The polar Diels-Alder (P-DA) reaction of TCE (2,3-Dicyano-but-2-enedinitrile), diene Cp, toward Bicyclo(2. 2. 1)hept-5-ene-2, 2, 3, 3-tetracarbonitrile , was theoretically studied using DFT methods at the B3LYP/ 6-31G(d) level and 6-31G(d,p) in the presence of water. Calculated relative enthalpy associated with the two feasible reactive channels indicate that this P-DA cycloaddition takes place via C2-C3 regioselectivity, furnishing a formal (4+2) P1 in excellent agreement with experimental outcomes. In the considered P-DA reaction, while C2-C3 regioselectivity can be explained using calculated Parr functions at the interacting sites of reagents. In addition, Hydrochloric acid does not react with the TCE (2,3-Dicyano-but-2-enedinitrile) due to the high activation energy of this reaction.
Iron oxide nanoparticles have been found to effectively catalyze the multicomponent synthesis of 1,2,3-triazoles from azide precursors, such as epoxides and organic halides in water. The formation of the product proceeds in one pot through a mechanism that involves in situ generated organic azide intermediate, followed by rapid ring closure of this intermediate with terminal alkynes. In the presence of nano-Fe2O3, click reaction proceeds in short reaction times and the resulting products are obtained in good yields. Aqueous reaction medium, easy recovery of catalyst, efficient recycling and high stability of the catalyst render the protocol sustainable and economic.
Cross-link property has been used to improve the insolubility, mechanical strength, stiffness, and rigidity of polymer microbeads having potential applications in solid-phase synthesis, solid-phase extraction, and biomedical fields. Therefore synthesis of polymer with desired cross-linker (hydrophilic/hydrophobic/rigid/flexible) and concentration of cross-linker (cross-link density) is an important. In the present review, chemical cross-linking by free-radical, condensation, UV radiation, and small-molecule cross-linking are discussed in details. Further, effects of cross-linker (type/concentration) on polymer properties like surface area, pore volume, pore size, particle size, thermal degradation, glass transition temperature, and polymer swelling are also discussed. Importantly, present review discusses the influences of rigidity, flexibility, hydrophilicity, and hydrophobicity of a cross-linker on polymer properties.
Conventional unsupported Lewis acids are more sensitive towards moisture rather than substrate resulting into deactivation of the catalyst and difficult to use in an anhydrous reaction. In the present work, deactivation of the conventional Lewis acids was strongly avoided by using hydrophobic polymer-supported Lewis acids (PSLAs). The obtained PSLAs were characterized by different techniques including surface area, particle size, thermostability, glass transition temperature, and morphology. Surface areas of PSLAs were in the range of 50-80 m 2 /g whereas particle sizes of polymer beads were in the range of 15-35 μm before and after polymer modification. Further, degradation of base polymer and PSLAs were in the range of 440-450 o C whereas glass transition temperature (Tg) of base polymer was upto 400 o C. However, Tg was attenuated for polymer containing AlCl3 and further for HgCl2. Importantly, leakage problem of the Lewis acids was eliminated due to strong co-ordinate bonding between polymer and catalyst.
The kinetics of oxidation of some substituted N,a-diphenylnitrones by N-chlorosuccinimide (NCS) to yield benzaldehyde and nitrosobenzene was studied. The reaction follows first order kinetics with respect to (NCS) and fractional order with respect to (nitrone). The order with respect to alkali was inverse fractional order. The reaction exhibited both negative and positive Hammett reaction constants depending upon the nature of substituents. A plot of rate constant (log k) and s gave a concave downward curve. The electron releasing substituents fall on one side of curve and electron withdrawing substituents fall on another side. The activation parameters were calculated. A probable mechanism consistent with experimental observations has been proposed.
Four new tetradentate amine-N donor ligands have been prepared by reducing Schiff bases derived from the condensation of 2-aminonicotinaldehyde with 1,2-diaminoethane (APMED)/ 1,2diaminopropane (APMPD)/1,3-diaminopropane (APMP'D)/trans-cyclohexane-1,2-diamine (APMCD). The ligands react with transition metal [Co(II)/Ni(II)/Cu(II)/Zn(II)] salts to give microcrystalline solid complexes of 1 : 1 (M : L) composition. The ligands and the metal complexes have been characterized with analyses, molar conductance measurements, magnetic susceptibility measurements and spectroscopic investigations like mass, IR, electronic, NMR and ESR. All the complexes were found to have octahedral geometry holding 0-6 water molecules in the lattice with a general molecular formula [MLCl2].n H2O.
