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      Volume 129, Issue 9

      September 2017,   pages  1326a-1512

    • Table of Contents

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    • Thermodynamics of association of water soluble fullerene derivatives [C ₆₀ (OH)n, n = 0, 2, 4, 8 and 12] in aqueous media


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      The thermodynamics of association of fullerene [C₆₀] and water-soluble fullerene derivatives, i.e., fullerols [C ₆₀ (OH)n, n = 0, 2, 4, 8 and 12] in aqueous solutions have been studied using molecular dynamics simulations. The potentials of mean force (PMFs) bring out the tendency of aggregation of these nanostructuresin water. The extent of hydroxylation seems to have a minor effect on the depth of the contact minima (the first minimum in the PMFs). The positions of the subsequent minima and maxima in the PMFs change with the size of the solute molecules. Higher stability of the contact state of highly hydroxylated fullerols is due to the van der Waals interactions whereas intermolecular solute-solvent hydrogen bonding nearly flattens the PMFs beyond the 2nd minima for higher fullerols. The solvent contributions to the PMFs for all the solute particles studied here are positive. Entropic and enthalpic contributions to the association of solute molecules are calculated in the isothermal-isobaric (NPT) ensemble. We find that the contact pair formation is governed by entropy with the enthalpic contributions being highly unfavorable, whereas the solvent assisted and solvent separated configurations show entropy-enthalpy compensation.

    • Density functional theory calculations of charge transport properties of ‘plate-like’ coronene topological structures


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      Charge transport rate is one of the key parameters determining the performance of organic electronic devices. In this paper, we used density functional theory (DFT) at the M06-2X/6−31+G(d) level to compute the charge transport rates of nine coronene topological structures. The results show that the energy gap of these nine coronene derivatives is in the range 2.90–3.30 eV, falling into the organic semiconductor category. The size of the conjugate ring has a large influence on the charge transport properties. Incorporation of methyl groupson the rigid core of tetrabenzocoronene and hexabenzocoronene is more conducive to the hole transport of the molecule than incorporating methoxyl groups. The derivatisation of a ‘long plate-like’ coronene with methoxylgroups facilitates both hole and electron transport. This class of molecules can thus be used in the design of ambipolar transport semiconductor materials.

    • Enhanced NLO response in BODIPY-coumarin hybrids: density functional theory approach


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      We have thoroughly investigated the first, second and third polarizability characteristics of four hybrid chromophores by spectroscopic and computational methods. B3LYP, CAMB3LYP and BHandHLYP functionals in combination with 6-311+G(d,p) basis set were used to evaluate the polarizability and hyperpolarizability characteristics of these chromophores. Generalized Mulliken Hush analysis and frontier molecular orbital electronic distribution images of chromophores obtained from Density functional theory computation has established the charge transfer characteristics of these hybrid chromophores. On the basis of charge transfer characteristic, these red absorbing and NIR emissive chromophores possess high nonlinear optical response. Comparison of isolated units with their analogous hybrid chromophores shows that fusion ofcoumarin with BODIPY enhances the nonlinear optical response.

    • High rates of catalytic hydrogen combustion with air over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ coated cordierite monolith


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      Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ was coated on γ -Al ₂O ₃-coated honeycomb structured cordierite monolith (AHCM) by solution combustion method using dip-dry-heat process. This is a modified conventional method to coat the catalysts on honeycomb structured cordierite monolith (HCM). Formation of Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ on AHCMwas confirmed by XRD. The XPS spectra of Pd(3d) core level confirmed Pd ion in Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ is in the form of +2 state.The surface morphology of coated catalystwas unchanged by long time exposure to hydrogencombustion reaction; i.e., H ₂ +O ₂ recombination reaction which indicated the stability of coating on monolith. Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ showed high rates of H ₂ + O ₂ recombination compared to 2 atom% Pd(metal)/γ -Al ₂O ₃, Ce ₀. ₉₈Pd ₀. ₀ ₂O₂ δ ,Ce ₀. ₉₈Pt ₀. ₀ ₂O₂ δ Ce ₀. ₇₃Zr ₀. ₂₅Pd ₀. ₀ ₂O₂ δ, Ti ₀. ₉₉Pd ₀. ₀ ₁O₂ δ and Ti ₀. ₉₈Pd ₀. ₀ ₂O₂ δ. The activation energy of H ₂ + O ₂ recombination reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ is 7.8 kcal/mol. The rates of reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ at 60◦C are in the range between 10 and 20 μmol/g/s. The rate of reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ increased with increase in the concentration of H ₂. For 50 mL of H ₂, it showed rates of the reaction around 36.45 μmol/g/s at room temperature and 230 μmol/g/s at 60◦C. It was found that the rate of reaction due was lower due to hindering effect by adsorption of other gas molecules on the catalytic site.Finally, we propose a mechanism of hydrogen and oxygen recombination reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ.

