A resonance Raman spectroscopic study of the protonation of Disperse Orange 25 in solution and adsorbed on oxide surfaces

The protonation of Disperse Orange 25 (DO25) in aqueous solution, and upon adsorption on oxide surfaces, was studied by resonance Raman (RR) spectroscopy. The neutral and protonated forms of DO25 were modelled by DFT calculations of the isolated molecules in the gas phase at the B3‐LYP/DZ level, enabling calculation of the vibrational spectra of these species, together with vibrational assignments. RR spectra show that DO25 is physisorbed on the SiO₂ surface, but its adsorption on SiO₂ Al₂O₃ or H‐mordenite results in protonation. This observation indicates the presence of Brønsted acidic sites on these oxide surfaces with pK_a values ⩽2.5. RR studies of the adsorption of DO25 can therefore provide useful information on the nature of surface acidity on oxides, which is complementary to that obtained from other probe molecules. Copyright © 2007 John Wiley & Sons, Ltd.     

Ab initio quantum chemistry on the Cray T3E massively parallel supercomputer: II

Gaussian-94 is the series of electronic structure programs. It is an integrated system to model a broad range of molecular systems under a variety of conditions, performing its calculations from the basic laws of quantum chemistry. This new version includes methods and algorithms for scalable massively parallel systems such as the Cray T3E supercomputer. In this study, we discuss the performance of Gaussian using large number of processors. In particular, we analyze the scalability of methods such as Hartree–Fock and density functional theory (DFT), including first and second derivatives. In addition, we explore scalability for CIS, MP2, and MCSCF calculations. Scalability and speedups were investigated for most of the examples with up to 64 process elements. A single-point energy calculation (B3-LYP/6-311++G3df,3p) was tested with up to 512 process elements. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1053–1063, 1998     

Synthese und Konfiguration einiger Spiro [indan-2,2′-pyrrolidin]- und Spiro [pyrrolidin-2,2′-tetralin]-Derivate,

Synthesis and configuration of some spiro [indan-2,2′-pyrrolidine] and spiro [pyrrolidine-2,2′-tetraline] derivatives Catalytic hydrogenation of the nitrosoindan and nitrosotetralin derivatives 8 yielded trans-1-hydroxy-spiro [indan-2,2′-pyrrolidin]-5′-one ( 9 ) and trans-1′-hydroxy-spiro [pyrrolidine-2,2′-tetralin]-5-one ( 10 ) respectively, whilst the corresponding cis compounds 12 and 15 were prepared via the chlorides 11 and 14 . The configurations of 10 and 13 were determined by X-Ray analysis.     

Strain and stereoelectronics in cycloalkyne click chemistry

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The structures of the active intermediates in Catalyst-Enhanced Molten Salt Oxidation and a new method for the complete destruction of chemical warfare arsenicals

Catalyst-Enhanced Molten Salt Oxidation (CEMSO) is our improvement of the earlier process, Molten Salt Oxidation (MSO), originally employed for the destruction of hazardous materials by high temperature oxidation in a carbonate melt. MSO was abandoned because it was slow and only partially oxidized cotton, paper, and plastics. It was very efficient for many other chemicals and had oxidized the nerve gas sarin with >99.9999% efficiency. We came to realize that the concentration of the oxidizing species, superoxide and peroxide ions, produced from the oxygen entering the carbonate melt, could be increased and maintained by the addition of nitrate ions as catalyst. The structure and interatomic distances for the various possible adducts between nitrate and nitrite with oxygen and peroxide have been calculated for the first time by Density Functional Theory (DFT). Their calculated enthalpies, as a function of temperature, revealed which adducts can be formed in the carbonate melt. The Japanese still have large stocks of the chemical warfare arsenicals Clark I and Clark II awaiting a destruction procedure that ensures removal of all volatile As(III) compounds. We have established that As(V) salts are stable at high temperature and here discuss how CEMSO can efficiently achieve this for the Clark arsenicals.     

Oxo ligand functionalization in the uranyl ion (UO22+)

Uranyl (UO₂²⁺) is an exceptionally stable molecular species, characterized by a linear OUO geometry and short U–O bonds. Its two oxo ligands are thought to be inert to exchange and resistant to functionalization. However, a growing body of literature suggests that this assessment may need to be reevaluated. This review summarizes the chemistry of the two oxo ligands of the uranyl ion. In particular, we explore the interaction of the uranyl oxo ligands with Lewis acids, and outline attempts to selectively functionalize the oxo ligands of uranyl by chemical means. We also discuss the kinetic and mechanistic knowledge for oxo ligand exchange under acidic, basic and photolytic conditions.     

A copper–polyol complex: [Na2(C2H6O2)6][Cu(C2H4O2)2]

The ionic title complex, bis(μ‐ethylene glycol)‐κ³O,O′:O′;κ³O:O,O′‐bis[(ethylene glycol‐κ²O,O′)(ethylene glycol‐κO)sodium] bis(ethylene glycolato‐κ²O,O′)copper(II), [Na₂(C₂H₆O₂)₆][Cu(C₂H₄O₂)₂], was obtained from a basic solution of CuCl₂ in ethylene glycol and consists of discrete ions interconnected by O—H...O hydrogen bonds. This is the first example of a disodium–ethylene glycol complex cation cluster. The cation lies about an inversion center and the Cu^II atom of the anion lies on another independent inversion center.     

Observation of magnetophonon resonance of Dirac fermions in graphite

Coherent coupling of Dirac fermion magnetoexcitons with an optical phonon is observed in graphite as marked magnetic-field dependent splittings and anticrossing behavior of the two coupled modes. The sharp magnetophonon resonance occurs in regions of the graphite sample with properties of superior single-layer graphene having enhanced lifetimes of Dirac fermions. The greatly reduced carrier broadening to values below the graphene electron-phonon coupling constant explains the appearance of sharp resonances that reveal a fundamental interaction of Dirac fermions.     

Low-threshold lasing eigenmodes of an infinite periodic chain of quantum wires

We study the lasing eigenvalue problems for a periodic open optical resonator made of an infinite grating of circular dielectric cylinders standing in free space, in the E- and H-polarization modes. If possessing a "negative-absorption" refractive index, such cylinders model a chain of quantum wires made of the gain material under pumping. The initial-guess values for the lasing frequencies are provided by the plane-wave scattering problems. We demonstrate a new effect: the existence of specific grating eigenmodes that have a low threshold of lasing even if the wires are optically very thin.     

Tomographic molecular imaging of x-ray-excitable nanoparticles

X-ray luminescence computed tomography (XLCT) is proposed as a new dual molecular/anatomical imaging modality. XLCT is based on the selective excitation and optical detection of x-ray-excitable nanoparticles. As a proof of concept, we built a prototype XLCT system and imaged near-IR-emitting Gd(2)O(2)S:Eu phosphors in various phantoms. Imaging in an optically diffusive medium shows that imaging performance is not affected by optical scatter; furthermore, the linear response of the reconstructed images suggests that XLCT is capable of quantitative imaging.