Three-dimensional configurations of organic/inorganic hybrid nanostructural blocks (Ⅰ).A quantum mechanical investigation for ladder-like structure of vinylsilsesquioxane

The organic/inorganic hybrid nanostructural vinylsilsesquioxanes (VSSO) were prepared from the hydrolytic condensation of vinyltrimethoxysilane (VMS). The proposed formulas of VSSO were assigned with standard spectroscopic techniques, FTIR, NMR (1H, 13C and 29Si) and MALDI-TOF MS, and a generic formula of the SSO, Tn(OH)x(OR')y (x, y = 0, 1, 2...; n =1, 2...; T = RSiO1.s-(x+y)/2n). Geometric parameters (Si-O and Si-C bond lengths, Si-O-Si and O-Si-O bond angles) and total energies of the multi-structures of VSSO were calculated by a quantum mechanical investigation and molecular symmetries. According to the results of the calculation, most molecules had stabler ladder structures than the cage isomers, therefore, the most probably reasonable and optimum structure of the VSSO system was the ladder type.     

Crystal structure and quantum chemical investigation of [Cd(NTO)_4Cd(H_2O)_6]·4H_2O

The common explosives, RDX (1,3,5-trinitro-1,3,5-triazacyclohexane), HMX (1,3,5,7- tetranitro-1,3,5,7-tetraazacyclooctane) and TNT (trinitrotoluene), were considered adequately for all weapons applications. Due to many catastrophic explosions resulting from unintentional initia-tion of impact, friction or shock, these explosives have become less attractive. TATB (1,3,5-tria- mino-2,4,6-trinitrobenzene) is noted for its insensitivity, however, it does not have the energetic performance of e…     

On the mechanical properties of poly(ethylene terephthalate). Force-field parametrization and conformational analysis for the prediction of the crystal moduli

A force-field suitable for the calculation of the mechanical properties of poly(ethylene terephthalate) and their relation with the molecular structure of the polymer has been developed. The force-field parameters were derived from quantum mechanical AM1 calculations and tested against thermodynamic and vibrational spectroscopy data available for a set of closely related small molecules. The crystal moduli of the two solid phases known for poly(ethylene terephthalate) were estimated by means of this new force-field considering both the isolated chain and the chain within the unit cell. Results were qualitatively consistent with reported x-ray data showing that the triclinic crystal form is stiffer than the mesomorphic phase provided that sample heterogeneities were taken into account. Although overestimated moduli resulted for both cases, divergences with experimental values were found to be slighter than those obtained by other theoretical methods. © 1996 John Wiley & Sons, Inc.     

Spectrophotometric investigation of complexes with organic reagents for the optimization of spectrophotometric determinations (uv + vis) of inorganic analytes

Summary The knowledge of complex equilibria of elements with organic analytical reagents in solutions and that of thermodynamic and optical parameters of complexes and their distribution in the system is of considerable importance for the selection of optimal conditions for an exact spectrophotometric determination (uv + vis) of an element. All necessary parameters are available by means of a detailed graphical and numerical interpretation of spectrophotometric data. This approach is shown by example of some chromogenic reactions of 4-(2-pyridylazo)resorcin, 2-(2-thiazolylazo)-4-methoxyphenol and 2-(2-pyridylazo)-1-naphthol-4-sulphonic acid.

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Spektralphotometrische Untersuchung von Komplexverbindungen mit organischen Reagentien für die Optimierung spektralphotometrischer Bestimmungen (uv + vis) eines anorganischen Analyts

Zusammenfassung Die Kenntnis von Komplexbildungsgleichgewichten der Elemente mit organischen Reagentien in Lösung, der thermodynamischen und optischen Parameter der Komplexe und deren Verteilung im System ist für die Auswahl optimaler Bedingungen für eine spektralphotometrische Elementbestimmung (uv + vis) wichtig. Alle notwendigen Parameter sind auf Grund einer eingehenden graphischen und mathematischen Interpretation spektralphotometrischer Daten zugänglich. Dieser Weg wird als Beispiel an drei ausgewählten spektralphotometrischen Reagentien, 4-(2-Pyridylazo)resorcin, 2-(2-Thiazolylazo)-4-methoxyphenol und 2-(2-Pyridylazo)-1-naphthol-4-sulfonsäure, gezeigt.

Dedicated to Prof. Dr. Fritz Umland on the occasion of his 60th birthday     

Synthesis and characterization of organic/inorganic hybrid star polymers of 2,2,3,4,4,4‐hexafluorobutyl methacrylate and octa(aminophenyl)silsesquioxane nano‐cage made via atom transfer radical polymerization

Well‐defined organic/inorganic hybrid fluorinated star polymers were synthesized via atom transfer radical polymerization (ATRP) of 2,2,3,4,4,4‐hexafluorobutyl methacrylate (HFBMA) using octa(aminophenyl)silsesquioxane (OAPS) nano‐cage as initiator. For this purpose, OAPS was transformed into ATRP initiator by reacting with 2‐bromoisobutyrylbromide. ATR polymerization of HFBMA was carried out in trifluorotoluene at 75 °C using CuCl/2,2‐bipyridine or N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst system. GPC and ¹H NMR data confirmed the synthesis of OAPS/PHFBMA hybrid star polymer. Kinetics of the ATR polymerization of HFBMA using OAPS nano‐cage initiator was also investigated. The OAPS/PHFBMA hybrid stars were found to be molecularly dispersed in solution (THF); however, TEM micrographs revealed the formation of spherical particles of ～ 120–180 nm by the OAPS/PHFBMA hybrid star polymer after solvent evaporation. Thermal characterization of the nanocomposites by differential scanning calorimetry (DSC) revealed a slightly higher glass transition temperature (T_g) (when compared with the linear PHFBMA) of higher molecular weight OAPS/PHFBMA hybrid star polymers. In contrast, lower T_g than the linear PHFBMA was observed for OAPS/PHFBMA of relatively lower molecular weight (but higher than the linear PHFBMA). Thermal gravimetric analysis (TGA) showed a significant retardation (by ～60 °C) in thermal decomposition of nanocomposites when compared with the linear PHFBMA. Additionally, surface properties were evaluated by measuring the contact angles of water on polymer surfaces. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7287–7298, 2008     

2-(α-Pyridyl)-thioquinaldinamide (PTQA)-A novel fluorimetric reagent in inorganic trace analysis. I: The nonextractive,nonquenching fluorescent method for the determination of chromium(VI)

A direct fluorimetric method for determining Cr(VI) in aqueous solutions is described. The nonfluorescent reagent 2-(-pyridyl)-thioquinaldinamide (PTQA) and Cr(VI) interact to produce an intensely fluorescent species [_ex(max) 360 nm; _em(max) 500 nm] showing constant and maximum fluorescence intensity in slightly acidic media (0.18N–1.08N H₂SO₄). The fluorescence attains its maximum value within 5 min and remains unchanged for 24 h. The system obeys Beer's law from 2 ng/ml to 0.8 g/ml of Cr(VI). Over sixty cations, anions and complexing agents are without any effect on the fluorimetric determination of 0.1 g/ml of Cr(VI). The method has been tested with synthetic mixtures, steels, solutions containing both Cr(III) and Cr(VI), and environmental samples.