Strategic Substitution of −OH/−NR2 (R=Et,Me) Imparts Colorimetric Switching between F− and Hg2+ by Salicyaldehyde/Benzaldehyde-Quinoxaline Conjugates

We herein report two salicyaldehyde-quinoxaline ( HQS and HQSN ) conjugates and a benzaldehyde-quinoxaline ( QBN ) conjugate to fabricate selective chemosensors for F⁻ and Hg²⁺ in the micromolar range. This work demonstrates how sensing outcomes are affected by modulating proton acidity by introducing an electron donating group, −NEt₂, in the probe backbone. Interestingly, the un-substituted probe HQS can selectively detect F⁻, whereas HQSN and QBN are selective for Hg²⁺. In order to gain insights into the mechanism of sensing, geometry optimizations have been carried out on QS⁽⁻¹⁾ , QS⁽⁻¹⁾⋅⋅⋅HF , QSN⁽⁻¹⁾ and QSN⁽⁻¹⁾⋅⋅⋅HF and the experimental data are validated in terms of free energy and pK_a values. Detailed DFT and TD-DFT analyses provide ample support towards the mechanism of sensing of the analytes.     

CO2 Fixation and Catalytic Reduction by a Neutral Aluminum Double Bond

CO₂ fixation and reduction to value‐added products is of utmost importance in the battle against rising CO₂ levels in the Earth's atmosphere. An organoaluminum complex containing a formal aluminum double bond (dialumene), and thus an alkene equivalent, was used for the fixation and reduction of CO₂. The CO₂ fixation complex undergoes further reactivity in either the absence or presence of additional CO₂, resulting in the first dialuminum carbonyl and carbonate complexes, respectively. Dialumene ( 1 ) can also be used in the catalytic reduction of CO₂, providing selective formation of a formic acid equivalent via the dialuminum carbonate complex rather than a conventional aluminum–hydride‐based cycle. Not only are the CO₂ reduction products of interest for C₁ added value products, but the organoaluminum complexes isolated represent a significant step forward in the isolation of reactive intermediates proposed in many industrially relevant catalytic processes.     

Synthesis of organic–inorganic chiral block poly(methylphenylsilane) functional polymers,and study of their optical and chiroptical properties

Polysilanes upon UV irradiation give rise to silyl macroradicals which are capable to initiate radical polymerization. Hence, chiral block functional polysilanes were synthesized by UV irradiation of poly(methylphenylsilane) (PMPS) with a vinyl chiral monomer, (R)‐N‐(1‐phenylethyl)methacrylamide (R‐NPEMAM). The synthesized copolymer samples were characterized by FTIR, NMR, and UV–vis spectroscopy. The number and weight average molecular weights of PMPS and synthesized chiral‐block‐PMPS were measured by GPC analysis. Two glass transition temperatures (T_g) of the synthesized materials clearly indicate the formation of chiral‐block‐PMPS copolymers. SEM analysis also indicated the synthesized organic–inorganic block copolymers. The optical and chiroptical properties of the synthesized materials were studied. The cotton effect is observed not only at 276 nm due to aromatic ring of the chiral monomer units but also at 325 nm which is associated with the Si–Si conjugation of PMPS block of synthesized functional polysilanes. Such tunable chirality may find potential application in optoelectronics. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3626–3634     

Sensing of Micellar Microenvironment with Dual Fluorescent Probe, Triazolylpyrene (TNDMBPy)

We report a dual fluorescent triazolylpyrene ( ^TNDMB Py) as an efficient fluorescent light-up probe of various micellar microenvironments. The absorption spectra of ^TNDMB Py in an aqueous solution of varying surfactant concentration, CTAB, SDS and TX-100 showed that as the surfactant concentration was increased the absorbance increased with no shift in wavelength maxima. The increase of absorbance in each surfactant solution with increase in surfactant concentration was due to the enhanced solubilization of ^TNDMB Py in surfactant solutions. Our investigations based on steady state and time resolved fluorescence techniques showed that the probe reports the microenvironment of ionic surfactant solutions (CTAB and SDS) via dual emission (LE and ICT) at low surfactant concentration. The ICT band showed a blue shifting pattern with enhanced intensity that disappeared as the concentration of surfactant increases (> 1 mM for CTAB and > 3 mM for SDS). In non-ionic surfactant (Triton X-100) solution, the fluorophore showed dual emission with dominant ICT behaviour over LE emission at low concentration (up to 0.35 mM). In reverse micelle we observed a blue shifted ICT band with no LE band with increasing molar concentration of water. We found 100 nm blue shifting when we moved from R?=?0 to R?=?7, where R is the molar ratio of water to TX-100 (R?=?[H2O]/[TX-100]). The blue shifting of ICT band is because of the movement of the probe from hydrophilic core to hydrophobic core (surface) of the reverse micelle. Thus from the steady-state fluorescence study it was observed that the ICT band of the probe, ^TNDMB Py was more influenced by the micellar environment in comparison to the LE band. This difference in behaviour of the fluorophore is probably because of varying extent of hydrophobic/hydrogen bonding interactions experienced by the probe and its relative disposition inside the various micellar nanocores.      

