Hydrolytic Kinetic Resolution of Terminal Epoxides catalyzed by Novel Bimetallic Chiral Co (Salen) Complexes

Novel bimetallic chiral Co (salen) complexes bearing transition‐metal salts have been synthesized. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity in hydrolytic kinetic resolution (HKR) of racemic terminal epoxides and consequently provided enantiomerically enriched epoxides (up to 99% ee).     

Diphenyltin(IV) dithiocarbamate macrocyclic scaffolds as potent apoptosis inducers for human cancer HEP 3B and IMR 32 cells: synthesis,spectral characterization,density functional theory study and in vitro cytotoxicity

Binuclear diphenyltin(IV) dithiocabamate macrocyclic complexes [(Ph₂Sn^IV)₂‐μ²‐bis{(κ²S,S‐S₂CN(R)CH₂CONHC₆H₄)₂O}] (R = ⁱPr ( 1 ), ^sBu ( 2 ), ⁿBu ( 3 ), Cy ( 4 ), 2‐furfuryl ( 5 ) or benzyl ( 6 )) were synthesized through a self‐assembly process involving novel diamino precursors 4,4′‐bis(2‐(alkylamino)acetamido)diphenyl ethers ( L¹ , L² , L³ , L⁴ , L⁵ , L⁶ ), CS₂ and Ph₂SnCl₂. These were characterized using microanalysis and relevant spectroscopic methods. The geometry of all compounds was optimized using the density functional theory method. In vitro cytotoxic activity was evaluated against HEP 3B (hepatoma) and IMR 32 (neuroblastoma) using the MTT assay. Notably, complexes 1 , 2 , 3 , 4 , 5 , 6 were found to be extremely active against both cell lines and cytotoxicity data confirmed their 16‐fold better potency compared to cisplatin, a well‐known antineoplastic drug. Flow cytometric analysis of annexin V–propidium iodide‐stained cells demonstrated the ability of L⁵ , 4 and 6 to induce apoptosis in HEP 3B and IMR 32 cells, required for major therapeutic implication in cancer therapy. The extraordinary potency of binuclear complex 4 can be correlated with higher LUMO energy together with the greatest value of residual charge on the Sn(IV) centre among the compounds under investigation. Copyright © 2015 John Wiley & Sons, Ltd.     

Cooperative catalysis: Condensation-aromatization for synthesis of 2-(4-nitrophenyl)-1H-benzimidazole by silica immobilized Brønsted-Lewis acidic ionic liquid (Si-BLAIL)

Herein, pleasing the advantageous of both Brønsted and Lewis acidic site of Si-BLAIL the condensation-aromatization reaction has been carried out. The striking distinctiveness of work is optimum reaction condition, easy work-up, high yield, catalyst recyclability, non-inertness of reaction flask, simple catalyst loading method. The decreases in the amount of catalyst and reaction time shows good to high (71%–93%) yield suggests about the involvement of some interesting mechanism such as cooperative catalysis. The mechanism has been hypothesizes as, the Si-BLAIL increase the efficiency of condensation reaction possibly by providing the proton in 2-position of cationic imidazolium ring of BLAIL through the hydrogen bond interaction with carbonyl group and nucleophilic activation during aromatization by hydrogen bond acceptor ability of Lewis adduct anion of BLAIL. The catalyst Si-BLAIL shows massive affirm for industrial applications. The Si-BLAIL has identified as the best acid catalyst for 2-(4-nitrophenyl) benzimidazole synthesis with additional benefits of cooperative catalysis.     

Positron annihilation spectroscopic studies of Mn substitution-induced cubic to tetragonal transformation in ZnFe2–xMnxO4 (x = 0.0–2.0) spinel nanocrystallites

The replacement of cations at the B-sites in the spinel ferrite ZnFe₂O₄ by Mn³⁺ ions brings in several interesting changes, the most striking among them being a transformation from the spinel cubic structure to a body-centered tetragonal one. Concomitantly, there are variations in the nanocrystallite sizes and also in the lattice parameters. These are examined through high-precision X-ray diffraction measurements and transmission electron microscopic analysis. A more interesting aspect is the success of positron annihilation spectroscopy comprising of the measurements of positron lifetime and coincidence Doppler broadening measurements in understanding the effects of cation replacement and the resultant generation of vacancy-type defects. There are definite changes in the positron lifetimes and intensities which show positron trapping in trivacancy-type defect clusters and the nanocrystallite surfaces. The presence of ortho-positronium atoms within the extended intercrystallite region is also identified, although in small concentrations. The cubic to tetragonal transformation is indicated through definite decrease in the values of the positron lifetimes. We also performed a model analysis to predict the expected effect of substitution on the positron lifetime in the bulk of the sample and the experimentally obtained positron lifetimes significantly differed, indirectly hinting at the possibility of a structural transformation. Finally, Mössbauer spectroscopic studies have indicated a ferromagnetic nature for one of the samples, i.e. the one with Mn³⁺ doping concentration x = 0.4, which incidentally had the lowest crystallite size ~10 nm.     