The present work attempts to scan the effect of preparation methods (co-precipitation, sol-gel and solution combustion synthesis) and calcination temperature (600-800 o C) on the efficiency of LaCoO3 catalysts for soot oxidation. All the catalysts were highly selective towards CO2 as no CO was detected in the flue gas. Catalyst produced following co-precipitation method revealed total soot oxidation at the lowest temperature (Tf = 370 o C) than other two catalysts prepared by sol-gel (Tf = 420 o C) and solution combustion synthesis (Tf = 456 o C) methods. Irrespective of the preparation methods, 750 o C was the optimum calcination temperature of the precursors resulting LaCoO3 catalysts which exhibited maximum activity for soot oxidation. In addition, the results showed that the specific surface areas of the catalysts decreased with increasing calcination temperature beyond 750 o C and consequently decreasing the activity of the catalyst.
Biological degradation of terrestrially derived macromolecules including lignin and cellulose has been shown to produce a large number of environmentally relevant phenolic compounds. It has demonstrated that extracellular superoxide (O2 ) is produced by heterotrophic bacteria that are common in lakes, soil, hydrothermal vents, marine sediments, estuaries and oceans. Rates of superoxide production normalized to the proportion of metabolically active cells vary between 0.02 0.02 amol cell −1 hour −1 (mean ± standard error) and 19.4 5.2 amol cell −1 hour −1 . Such findings provide insights into the mechanism of two key and yet unclear processes, including the biological degradation of particulate organic matter (POM) that can form dissolved organic substances, and the structural diversification of dissolved organic substances originated from POM such as plant material or algal biomass.
The present work was conducted to study the antioxidant property of phthalimide derivatives 3(a-g) and were synthesized by the reaction of isoindoline-1,3-dione (1) with various amines 2(a-g). Newly synthesized compounds were characterized by UV-visible, FT-IR, mass and 1 H NMR spectral studies. The free radical scavenging properties of synthesized compounds were evaluated employing different methodologies, including the bleaching of a stable free radical (2,2-diphenyl-1-picrylhydrazyl, DPPH) and the metal chelating assay (Ferrous ion chelating assay). Compounds 3b, 3d and 3e exhibited good antioxidant activity when compared with other compounds in the series.
In this work, 5-methyl-5H-Benz(g)indolo(2,3-b)quinoxaline (BIQCH3) and its derivatives were prepared in good yield by condensing 5-Substituted-1-methyl-1H-Indole-2,3-dione and 2,3- diaminonaphthalene in glacial acetic acid. The structure of BIQCH3 and its derivatives were confirmed using FT−IR, 1 H NMR, 13 C NMR, Mass spectra and elemental analysis. The photophysical and electrochemical studies of BIQCH3 and its derivatives were studied by UV-Visible spectroscopy, fluorescence spectroscopy and cyclic voltammetry respectively. The optical energy band gap of BIQCH3 and its derivatives lies in the range of 2.53 2.58 eV. Thermal analysis of BIQCH3 and its derivative were studied by Thermo Gravimetric Analysis (TGA) and Differential Thermal Analysis (DTA).
Zn,Al layered double hydroxides (LDHs) intercalated by a series of organic chelating ligands (L), including anionic ethylenediamine-N,N-diacetate (EDDA), nitrilotriacetate (NTA), ethylenediaminetetraaetate (EDTA), and diethylenetriaminepentaacetate (DTPA) as guests, were prepared by co-precipitation and anion exchange of precursor Zn,Al-NO3 LDHs. The chelation of transition metal ions (Co 2+ and Ni 2+ ) from aqueous solution and the intercalation of pre-formed complexes of the type (M(edda)) 2- , (M(nta)) - , (M(edta)) 2- and (M(dtpa)) 3- , have been investigated. Powder X-ray diffraction (PXRD) showed that the basal spacing increased from 9.0 A for the precursor materials to 12.0-15.3 A for the pillared hybrids. Elemental analysis and FT-IR spectroscopy indicated that most of the interlayer nitrate anions were displaced by L anions to form LDHs-L, which then reacted with the metal ions to form (M(L)) n- complexes between the LDHs layers. The compounds were studied by thermal gravimetric (TG) and differential thermal analysis (DTA).
DFT calculations have been performed on the interactions of carbon nanotubes and carbenes, in order to perform a comparative study of the sidewall functionalization of the two classes of nanotubes, i.e. armchair and zigzag. The systematic investigation of cycloaddition of both zigzag and armchair carbon nanotubes with :CX2 (where X = H, F, Cl, Br, I) has been undertaken. The models selected for zigzag and armchair CNT are (10,0) and (6,6), respectively, since they have comparative radii (~8 A). The bond lengths and binding energies of products are analysed in great detail. The band gaps of these non periodic structures are investigated and correlated with the electronic behavior of 'armchair' and 'zigzag' nanotubes. Our results also confirm the previous studies that armchair nanotubes are thermodynamically more stable than zigzag nanotubes. On comparison of armchair carbon nanotubes with zigzag nanotubes, it is found that trends towards carbenic reactivity are the same in both the cases. The dependence of addition of carbenes on the diameter of the carbon nanotubes is also investigated. The models used for nanotubes in this study range from (3,3) to (10,10). Their reactions with :CH2 have been studied with first principles DFT calculations. An attempt to rationalize the diameter effects is made on the basis of the structures of the nanotubes. It seems that diameter dependence of the reactivity is because of different pyramidalization and π-orbital misalignment angles in different carbon nanotubes. This leads to higher local strain for tubes of smaller diameter that can be partially relaxed by sidewall addition.