Substoichiometric extraction of chromium(III) with 2-picolinic acid into n-butanol

A substoichiometric radiochemical extraction procedure has been designed for the estimation of trace amounts of chromium(III). The method employs the extraction of spiked (⁵¹Cr) chromium by chelation with 2-picolinic acid in n-butanol solvent at pH 4. The interference effects of various closely related foreign ions on the extraction efficiency were found to be negligible, thus establishing the selectivity of the proposed technique over other standard analytical procedures available for the estimation of chromium(III). The validity of this method has been established by successful estimation of chromium present in various certified alloys. Investigations have been made to understand the parameters controlling the extraction of chromium(III).     

Automated separation of 99Tc using plastic scintillation resin PSresin and openview automated modular separation system (OPENVIEW-AMSS)

Automated methods for the analysis of radionuclides potentially increase laboratory productivity by reducing operator intervention and increasing the number of samples that can be treated in a given time. To this end, here we report a new openview automated modular separation system which can be used in combination with PSresin, in this case, for the analysis of ⁹⁹Tc. Quality parameters of this method using the automated system were comparable to those obtained manually and quantification of water samples spiked with low levels of ⁹⁹Tc resulted in deviations lower than 10% for all the samples analysed.

     

Buffer Influence on the Amino Acid Silica Interaction

Protein-surface interactions are exploited in various processes in life sciences and biotechnology. Many of such processes are performed in presence of a buffer system, which is generally believed to have an influence on the protein-surface interaction but is rarely investigated systematically. Combining experimental and theoretical methodologies, we herein demonstrate the strong influence of the buffer type on protein-surface interactions. Using state of the art chromatographic experiments, we measure the interaction between individual amino acids and silica, as a reference to understand protein-surface interactions. Among all the 20 proteinogenic amino acids studied, we found that arginine (R) and lysine (K) bind most strongly to silica, a finding validated by free energy calculations. We further measured the binding of R and K at different pH in presence of two different buffers, MOPS (3-(N-morpholino)propanesulfonic acid) and TRIS (tris(hydroxymethyl)aminomethane), and find dramatically different behavior. In presence of TRIS, the binding affinity of R/K increases with pH, whereas we observe an opposite trend for MOPS. These results can be understood using a multiscale modelling framework combining molecular dynamics simulation and Langmuir adsorption model. The modelling approach helps to optimize buffer conditions in various fields like biosensors, drug delivery or bio separation engineering prior to the experiment.     

Radical copolymerization of fullerene (C60) and n‐butyl methacrylate (BMA) using triphenylbismuthonium ylide and characterization of C60–BMA copolymers

Radical copolymerization of fullerene (C₆₀) and n‐butyl methacrylate (BMA) has been carried out using triphenylbismuthonium ylide as an initiator at 70°C for 4 h in a dilatometer under nitrogen atmosphere. The kinetic expression of the polymerization is R_pα [Ylide]^0.5[C₆₀]^?1.0[BMA]^1.2, which is similar to that expected for ideal kinetics. The rate of polymerization increases with an increase in the concentration of initiator and BMA. However, it decreases with an increase in the concentration of fullerene. Fullerene acts as radical scavengers causing retardation in polymerization. The activation energy of copolymerization was estimated to be 72.2 K J mol^?1. The fullerene‐containing BMA copolymers were characterized by FTIR, ¹H NMR, ¹³C NMR, UV–vis, and GPC analyses. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 608–619, 2011