    • Liquid-phase oxidation of naphthalene with H ₂O ₂ in the presence of ordered mesoporous V-m-Al ₂O ₃ catalysts


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      The ordered mesoporous V-m- Al ₂O ₃ catalysts were successfully synthesized via a facile one-pot evaporation-induced self-assembly (EISA) strategy and applied in the liquid-phase oxidation of naphthalene with hydrogen peroxide in the presence of ascorbic acid as a reductant. The physicochemical properties of the catalysts were investigated using various techniques, like XRD, N₂ sorption, UV-Vis spectra, Raman spectroscopy, XPS, XRF and TEM. Small-angle XRD, N₂ sorption and TEM results show that mesoporous V-m- Al ₂O ₃ catalysts possess a highly ordered mesostructure with large surface areas and narrow pore-size distributions. Highangle XRD, UV-Vis spectra and Raman spectroscopy results indicate that VOx species were homogeneously incorporated in thematrix ofmesoporous Al ₂O ₃.The catalytic performance in the liquid oxidation of naphthalene with H ₂O ₂ over 8V-m- Al ₂O ₃ catalyst (naphthalene conversion 45.4% and phthalic anhydride selectivity 61.0%) was higher than other catalysts. The vanadium species incorporated in the 8V-m- Al ₂O ₃ sample were stable, and its catalytic stability was kept well even after repeated use for 5 times, which indicates a green and economical pathway for naphthalene degradation.

    • Exploring antioxidant reactivity and molecular structure of phenols by means of two coupled assays using fluorescence probe (2,3-diazabicyclo[2.2.2]oct-2-ene, DBO) and free radical (2,2-diphenyl-1-picrylhydrazyl, DPPH·)


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      Phenolic compounds can be considered as themost important bioactive compounds in Mediterranean diet. However, many of the complex connections between phenols antioxidant reactivity and their molecular structure remain unsolved. To shine light on these issues, the antioxidant reactivity of 15 relevant phenolic compounds was studied. Two different analytical approaches were combined: (a) the well-established 2,2- diphenyl-1-picrylhydrazyl (DPPH·) stable free radical assay, and (b) the 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO)fluorescent probe assay. The results obtained confirm how certain structural features (i.e., hydroxyl and methoxy groups, alkyl and alkenyl chains) play a critical role in the singular antioxidant response exhibited by eachphenolic compound. This knowledge provides decisive information to select a specific phenolic compound as an antioxidant additive or for the chemical design of new antioxidants.

    • Synthesis, photophysical, electrochemical and electroluminescence studies of red emitting phosphorescent Ir(III) heteroleptic complexes


