Scalar Relativistic Density Functional Theoretical Investigation of Higher Complexation Ability of Substituted 1,10‐Phenanthroline over Bipyridine Towards Am3+/Eu3+ Ions

The better selectivity of Am³⁺ over Eu³⁺ ion with N‐based CyMe4‐BTPhen compared to CyMe4‐BTBP for experimentally observed [ML₂(NO₃)]²⁺ complexes was demonstrated using scalar relativistic DFT in conjunction with Born‐Haber thermodynamic cycle and COSMO solvation model. The calculated free energy of extraction, ΔG_ext reveals strong dependence on the hydration free energies of Am³⁺ and Eu³⁺ ions and week dependence to the difference in Gibbs free energy of solvation of the ligand or metal‐ligand complexes. Further, for the first time, we have computed the effect of co‐anion species ([M(NO₃)₅]^2–) on ΔG_ext of Am³⁺ and Eu³⁺ ions with CyMe4‐BTPhen and CyMe4‐BTBP, which adds a positive contribution and thus reduces the ΔG_ext. The calculated values of ΔΔΔG_ext (= ΔΔG_ext,L1 – ΔΔG_ext,L2, ΔΔG_ext = ΔG_ext,M1 – ΔG_ext,M2) can be used to avoid the very sensitive metal ion solvation energy, effect of co‐anionic species and thus provides a robust approach to determine the selectivity between two metal ions towards different competitive ligands. The natural population analysis (NPA), molecular orbital analysis, Mayer bond order analysis, and bond character analysis using Bader's quantum theory of atoms in molecules indicates slightly more covalency for complexes of Am³⁺ ion that are correlated to the experiental selectvity of Am³⁺ ion over Eu³⁺ ion and hence might be useful in the design and development of next generation extractants.     

Spatial symmetry breaking in the Belousov-Zhabotinsky reaction with light-induced remote communication

Domains containing spiral waves form on a stationary background in a photosensitive Belousov-Zhabotinsky reaction with light-induced alternating nonlocal feedback. Complex behavior of colliding and splitting wave fragments is found with feedback radii comparable to the spiral wavelength. A linear stability analysis of the uniform stationary states in an Oregonator model reveals a spatial symmetry breaking instability. Numerical simulations show behavior in agreement with that found experimentally and also predict a variety of other new patterns.     

Tetrabutylammonium tribromide (TBATB) as an efficient generator of HBr for an efficient chemoselective reagent for acetalization of carbonyl compounds

Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields under a mild reaction condition in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide (TBATB) in absolute alcohol. Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.     

Intermediate frequency modes in Raman spectra of Ar+‐irradiated single‐wall carbon nanotubes

We study the effect of Ar⁺ irradiation on the intermediate frequency modes (IFM) in Raman spectra of single‐wall carbon nanotubes. We observe new features in the intermediate frequency region from 386 to 635 cm^–1 as the defect concentration increases, whereas at the same time there is a decrease of other IFM modes. After annealing in vacuum, the IFM modes recover and become similar to those of the nanotubes before irradiation. We interpret the new features in the Raman spectra as originating from the phonon density of states that becomes visible in the Raman process due to the presence of defects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

From finite to infinite crystals: Some electronic properties of BCC clusters

Using results obtained within the framework of the tight binding nearest neighbour approximation (Bílek O.,Skála L., Czech. J. Phys.B 28 (1978), 1003) the analytical formulae for the band width, binding energy per atom, charge orders and bond orders of bcc clusters having a rectangular parallelepiped geometry are given. Numerical results for the number of atoms in the cluster in the range 9-2×10⁶ illustrate the convergence of these properties. The asymptotical form of the formulae yields further detailed information. The band width and bond orders converge more quickly than the binding energy while the charge orders are equal to unity independently of the size of the cluster.One of the authors (L. K.) should like to thank the Faculty of Mathematics and Physics of Charles University in Prague for its kind hospitality.     

On the nematic-isotropic phase transition in liquid amyl-ethoxy-cyanstilbene

Measurements of the index of refraction were used to evaluate the temperature dependence of the order parameterS in amyl-ethoxy-cyanstilbene (AECS). The results obtained may be described successfully in the frame of the Landau theory of phase transitions.Dedicated to Academician Vladimír Hajko on the occasion of his 65th birthday.One of us (O. V.) would like to express her sincere gratitude to Dr. L. Bata and his co-workers at the Laboratory of Liquid Crystals, Central Research Institute for Physics of the Hungarian Academy of Sciences, Budapest, for having enabled her to perform some of the measurements in their Laboratory and for their friendly help and hospitality.