Structures of three substituted pentacyclo[5.4.0.02, 6.03, 10.05, 9]undecanes and a computational analysis of bond lengths

5-Methyl-2-phenylpentacyclo[5.4.0.0^{2, 6}.0^{3, 10}.0^{5, 9}]undecane-8, 11-dione,5-methyl-2-phenylpentacyclo [5.4.0.0^2,6.0^3,10.0^5,9]undecane-8-one-11-ol,and 5-methyl-2-phenylpentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8,11-diol are three cage compounds which differ only in the oxidation state at C(8) and C(11). The three compounds contain a four-membered, a six-membered, and four five-membered rings fused into a cagelike structure. An X-ray structure analysis shows the C(1)-C(7) and C(9)-C(10) bonds in the diketo cage to be 1.606(2) and 1.586(2) Å, which are significantly longer than in the other two molecules. In order to assess the effects of strain, steric, and electronic factors in these compounds, we investigated the unsubstituted parent cage compounds and a series of derivatives by molecular mechanics (MM3), AMPAC (AM1), MOPAC (PM3), and GAUSSIAN 90 calculations. These data suggest that dipolar through space interactions are responsible for the bond elongation and not a _– ^* interaction, which has been postulated in parallel-systems originating from a common bond. A small degree of _– ^* through-bond interaction may contribute to the lengthening in the dimethylene cage analogues.     

Stacking of nucleic acid bases: optimization of the computational approach—the case of adenine dimers

Structural Chemistry - Stacking interactions play an important role in stabilizing DNA and RNA secondary structure. To select a computational level to study the stacking interactions, both energy...     

The Effect of Metal Salts on the Separation of Carbohydrates by TLC

JPC – Journal of Planar Chromatography – Modern TLC - Carbohydrates have been examined by TLC on layers modified with metal ions, in the form of salts, by dipping commercial plates in...     

Ramsey numbers for a disjoint union of good graphs

We give the Ramsey number for a disjoint union of some G-good graphs versus a graph G generalizing the results of Stahl (1975) [5] and Baskoro et al. (2006) [1] and the previous result of the author Bielak (2009) [2]. Moreover, a family of G-good graphs with s(G)>1 is presented.     

Estimation and status prediction in a discrete mover‐stayer model with covariate effects on stayer's probability

A discrete‐time mover‐stayer (MS) model is an extension of a discrete‐time Markov chain, which assumes a simple form of population heterogeneity. The individuals in the population are either stayers, who never leave their initial states or movers who move according to a Markov chain. We, in turn, propose an extension of the MS model by specifying the stayer's probability as a logistic function of an individual's covariates. Such extension has been recently discussed for a continuous time MS but has not been considered before for a discrete time one. This extension allows for an in‐sample classification of subjects who never left their initial states into stayers or movers. The parameters of an extended MS model are estimated using the expectation‐maximization algorithm. A novel bootstrap procedure is proposed for out of sample validation of the in‐sample classification. The bootstrap procedure is also applied to validate the in‐sample classification with respect to a more general dichotomy than the MS one. The developed methods are illustrated with the data set on installment loans. But they can be applied more broadly in credit risk area, where prediction of creditworthiness of a loan borrower or lessee is of major interest.     

The X-ray revision of the structure of bis(4-hydroxybenzhydrazide)copper(II) sulfate(VI) dihydrate and its vibrational spectroscopy

The structure of known copper(II) complex with 4-hydroxybenzoic acid hydrazide has been corrected on the basis of a new X-ray analysis. It has been found, that the sulfate(VI) ion is bonded in apical position of Cu(II) coordination pyramid having two organic ligands at the base. Two water molecules are not coordinated as has been postulated before, but stabilizes the sulfate(VI) group orientation and link the layers of complex molecules by strong hydrogen bonds. The detailed interpretation of the measured IR and Raman spectra has been performed with aid of both: quantum calculations as well as H/D and ⁶³Cu–⁶⁵Cu isotope substitution.     

Komplexbildende Eigenschaften des 3,5-Dimethylpyrazols. II

Zusammenfassung Die Bedingungen der Entstehung und der Extraktion der aus Cu²⁺, Rhodanid und 3,5-Dimethylpyrazol entstehenden Komplexe wurden untersucht. Mittels optischer Untersuchungen wurde bewiesen, daß sich aus diesen Komponenten Triplettkomplexe mit verschiedener Koordinationszahl bilden. Chloroform extrahiert einen Komplex mit der Formel [Cu(CNS)₂(DMP)₂], Benzol dagegen einen Komplex mit der Formel [Cu(CNS)₂(DMP)₄].

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Summary The conditions for the production and the extraction of complexes formed in the Cu-SCN-DMP system were examined. Optical studies revealed that this system gives rise to triplet complexes with various coordination numbers. Chloroform extracts a complex whose formula is [Cu(SCN)₂(DMP)₂]. On the other hand, benzene extracts a complex with the formula [Cu(SCN)₂(DMP)₄].

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Résumé On a fait l'étude expérimentale des conditions de formation et d'extraction du complexe qui se forme avec le système Cu/SCN/DMP. Il s'est révélé qu'un complexe triple se formait pour ce système avec un nombre différent de coordination. Le chloroforme extrait un complexe de formule [Cu(SCN)₂(DMP)₂], le benzène, par contre, un complexe de formule [Cu(SCN)₂(DMP)₄].