Excited Π states of divinyl chalcogenides and chalcophenes

Electron transitions in divinyl chalcogenides (CH₂=CHXCH=CH₂, where X is S, Se, or Te) have been analyzed using UV absorption spectra of dialkyl and alkyl vinyl chalcogenides. The following relations for the orbital energies are found: ^* < ^* < ^* < ^* for Te and ^* < ^* < ^* < ^* for S and Se. For chalcophenes, a correlation between the energy of the excited state (E ^*) of specific symmetry, the ionization potential (I) and the electron affinity (EA) is obtained:E ^*=const+(I+EA)/2. The electron affinity of divinyl chalcogenides is estimated. The correlation between the excited ^* states of divinyl chalcogenides and chalcophenes is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–835, May, 1994.     

Infrared spectra of vinyl compounds and the effects of conjugation involving the π-electrons of the vinyl group

Conclusions The frequencies of the =CH₂ group wagging vibration in CH₂=CH-X compounds reflects both the inductive effect of the substituents X, and the effects of, -, ,p- and (d-p)-conjugation in which these substituents take part.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.l, pp. 152–154, January 1970.     

Electronic interaction between the nitrogen,oxygen, and silicon atoms in the molecules of α-aziridin-1-ylalkoxy(triethyl)silanes

By the PMR method we have established the existence of a high frequency of the inversion of the nitrogen atom in the molecules of -aziridin-1-ylalkoxysilanes. This is due to the fact that the high (because of p-d bonding with the silicon atom) electronegativity of the oxygen atom in the Si-O-C-N system makes possible an interaction between the unshared electron pair of the nitrogen atom and the antibonding orbital of the C-O bond. The latter, in its turn, increases the degree of p-d bonding between the oxygen and silicon atoms (in these compounds the order of the Si-O bond is greater than in the alkoxysilanes).     

Hyperconjugation of unsymmetrical groups

The interaction of the -bond system with the -electron system in molecules of type {ie427-01} is easily determined for the symmetrical CH₃ group by isolating the -component from the system of three -bonds; CH₃ is thus treated as a C=X quasivinyl group. The theory is extended to unsymmetrical groups.Read at the Symposium on Quantum Chemistry, Palanga, June 1965.     

Kinetic models of CO oxidation on Pd-containing catalysts (with and without SO2)

The effect of reactants and experimental conditions on the Pd/C catalyzed oxidation of DS at 110–150°C and 0.3–1.0 MPa in alkaline aqueous solution is described with emphasis on the maximal reaction rate, yield of DGA and catalyst deactivation. Oxygen causes practically irreversible deactivation of catalyst.

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DS Pd/C 110–150°C 0.3–1.0 . , DGA . .

     

Complexation of three uranium(IV) ions at two α-B-[SbW9O33]9- trilacunary Keggin units: A spectroscopic investigation

The sandwich-type uranium(IV)-polyoxometalate Na₆ [U₃ (SbW₉ O₃₃ )₂ ]·22H₂ O was prepared and investigated by FT-IR and UV-VIS methods. The uranium(IV) coordination at the trilacunary Keggin units shifts the _as (W-O_b,c -W), _as (W=O_d ), _as (W-O_a ) antisymmetric stretching vibration bands in the 700 ÷ 950 cm^-1 region of the FT-IR spectrum of U(IV)-complex. The visible electronic absorption spectrum of the complex indicates a ³ H₄ electronic ground state of uranium ions and a quasicubic local symmetry around them. The UV electronic spectra of the U(IV)-POM complex and of the ligand present the broad bands assigned to p -d electronic transitions in the W=O bonds (at 46640 cm^-1 for the ligand and 47280 cm^-1 for the complex) and d -p -d transitions in tricentric W-O-W bonds (at 40880 cm^-1 for the ligand and 39920 cm^-1 for the complex).     

Molecular orbital calculations on the optical rotatory properties of chiral allene systems

The chiroptical properties associated with the ^* transitions in dissymmetric allene systems are calculated and relationships between the chiroptical observables and the stereochemical and electronic structural features of these systems are examined. The calculations are based on the INDO and CNDO/S semiempirical molecular orbital models for the electronic structure of the molecular systems and excited states are constructed in the virtual orbital-configuration interaction approximation. The dipole strengths, rotatory strengths, and dissymmetry factors for the three lowest energy ^* transitions are computed and reported for eleven chiral allene structures. Relationships between absolute configuration and the signs of the ^* rotatory strengths are examined and discussed.     

