Aqueous polymerization of methyl methacrylate initiated by peroxydisulfate–citric acid redox system catalyzed by silver ion

The kinetics of the aqueous polymerization of methyl methacrylate initiated by potassium peroxydisulfate–citric acid catalyzed by silver ion was investigated in nitrogen atmosphere. The rate of polymerization is proportional to the square root of peroxydisulfate concentration. The initial rate increases with increasing citric acid concentration up to 15 × 10^?3M, after which it decreases. The rate of polymerization also increases initially with monomer concentration and decreases at higher monomer concentration. The effects of temperature and the addition of some solvents and salts on the rate of polymerization have also been studied and a suitable kinetic scheme has been proposed for the reaction.     

Recent advances in therapeutical applications of the versatile hydroxypyridinone chelators

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Hydroxypyridinones (HOPOs) are excellent class of chelators that have been gaining attention in the field of pharmaceutical drugs by their...     

Aqueous Polymerization of Methyl Methacrylate Initiated by the Mn(lll)-Fructose Redox System

The kinetics of vinyl polymerization of methyl methacrylate initiated by the redox system Mn³-fructose were investigated in aqueous sulfuric acid in the temperature range of 20-25°C, and the rates of polymerization and disappearance of Mn³⁺ were measured. The effect of certain water-miscible organic solvents and certain cationic and anionic surfactants on the rate of polymerization has been investigated. A mechanism involving the formation of a complex between Mn³⁺ and fructose whose decomposition yields the initiating free radical with the polymerization being terminated by the metal ion has been suggested.     

Complexation of a tripodal amine-catechol ligand tris((2,3-dihydroxybenzylamino)ethyl)amine towards Al(III), Ga(III), and In(III)

Abstract  The complexation of a tripodal amine-catechol ligand tris((2,3-dihydroxybenzylamino)ethyl)amine (TRENCAT, L) with group-13 metal ions, viz., Al(III), Ga(III), and In(III), were investigated by means of potentiometric titrations and spectrophotometric measurements in an aqueous medium of 0.1 M KCl at 25 ± 1 °C. The ligand shows the potential to form various monomeric complexes of the types MLH₃, MLH₂, MLH, and ML. At low pH, the ligand is coordinated through three more acidic ortho-catecholic O-atoms to give MLH₃ species. With the rise in pH, the species MLH₃ releases three protons in steps from the meta-catecholic O-atoms to form MLH₂, MLH, and ML. The order of stability Ga(III) > Al(III) > In(III) for the species MLH₃ and MLH₂ is changed into Al(III) > Ga(III) > In(III) for the species MLH and ML. The coordination modes, binding ability, selectivity, and the change in stability order were explained with the help of experimental evidence, molecular modeling calculations, and available literature. Graphical Abstract        

Microwave‐assisted One‐pot,Three‐component Regiospecific and Sterospecific Synthesis of Spiro Indanone Pyrrolidine/Piperidine Fused Nitrochromene Derivatives Through 1,3‐Dipolar Cycloaddition Reactions

A simple, straightforward, and versatile protocol for the synthesis of spiro indanone pyrrolidine/piperidine fused nitrochromene derivatives is described. The synthesis of a new series of spirocyclic molecules has been expediently accomplished via a one‐pot, three component 1,3‐dipolar cycloaddition reaction. 2‐Phenyl‐nitrochromene dipolarophiles were reacted with azomethine ylides, generated in situ by the condensation of dicarbonyl compound indane‐1,3‐dione and secondary amino acid (L‐proline/pipecolic acid), to produce the corresponding cycloadducts in good yields (85–90%) under classical as well as under microwave irradiation. The cycloaddition reaction was found to be highly regiospecific and diasterospecific. The regiochemical and sterochemical outcome of the cycloaddition reaction is ascertained by 2D NMR (COSY and NOESY) studies.     

Interval-type and affine arithmetic-type techniques for handling uncertainty in expert systems

Expert knowledge consists of statements _Sj$S_j$ (facts and rules). The facts and rules are often only true with some probability. For example, if we are interested in oil, we should look at seismic data. If in 90% of the cases, the seismic data were indeed helpful in locating oil, then we can say that if we are interested in oil, then with probability 90% it is helpful to look at the seismic data. In more formal terms, we can say that the implication “if oil then seismic” holds with probability 90%. Another example: a bank A trusts a client B, so if we trust the bank A, we should trust B too; if statistically this trust was justified in 99% of the cases, we can conclude that the corresponding implication holds with probability 99%.     

