Conformational changes accompanying electronic excitation of CD3 NO

Analysis of the 675 nm absorption of CD₃NO shows that the conformation changes from eclipsed in the ground state to staggered in the à ¹A″(ne*) excited state. The internal-rotation barrier V₃ increases from 383 to 475± 50 cm^?1.     

Ruthenium complexes of analogues of the antitumor antibiotic streptonigrin

The complexes Ru(L1-CH3)(CO)3Cl, RuL2(CO)2Cl2, and RuL3(CO)2Cl2 (L1= 6-methoxy-5,8-quinolinedione, L2 = 7-amino-6-methoxy-5,8-quinolinedione, L3 = 6,6'-dimethoxycarbonyl-2,2'-bipyridine) were prepared by reaction of L1-L3 with the tricarbonyldichlororuthenium(II) dimer. L1-L3 act as bidentates through the ortho oxygen atoms, the pyridyl nitrogen and the adjacent quinone oxygen, and the bipyridyl nitrogens, respectively. RuL3(CO)2Cl2 is characterized by X-ray crystallography. 15N NMR correlation spectra give upfield shifts of around 60 ppm for the pyridyl nitrogens that are coordinated to the metal, while 13C NMR correlation spectra give a downfield shift of 10 ppm for the quinone carbonyl group that is coordinated to the metal. The electrochemistry of RuL2(CO)2Cl2 is examined, and the implications for the formation of metal complexes of the antitumor antibiotic streptonigrin, which cleaves DNA in the presence of metal ions, are discussed.     

The Lyapunov Exponent of Products of Random 2×2 Matrices Close to the Identity

We study products of arbitrary random real 2×2 matrices that are close to the identity matrix. Using the Iwasawa decomposition of SL(2,?), we identify a continuum regime where the mean values and the covariances of the three Iwasawa parameters are simultaneously small. In this regime, the Lyapunov exponent of the product is shown to assume a scaling form. In the general case, the corresponding scaling function is expressed in terms of Gauss’ hypergeometric function. A number of particular cases are also considered, where the scaling function of the Lyapunov exponent involves other special functions (Airy, Bessel, Whittaker, elliptic). The general solution thus obtained allows us, among other things, to recover in a unified framework many results known previously from exactly solvable models of one-dimensional disordered systems.     

The effects of grain shape and frustration in a granular column near jamming

We investigate the full phase diagram of a column of grains near jamming, as a function of varying levels of frustration. Frustration is modelled by the effect of two opposing fields on a grain, due respectively to grains above and below it. The resulting four dynamical regimes (ballistic, logarithmic, activated and glassy) are characterised by means of the jamming time of zero-temperature dynamics, and of the statistics of attractors reached by the latter. Shape effects are most pronounced in the cases of strong and weak frustration, and essentially disappear around a mean-field point.     

Stoichiometry and impurity concentration in synthetically grown iron pyrite crystals and their constituents

Summary The iron to sulfur ratio in different synthetic iron pyrite samples, prepared as powders and crystals, was measured by means of ICP-AES (Inductively Coupled Plasma with Atomic Emission Spectrometry). A remarkably high sulfur deficiency in single crystals grown by chemical vapor transport has been established which leads to the gross formula FeS_2–xfor 0.242, Te) and the quartz container material (Si, O). The advantage of the ICP-methods is the direct employment of the samples after a dissolution process without further preparation steps.

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Stöchiometrie und Verunreinigungskonzentration in synthetisch gewachsenen Eisenpyrit-Kristallen und ihren Ausgangsstoffen

     

Comparison of calorimetric and IR-spectroscopic data for alcohols and alcoholic solutions

The heats of solution of alcohols in hexane can be considered as the energy necessary to break hydrogen bonds (H-bond). The amount of non H-bonded OH groups estimated from caloric data, are in good agreement with IR-spectroscopic data. Comparison of calorimetric and IR-spectroscopically determined H-bond energies permit the separation of intermolecular van der Waals effects from H-bond interactions. This separation shows that van der Waals interactions of alcohols or water should not be underestimated.