The preparation,phase relationships,and Eu-151 Mössbauer spectroscopy of europium tungsten bronzes and related phases

Crystal chemistry and phase relations for the bronze-forming region of the EuWO system have been investigated. A bronze Eu_xWO₃ is stable up to 1000°C when x ? 0.125 and in the region 0.085 ? x ? 0.125 the symmetry is cubic. A tetragonal bronze exists at x = 0.05, and an orthorhombic bronze with a structure closely related to the orthorhombic form of WO₃ exists below x = 0.01. Mössbauer spectra at room temperature and at 80 K indicate that in all these phases the europium is highly ionized as Eu(III) with no electron localization to give (EuII) even at low values for x. The decomposition products of the bronzes have been established, and the Mössbauer parameters for the highly nonstoichiometric tungstates Eu_xWO₄ were determined. Both Eu(II) and Eu(III) resonances were obtained, and a cation vacancy model for Eu_xWO₄ was found to fit the data best. In conformity with the foregoing data, a sample of composition “Eu₂W₂O₇” was found not be be a pyrochlore but to comprise a mixture of Eu₆WO₁₂, Eu_xWO₄, and W. The phase relationships for the europium bronze system Eu_xWO₃ are compared with those of other ionic bronzes Na_xWO₃, Li_xWO₃, and Al_xWO₃.     

Use of the CNDO method for the study of the electronic structure and properties of complexes of the transition metals

Conclusions In our view, the material examined in the present review indicates that, in spite of the appearance of more accurate methods of calculating the electronic structure and the increasing possibilities provided for their realization for fairly complex systems, the applied value of simple semiempirical methods, in particular the CNDO method, is far from exhausted. In the near future, semiempirical calculations will probably provide the chief means of studying the electronic structures of complex molecules, by becoming accessible to an increasing circle of chemists.Leningrad State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 17, No. 3, pp. 549–577, May–June, 1976.     

O,O-dialkyl-S-(1-silatranylalkyl) dithiophosphates

Conclusions The reactions of 1-(3-chloropropyl)silatrane with potassium O,O-diethyl dithiophosphate gave O,O-diethyl-S-(1-silatranylpropyl) dithiophosphate. O,O-Diethyl- and O,O-dipropyl-S-(1-silatranylmethyl) dithiophosphates were synthesized by the tranesterification of O,O-diethyl-and O,O-dipropyl-S-(trimethoxysilylmethyl) dithiophosphates by tris(2-hydroxyethyl)amine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1882–1884, August, 1987.     

Phenylmercury derivatives of aminomethylene- and hydroxymethylene-substituted 1-methyloxindoles, 1-indanones,and 1,3-indanediones

A number of phenylmercury derivatives of 3-hydroxymethylene- and 3-aminomethylene-substituted 1-methyloxindoles, 1-indanones, and 1,3-indanediones were synthesized. It is shown that the preferred tautomeric structures of the potentially metallotropic and prototropic hydroxymethylene keto (hydroxy vinyl aldehyde) derivatives of the indicated compounds and 3-hydroxybenzo[b]-2-formylthiophene coincide precisely. An aminomethylene structure with an N-H bond is realized for the phenylmercury derivatives of the corresponding azomethines in all cases.Communication 28 from the series Benzenoid-Quinoid Tautomerism of Azomethines and Their Structural Analogs. See [1] for communication 27.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 65–68, January, 1979.     

Local doses associated with119mSn isomeric transition

The energy absorbed by immediate surrounding of disintegrating^119mSn nuclei have been estimated by comparing the Mössbauer emission spectra of¹¹⁹Sn in some tin compounds with the absorption spectra of the same substances after -irradiation and by simple calculations of Auger electrons energy losses. The results obtained indicate that the observed post-effects of the^119mSn decay are due to self-radiolysis and other processes, whose contributions depend on the individual properties of the matrices.     

Extended average energy perturbation calculation of the 2s2 and 2p21S resonance state energies of two-electron atoms

An extended average energy (EAE) calculation of the 2s² and 2p²¹S resonance state energies of two-electron atoms is carried out. We take the bare-nucleus hamiltonian as the initial approximation and treat the zeroth-order degeneracy by van Vleck perturbation theory, For both H^? and He the lower state energies agree quite well with experiment while the upper state is about 1–2 eV too high. Our remits for He are comparable in accuracy to those obtained by the 1/Z Hartree—Fock perturbation method. A brief concluding discussion of ways to improve the simple EAE technique is presented.     

Synthesis of a seven-membered analog of eledoisin using the solid-phase method of peptide synthesis

Summary 1. The solid-phase method of peptide synthesis has been used to obtain the heptapeptide HGly-L-Ala-L-Phe-L-Val-Gly-L-Leu-L-Met which is an analog of eledoisin.2. The possibility has been shown of using o-nitrophenylsulphenyl derivatives of amino acids in the solid-phase method of peptide synthesis.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 3, pp 200–202, 1966     

Influence of mobility of medium on dynamics of metallotropy in tin-containing 2-R-oxyphenoxyls

The rate of intramolecular migration of the triphenylstannyl group in 3,6-ditert-butyl-2(triphenylstannyl) oxyphenoxyl decreases with increasing viscosity of the medium. A linear relationship _ex=·_c is observed between the characteristic time of stannotropy _ex and the correlation time for reorientational motions of the radical _c within a range of temperature variation no greater than 30°C. The parameter depends on the medium; this is explained by the possibility of complexation of the radical with the solvent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 781–786, April, 1990.     

Gibberellin metabolites from ent-kaura-2,16-dien-19-ol and its succinate in Gibberella fujikuroi

Exposure of ent-kaura-2,16-dien-19-ol (1) or its succinate (2) to resuspended mycelia of G. fujikuroi has produced a complex mixture of acids which after methylation gave the esters of two C₁₉ (24) and (30) and five C₂₀ gibberellins (4, 11, 20, 32 and 33). The triester (32) and the lactone ester (24) have been prepared before from the esters of gibberellin A₁₃ (8) and gibberellin A₄ (26) respectively. The structures of the other metabolites were assigned on spectroscopic data and by chemical transformations. Thus the lactone diester (4) has been converted to the known keto triester (6). The epoxide (11) has been related to gibberellin A₁₄ (14) and the aldehyde (33) has been related to gibberellin A₁₃ trimethyl ester (8) by way of the triol (34). Selective de-epoxidation of the 16,17-epoxy function in diepoxides has provided a route from the dienes (20 and 24) to the epoxides (11 and 30) respectively, but not from the ester of gibberellin A₅ (23) to that of gibberellin A₆ (29). On the other hand the latter can be obtained by epoxidation of gibberellin A₅ methyl ester trifluoroacetate. Backfeeding experiments carried out with the epoxy diacid (12), the diene diacid (21) and the derived diol (39) indicate pathways connecting the various metabolites. The natural gibberellins A₅ and A₆ were shown to be formed in some of the backfeeding experiments.