Facile Chan‐Lam coupling using ferrocene tethered N‐heterocyclic carbene‐copper complex anchored on graphene

Ferrocene tethered N‐heterocyclic carbene‐copper complex anchored on graphene ([GrFemImi]NHC@Cu complex) has been synthesized by covalent grafting of ferrocenyl ionic liquid in the matrix of graphene followed by metallation with copper (I) iodide. The [GrFemImi]NHC@Cu complex has been characterized by fourier transform infrared (FT‐IR), fourier transform Raman (FT‐Raman), CP‐MAS ¹³C NMR spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), energy dispersive X‐ray (EDX) analysis, X‐ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area analysis and X‐ray diffractometer (XRD) analysis. This novel complex served as a robust heterogeneous catalyst for the synthesis of bioactive N‐aryl sulfonamides from variety of aryl boronic acids and sulfonyl azides in ethanol by Chan‐Lam coupling. Recyclability experiments were executed successfully for six consecutive runs.     

Efficient monooleoyl glycerol synthesis employing hybrid ultrasonic-infrared-wave promoted reactor: Concurrent catalytic and noncatalytic esterification kinetics

For the first time, intensification of monooleoyl glycerol (MOG) synthesis has been investigated in an ultrasonic-infrared-wave (USIRW) promoted batch reactor. Esterification of octadecanoic acid (ODA) with glycerol (Gl) has been conducted [using Amberlyst 36 wet catalyst] in three different reactors, namely traditional batch reactor (TBR), infrared wave promoted batch reactor (IRWPBR), and USIRW-promoted batch reactor (USIRWPBR) to assess the relative efficacy. The energy-efficient USIRWPBR remarkably intensifies the ODA-Gl esterification as manifested through superior ODA conversion (92.5 ± 1.25%) compared to that achieved in IRWPBR (79.8 ± 1.2%) and TBR (36.39 ± 1.25%). The most favorable reaction condition for optimum ODA conversion and maximum MOG yield was identified through statistical optimization over a selected parametric range, namely 3-5 Gl/ODA mole ratio, 0.004-0.006 g/mL Amberlyst 36 catalyst concentration, 300-700 rpm impeller speed, and 333-353 K reaction temperature. The present study also reports the formulation and validation of an innovative reaction kinetics, that is, concurrent noncatalytic and heterogeneously catalyzed (CNCHC) reaction mechanism in addition to the conventional heterogeneous kinetic models (LH and Eley-Rideal mechanisms). Under combined USIRW, the CNCHC esterification mechanism could best describe ODA-Gl esterification (R² = 0.98) compared to LH (R² = 0.97) and Eley-Rideal (R² = 0.88) mechanisms. The optimal product (MOG) was characterized by differential scanning calorimetry and thermogravimetric analysis to assess its crystallization property and thermal stability for possible application as plasticizer/fuel additives.     

Universality in structure and elasticity of polymer-nanoparticle gels

We propose a combination of polymer field theory and off-lattice computer simulations to study polymer-bridged gelation in polymer-nanoparticle mixtures. We use this method to study the structure of gels formed in attractive polymer-colloid systems. Our results indicate that such gels exhibit a universal structure with a fractal dimension d(f) approximately 2.5 characteristic of random percolation. By mapping to an affine-network model, the enhancement in elastic moduli is predicted to follow a critical exponent nu(eta) approximately 1.8 characteristic of the resistor network percolation. We analyze selected experimental results to suggest the existence of a universality class corresponding to our results.     

Supramolecular Arrangement and DFT analysis of Zinc(II) Schiff Bases: An Insight towards the Influence of Compartmental Ligands on Binding Interaction with Protein

We report, for the first time, a detailed crystallographic study of the supramolecular arrangement for a set of zinc(II) Schiff base complexes containing the ligand 2,6-bis((E)-((2-(dimethylamino)ethyl)imino)methyl)-4-R-phenol], where R=methyl/tert-butyl/chloro. The supramolecular study acts as a pre-screening tool for selecting the compartmental ligand R of the Schiff base for effective binding with a targeted protein, bovine serum albumin (BSA). The most stable hexagonal arrangement of the complex [Zn − Me] (R=Me) stabilises the ligand with the highest FMO energy gap (ΔE=4.22 eV) and lowest number of conformations during binding with BSA. In contrast, formation of unstable 3D columnar vertebra for [Zn − Cl] (R=Cl) tend to activate the system with lowest FMO gap (3.75 eV) with highest spontaneity factor in molecular docking. Molecular docking analyses reported in terms of 2D LigPlot+ identified site A, a cleft of domains IB, IIIA and IIIB, as the most probable protein binding site of BSA. Arg144, Glu424, Ser428, Ile455 and Lys114 form the most probable interactions irrespective of the type of compartmental ligands R of the Schiff base whereas Arg185, Glu519, His145, Ile522 act as the differentiating residues with ΔG=−7.3 kcal mol⁻¹.     