Electrical study and dielectric relaxation behavior in?nanocrystalline Ce0.85Gd0.15O2?δ material at intermediate temperatures

The nanocrystalline material of 15 mol% Gd-doped ceria (Ce_0.85Gd_0.15O_2−δ ) was prepared by citrate auto ignition method. The electrical study and dielectric relaxation technique were applied to investigate the ionic transport process in this nanocrystalline material with an average grain size of 13 nm and the dynamic relaxation parameters are deduced in the temperature range of 300–600°C. The ionic transference number in the material is found to be 0.85 at 500°C at ambient conditions. The oxygen ionic conduction in the nanocrystalline Ce_0.85Gd_0.15O_2−δ material follows the hopping mechanism. The grain boundary relaxation is found to be associated with migration of charge carriers. The frequency spectra of modulus M″ exhibited a dielectric relaxation peak corresponding to defect associates (Gd-V_{o^{\blacksquare \blacksquare}})^{_\blacksquare}(\mathrm{Gd}\mbox{-}\mathrm{V}_{\mathrm{o}}^{_{_{{\blacksquare\,\blacksquare}}}})^{_{_{{\blacksquare}}}}. The material exhibits very low values of migration energy and association energy of the oxygen vacancies in the long-range motion, i.e., 0.84 and 0.07 eV, respectively.     

Potentiometric and spectrophotometric study of a new dipodal ligand N,N'-bis{2-[(2-hydroxybenzylidine)amino]ethyl}malonamide with Co(II), Ni(II), Cu(II) and Zn(II)

A new dipodal ligand, N,N'-bis{2-[(2-hydroxybenzylidine)amino]ethyl}malonamide (BHAEM) was synthesized by Schiff base condensation of N,N'-bis(2-aminoethyl)malonamide with two equivalent of salicylaldehyde and characterized on the basis of elemental analyses and various spectral (UV-vis, IR, (1)H NMR and (13)C NMR) data. The complexation reaction of the ligand with H(+), Co(II), Ni(II), Cu(II) and Zn(II) in solution was investigated by spectrophotometric and potentiometric method. Two protonation constants of BHAEM assigned for two hydroxyl groups of aromatic ring were determined and its hydrolysis mechanism was proposed through potentiometric result. In presence of metal ions, BHAEM shows different coordination properties. All metal ions form ML type complex where the ligand coordinates to the metal ion through two N-amine and two O-phenolate groups. In addition, Ni(II) and Cu(II) form additional complex species of the type MLH(-1) and MLH(-2), respectively due to ionization of amide protons. The molecular geometry of BHAEM was examined theoretically using the molecular mechanics MM3 force field followed by semi-empirical PM3 method and various spectral data UV-vis, IR and (1)H NMR were calculated from the energy-minimized structure applying semi-empirical ZINDO, PM3 and TNDO/2 method, respectively and compared with the experimental data. The probable structure of metal complexes in solution were proposed through calculated minimum strain energy by applying molecular mechanics MM(+) force field coupled with molecular dynamics simulation. Further the proposed structure of Cu(BHAEM) was refined through semi-empirical AM1/d method.     

Synthesis,thermodynamic, photophysical and DFT studies of some trivalent metal chelates of a hexadentate tripodal hydroxyquinolinate-based ligand

The synthesis, complexation, evaluation of solution thermodynamics and photophysical properties of multidentate chelator 5-[[3-[(8-hydroxy-5-quinolyl)methoxy]-2-[(8-hydroxy-5-quinolyl)methoxy methyl]-2-methylpropoxy]methyl]quinolin-8-ol (TMOM5OX) with trivalent Fe, Al and Cr ions is described. The corresponding complexes were probed by elemental analysis, mass, infrared, absorption and emission spectroscopy, potentiometry, and theoretical (DFT) studies. The thermodynamically stable and soluble M³⁺ complexes show stability constants in the range log β₁₁₀ = 23–30 and pM in the range of 19–30. The ligand forms distorted octahedral complexes in a tripodal orchestration and firmly binds metal ion over wide pH range. Density functional theory with B3LYP functional and 6-311G* basis set was employed for optimization, vibrational modes, NBO analysis, excitation and emission properties of the protonated, neutral, deprotonated states of the ligand and its ferric complex. The photophysical properties of TMOM5OX obtained by TD-DFT calculations showed good agreement with the experimental data. The result of NBOs and frontier molecular orbital analysis of ground and excited states of the metal complexes of TMOM5OX were used to explain the nature of the metal center.     

3-Naphthylindoles as new promising candidate antioxidant,antibacterial, and antibiofilm agents

Research on Chemical Intermediates - Indole derivatives have attracted significant attention in organic synthesis and bioactivity research owing to their substantial biological activity. In the...