Monolayer metal coverage of fullerenes: the optical response

A first-principles investigation of the photoabsorption cross section of the specially stable cluster Li₁₂C₆₀ is carried out, including the icosahedral symmetry of the cluster and treating the ions via ab initio pseudopotentials. The role of the coating metal is assessed by computing the same quantity for the fullerene “seed”. It is found that the main absorption features are determined by the carbon molecule, both at low and high excitation energies, in spite of a reduction of 60% for the ionization threshold of Li₁₂C₆₀ as compared to C₆₀. Nonetheless the lithium coating is responsible for small yet clearly observable effects throughout the spectrum, in particular for a more structured and broad strength distribution at excitation energies below the ionization threshold of C₆₀, and a double peak structure in the Mie resonance at ≈20 eV.     

Oxygen equilibrium pressure as a measure of oxygen binding energy in the V2O5−x system

Using the redox mechanism of vanadia catalyst action as a starting point, oxygen binding energy and its measurement have been discussed. Experimental results on the equilibrium oxygen pressure are presented and two types of equilibrium are distinguished: chemisorbed and redox. It has been shown that univariant redox equilibrium is appropriate for characterizing vanadia catalysts.     

Quinoxaline N-oxide ion radicals. 2. Structures of anion radicals of N-oxides of hydroxymethyl derivatives of quinoxaline and products of their electrochemical reduction

The redox properties of 1,4-dioxides of hydroxymethyl and formyl derivatives of quinoxaline were studied by means of EPR spectroscopy and polarography. The electrochemical reduction of the 1,4-dioxides proceeds in several steps with successive deoxidation and the formation of dianions of substituted quinoxalines and is also accompanied by an intramolecular redox process. The experimentally observed hfs constants in the EPR spectra of the anion radicals formed in the reduction are in agreement with the corresponding values calculated by the INDO method.See [1] for communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1412–1416, October, 1985.The authors thank I. A. Abronin for his assistance in performing the quantum-chemical calculations.     

Thermal Analysis of the System Na3AlF6–NaVO3

Summary. The phase diagram of the system Na₃AlF₆–NaVO₃ was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated at x(NaVO₃) = 0.975 and t _eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO₃ only supporting the above assumption of a simple eutectic binary system.     

Changes in surface composition of Fe-Si-Cr-K oxide alkylation catalyst: the marked role of potassium ferrites

The influence of gas-phase methylation of phenol on the state of the Fe-Si-Cr-K oxide catalyst surface was investigated by thermodesorption of K atoms and ions. Changes in potassium desorption energies, as determined from Arrhenius-like plots, varied from 3.07 eV to 1.21 eV for the atoms and from 2.59 eV to 2.89 eV for ion desorption from the active and deactivated samples, respectively. The results were discussed in terms of transformation of the catalyst surface and formation of β-ferrite.     

Phlogophites intercalated with Al2O3 pillars and modified with transition metals as catalysts of the DeNOx process

Natural phlogophite, pre-treated with acids and intercalated with alumina pillars, was used as catalytic support. Transition metals (Fe, Cu) were deposited on the surface of the modified clay materials by an ion-exchange method. The obtained samples were characterized with respect to structure (XRD), texture (BET), composition (EPMA) and chemical nature of the deposited transition metals species (UV-vis-DRS). The phlogophite based materials have been found to be active and selective catalysts of the DeNOx process. The Fe-containing samples were catalytically active at lower temperatures than the clays modified with copper. A competitive ammonia oxidation by oxygen decreased the effectiveness of the DeNOx process in the high temperature range.     

New Carbonyl Compounds in the High-Boiling Fraction of Lavender Oil. 3rd Communication

The occurrence of a series of new constituents which can be considered as Diels-Alder adducts of methyl vinyl ketone and ocimene (→1–4), myrcene (→ 9 , 10 ) or β-far-nesene ( → 11 , 12 ), respectively, was reported. Furthermore, the structures of four isomeric cyclohexene derivatives could be established as adducts 21–24 of (E, Z)- and (E, E)-1,3,5-undecatrience and methyl vinyl ketone. Another series of constituents having the norbornane skeleton represents adducts 25–32 , and 33–40 of methyl cyclopentadiene and 1-octen-3-one or methyl vinyl ketone, respectively. In accordance with Alder's endo-rule the endo-isomers are preponderant in the natural as well as in the synthetic mixtures. Most of these constituents could also be identified in a lavender absolute as well as in a freshly prepared hexane extract of lavender flowers (Lavandula officinalis CHAIX ).     