Simple Platform Method for the Synthesis of Densely Functionalized Microgels by Modification of Active Ester Latex Particles

This study reports a simple and versatile synthesis route for the preparation of highly uniform and densely functionalized aqueous microgels by modification of latex particles composed of an active ester monomer (pentafluorophenyl acrylate; PFPA). The hydrophobic nature of the PFPA allows synthesizing very uniform latex particles via emulsion polymerization, whose size can be controlled by the surfactant concentration, while the degree of crosslinking is a function of the added crosslinker. The high reactivity of the PFPA groups toward nucleophilic substitution delivers a platform method to synthesize functional microgels by reaction with functional amines. This study demonstrates this process for the dense functionalization of the entire particle with an amine carrying a pH‐responsive unit. This study further describes the influence of the crosslinking degree on the ability for swelling of the resulting microgels in aqueous dispersion.

     

Effect of solvents having different dielectric constants on reactivity: A conceptual DFT approach

Conceptual density functional theory is exploited to understand the reactivity in a medium of solvents with increasing dielectric constants. Aprotic as well as protic solvents are used for this study. It is found that the global parameters, such as chemical potential and hardness, decrease from gas phase to solvent phase with increasing dielectric constant. However, it is observed that the Fukui functions of the reactive atoms increase significantly with the dielectric constants of the aprotic solvents while for the protic solvents the variation of the reactivity indices is insignificant. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Biocatalytic anode for glucose oxidation utilizing carbon nanotubes for direct electron transfer with glucose oxidase

Covalently linked layers of glucose oxidase, single-wall carbon nanotubes and poly-l-lysine on pyrolytic graphite resulted in a stable biofuel cell anode featuring direct electron transfer from the enzyme. Catalytic response observed upon addition of glucose was due to electrochemical oxidation of FADH₂ under aerobic conditions. The electrode potential depended on glucose concentration. This system has essential attributes of an anode in a mediator-free biocatalytic fuel cell.     

Studies of Thermodynamic Properties of Binary and Ternary Methanolic Solutions Containing KBr and 18-Crown-6 at 298.15 K

Experimental measurements of the speed of sound, density and osmotic vapour pressure are reported for binary 18-Crown-6 (18C6) + CH₃OH, KBr + CH₃OH and ternary KBr + 18C6 + CH₃OH solutions at 298.15 K. The density and compressibility data were processed to obtain the apparent molar volume (ø _V ) and apparent molar isentropic compressibility ( $\phi _{K_S } Experimental measurements of the speed of sound, density and osmotic vapour pressure are reported for binary 18-Crown-6 (18C6) + CH₃OH, KBr + CH₃OH and ternary KBr + 18C6 + CH₃OH solutions at 298.15 K. The density and compressibility data were processed to obtain the apparent molar volume (? _V ) and apparent molar isentropic compressibility () of the solutes in methanol. Expansivity data were obtained for the 18C6 + CH₃OH system from density data at different temperatures and were used for calculation of the isothermal compressibility values at 298.15 K. The isothermal compressibility and expansivity data are further used to obtain the apparent molar isothermal compressibility () and apparent molar expansivity (? _E ) of 18C6 in methanolic solutions and as well as the energy-volume coefficient parameter (∂ U/∂ V) _T in methanol solutions. The volume and compressibility changes due to complexation of KBr with 18C6 are obtained at infinite dilution for ? _V and ? _K . The results are compared with the similar data obtained by us previously for aqueous and CCl₄ solutions. The osmotic coefficient data were used to calculate activities and activity coefficients of each component at 298.15 K as a function of the concentration of binary and ternary methanolic solutions containing KBr and 18C6. The activity and activity coefficient data are used to evaluate the pair and triplet interaction parameters by making appropriate use of the McMillan-Meyer theory of solutions. The calculation of the thermodynamic equilibrium constant (K) is made using the pair interaction parameter, g _NE (non-electrolyte – electrolyte pair interaction), for the complexation equilibria. The nature of interactions present in the CH₃OH solutions is discussed.     

Dynamic unfolding of a regulatory subunit of cAMP-dependent protein kinase by capillary electrophoresis: Impact of cAMP dissociation on protein stability

Characterization of the unfolding dynamics of a recombinant type IA regulatory subunit (RIalpha) of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (cAPK) was examined by CE with UV detection. Electrophoretic separation of RIalpha by CE in a buffer devoid of cAMP resulted in rapid dissociation of the complex from the original sample due to the high negative mobility of the ligand relative to receptor. This process enabled in-capillary generation of cAMP-stripped RIalpha, which was used to estimate the apparent dissociation constant (Kd) of 0.6 +/- 0.2 microM. A comparison of RIalpha dynamic unfolding processes with urea denaturation was performed by CE with (i.e., RIalpha-cAMP) and without (i.e., cAMP-stripped RIalpha) excess cAMP in the buffer during electromigration. The presence of cAMP in the buffer confirmed greater stabilization of the protein, as reflected by a higher standard free energy change (DeltaG(U) degrees) of 10.1 +/- 0.5 kcal x mol(+1) and greater cooperativity in unfolding (m) of -2.30 +/- 0.11 kcal x mol(-1) M(-1). CE offers a rapid, yet versatile platform for probing the thermodynamics of cAPK and other types of receptor-ligand complexes in free solution.