The isatin based thiosemicarbazones exhibit a number of biological applications. In this paper, we explore various rotamers and tautomers of the title molecule using density functional theory at the B3LYP/6-311++G** level. Investigation reveals that one tautomer dominates the gas phase, of which one of the rotamers constitutes 87% of the gas phase population. The Z configuration about the imine linkage is satisfactorily accounted for by the C=O…H hydrogen bonding that results in this planar structure. The orientation of the amine group is also explained by N-H…N hydrogen bonding. The weakening of the C=S bond by hyperconjugative interactions and extended conjugation involving the five membered ring are revealed by an NBO analysis. Comparison of computed geometrical parameters and vibrational frequencies with experimental ones shows good correlation.
Density functional theory (DFT) calculations were performed to examine the triplet states of ten iridium(III) complexes and the relationship between these states and the emission spectra of the complexes. Those complexes have ligands of terpyridine derivatives. Among them, complexes (IrBr(phen)(terpy))(PF6)2 (2) and (IrBr(phen)(tterpy))(PF6)2 (3) were newly synthesized for this study and exhibited pronounced phosphorescent emission. Here, phen is 1,10-phenanthroline, terpy is 2,2':6',2''- terpyridine and tterpy is 4'-(4-tolyl)-2,2':6',2''-terpyridine. All complexes were calculated to possess either one or two low-energy triplet excited states, designated as Tb and Tc. The Tc triplet states arise typically from the one-electron excitation from HOMO of the out- of-phase 5d- overlap to the low-lying vacant orbital of the (5d-N) antibonding overlap. The Tb states of the complexes are primarily associated with metal-to-ligand charge transfer (MLCT) and π-π* transitions. The energy gaps between Tb triplet states and ground states were compared with those corresponding to peaks in the emission spectra of 2, 3 and the other eight reported complexes. A high degree of the correlation between calculated and observed energies was obtained.
A theoretical study for three derivatives of pyrazine namely 2-methylpyrazine (MP), 2- aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP), which are recently used as corrosion inhibitors for steel in 1.0 M H2SO4 medium, was undertaken by Density Functional Theory (DFT) at the B3LYP level. Their properties are most relevant to their potential action as corrosion inhibitor and have been calculated by EHOMO, ELUMO, energy gap (Δ E), dipole-moment (µ), electronegativity (χ), global hardness (η) and fraction of electron transferred from the inhibitor molecule to the metallic atom (Δ N). To explain their inhibition performance, local reactivity of the molecule has been analyzed through Fukui function. Furthermore, the binding energies of the inhibitors with the Fe (0 0 1) surface are studied using Molecular Dynamics (MD) simulation method. The theoretical results are in well accordance with the recently reported experimental outcomes.
A series of new 2,4-difluorophenyl(piperidin-4-yl)methanone oxime derivatives 4a-h and 5a-e were synthesized by the reaction of 2,4-difluorophenyl(piperidin-4-yl)methanone oxime with various sulfonyl and acid chlorides. The synthesized compounds were characterized by elemental analyses, FT- IR, 1 H NMR and LCMS spectral studies. All compounds were evaluated for in vitro antibacterial and antifungal activities. Compounds 4b, 4g and 5e exhibited good antimicrobial activity against tested pathogenic bacterial and fungal strains. Compound 4b would be a more activity deserves further research.
To provide insight and to identify the occurrence of mechanistic changes in relation to variance in solvent-type, the solvent effects on the rates of solvolysis of three substrates, 2,2,2-trichloro-1,1-dimethylethyl chloroformate, 2,2,2-trichloroethyl chloroformate, and 1-chloroethyl chloroformate, are analyzed using linear free energy relationships (LFERs) such as the extended Grunwald-Winstein equation, and a similarity-based LFER model approach that is based on the solvolysis of phenyl chloroformate. At 25.0 °C, in four common solvents, the α-chloroethyl chloroformate was found to react considerably faster than the two β,β,β-trichloro-substituted analogs. This immense rate enhancement can be directly related to the proximity of the electron-withdrawing α-chlorine atom to the carbonyl carbon reaction center. In the thirteen solvents studied, 1-chloroethyl chloroformate was found to strictly follow a carbonyl addition process, with the addition-step being rate-determining. For the two β,β,β-trichloro-substrates, in aqueous mixtures that are very rich in a fluoroalcohol component, there is compelling evidence for the occurrence of side-by-side addition-elimination and ionization mechanisms, with the ionization pathway being predominant. The presence of the two methyl groups on the α-carbon of 2,2,2-trichloro-1,1-dimethylethyl chloroformate has additive steric and stereoelectronic implications, causing its rate of reaction to be significantly slower than that of 2,2,2-trichloroethyl chloroformate.