AES and ELS study of titanium oxidation in high vacuum

In the present work, results of the interaction of O₂ with polycrystalline titanium using AES, and ELS techniques, are presented. Changes in the shapes of Ti(LMV) and Ti(LMM) transitions and in the Ti(LM)O(V)/Ti(LMV) and Ti(LMV) Ti(LMM) amplitude ratios as well as a shift of the 34 eV loss peak [Ti(3p level], are studied as function of the oxygen exposure.At O₂ pressures equal or less than 10^–6 Pa and exposure up to 2000 L(O₂) (weak oxidation), the Ti(LM)O(V)/Ti(LMV) and Ti(LMV)/Ti(LMM) ratios show three clearly distinct regions: (i) up to 20L there is a chemisorbed phase with the Ti(LMV)/Ti(LMM) ratio remaining constant and a fast linear increase in the Ti(LM)O(V)/Ti(LMM) ratio. (ii) At exposures higher than 20L the oxidation begins being characterized by a linear variation of the Ti(LM)O(V)/Ti(LMV) and Ti(LMV)/Ti(LMV) ratios, with positive and negative slopes, respectively. (iii) At 125L there is a change in both slopes but no stable value is achieved, despite the O(KLL)/Ti(LMM) ratio remains constant. Hence, it can be concluded that TiO is the final oxide obtained after that treatment, from features like the shape of the transitions and a maximum shift of 3eV of the Ti(3p) level, complemented with ESD experiments.On the other hand, experiments at pressures higher than 10^–4Pa with or without the surfaces at 900K (strong oxidation) indicate that the most likely final oxide is TiO₂.Work presented to the IXIVC-VICSS. Madrid (1983)     

Synthesis and rearrangement of 4-imino-4H-3,1-benzoxazines

Summary N-Acylanthranilamides react with dibromotriphenylphosphorane in the presence of triethylamine as HBr captor to give 4-imino-4H-3,1-benzoxazines in good yields. If the reaction is carried out without acid acceptor, N-acetylanthranilamides yield 2-methyl-4-quinazolones, whereas N-benzoylanthranilamides give 2-phenyl-4-imino-4H-3,1-benzoxazines. It has also been found that 2-methyl-4-imino-4H-3,1-benzoxazines rearrange under the influence of HCl or HBr into the respective 2-methyl-4-quinazolones; 2-phenyl-4-imino-4H-3,1-benzoxazines, however, do not undergo such a rearrangement.

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Synthese und Umlagerung von 4-Imino-4H-3,1-benzoxazinen

Zusammenfassung Die Umsetzung von N-Acyl-anthranilsäure-amiden mit Triphenyldibromphosphoran in Gegenwart von Triethylamin als HBr-Akzeptor führt mit guten Ausbeuten zu 4-Imino-4H-3,1-benzoxazinen. Wird die Reaktion ohne säurebindendes Mittel durchgeführt, dann entstehen aus N-Acetyl-anthranilsäure-amiden 2-Methylchinazolone-4, jedoch erhält man aus N-Benzoylanthranilsäure-amiden 2-Phenyl-4-imino-4H-3,1-benzoxazine. 2-Methyl-4-imino-4H-3,1-benzoxazine erleiden unter dem Einfluß von HBr oder HCl eine Umlagerung in entsprechende 2-Methylchinazolone-4, während 2-Phenyl-4-imino-4H-3,1-benzoxazine zu einer solchen Umlagerung nicht befähigt sind.

     

Luminescent properties of PP and LDPE films and rods doped with the Eu(III)‐La(III) complex

The work is devoted to luminescent properties of trivalent lanthanide complexes dispersed in thermoplastic host matrices. Polyethylene films and polypropylene‐rods, both doped with these complexes, were manufactured using an extrusion technique. Two kinds of dopants were used: Eu(III)‐thenoyltrifluoroacetone‐1,10‐phenanthroline complex (1) and Eu(III)‐La(III)‐1,10‐phenanthroline complex (2). Absorption, excitation, emission spectra and lifetime of luminescence were studied. The impact of the polymer matrix on the emission spectra was investigated. Emission spectra of the films were studied at room and helium temperatures. Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) surface mapping showed that in the Eu(III)‐La(III) complex europium forms islands (clusters) with a dimension of 1 µm, whereas lanthanum was dispersed more uniformly in the polymer matrix. Dependence of emission intensity on the excitation was determined. Copyright © 2006 John Wiley & Sons, Ltd.