Theory of location and associated hyperfine properties of the positive muon in La2CuO4

The current understanding regarding the location of the positive muon, which is a valuable tool for probing the magnetic properties of copper oxide superconducting systems, will be reviewed for La₂CuO₄. The results of our present investigations by the Unrestricted Hartree-Fock Cluster procedure, which leads to a location for the muon of about 1.08 Å away from an apical oxygen and with the O-⁺ direction making an angle of 25° with the O-Cu direction, will be discussed, including the magnitude and direction of the hyperfine field obtained from the calculated wave functions. These latter results, which are in reasonable agreement with earlier muon spin rotation data in powdered samples and recent data in single crystals, show the importance of including the local contact and dipolar contributions to the hyperfine field associated with the unpaired electron spin distribution in the neighborhood of the muon. Possible additional factors besides those included here, that will involve substantial computational efforts but could lead to a bridging of the remaining quantitative differences with experimental hyperfine data, will be discussed.     

Ring closure of diethyl 2-methoxy-2-[N-(5-amino-1-benzylimidazolyl-4-carbonyl)amino]malonate: Product structures and pathways of product formation

Ring closure of the title compound (1) with sodium methoxide in methanol yielded three products, one 56-fused and two 57-fused heterocyclic systems: 9-benzyl-2-methoxycarbonylhypoxanthine (2), 3-benzyl-4,5,7,8-tetrahydro-6-methoxy-6-methoxycarbonyl-6H-imidazo[4,5-e][1,4]-diazepine-5,8-dione (3), and 3-benzyl-4,5,7,8-tetrahydro-6-methoxy-6H-imidazo[4,5-e][1,4]-diazepine-5,8-dione (4). Structures and pathways of formation of all three products have been described. Structures of2 and3 were confirmed by single-crystal X-ray diffraction analyses.     

GC-FTIR-MS analysis of volatile radiolysis products of nitrophenol solutions in carbon tetrachloride

Capillary gas chromatography — Fourier transform infrared spectroscopy combined with capillary gas chromatography — mass spectrometry is employed for the analysis of major volatile products in the -radiolysis of isomeric nitrophenol solutions in carbon tetrachloride. Isomeric di- and trichlorophenols, chloronitrophenols and dichloroisocyanatobenzenes in addition to those formed with m- and p-isomers, are among the important products formed in the solution of o-nitrophenol in carbon tetrachloride. Formation of dichloroisocyanatobenzene is explained by the interaction of dichlorocarbene with the nitro group followed by the ipso-substitution of OH and H atom by chlorine atom.This paper constitutes part of the Ph.D. thesis of M.K. Sahoo and was presented at the 10th conference on Chromatographic method and its significance for human health with international participation, Stará Lesná, High Tatras, Slovakia, Nov. 4–6, 1992.     

GC-FTIR-MS analysis of volatile radiolytic products in the radiolysis of nitroaniline-carbon tetrachloride solutions+

A good deal of products formed in the -radiolysis of isomeric nitroaniline solutions in carbon tetrachloride have been identified using GC-FTIR-MS technique. Tetrachloroethylene, chloroeenzene, hexachloroethane isomeric di-, tri- and tetrachlorobenzenes and chloroisocyanatobenzenes are among the important products formed in the radiolysis. Formation of dichlorobenzene is the result of ipso-substitution of both the nitro and aniline group by chlorine atom and the subsequent chlorination of dichlorobenzene results in the formation of polychlorobenzenes. Chloroisocyanatobenzene is proposed to be the product arising from the interaction of dichlorocarbene and the nitro group of nitroaniline followed by chlorination of the resulting product, isocyanatobenzene. A 94% yield of undissolved 1,2-aminonitrobenzene chloride salt is obtained from the radiolysis of o-nitroaniline solution in carbon tetrachloride with a radiation yield of 1.83 molecules per 100 eV absorbed energy for an irradiation dose of 267 kGy.This paper constitutes part of the Ph.D. Thesis of M.K. Sahoo and forms Part X. of a series entitled Radiolysis and Photolysis of Nitroaromatic Compounds halogenoalkane Mixtures. Part IX, Ref. (1).     

Single-precursor,one-pot versatile synthesis under near ambient conditions of tunable,single and dual band fluorescing metal sulfide nanoparticles

We present a simple and versatile method for the synthesis of high-quality size-controlled metal sulfide nanoparticles. A single compound (metal xanthate) is the precursor. A Lewis-base solvent is used to achieve a low reaction temperature of 50-150 degrees C, usually in air. Demonstrated with CdS, the precise control over the particle size (by regulating the temperature or the concentration) enables tuning the absorption and emission spectra of the particles. We also can control the relative intensity of the narrow (30-35 nm wide) excitonic emission (tunable in the range 430-480 nm with approximately 2% fluorescence quantum efficiency) and the broad emission associated with deep surface traps (in the range 550-700 nm). Using the same precursor CdS/ZnS core/shell particles are produced with a high PL yield ( approximately 14%).     

Reactions of pentafluorosulfanyl isocyanate with NR3 and PR3 compounds; Preparation and characterization of novel compounds SF2NC(O)NHC(O)OCH3 and 1,4-SF5NHC(O)OC6H4OH

The reaction of Pentafluorosulfanyl Isocyanate, SF₅NCO, with tertiary amines has led to 1:1 adducts which have been shown to be zwitterionic in nature by infrared and NMR spectroscopy.

These adducts are far less thermally stable than the analogous fluorosulfonyl derivatives recently reported by Appel and Montenarch¹. The reaction of SF₅NCO with triphenyl- phosphine gave some evidence for the zwitterionic derivative, but the product could not be isolated even when SF₅NCO was used in excess. Recently we have also isolated

from the reaction of SFE₂NC(O)NCO with methanol, and

from the reaction of SF₅NCO with hydroquinone. Both of these novel compounds were unexpected.The physical properties of

, SF₂NC(O)NHC(O)OCH₃, and 1,4-SF₅NHC(O)OC₆H₄OH, prepared during this study, will be discussed in detail.     

Three dimensional quantum dynamics of (H-, H2) and its isotopic variants

We present the results of a time-dependent quantum mechanical investigation using centrifugal sudden approximation in the form of reaction probability as a function of collision energy (E(trans)) in the range 0.3-3.0 eV for a range of total angular momentum (J) values and the excitation function sigma(E(trans)) for the exchange reaction H(-) + H(2) (v = 0, j = 0) --> H(2) + H(-) and its isotopic variants in three dimensions on an accurate ab initio potential energy surface published recently (J. Chem. Phys. 2004, 121, 9343). The excitation function results are shown to be in excellent agreement with those obtained from crossed beam measurements by Zimmer and Linder for H(-) + D(2) collisions for energies below the threshold for electron detachment channel and somewhat larger than the most recent results of Haufler et al. for (H(-), D(2)) and (D(-), H(2)) collisions.     

A tactically novel alternative to acyclic stereoselection based on the concept of a replicating chiron — access to 1,3-polyols

(S)-Glutamic acid is used as a chiral template to construct seven carbon subunits containing alternating hydroxyl groups with stereochemical control. Enantiomeric and/or diastereomeric 3,5-dideoxy-heptitols are thus obtained.