The key challenge in the treatment of bacterial infection is rapid identification of bacteremia at an early stage of the diseases. Currently available imaging systems such as computed tomography (CT) and magnetic resonance imaging (MRI) can only detect bacterial infection after they have become systemic or have caused significant anatomical tissue damage, and at this stage infection are challenging to treat due to the high bacterial burden. To this day positron emission tomography (PET) imaging has showed the great potential for improving the diagnosis of bacterial infection because of the high sensitivity of PET radionuclides, capability of detecting molecular biology in details (even prior to anatomic change). Fluorodeoxyglucose (FDG) PET has been developed for bacterial imaging with incredible success. Whole body PET imaging with FDG for the diagnosis of bacterial infection and monitoring response to treatment has been well established. FDG-PET will not only help to accelerate the diagnosis of infection but improve the bacterial treatment. In this review, we focus on FDG-PET imaging for diagnosing bacterial infection in the clinic.
The aim of the current study was to evaluate the antioxidant, antimicrobial and thrombolytic potentials of the exocarp of Spondias pinnata fruits. The crude ethanolic extract of the exocarp of S. pinnata fruit was partitioned successively by solvents of different polarity. All fractions were then investigated for qualitative preliminary phytochemical screening by specific standard procedure. The antioxidant potential of all fractions were then evaluated in terms of total phenolic content, total flavonoid content, DPPH free radical scavenging potential, reducing potential and total antioxidant capacity by specific standard procedure. The disc diffusion method was incorporated to evaluate the in vitro antimicrobial activity on nutrient agar medium. The highest total phenolic content was found in aqueous fraction (570.20±0.48 mg GAE/g of dried extract) while the lowest in the n-Hexane fraction (337.51±0.21 mg GAE/g of dried extract). However, ethyl acetate fraction exhibited the highest flavonoid content which amounted to 132.27±0.25 mg quercetin equivalents/g of dried extract. Likewise, ethyl acetate fraction showed the highest antioxidant capacity (21.61±0.11 g of L-ascorbic acid equivalents/g of dried extract) along with the lowest IC50 (1.72±0.39 µg/ml) & EC50 (2.25±0.75 µg/ml) value. However, DPPH free radical scavenging activity and reducing power of all fractions were found to be concentration dependent. Nonetheless, comparatively more polar fractions (ethyl acetate and aqueous fraction) were found to be ineffective against all the microbial strains except S. dysentery and P. aeruginosa while non- polar fractions (n-hexane and dichloromethane fraction) showed variable antimicrobial activity. In addition, all fractions produced statistically significant (P<0.05 for ethyl acetate and aqueous fraction, P<0.001 for others) thrombolytic activity. To conclude, our present study suggested that exocarp of S. pinnata fruit exhibits antimicrobial activity against a wide variety of strains while it produces noteworthy
We report two zinc complexes of molecular formulae [ZnCl 2 (Mes - BIAO)] 2 ( 3 ) and [ZnCl 2 (Dipp - BIAO)] 2 ( 4 ) ( Mes = Mesityl, Dipp = 2,6 - diisopropylphenyl) of rigid unsymmetrical bidentate iminoacenapthenone ligands (Mes - BIAO) ( 1 ) and Dipp - BIAO) ( 2 ). The zinc complexes 3 and 4 can be achieved by the reaction of ZnCl 2 and neutral [ N - (mesityl) - iminoacenapthenone] ( 1 ) and [ N - (2,6 - diisopropylphenyl) - iminoacenapthenone] ligand ( 2 ) respectively in dichloromethane at ambient temperature. The solid state structures of the complexes 3 and 4 were established by single crystal X – ray diffraction analysis. In the solid state structures, bo th the complexes are dimeric in nature. In complexes 3 and 4 , each of the zinc coordination polyhedron is formed by the ligation of imine nitrogen, carbonyl oxygen atoms of the ligand 1 and 2 respectively along with three chlorine atoms. Out these three ch lorine atoms, two are 2 bridged with adjacent zinc atom to form the dimer. Thus overall zinc atom is penta - coordinated and the geometry can be best described as a distorted trigonal bipyramidal or a distorted square pyramidal.
