Intercalation compounds of γ-zirconium and γ-titanium phosphates: Kinetic study of dehydration and decomposition processes for 2,9-dimethyl-1,10-phenanthroline and its intercalated copper complex materials

γ-Zirconium and γ-titanium phosphates containing organic diamine 2,9-dimethyl-1,10-phenanthroline and its in situ formed copper complex were studied by thermal analysis and physical measurements. All the derived materials show a layered structure and their interlayer distance is increased with respect to that of their precursors. Melting, simultaneous vaporization and oxidation, as well as a decomposition process take place in the pure diamine. After dehydration, all the intercalation materials undergo a two-step decomposition. The presence of the formed copper complex between the layers of the two ion-exchangers considered shows a destabilizing effect with respect to the intercalated diamine materials, resulting in a decrease of the decomposition temperatures and the activation energy of decomposition. The application of the isoconversional Ozawa-Flynn-Wall method substantially confirms the obtained results.     

Investigation of collisional lineshapes of neon transitions in noble gases' mixtures

Summary We have investigated sub-Doppler lineshapes of neon transitions by means of intermodulated optogalvanic technique in a direct current hollow cathode and a radio frequency glow discharge. The intermodulated Doppler-free signal, as usual, is superimposed on a broad Gaussian background due to velocity-changing collisions. The ratio between the collisional and the homogeneous signal has been systematically investigated as a function of gas pressure and discharge current. By detecting neon as a trace in other buffer gases, the lineshapes have been also carefully investigated as a function of the mass of the perturbers (helium and argon). Comparison between theoretical predictions and experimental data leads to quantitative evaluations of collisional parameters.

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Riassunto Sono state investigate le forme di riga di transizioni del neon mediante la spettroscopia optogalvanica in intermodulazione. Il segnale intermodulato, privo di allargamento Doppler, è dat da una Lorenziana, corrispondente all'allargamento omogeneo della transizione, sovrapposta ad un fondo Gaussiano dovuto alle collisioni che producono un cambiamento della velocità degli atomi lungo la direzione dei due fasci laser contropropaganti. è stato compiuto uno studio sistematico del contrasto tra il fondo Doppler e l'ampiezza omogenea della riga al variare della pressione del gas e della corrente di scarica. Inoltre, rivelando il neon come traccia in altri gas nobili (argon, elio), si è investigato l'effetto della massa dell'atomo perturbatore nei processi collisionali. I dati sperimentali sono stati confrontati con i modelli teorici esistenti deducendone stime dei parametri collisionali.

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Резюме Мы исследуем суб-доплеровские формы линий для переходов неона. Вэаимно модулнрованный сигнал, как обычно, накладывается на шнрокнй гауссов фон, обысловленный соударениями с изменением скоростей Систематически исследуется зависимостй отношения между столкновителйным и однородным сигналами от давленя газа и тока разряда. С целйю детектирования неона, как следа в другнш вуферныш газаш, мы также нзучаем зависимость форм линий от массы других инертиых газов (гелий и аргон). Сравнение теоретических предсказаний и эксперименталйных данных позволяет получнтй количественныэ оценкн параметров соударений.

     

Addendum to the paper: diffusion of quinidine sulphate through polydimethylsiloxane membranes containing silica filler. I. Theoretical

This paper deals with the demonstration of the nonexistence of complex conjugate roots and of real positive roots in the working equations of a previous work [1], where this nonexistence was not proved.     