Adsorption of Safranin-T from wastewater using waste materials- activated carbon and activated rice husks

Textile effluents are major industrial polluters because of high color content, about 15% unfixed dyes and salts. The present paper is aimed to investigate and develop cheap adsorption methods for color removal from wastewater using waste materials activated carbon and activated rice husk-as adsorbents. The method was employed for the removal of Safranin-T and the influence of various factors such as adsorbent dose, adsorbate concentration, particle size, temperature, contact time, and pH was studied. The adsorption of the dye over both the adsorbents was found to follow Langmuir and Freundlich adsorption isotherm models. Based on these models, different useful thermodynamic parameters have been evaluated for both the adsorption processes. The adsorption of Safranin-T over activated carbon and activated rice husks follows first-order kinetics and the rate constants for the adsorption processes decrease with increase in temperature.     

Variation in chemical,colloidal and electrochemical properties of carbon nanotubes with the degree of carboxylation

Multiwalled carbon nanotubes (CNTs) were carboxylated via microwave irradiation where the treatment time was varied to alter the degree of functionalization, and as many as one in 15 carbons in the CNT could be oxidized. Chemical, physical, electrochemical, and colloidal behavior of the carboxylated CNTs was studied. All properties changed with the degree of functionalization to a point beyond which they appeared to remain constant. The surface area increased from 173.9 to 270.9 m²/g while the critical coagulation concentration (CCC) values increased from 142.14 to 168.69 mM in the presence of NaCl, and the corresponding increase was from 0.97 to 5.32 mM in the presence of MgCl₂. As seen from cyclic voltammetry curves, the functionalized CNTs showed mainly non-Faradic interactions with Na₂SO_4, but showed Faradic behaviors in alkaline KOH.     

Intramolecular O‐arylation using nano‐magnetite supported N‐heterocyclic carbene‐copper complex with wingtip ferrocene

Nano‐magnetite supported N‐heterocyclic carbene‐copper complex with wingtip ferrocene has been prepared via multi‐step procedure. The complex has been characterized by various analytical techniques such as fourier transform infrared (FT‐IR), fourier transform Raman (FT‐Raman), X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) analysis. The catalytic activity of the complex has been exploited in intramolecular O‐arylation of o‐iodoanilides under heterogeneous conditions. The complex could be successfully recycled up to twelve consecutive cycles.     

Nanoparticles in solutions of adsorbing polymers: pair interactions, percolation, and phase behavior

We study the polymer adsorption characteristics, pair-interaction potentials, and phase and percolation behavior in nanoparticle-polymer mixtures. We propose a "saturable" adsorption model to capture the effect of the finite surface saturation capacity for adsorption, and use polymer self-consistent field theory in combination with a McMillan-Mayer framework [McMillan, W. G., Jr.; Mayer, J. E. J. Chem. Phys. 1945, 13, 276] to compute the pair-interaction potentials. Our results demonstrate novel size effects that distinguish the adsorption characteristics of nanoparticles from that of larger particles. Specifically, we predict that the nanoparticle regime is characterized by a significant adsorbance of polymers, albeit distributed predominantly in the form of tails. We also demonstrate that an interplay between the surface saturation, polymer-to-particle size ratios, and the polymer concentrations governs the overall effective interactions between nanoparticles in the presence of an adsorbing polymer. We use simple, mean-field models to relate these characteristics to the phase and percolation behavior in such systems. Our results show that the percolation thresholds for smaller particles are significantly smaller (and, overall, correspond only to a few volume percent) compared to that of the larger particles. Further, with a decrease in the size of the particles, we also predict a considerable increase in the miscibility of the polymer-particle mixtures. Our results are qualitatively in accord with many experimental observations in the nanoparticle regime.