Spreading of dipalmitoyl phosphatidylcholine on the surface of sodium deoxycholate aqueous solution

The surface pressure vs. mokcular surface area relations for dipalmitoyl phosphatidylcholine (DPPC) insoluble monolayer and sodium deoxycholate (SDC) adsorbed monolayer,L and D1, respectively, were obtained from the analyses of surface tensions measured by the Wilhelmy glass plate. Also, D1 was obtained by a drop-weight method. Next, the surface pressure time course,(t), of the SDC aq. was measured by the Wilhelmy plate before and after DPPC was spread on the liquid surface. At DPPC spreading,(t) jumped to a maximum,, and decreased along an exponential curve. The values of with various surface amounts of DPPC and bulk concentrations of SDC were analyzed using a dual surface-region model. The model enabled the estimation of. For better fitting, modified relations were constructed in place of D1. The exponential decrease of(t) was also observed on the SDC adsorbed monolayer which was rapidly compressed by a moving barrier. The(t) relaxation rate constants of the SDC monolayers which were compressed by DPPC spreading and the moving barrier agreed with each other, suggesting a desorption of SDC from the surface.     

Proton-magnetic-resonance spectra of some organoethoxysilanes

The PMR spectra of 33 organoethoxysilanes have been investigated. Comparison of the chemical shifts of C₂H₅O and CH₃ groups attached to the silicon atom with the values of the remaining substituents at the central silicon atom gives reason to suppose that the contribution of each atom in p– interaction decreases with increased number of ethoxy groups at the silicon atom, while the over-all effect of increased electron density at the silicon heteroatom arising from this interaction increases. The Taft constants for several substituents are calculated.     

An ab initio study of formamide

Calculated energy and molecular properties of the ground and low-energy excited states of formamide are presented at the ground state geometry. Satisfactory results are obtained except for the ¹* energy which remains too high by 1 eV (which is nevertheless a large improvement over previous calculations). The predicted triplet energies lie at 5.4 eV (³ n*) and 5.8 eV (³*).     

Quantum-chemical study of allylstannanes

It has been shown by the MNDO method that in allyl compounds of tin, the atomic orbitals of the heteroatom interact with the -orbital through the bridge group, but interact with the ^*-orbital mainly through space. The position and intensity of the long-wave electronic transitions for methylvinylstannane should not depend on the conformation, with the ,- and , pseudo--conjugation effects being approximately identical, whereas for allylstannane, the ,-conjugation is considerably stronger. In molecules containing several allyl fragments bonded to heavy atoms, ,-conjugation is far weaker than ,-conjugation in polyenes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2071–2076, September, 1991.     

Stereochemistry and thermodynamics ofπ-Complexation of a series of pseudo-conjugated cyclic diolefins with silver salts

A comparison has been made of results obtained in studies of the stereochemistry and thermodynamics of-complexation of pseudoconjugated cyclic diolefins with silver salts. The structure of the-complexes in solution was evaluated by means of silver-lanthanide shift reagents in PMR spectrometry. The thermodynamic parameters of-complexation of AgNO₃ with cyclic diolefins in methanol were obtained by direct calorimetric titration. As a result, thermodynamic preference was established for the formation of-complexes of the chelate type. The dependence of the stability constants of-complexes on the structural features of diolefin substrates has been examined critically.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 6, pp. 681–685, November–December, 1985.     

Verfolgung der Verbrennungsreaktionen Exothermer Massen auf Basis von Aluminium,Fluoriden und Natriumverbindungen mit Differenzialthermoanalyse

Zusammenfassung Das Verbrennen von Mischungen der exothermen Systeme Al-NaF-NaNO₃ und Al-CaF₂-NaNO₃ wurde durch Röntgenanalyse ergänzte DTA untersucht. Um den Einfluß des durch Dissoziation von NaNO₃ gebildeten Sauerstoffs zu bestimmen wurden auch Mischungen, welche anstatt NaNO₃ NaNO₂ oder Na₂O₂ enthielten, geprüft.Zwei, bei 310° bzw. 850° einsetzende exotherme Reaktionen wurden in den Gemischen vom Typ Al-NaF-NaNO₃ gefunden. Die erste ist der Dissoziation von NaNO₃ zuzuschreiben, die zweite ist der Anwesenheit von Luft zuzuordnen.Beide exothermen Reaktionen wurden im System Al-CaF₂-NaNO₃ in Richtung höherer Temperaturen verschoben. Die Untersuchung der NaNO₂- oder Na₂O₂-haltigen Gemische anstatt NaNO₃ zeigte, daß die Dissoziation von NaNO₃ den zum Verbrennen benötigten Sauerstoff liefert, andererseits würde letztere Reaktion sonst nur in begrenztem Ausmaß stattfinden.

