Chemically modified silicon dioxide surfaces. Wetting properties of compact n-alkyl-dimethylsiloxy layers,and their mixed surface crystals. The Question of Wetting of Molecularly Rough and of Swollen Surfaces

By means of contact angle measurements, it has been shown that compact alkyl-dimethyl-siloxy layers can be obtained on the surface of acid leached glass using the method previously developed for fume silica. Subsequently, a series of densest possible alkyl-dimethylsiloxy layers were prepared having non-branched alkyl substituents, C_zH_2z+1, (with z=1, 2, 3, 6, 10, 14, 18 and 22) and wetting angles were measured as a function of the temperature. On surfaces coated with longer alkyl substituents the formation of mixed crystals, consisting of the sparse chemically bonded alkyl layer and a n-alkane acting as a wetting agent, has been observed at low temperatures. At higher temperatures such surfaces appeared to be «molten», and at the same time swollen by the wetting agent. Equations have been derived to deduce the free surface energies and to account for the wetting properties of rough and swollen surfaces. Application of the results to the data presented in this paper revealed that glass surfaces covered with short alkyl chains (methyl, ethyl and propyl) are rough and those covered with long chains (tetradecyl, octadecyl and docosyl) are swollen. Surfaces formed by hexyl- and decyl-dimethylsiloxy substituents exhibit intermediate properties.     

Die photokolorimetrische Bestimmung des Palladiums mit 2-Mercapto-5-Anilin-1,3,4,-thiodiazol

Zusammenfassung Pd(II) gibt mit 2-Merkapto-5-anilin-1,3,4-thiodiazol eine Komplexverbindung; diese ist löslich und intensiv gelb gefärbt. Das stöchiometrische Verhältnis der beiden Komponenten beträgt 12. Die Komplexkonstante hat den Wert 4,17·10^–10. Eine empfindliche kolorimetrische Bestimmungsmethode für 0,12 bis 30 ppm Pd(II) wurde angegeben. Das UV-Spektrum der Komplexverbindung wurde ermittelt und der molare Extinktionskoeffizient bestimmt.

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Summary 2-Mercapto-5-aniline-1,3,4-thiodiazole yields a complex compound with palladium(II). This product is soluble and has an intense yellow color. The stoichiometric ratio of the components is 12; the complex constant is 4,17 ·10^–10. A sensitive colorimetric method for determining 0.12–30 ppm of palladium(II) is given. The ultraviolet spectrum of the complex compound has been mapped and also the molar extinction coefficient has been determined.

     

Microcanonical analysis of the kinetic method. the meaning of the "apparent entropy"

A rigorous analysis of the kinetic method is carried out using Rice-Ramsperger-Kassel-Marcus (RRKM) theory of microcanonical statistical unimolecular dissociation rates. The model employs a kinetics treatment appropriate for metastable ion dissociation. Proton-bound alkoxide dimer anions are used as model systems, with realistic vibrational and rotational parameters calculated by ab initio methods for the cluster ion and transition states leading to the competitive dissociation channels. The numerical simulations show that the kinetic method plots of ln(I2/I1) versus AAH are nearly linear but can exhibit significant curvature. The apparent entropy obtained in the extended kinetic method is not approximately equal to the thermodynamic entropy difference for dissociation, AAS(T), or for activation, deltadeltaS++(T), either at the effective temperature or at any fixed equilibrium temperature. Instead, the apparent entropy term can be related to the ratio of the microcanonical sum of states of the dissociation transition states for the kinetically selected internal energy of the dissociating ions.     

5,12-Diacylated-5,6,11,12-tetrahydrodibenzo[b,f][1,4]-diazocines and related compounds

Both N,N′ -(o-phenylene)diformamide (1) and N,N′ -(4-chloro-1,2-phenylene)diformamide (30) reacted with α,α-dibromo-o-xylene (2) in DMF at 95–100° to give 5,6,11,12-tetrahydrodibenzo-[b,f][1,4]diazocine-5,12-dicarboxaldehyde (3a) and the corresponding 2-chloro derivative (3b). With potassium hydroxide in ethylene glycol at 110°, 3a and 3b were selectively saponified to the 5-carboxaldehyde derivatives (4) and either 21a or 22a. Reacylation of the latter led to a series of 5,12-unsymmetrically diacylated derivatives, 5–18. Additionally, 4 was subjected (a) to a basecatalyzed addition to acrylonitrile to give the 12-cyanoethyl derivative (19) and (b) alkylation with α-bromotoluene to give the 12-benzyl compound (20). Saponification of both carboxaldehyde groups in 3a,b required potassium hydroxide in ethylene glycol at 135° and gave the N,N′ -unsubstituted heterocycles (23 and 24) ; these were subsequently reacted with several aldehydes to yield the 5,12-methano derivatives (25–29) .     

Synthesis of platinum nanowheels using a bicellar template

Disk-like surfactant bicelles provide a unique meso-structured reaction environment for templating the wet-chemical reduction of platinum(II) salt by ascorbic acid to produce platinum nanowheels. The Pt wheels are 496 +/-55 nm in diameter and possess thickened centers and radial dendritic nanosheets (about 2-nm in thickness) culminating in flared dendritic rims. The structural features of the platinum wheels arise from confined growth of platinum within the bilayer that is also limited at edges of the bicelles. The size of CTAB/FC7 bicelles is observed to evolve with the addition of Pt(II) complex and ascorbic acid. Synthetic control is demonstrated by varying the reaction parameters including metal salt concentration, temperature, and total surfactant concentration. This study opens up opportunities for the use of other inhomogeneous soft templates for synthesizing metals, metal alloys, and possibly semiconductors with complex nanostructures.     

Threshold collision-induced dissociation of hydrogen-bonded dimers of carboxylic acids

Energy-resolved competitive collision-induced dissociation is used to investigate the proton-bound heterodimer anions of a series of carboxylic acids (formic, acetic, and benzoic acid) and nitrous acid with their conjugate bases. The dissociation reactions of the complexes [CH3COO.H.OOCH]-, [CH3COO.H.ONO]-, [HCOO.H. ONO]-, [C6H5COO.H.OOCH]-, and [C6H5COO.H.ONO]- are investigated using a guided ion beam tandem mass spectrometer. Cross sections of the two dissociation channels are measured as a function of the collision energy between the complex ions and xenon target gas. Apparent relative gas-phase acidities are found by modeling the cross sections near the dissociation thresholds using statistical rate theory. Internal inconsistencies are found in the resulting relative acidities. These deviations apparently result from the formation of higher-energy conformers of the acids within the complex ions induced by double hydrogen bonding, which impedes the kinetics of dissociation to ground-state product acid conformations.     

Intrinsic Fluorescence of Metabolite Amyloids Allows Label‐Free Monitoring of Their Formation and Dynamics in Live Cells

The formation of apoptosis‐inducing amyloidal structures by metabolites has significantly extended the “amyloid hypothesis” to include non‐proteinaceous, single metabolite building blocks. However, detection of metabolite assemblies is restricted compared to their larger protein‐based counterparts owing to the hindrance of external labelling and limited immunohistochemical detection tools. Herein, we present the detection of the formation, dynamics, and cellular distribution of metabolite amyloid‐like structures and provide mechanistic insights into the generation of supramolecular chromophores. Moreover, the intrinsic fluorescence properties allow the detection of metabolite assemblies in living cells without the use of external dyes. Altogether, this intrinsic fluorescence of metabolite assemblies further verifies their amyloidal nature, while providing an important tool for further investigation of their pathological role in inborn error of metabolism disorders.