Time Positron Diagnostics of Metal β-Diketonates

The effects of the nature of the metal atom and -substituents in aluminum(III), chromium(III), cobalt(III), and iron(III) acetylacetonates on the lifetime and intensity of a long-lived component in positron and positronium annihilation were studied by the method of positron diagnostics. An addition of a positron to the -system of a chelate ring is supposed, which makes it possible to qualitatively estimate the basicities of the complexes. Annihilation of positrons and halogen-containing positronium -diketonates is accompanied by the formation of a protonated complex; for -organylthioacetylacetonates, annihilation follows the inhibition mechanism.     

Coordination Compounds of Copper(II) with Bis(5-amino-1,2,4-triazol-3-yl)alkanes

Procedures for synthesis of coordination compounds of copper(II) with bis(5-amino-1,2,4-triazol-3-yl)alkanes as ligands. A conclusion was drawn that the coordination polyhedron of copper(II) has different configurations depending on the structure of the ligand and on the coordination mode.     

Syntheses of a Cp'Re=S derivative and more complex products

The reaction of Cp'ReCl(2)S(3) (Cp' = Me(4)EtC(5)) with slightly less than 2 equiv of a phosphine reagent results in the formation of [Cp'Re(Cl)(2)(mu-S)](2), 2, which has been characterized by an X-ray diffraction study. Reactions of 2 with nucleophiles did not lead to monomeric derivatives of the type Cp'ReS(Cl)(2)(Nuc). The reaction of Cp'ReCl(2)(SC(2)H(4)S) with (Me(3)Si)(2)S resulted in the formation of three new products: Cp'ReS(SC(2)H(4)S), 4; Cp'Re(S(3))(SC(2)H(4)S), 5; and a tetranuclear derivative, [(Cp'Re)(2)(mu-S)(mu,eta(2)-SC(2)H(4)S)(mu,eta(1)-SC(2)H(4)S](2)Cl(2), 6. Complexes 4 and 6 have been characterized by X-ray diffraction studies. The electrochemical properties of the mononuclear Re=S derivative, 4, are compared with those of Re=O and Re=NR analogues.     

Reactions of dithiolate ligands in mononuclear complexes of rhenium(V)

The thermal reactions of the Re(V) dithiolate complex Cp'ReCl2(SCH2CH2S), 1 (where Cp' = EtMe4C5), and related derivatives have been studied. When 1 is heated in toluene in a sealed evacuated tube at 100 degrees C, a dehydrogenation reaction occurs to form a new rhenium complex with a dithiolene ligand, Cp'ReCl2(SCHCHS), 6, in ca. 40% yield. The structure of 6 has been confirmed by an X-ray diffraction study. Under the thermal conditions studied, 1 also undergoes an olefin extrusion reaction. Free ethene is detected in the NMR spectrum of the products, and insoluble rhenium products are also formed. When 1 is reacted with excess ethene under mild conditions, a new organic product, 1,4-dithiane, is formed. Complex 1 is also found to react with oxidants, such as O2 and S8, under mild conditions to form the dehydrogenation product 6. Kinetic studies of the thermal reaction of 1 and related derivatives have been completed, and possible mechanisms for the thermally induced dehydrogenation reaction are discussed.     

A mathematical evaluation of dose-dependent PpIX fluorescence kinetics in vivo

The in vivo pharmacokinetics of protoporphyrin IX (PpIX) after administration of 5-aminolevulinic acid (ALA) cannot be described accurately by mathematical models using first-order rate processes. We have replaced first-order reaction rates by dose-dependent (Michaelis-Menten [MM]) reaction rates in a mathematical compartment model. Different combinations of first-order and dose-dependent reaction rates were evaluated to see which one would improve the goodness-of-fit to experimentally determined in vivo PpIX fluorescence kinetics as a function of concentration. The mathematical models that were evaluated are all based on a three-compartment model for drug distribution, conversion to PpIX and subsequent conversion to heme. Implementation of dose-dependent reaction rates improved the goodness-of-fit and enabled interpolation to other drug doses. For most data sets the time constant for delivery to the target cells turned out to be dose dependent. For all data sets the use of MM rates for the conversion of ALA to PpIX yielded better fits. The clearance of PpIX turned out to be a first-order process for all doses and types of administration. Fluorescence curves measured on a specific tissue type but obtained in different studies with different measurement techniques could be described with a single set of parameters.     