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Combustion of exothermic mixtures belonging to the system Al-NaF-NaNO₃ and Al-CaF₂-NaNO₃ was investigated by DTA and X-ray analysis. In order to determine the influence of the oxygen generated by dissociation of NaNO₃, the mixtures containing NaNO₂ or Na₂O₂ instead of NaNO₃ were also examined.Two exothermic reactions starting at 310° and 850° rsp. were found in the mixtures of the Al-NaF-NaNO₃ type. The first is due to the dissociation of NaNO₃ and the second proceeds independence of the availability of air.Both exothermic reactions were shifted to higher temperatures in the system Al-CaF₂-NaNO₃. Investigation of the mixtures containing NaNO₂ or Na₂O₂ instead of NaNO₃ has proved that the dissociation of NaNO₃ supplies the oxygen required for combustion which should otherwise proceed only in a limited extent.

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Résumé On a étudié, par ATD et par analyse aux rayons X, la combustion des mélanges exothermiques appartenant aux systèmes Al-NaF-NaNO₃ et Al-CaF₂-NaNO₃. Afin de déterminer l'influence de l'oxygène engendré par la dissociation de NaNO₃, on a étudié de même des mélanges contenant NaNO₂ ou Na₂O₂ au lieu de NaNO₃.On a trouvé, dans les mélanges du type Al-NaF-NaNO₃, des réactions exothermiques à partir des temperatures respectives de 310° et 850°. La première est due à la dissociation de NaNO₃ et la seconde dépend de l'air disponible.Dans le système Al-CaF₂-NaNO₃ les deux réactions sont déplacées vers les températures plus élevées. L'examen de mélanges contenant NaNO₂ ou Na₂O₂ au lieu de NaNO₃ à montré que c'est la dissociation de NaNO₃ qui fournit l'oxygène nécessaire pour la combustion. Celleci n'aurait lieu, autrement, que d'une manière limitée.

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, l-NaF-NaNO₃ Al-CaF₂-NaNO₃. , NaNO₃, , NaNO₃, , NaNO₂ Na₂. , Al-NaF-NaNO₃ , 310° 850°. , . Al-CaF₂-NaNO₃ . , NaNO₂ Na₂O₂, , , , , .

     

Spectral properties and temperature-dependence of semiconductivity of various doped bismuth trioxide polycrystals

Several samples of Nb₂O₅-doped Bi₂O₃ and Y₂O₃-doped Bi₂O₃ were carefully prepared and sintered at 700° for 3 hours. Extensive measurements were carried out on these samples, including X-ray diffraction spectra, infrared absorption spectra and the temperature-dependence of the DC-electrical conductivity in the solid state. The results obtained were discussed, correlated and interpreted. Finally, the optimum compositions were established and recommended for doped-Bi₂O₃ in the electronics industry.

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Zusammenfassung Einige Proben von mit Nb₂O₅ und Y₂O₃ gedopten Bi₂O₃ wurden hergestellt und bei 700 °C 3 Stunden gesintert. Von den Proben wurden Röntgendiffraktogramme und IR-Absorptionsspektren aufgenommen und die Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit im festen Zustand gemessen. Die erhaltenen Ergebnisse werden diskutiert, zueinander in Beziehung gesetzt und interpretiert. Optimale Zusammensetzungen werden ermittelt und für gedoptes Bi₂O₃ in der Elektronikindustrie empfohlen.

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Bi₂O₃, Nb₂O₅ Y₂O₃, 3 700°. , . . , .

     

Calculation of σ→π* and π→σ* transitions in vinylboranes

Calculations are presented of the energies of the ground and excited and electronic states of ethylene and substituted vinylboranes. The Pople-Segal-Santry method was employed throughout. It is concluded that the excited state of lowest energy in ethylene has * character whilst the lowest energy ultra-violet spectral bands of the latter compounds stem from ^* transitions.

