A DFT study of the reactivity of Cp2AnMe2 with pyridine N-oxide: Towards a predicted different reactivity of U/Pu and Np

A predictive reactivity of Cp₂An(IV)Me₂ (with An = uranium [U], neptunium [Np] and plutonium [Pu]) with pyridine N-oxide has been studied at the theoretical level. The predictive reaction, which consists in the formation of a formaldehyde complex, begins after the initial formation of a cyclometalated complex produced by a C-H activation of the pyridine N-oxide. A difference of reactivity between U/Pu and Np has been observed and has been attributed to the presence of a more covalent bond between Np and the carbene group in the transition state of formation of a transient carbene intermediate.     

The Transition States for CO2 Capture by Substituted Ethanolamines

Quantum chemical studies are used to understand the electronic and steric effects on the mechanisms of the reaction of substituted ethanolamines with CO₂. SCS‐MP2/6‐311+G(2d,2p) calculations are used to obtain the activation energy barriers and reaction energies for both the carbamate and bicarbonate formation. Implicit solvent effects are included with the universal solvation model SMD. Carbamate formation is more favorable than bicarbonate formation for monoethanolamine (MEA) both kinetically and thermodynamically. Increase of the steric hindrance on the C atoms around the N atom in substituted ethanolamines favors bicarbonate formation over carbamate formation with lower activation barriers and thereby higher reaction rates. In contrast, substitution by an N‐methyl or N‐ethyl group on MEA leads to a lower activation barrier for both carbamate formation and bicarbonate formation. As a result, higher reaction rates are expected as compared to MEA, and therefore these compounds have significant potential as industrial CO₂ capturing solvents.     

Iron-Chloranilate Intercalation Compounds: Synthesis,Crystal Structures,and Thermal Properties

Abstract

Hydrogen bond supported new iron-chloranilate assemblies, {(Hpy)[Fe(CA)₂(H₂O)₂](H₂O)}_n (py = pyridine, H₂CA = chloranilic acid, C₆H₂O₄Cl₂) (1), and [(phz)₂[Fe(CA)₂(H₂O)₂](H₂O)₂]_n (phz = phenazine, C₁₂H₈N₂) (2) have been synthesized and characterized. Compound 2 crystallizes in the monoclinic, space group C2/m (#12), with a= 29.135(6) Å, b= 16.886(6) Å, c = 15.017(5) Å, ß = 165.907(1)°, V= 1798(2) ų, Z = 2. In both the compounds two chloranilate dianions and two water molecules are coordinated to the iron ion making anionic monomers [Fe(CA)₂(H₂O)₂]^?, which are the building blocks of the compounds. The coordination environment around the iron ion in the building block is a distorted octahedron, where two water molecules sit on the trans position to each other. [Fe(CA)₂(H₂O)₂]^? anions form common layer structures, supported by hydrogen bonds. Hpy⁺ are intercalated in between the layers of 1 by electrostatic and hydrogen bonding interactions and phz are intercalated in that of 2 by electrostatic interactions. DSC traces of 1 show anomaly at 174 K, indicating phase transition in the compound.     

Photochemistry of 3-aryl-2-isoxazoline1

3-Phenyl-2-isoxazoline (1) was irradiated to give 4-phenyl-2-oxazoline (3), β-aminoaldehyde (14) and benzonitrile from its π-π^* singlet excited state. Several related derivatives afforded similar photoproducts on irradiation. The quantum yields of the photoreactions were dependent on the magnitudes of the singlet energies of the 2-isoxazolines. p-Cyanophenyl-2-isoxazoline (1c) formed a one-to-one photoadduct (22) with benzene.     

An optical catechol biosensor based on a desert truffle tyrosinase extract immobilized into a sol–gel silica layered matrix

An optical biosensor for the determination of catechol, a widely used yet toxic and carcinogenic molecule, is proposed using a crude extract of desert truffle (Terfezia leonis Tul.) as an enzymatic source of tyrosinase. The biosensor is constructed by the immobilization of tyrosinase crude extract in a bi-layered silica gel film prepared by dip-coating of an alkoxide/colloidal silica solution containing the enzyme on glass slide. Encapsulation has a moderate effect of the enzyme optimal pH stability but largely increases its thermal stability. Immobilized enzymes have a higher substrate affinity towards catechol but smaller maximum conversion velocity. The optical biosensor provides a linear response for catechol in the concentration range of 50–400?µM and a limit of detection was 52?µM. AFM studies show that the enzymes impact on the silica gel structure, preventing further deposition of additional layers. Comparison with similar dopamine biosensors points out that the impact of encapsulation on enzymatic activity may depend on the considered substrate.

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Electrolytic reduction of Tc(VII) in nitric acid solution using glassy carbon electrode

Electroreduction of Tc(VII) was studied in nitric acid solution using glassy carbon electrode. The electroreduction was conducted at a constant potential –300 mV (vs. Ag/AgCl) with a potentiostat. It was found that the difference of the Tc concentration in the solutions before and after the electrolysis was negligibly small. This means that there were almost no TcO₂ or Tc deposited on the carbon fiber electrode during the electroreduction. Absorption spectra and distribution coefficients obtained by ion-exchange analysis indicated that Tc(VII) was reduced to Tc(IV).This work was financed by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) under the framework of The Development of Innovative Nuclear Technologies.