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      Five heteroleptic, cyclometalated (CN) Iridium(III) complexes of acetylacetone (acac) and 1-phenyl-isoquinoline (piq) derivatives, Ir(acac)(piq) ₂, Ir(acac)(2,4-difluoro-piq) ₂, Ir(acac)(4-trifluoromethylpiq) ₂, Ir(acac)(4-N,N-dimethyl-piq) ₂, Ir(acac)(4-acetyl-piq) ₂, were synthesized and characterized. The ((CN) ₂ Ir(acac) complexes in toluene showed phosphorescence (λmax = 598 nm to 658 nm) with quantum yields (0.1 to 0.32) and microsecond lifetimes (0.43 to 1.9 μs). The complexes were non-luminescent in thin films due to self-quenching but luminescent when lightly doped (5%) in a host organic material, 4,4' -Bis(Ncarbazolyl)- 1,1' -biphenyl (CBP). The HOMO levels determined using cyclic voltammetric oxidation potentials were in the range−5.48 to−5.80 eV. Electroluminescence properties and performance of the Ir complexes dopedin CBP (active layer) were studied in a multilayer (ITO/F4TCNQ/TPD/doped CBP/BCP/LiF/Al) organic light emitting device (OLED). The electroluminescense (EL) spectra of the device matched with the phosphorescent spectra of the Ir complexes. The turn-on voltage at ∼4.5 V, maximum brightness of 7600 cd/m² and current efficiency of ∼7.0 cd/A at a brightness of ∼100 cd/m² indicate that these are promising OLED materials.

    • Electrochemical investigation of electrodeposited platinum nanoparticles on multi walled carbon nanotubes for methanol electro-oxidation


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      The electrodeposition of platinum nanoparticles (PtNPs) on multiwall carbon nanotubes (MWCNTs)/fluorine-doped tin oxide glass (FTO) was investigated. Nucleation and growth mechanisms were studied via Scharifker and Hills model. Chronoamperometry results clearly show that the electrodepositionprocesses are diffusion-controlled and the diffusion coefficient is 1.5×10 ⁻⁵ cm ²/s. The semi-spherical particles with lamellar morphology were observed in 1M H2SO4, while a petal shape was discerned in 0.5M H ₂SO ₄. Also, dispersion, size, and uniformity of PtNPs were investigated, where the finer distribution of PtNPs with the average size less than 100 nm was obtained in 0.5M H ₂SO ₄ solution, and the mean diameter of Pt crystals was 20 nm. Finally, the electro-oxidation of methanol and oxygen reduction studied via cyclic voltammetry showed that as-prepared PtNPs/MWCNTs electrodes had superb electrocatalytic activity.

    • Nano-sized glass as an economically viable and eco-benign support to anchor heteropolyacids for green and sustainable chemoselective oxidation of sulfides to sulfoxides


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      In this work, glass wastes were employed as cost-effective supports for the immobilization of phosphomolybdic acid (5–25 wt.% PMA) through an impregnation method. The highly efficient and retrievable nanocatalyst named nano-glass waste-supported phosphomolybdic acid (n-GW/PMA) was fully characterized by several techniques such as: XRD, FE-SEM, EDX, FT-IR and TGA. The catalytic performance of the assynthesized heterogeneous nanocatalystwas effectively investigated for the chemoselective oxidation of sulfides to sulfoxides in the presence of 30% H₂O₂ as an oxidant at room temperature under solvent-free condition. Optimization of the reaction conditions was performed by means of central composite design (CCD), which isone of the powerful response surface methodologies. Based on the results obtained under the optimum condition, the sample of 16 wt.% of PMA loading offered high conversion rates and yields (97%). Besides, the beneficialpoints of the prepared catalyst were its recoverability and reusability for several reaction cycles, low-cost and toxicity, easy availability and facile production.

    • A new rhodamine based ‘turn-on’ Cu²⁺ ion selective chemosensor in aqueous system applicable in bioimaging


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      Anewrhodamine-based Schiff base (L) has been synthesized and characterized by physicochemical and spectroscopic tools. This organic molecule selectively reacts with Cu²⁺ ions with a remarkably significant optical change, which supports the development of a chemosensor for Cu²⁺ ions as low as nanomolar level in aqueous medium. On the basis of the experimental work, the ‘turn-on’ colorimetric/fluorimetric spectroscopic change is due to Cu²⁺ ion-assisted hydrolysis followed by spirolactam ring opening of the probe (L) in 20mM HEPES buffer [pH 7.4; water/acetonitrile (9:1 v/v)]. The competitive ions do not affect the selectivity and specificity of the probe (L) in the detection of Cu²⁺ ions. The cell imaging study using fluorescence microscope showed that this non-cytotoxic probe is useful to detect the distribution of Cu²⁺ ions in AGS cells lines.

