Photophysical behaviour of azaphenanthrenes

Nitrogen position and internal heavy atom effects on the radiative and radiationless transitions from the lowest excited states of the isomeric azaphenanthrenes and some of their methyl, chlorine and bromine derivatives have been studied in E.P.A. solutions at 77 K. The nitrogen position affects the fluorescence and S₁-T₁ intersystem crossing rates more than the phosphorescence and T₁-S₀ intersystem crossing rates. Small differences in the behaviour of 9-azaphenanthrene are enhanced in non-hydroxylic solvents and at room temperature, and it is inferred that (n, π*) states play a more important role in the photophysical behaviour of this isomer. Halogen, substitution in all the isomers increases the phosphorescence rate, induces a smaller increase in the T₁-S₀ intersystem crossing rates and has a negligible effect on the fluorescence rate.     

Calculations of the electronic structures of cage molecules using free-electron orbitals as a basis

A non-empirical molecular orbital method, particularly suitable for calculations on cage-like molecules, is described. The method uses as basis functions the set of free-electron functions which are the solutions of Schrödinger's equation for an electron confined between two concentric, spherical potential energy barriers. Application of the theory to the SCF calculation of the energies of the delocalized electrons in benzene and tetrasulphur tetranitride shows that the model is capable of interpreting the properties of such systems. However, it does highlight a difficulty in the calculation of excited state energies with one-centre models which appears to be largely unrecognized.Extension of the method to a consideration of all the valence electrons, using P₄ as an example, reveals problems the origin of which is an inadequate treatment of the core electrons. It is suggested that these problems may best be dealt with by use of a suitable pseudo potential.     

Vaporisation et dissociation thermique des sulfures de phosphore P4S3, P4S7 et P4S10 a l'etat gazeux

Résumé Nous avons montré par spectrométrie Raman à chaud et mesure des tensions de vapeur que P₄S₃ se vaporise de façon congruente tandis que P₄S₇ et P₄S₁₀ se dissocient dès le début de leur vaporisation. P₄S₇ donne réversiblement P₄S₃ et soufre. P₄S₁₀ se dissocie irréversiblement en P₄S₇ et soufre. A l'état de vapeur non saturante, P₄S₃ se dissocie au-dessus de 600° avec formation de phosphore, de soufre et d'autres espèces non identifiées.Nous avons mesuré expérimentalement la capacité calorifique de P₄S₃ liquide, calculé celle de P₄S₃ gazeux et son entropie standard. Nous avons aussi estimé l'enthalpie standard de vaporisation de P₄S₃ à l'aide des mesures des tensions de vapeur saturante. Nous en avons déduit l'entropie standard de P₄S₃ liquide et son point d'ébullition.

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It is shown by Raman spectroscopy at high temperature and by vapor tensimetric measurements that the vaporisation of P₄S₃ is congruent, whereas P₄S₇ and P₄S₁₀ dissociate at the beginning of vaporisation. P₄S₇ gives P₄S₃ and sulfur reversibly. The dissociation of P₄S₁₀ into P₄S₇ and sulfur is irreversible. Above 600°, in non-saturated vapour the dissociation of P₄S₃ gives phosphorus, sulfur and some unidentified gaseous species. The heat capacity of liquid P₄S₃ has been measured. That of gaseous P₄S₃ and its standard entropy have been calculated. The vaporisation standard enthalpy of P₄S₃ has been estimated from the experimental results on the saturated vapour pressures. The standard entropy of liquid P₄S₃ and its boiling point have been derived from these data.

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Zusammenfassung Mittels Raman-Spektrometrie bei erhöhter Temperatur und durch Messung der Dampfdrucke wurde festgestellt, daß sich P₄S₃ verflüchtigt, während P₄S₇ und P₄S₁₀ mit Beginn der Verflüchtigung dissoziieren. P₄S₇ ergibt reversibel P₄S₃ und Schwefel. Im Zustand ungesättigten Dampfes dissoziiert P₄S₃ oberhalb von 600° unter Bildung von Phosphor, Schwefel und anderer nicht identifizierter Substanzen.Die Wärmekapazität von flüssigem P₄S₃ wurde gemessen, während die vom gasförmigem P₄S₃ sowie seine Standard-Entropie berechnet wurden. Die Standard-Enthalpie der Verflüchtigung des P₄S₃ wurde durch Messungen der Sättigungs-Dampfdrucke ermittelt. Daraus wurden die Standard-Entropie des flüssigen P₄S₃ sowie sein Siedepunkt berechnet.