Mobility of some ions produced by tritium betas

The aqueous solution of coumarin has been studied spectrophotometrically as a -ray dosimeter and effects of temperature and light conditions on the stability of response during post-irradiation storage have been studied. Post-irradiation storage at room temperature in dark showed that after a very small increase in absorbance within the first 6 d, the response of the dosimeter was stable up to 42 d. At lower temperature (–15 °C), there was some decrease in absorbance within the first 24 h followed by a stable response up to 35 d. For post-irradiation storage at higher temperatures (40, 60 °C) the dosimeter, apart from some initial increase in absorbance, showed a nearly stable response up to 25 d. The effect of different light conditions during post-irradiation storage has also been studied. When stored in fluorescent light the response was almost stable from 6 d till about 40 d. In diffuse sunlight, the response was stable up to about 35 d at 360 nm and 370 nm but showed a somewhat unstable behavior at 347 nm. The dosimetric solutions were unstable when exposed to direct sunlight.     

Radiation degradation of copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate

Copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate (OM) were investigated as deep-UV and e-beam resists. Their increased sensitivity relative to PMMA (up to 50 times) was correlated with the radiation chemical yields of the volatile products and main chain scissions. The degradation of these copolymers, activated by the 3-oximino-2-butanone entity, is discussed in terms of energy absorption mechanisms and the subsequent scission reactions.     

Bisorthoesters as polymer intermediates. II. A facile method for the preparation of polybenzimidazoles

Aromatic bisorthoesters were found to be good polymer intermediates and could be condensed with aromatic tetramines under mild conditions, in DMSO at 100°C in a relatively short reaction time to give polybenzimidazoles. The hexapropyl orthoesters of terephthalic and isophthalic acid were the preferred aromatic orthoesters because they were relatively easily purified by vacuum distillation to polymer grade intermediates, since they are liquids. Higher orthoesters distill even under good vacuum near or above the decomposition temperature of the orthoester group. Hexaethyl orthooxalate was also used and is a very useful and stable derivative of oxalic acid, which can be used for condensation reactions. These three orthoesters were used for condensations with 3,3′,4,4′-tetraaminobiphenyl, 1,2,3,4-tetraaminobenzene, 3,3′,4,4′-tetraaminobiphenyl ether, and 3,3′,4,4′-tetraaminobenzophenone. All polybenzimidazoles were obtained in high to quantitative yields and with varying molecular weights (η_inh = 0.1?0.8 dl/g), which in some cases were in the fiber forming range.     

Singlet–triplet splittings as obtained from the Xα-scattered wave method: A theoretical analysis

The theoretical determination of singlet–triplet splittings of the excited states of closed-shell molecules is discussed with emphasis on the use of the Xα–scattered wave method. With this method, splittings can be computed in two independent ways. Both will have corrections due to orbital relaxation effects. The singlet–triplet splittings obtained with the Xα–scattered wave method for several large organic molecules are reviewed. It is seen that the results using the two splitting formulas differ by a large amount; in fact, they differ by the magnitude of the computed splitting. We provide a criterion for choosing the results obtained with one method over the other by showing that they both give upper bounds to the best result obtainable within the framework of the model. However, because of the large differences between the two methods, the quantitative value of the splitting should be viewed with caution.     

On the photometric determination of trivalent rhodium with eriochromecyanine RC

Summary Eriochromecyanine RC has been used as chromogenic reagent for the photometric determination of rhodium(III) on a micro scale. A coloured Rh(III)-ECRC chelate with _max 530 nm at pH 4.0 (25°C) is formed. A detailed study has been made concerning to characteristics, composition and stability of the chelate. Standard deviation was ±1.17%.

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Über die photometrische Bestimmung von dreiwertigem Rhodium mit Eriochromcyanin RC

Zusammenfassung Ergebnisse einer Untersuchung über die Zusammensetzung und Stabilität des Komplexes werden mitgeteilt. Das Absorptionsmaximum liegt bei 530 nm (pH 4,0; 25°C). Bestimmungen konnten mit einer Standardabweichung von ±1,17% durchgeführt werden.