The crystal and molecular structures of 3,3,6,6-Tetramethylbicyclo[2.2.1]heptane-2,5-dione and 6,6-Dibromo-1,3,3-Trimethylbicyclo[2.2.2] octane-2,5-dione

The X-ray crystal structures of two bicyclic diketones have been determined. 3,3,6,6-Tetramethylbicyclo[2.2.1]heptane-2,5-dione, C₁₁H₁₆O₂ (A), is monoclinic,C2/c (No. 15), with cell dimensionsa=9.071(3),b=9.748(5),c=12.322(6)Å,=110.15(3)°, andZ=4. The structure was determined by direct methods and refined toR ₁=0.065,R ₂=0.052 for 570 reflections. 6,6-Dibromo-1,3,3-trimethylbicyclo[2.2.2]octane-2,5-dione, C₁₁H₁₄Br₂O₂ (D), is orthorhombic,Pcab, (No. 61), with cell dimensionsa=11.206(3),b=18.818(6),c=11.695(4) Å, andZ=8. The structure was solved by the heavy-atom method and refined toR ₁=0.070,R ₂=0.065 for 1210 reflections. Bond lengths and angles within both structures do not differ from those in similar structures. The opening up of the internal ring angle of the ketone inA (vs. a normal bicyclo[2.2.1]heptane) and the consequent decrease of the adjacent internal ring angle brings the ketone carbon atoms nearer to the hydrogen atoms of the bridging methylene group.     

Experimental Study of the Excess Molar Volumes of Binary and Ternary Mixtures Containing Water + (1,2-Ethanediol,or 1,2-Propanediol,or 1,3-Propanediol,or 1,2-Butanediol) + (1-<Emphasis Type="Italic">n</Emphasis>-Butyl-3-methylimidazolium Bromide) at 298.15 K and Atmospheric Pressure

Densities of binary and ternary mixtures containing water + (1,2-ethanediol or 1,2-propanediol or 1,3-propanediol or 1,2-butanediol) + (1-n-butyl-3-methylimidazolium bromide at 0.01 mole fraction) at 298.15 K and atmospheric pressure have been determined as a function of composition using an Anton Paar densimeter (Model DMA 55). Excess molar volumes (V_m^EV_{\mathrm{m}}^{\mathrm{E}}) were calculated. The values are negative for all mixtures over the whole composition range.     

Chiral diaminopyrrolic receptors for selective recognition of mannosides, part 2: a 3D view of the recognition modes by X-ray, NMR spectroscopy, and molecular modeling

The structural features of a representative set of five complexes of octyl α- and β-mannosides with some members of a new generation of chiral tripodal diaminopyrrolic receptors, namely, (R)-5 and (S)- and (R)-7, have been investigated in solution and in the solid state by a combined X-ray, NMR spectroscopy, and molecular modeling approach. In the solid state, the binding arms of the free receptors 7 delimit a cleft in which two solvent molecules are hydrogen bonded to the pyrrolic groups and to the benzenic scaffold. In a polar solvent (CD(3)CN), chemical shift and intermolecular NOE data, assisted by molecular modeling calculations, ascertained the binding modes of the interaction between the receptor and the glycoside for these complexes. Although a single binding mode was found to adequately describe the complex of the acyclic receptor 5 with the α-mannoside, for the complexes of the cyclic receptors 7 two different binding modes were required to simultaneously fit all the experimental data. In all cases, extensive binding through hydrogen bonding and CH-π interactions is responsible for the affinities measured in the same solvent. Furthermore, the binding modes closely account for the recognition preferences observed toward the anomeric glycosides and for the peculiar enantiodiscrimination properties exhibited by the chiral receptors.     

Thermodynamics of binary liquid mixtures: application of the Prigogine–Flory–Patterson theory to excess molar volumes of acetonitrile+1-alkanol systems

Excess molar volumes of {(1−x_A)CH₃(CH₂)_n−1OH+x_ACH₃CN} for n=1, 2, 3 or 4 as a function of composition under atmospheric pressure at 288.15, 293.15, 298.15 and 303.15 K have been used to test the applicability of the Prigogine–Flory–Patterson theory. According to the model, interactional contribution is the most important one to explain the V_m^E behavior. Good agreement is only achieved for the mixtures containing methanol (C₁) or 1-butanol (C₄). For the mixtures containing ethanol (C₂) and 1-propanol (C₃), which show an S-shaped V_m^E behavior, the correlation fails.