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Zusammenfassung Valenzelektronenrechnungen nach Pople-Segal-Santry wurden für Äthylen und Vinylborane durchgeführt. Danach hat der niedrigste angeregte Zustand von Äthylen ^*-Charakter, während die längstwellige UV-Bande der Vinylborane einem ^* -Übergang entspricht.

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Résumé Calculs de l'énergie pour les états fondamentaux et excités et de l'éthylène et des vinylboranes substitués. Utilisation de la méthode de Pople-Ségal-Santry. L'état excité le plus bas pour l'éthylène résulte d'une transition ^* , alors qu'il résulte d'une transition ^* pour les vinylboranes.

     

Reactions of Tertiary Alcohols with Palladium(II) Tetraaqua Complex. Formation of Palladium π-Allyl Complexes

Transformations of 2-methyl-2-propanol, 2-methyl-2-butanol, 2-methyl-2-pentanol, 1-methyl-1-cyclohexanol, and 1-ethyl-1-cyclohexanol in the presence of tetraaquapalladium(II) ions in perchloric acid madium were studied. It was found that the reactions give rise to palladium(II) -allyl complexes. The reaction rate increases and the yield of the corresponding -allyl complex decreases with increasing hydrocarbon chain length. Addition of iron(III) ions to the systems essentially increases the yield of palladium -allyl complexes. The olefin formed from the corresponding tertiary alcohol participates in the formation of the palladium -allyl complex. Oxidation of 2-methyl-2-butanol with tetraaquapalladium(II) ions gives the isomeric palladium -allyl complexes [Pd(³-(CH₃)₂CCHCH₂)bpy]ClO₄ and [Pd(³-(CH₂C(CH₃)CHCH₃))bpy]ClO₄, which were isolated using 2,2'-bipyridyl and characterized by ¹H and ¹³C NMR spectroscopy.     

Metal complexes of allyl derivatives of C60 fullerene: molecular and electronic structure prediction from density functional calculations

The problem of existence of ³—-complexes of C₆₀ fullerene with transition metal atoms is discussed. The complexes C₆₀R₃Co(CO)₃ (R = H, F, Cl, Br), C₆₀H₃NiCp, and C₆₀H₃Fe(CO)Cp, where C₆₀R₃ is an allyl derivative of C₆₀ fullerene, were shown to be sufficiently stable. In these complexes the metal atoms are ³—-bound to the fullerene cage. In contrast to this, the metal atoms in the C₆₀H₃Li and C₆₀H₃FeCp complexes are ⁵—-coordinated to the carbon cage. Density functional calculations were carried out with the Perdew—Burke—Ernzerhof exchange-correlation potential (PBE). It was concluded that the type of bonding in the complexes of allyl derivatives of C₆₀ fullerene depends on the nature of the species attached. Among the systems studied, the maximum energy of the ³—-bond was obtained for the C₆₀H₃NiCp complex. The results obtained can be useful in the design of synthesis of new fullerene derivatives with the ³—-coordination of the transition metal atoms to the carbon cage.     

On the Distribution of π Bonds in Cyclofusene

We present a type of coronafusene termed cyclofusene, in which each hexacycle shares exactly two nonadjacent edges with other hexacycles. Cyclofusene has exactly four configurations of bonds such that each bond belongs to the inner or outer boundary. In each of these configurations, the outer boundary has six more bonds than the inner boundary. The number of shared bonds in any mixed configuration is even. Let m be the number of shared bonds in a mixed configuration for a cyclofusene with exactly k linear chains. Then m k. Furthermore, there exists a mixed configuration with exactly k shared bonds.     

Ab initio SCF and CI study of the electronic spectrum of pyridine N-oxide

Configuration interaction (CI) studies of ground, n *, * * electronically excited states are reported for pyridine N-oxide. The transition energy to the lowest * excited ¹ B ₂ state is calculated at 4.35 eV, compared to the experimental spectrum range of 3.67–4.0 eV. This state lies below the lowest n * excited ¹ A ₂ state calculated at 4.81 eV above the ground state. The only experimentally reported triplet state at 2.92 eV above the ground state is predicted to be the ³ A ₁ (*) state. The calculated energy lies at 3.27 eV. Numerous other high-lying singlet states as well as the triplet states have also been calculated. The intramolecular charge transfer character of the ground and the excited states have been studied in terms of the calculated dipole moment and other physical properties.