    • Mechanism studies on thermal dissociation of tri-n-octylamine hydrochloride with FTIR, TG, DSC and quantum chemical methods


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      The thermal dissociation of tri-n-octylamine hydrochloride (TOAHCl) was investigated using both the quantum chemical simulation and experimental methods. The pathway through which a mixture of trin-octylamine (TOA) and hydrogen chloride (HCl), rather than di-n-octylamine (DOA) and 1-chlorooctane,are produced has been determined through transition state (TS) search with Intrinsic Reaction Coordinate (IRC) calculations. Particularly, strong agreement between the experimental FTIR spectra and that of TOA demonstrates the same result for the first time. Moreover, the thermal dissociation of TOAHCl proceeds intwo continuous steps, which is different from the low molecular mass amine hydrochlorides. The experimental enthalpy of the dissociation was 70.793 kJ mol⁻¹ with DSC measurement which is very close to the density functional theory (DFT) calculation result 69.395 kJ mol⁻¹. Furthermore, with the aid of DFT calculations, some other important thermochemical characteristics such as crystal lattice energy with the value of 510.597 kJ mol⁻¹ were evaluated by means of Born–Fajans–Haber cycle.

    • An eco-friendly synthesis of 2-pyrazoline derivatives catalysed by CeCl₃.7H₂O


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      1,3,5-triaryl-2-pyrazoline derivatives were synthesised by a condensation reaction between chalcones and phenyl hydrazine using cerium chloride heptahydrate as a catalyst. All these reactions were carried out in ethyl lactate (70%) as a green solvent. Easy and efficient work up, recyclability of solvent andcatalyst are the key merits of this protocol.

    • A novel tandem Betti/Ullmann oxidation reaction as an efficient route for synthesis of new oxazepine derivatives


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      A novel tandem Betti/Ullmann/oxidation reaction was used for synthesis of new oxazepine derivatives containing kojic acid. This protocol includes a three-component Betti reaction of 2-naphthol, 2- haloanilines and kojic aldehyde followed by copper-mediated intramolecular Ullmann C-O coupling reactionand subsequently aerobic oxidation. This method provides a new and useful strategy for the construction of heterocycles. Also novel Betti bases based on kojic acid derivatives have been synthesized. In this regard, boric acid functionalized silica supported Fe₃O₄ nanoparticle have been designed, synthesized and used as a highly efficient, environmentally benign and recyclable heterogeneous magnetic nanocatalyst for the direct synthesis of desired Betti bases under solvent free conditions.

    • Thermotropic liquid crystalline polyesters derived from 2-chloro hydroquinone


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      Synthesis of thermotropic liquid crystalline polyesters derived from bis[4-hydroxy benzoyloxy]- 2-chloro-1,4-benzene (BHBOCB) and aliphatic dicarboxylic acid chlorides by interfacial polycondensation methodology is presented. Synthesised polyesters consist of bis[4-hydroxy benzoyloxy]-2-chloro-1,4-benzeneas a mesogen and aliphatic diacid chloride as flexible spacer. The length of oligomethylene units in the polymer was varied from the trimethylene to the dodecamethylene groups. Synthesized polyesters were characterizedby differential scanning calorimetry and optical microscopy. The transition temperatures and thermodynamic properties were studied for all these polymers. These polyesters exhibited thermotropic liquid crystalline behavior and showed nematic texture except decamethylene spacer. Decamethylene spacer based polyester showed marble texture of smectic C. Mesophase stability of these polyesters was higher than 123◦C (except first heating cycle of PE-1).

