is laid on the oxidation of NO to NO/sub 2/, without reducing NOx concentration (i.e., minimum reaction byproducts), with least power consumption. The produced NO/sub 2/ will be totally converted to N/sub 2/ and Na/sub 2/SO/sub 4/ using Na/sub 2/SO/sub 3/. The AC packed bed reactor and pelletless pulsed corona reactor showed better performance, with minimum reaction products for a given power, when the NO concentration was low (/spl sim/100 ppm). At high engine loads (NO>300 ppm) there was not much decrease in NO/sub x/ reduction and more or less all the reactors performed equally. The paper discusses these observations in detail.

Intra-molecular hydrogen bonding with organic fluorine in the solution state: Deriving evidence by a two dimensional NMR experiment

The direct evidence for the existence of intra-molecular C-F center dot center dot center dot H-N hydrogen bond in organofluorine molecules, in the liquid state, is derived using NMR spectroscopy by the detection of long range interactions among fluorine, nitrogen and hydrogen atoms. The present study reports the determination of the relative signs and magnitudes of through space and through bond couplings to draw unambiguous evidence on the existence of weak molecular interactions involving organic fluorine. It is a simple, easy to implement, N-15 natural abundant two dimensional heteronuclear N-15-H-1 double quantum-single quantum correlation experiment. The existence of intra-molecular hydrogen bond is conclusively established in the investigated molecules. (C) 2011 Elsevier B.V. All rights reserved.

First-Principles Study of the Effect of Organic Ligands on the Crystal Structure of CdS Nanoparticles

We show with the aid of first-principles electronic structure calculations that suitable choice of the capping ligands may be an important control parameter for crystal structure engineering of nanoparticles. Our calculations on CdS nanocrystals reveal that the binding energy of model trioctylphosphine molecules on the (001) facets of zincblende nanocrystals is larger compared to that on wurtzite facets. Similarly, the binding energy of model cis-oleic acid is found to be dominant for the (10 (1) over bar0) facets of wurtzite structure. As a consequence, trioctylphosphine as a capping agent stabilizes the zincblende structure while cis-oleic acid stabilizes the wurtzite phase by influencing the surface energy, which has a sizable contribution to the energetics of a nanocrystal. Our detailed analysis suggests that the binding of molecules on the nanocrystalline facets depends on the surface topology of the facets, the coordination of the surface atoms where the capping molecule is likely to attach, and the conformation of the capping molecule.

Acenaphtho[1,2-b]quinoxaline based low band gap copolymers for organic thin film transistor applications

We report the synthesis of a novel class of low band gap copolymers based on anacenaphtho[1,2-b]quinoxaline core and oligothiophene derivatives acting as the acceptor and the donor moieties, respectively. The optical properties of the copolymers were characterized by ultraviolet-visible spectroscopy while the electrochemical properties were determined by cyclic voltammetry. The band gap of these polymers was found to be in the range 1.8-2.0 eV as calculated from the optical absorption band edge. X-ray diffraction measurements show weak pi-pi stacking interactions between the polymer chains. The hole mobility of the copolymers was evaluated using field-effect transistor measurements yielding values in the range 10(-5)-10(-3) cm(2)/Vs.