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- - , P₄S₃ , P₄S₇ P₄S₁₀ . P₄S₇ P₄S₃ , P₄S₁₀ P₄S₇ . 600° P₄S₃ , . P₄S₃, P₄S₃ . P₄S₃. P₄S₃ .

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Nous remercions Monsieur Letoffe du laboratoire du Professeur J. Bousquet, INSA de Lyon, 20 Avenue Albert Einstein 401, 69621 Villeurbanne, qui a r6alis6 pour nous les déterminations expérimentales des capacités calorifiques de P₄S₈ liquide.     

Metallacycloalkanes: I. Preparation and characterisation of α,α′-bipyridyl-5-nickela-3,3,7,7-tetramethyl-trans-tricyclo[4.1.0.02,4]heptane

Oxidative addition of 2 molecules of 3,3-dimethylcyclopropene (I) to α,α′-bipyridyl(1,5-cyclooctadiene)nickel(0) (III) gave the title compound (IV) in over 90% yield. Complex IV was characterized by mass, ¹H NMR and ¹³C NMR spectroscopy. Its structure was determined by X-ray diffraction (a 13.7081(2), b 14.638(2), c 9.5139(1) Å, β 110.82(1)°, C2/c, R = 0.05 for 1614 reflections).     

Relativistic molecular orbitals for the double group D3h

Relativistic symmetry orbitals are given for the double group D_3h. For atomic orbitals at the symmetry center a general expression is presented. The atomic orbitals of the s, p_½, and p_3/2 variety outside the center are also considered. The representation matrices are given in explicit form.     

Synthesis and antiinflammatory activity of the sulfoxides of 4-[3-(dimethylamino)propyl] - 3,4- dihydro- 2-(1-hydroxyethyl)-3-phenyl-2H-1,4-benzothiazine

Oxidation of 4-[3-(dimethylamino)propyl]-3,4-dihydro-2-(1-hydroxyethyl)-3-phenyl-2H-1,4-benzothiazine, hydrochloride (I) with hydrogen peroxide yielded a mixture of two sulfoxides (II). Since this mixture exhibited antiinflammatory activity, the two components (Isomers A and B) were prepared in purified form by oxidation of I with N-chlorosuccinimide and hydrogen peroxide, respectively. Isomer A was more potent than Isomer B in the carrageenin-induced edema test.     

Characterization of dynamic and steady-state protein phosphorylation using a fluorescent phosphoprotein gel stain and mass spectrometry

Protein phosphorylation plays a vital role in the regulation of most aspects of cellular activity, being key to propagating messages within signal transduction pathways and to modulating protein function. Pro-Q Diamond phosphoprotein gel stain is suitable for the fluorescence detection of phosphoserine-, phosphothreonine-, and phosphotyrosine-containing proteins directly in sodium dodecyl sulfate (SDS)-polyacrylamide gels. The technology is especially appropriate for profiling steady-state and dynamic phosphorylation on a proteome-wide scale, as demonstrated through detection of the native phosphorylation of cardiac mitochondrial phosphoproteins and changes in this profile arising from the activity of a protein kinase. For example, Pro-Q Diamond phosphoprotein gel stain was employed to demonstrate that among the 46 subunits of the mitochondrial respiratory chain complex, NADH:ubiquinone oxidoreductase (complex I), a 42 kDa subunit is phosphorylated in the steady-state. However, exposure of mitochondria to cAMP-dependent protein kinase increases phosphorylation of this 42 kDa subunit and results in de novo phosphorylation of an 18 kDa subunit as well. Since Pro-Q Diamond dye binds to phosphorylated residues noncovalently, the staining technology is fully compatible with modern microchemical analysis procedures, such as peptide mass profiling by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry and post-source decay analysis of peptide phosphorylation.     

A comparison of SCF-Xα and extended Hückel methods for metal clusters

A comparison of some results from Xα-scattered wave (Xα-SW) and extended Hückel (EH) calculations for metal clusters is given. It is found that small clusters of atoms (≈ 13 atoms) using the Xα-SW method reproduce many of the features of the electronic structure of the bulk metals, whereas this is not the case for the same clusters using the EH method. A more systematic approach to EH parametrizations is suggested in order to make this method a more viable approach to treating metal clusters.     

Infrared intensities of the external modes of crystalline nitrous oxide

The absorption intensities of two infrared active lattice modes of crystalline N₂O have been measured. Both the frequencies and intensities of the external modes of N₂O have been found to be very similar to those of CO₂, and most of the differences between the spectra of CO₂ and N₂O can be explained by the differences in the quadrupole moments.