    • Synthesis, crystallographic characterization, DFT and TD-DFT studies of Oxyma-sulfonate esters


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      Three oxyma sulfonate esters were prepared using dichloromethane-water (two-phase method) in the presence of sodium carbonate for scavenging HCl. The products were characterized by FT-IR, NMR (¹H and ¹³C), UV-Vis spectra and elemental analysis. X-ray single crystal diffraction experiments proved the molecular structures of three esters. Their molecular structures were also calculated using DFT/B3LYP method. The optimized structures agreed well with the X-ray structures. Time-dependent density functional theory (TDDFT)was used to assign the electronic absorption bands observed experimentally. Pyridine derivative showed two bands at shorter λmax compared to the others, both experimentally and theoretically. The NMR chemical shifts were computed for protons and carbons using GIAO method, which correlated well with the experimental data. Natural charges, dipole moments and chemical reactivity of these molecules, as well as their non-linear optical activity, were computed and compared.

    • Schiff base transition metal complexes for Suzuki–Miyaura cross-coupling reaction


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      Schiff base ligand and its complex with iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) ions were synthesized using 4-aminoacetophenone and salicylaldehyde and characterized. FTIR spectrum shows that bidentate coordination of metal ions with ligand where O, N are electron donating sites of azomethine group. The geometry of the complexeswas deduced from the calculated magnetic moment values and SCXRD analysis. All Complexes were studied for their catalytic activity in Suzuki–Miyaura cross-coupling reaction with Cu–L complex showing excellent coupling yield among others. The catalytic activity data show promising results in coupling efficiency, employing cheap, abundant and green metals.

    • Axially chiral benzimidazolium based silver(I) and gold(I) bis-NHC complexes of R-BINOL scaffold: synthesis, characterization and DFT studies


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      The axially chiral ligand of R-BINOL scaffold was synthesized by a series of manipulations which involved different chemical reactions to obtain the desired sliver(I) and gold(I) {[L(L' -NHC) ₂]M}Cl (L = 3,3' -dimethyl-2,2' -dimethoxy-1,1' -binaphthyl, L' = i-propyl-benzo[d]imidazole) (M =Ag and Au)complexes. Enantiopure R-BINOL was employed as a basic unit to synthesize a benzimidazole based bis- NHC ligand 1g which was obtained through the formation of different intermediate 1(a-f) compounds. The newly synthesized bis-NHC ligand precursor (1g) and its corresponding {[L(L' -NHC) ₂]Ag}Cl (1h) and {[L(L' _-NHC) ₂]Au}Cl (1i) complexes were characterized by different spectroscopic techniques. The geometries of the optimized structure of the complexes 1h and 1i were computed at the B3LYP/SDD, 6-31G(d) level. Lowtemperature fluorescence spectroscopic studies did not show any evidence for the weak metal-metal interaction in these complexes.

    • Sterically encumbered 2,6-dibenzhydryl-4-methylphenyl derived ligand systems: synthesis and structures


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      Bulky 2,6-dibenzhydryl-4-methylaniline, I undergoes diazotization upon treatment with H₂SO₄/NaNO₂, which upon further reaction with KI affords 1-iodo-2,6-dibenzhydryl-4-methylbenzene, 1. Reaction of I with one equivalent of acetylacetone in ethanol under reflux condition affords mono-Schiff base, 4-(2,6-dibenzhydryl-4-methylphenylamino)pent-3-ene-2-one, 2. Similarly, I reacts with half equivalent of 2-hydroxy-5-methylisophthalaldehyde or one-third equivalent of 2,4,6-trihydroxybenzene-1,3,5- tricarbaldehyde in ethanol under reflux condition to afford bis-Schiff base, 2,6-bis(((2,6-dibenzhydryl-4-methylphenyl)imino)methyl)-4-methylphenol, 3 and tris-Schiff base, 2,4,6-tris(((2,6-dibenzhydryl-4- methylphenyl)amino)methylene)cyclohexane-1,3,5-trione, 4, respectively. Further, I upon reaction with triflic acid affords (2,6-dibenzhydryl-4-methylphenyl)ammonium triflate, 5 whereas upon reaction with HBr and HCl affords co-crystals I·HBr, 6 and I·HCl, 7. All the new products were isolated in moderate to good yield and characterized by spectroscopic (IR,ESI-mass,NMR,UV-Vis) and microanalytical (CHN) techniques, in additionto a single crystal X-ray diffraction study for 1, 2 and 4-7.

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