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The effect of hydrogen passivation on the room temperature mobility and density is studied on n-type $Si_{0.62}Ge_{0.38}$/strained Si modulation-doped structures. Room temperature carrier densities reduced by an order of magnitude while a threefold maximum increase in mobility was observed. By using a two-carrier analysis, it was found that, apart from parallel conduction passivation, the hydrogenation process also improves the channel mobility directly. Plasma and electrolytic hydrogenation were carried out on samples with different spacer thicknesses and mobilities. The plasma method of hydrogenation was found to be more effective when compared to the electrolytic technique. A successful removal of incorporated hydrogen and partial recovery of the control sample was shown by annealing the hydrogenated sample in vacuum at $\sim400^0C$.

The stability of cisplatin in 0.9% sodium chloride solution was studied. Cisplatin was reconstituted with sterile water for injection to achieve a concentration of approximately 1 mg/mL in 0.9% sodium chloride solution. The solutions were placed in flexible polyvinyl chloride containers, clear and amber glass flasks, and plastic syringes and stored at 22-25 degrees C in the dark or exposed to measured amounts of light and assayed periodically for up to 96 days. The initial pH of some of the solutions was adjusted. The stability of cisplatin in the solutions was determined by measuring the concentrations of cisplatin, trichloroammineplatinate(II) (TCAP), and trans-dichlorodiammineplatinum(II) (transplatin) with high-performance liquid chromatography and by measuring solution pH. The effect of adding ethylene oxide and other materials was also determined. TCAP was identified as the predominant degradation product of cisplatin in all the solutions. The rate of degradation was dependent on pH: In the dark, about 0.04% and 0.21% of the cisplatin degraded to TCAP per week at pH 4.3 and 6.3, respectively. The presence of ethylene oxide accelerated cisplatin degradation. Degradation also occurred during exposure to short-wavelength (350-490-nm) visible light. Storage in amber glass flasks offered more protection than storage in clear flasks. Isomerization of cisplatin to transplatin was not observed. The major degradation product of cisplatin was trichloroammineplatinate(II). Solution pH was the predominant factor affecting cisplatin stability.

The products obtained from the reaction of OH radicals, generated radiolytically, with pyridine under conditions where the intermediate 1-azahydroxycyclohexadienyl radicals are oxidized to isomeric hydroxypyridines have been examined by high-performance liquid chromatographic methods. From product-analysis data, the initial radiation chemical yields of o-, m-, and p-hydroxypyridines are 1.0, 3.8, and 0.3, respectively. The high yield of m-hydroxypyridine exemplifies the electrophilic nature of OH. The low yield of p-hydroxypyridine is attributed to the failure to quantitatively oxidize the 1-aza-p-hydroxycyclohexadienyl radical by the more powerful oxidant such as IrCl/sub 6//sup 2 -/. The isomeric OH adducts of pyridine exhibit selectivity in reactivity with the two oxidants examined, and their reducing strength follows the order meta > ortho > para. From optical pulse radiolysis the second-order rate constant for the electron-transfer processes between hexachloroiridate and meta and ortho pyridine-OH adducts was determined to be 5.8 x 10/sup 8/ M/sup -1/s/sup -1/.

Using pulse radiolysis with optical detection and high-pressure liquid chromatography (HPCL), it has been shown that reaction of OH radicals with cinnamic acid (CA in aqueous solutions leads to addition to both the ring and the olefinic group. The relative extent of the above two pathways was estimated as 3:7, respectively. Benzyl- and hydroxycyclohexadienyl-type radicals were observed with absorption maxima at 320 (310) and 370 (365) nm depending on the pH of the solution. In the pH region 4.9 to 5.7 the absorption at 305 to 315 nm decays during the first 5 ..mu..s after the pulse. The dependence of the rate constants and absorption spectra on pH suggests that this decay is due to an equilibration process between acid-base forms of benzyl-type radicals formed through OH addition to te olefinic group.

It is shown that Zn(II) is able to form mixed ligand complexes in the presence of various amines, L, and oxac 2− . The rate of decarboxylation of the oxac 2− in these mixed ligand complexes is consistent with a rate constant that is little influenced by the nature of L, and a formation constant that is normal, but reflects the charge and denticity of L.

The structure of triphenylphosphine — (1 — (di(trifluoromethyl) — hydroxymethyl) — cyclopentadienyl) — (1,2 — di(carboxymethyl)ethylene — 1 — yl) — ruthenium (0) has been studied by single-crystal X-ray diffraction techniques. This compound, [C5 H4(CF3)2 COH] Ru(PPh3)C2(CO2Me)2H, crystallizes in the triclinic space groupP¯1 witha =10.131,b= 15.107,c= 10.798 A, α = 102.14,β = 107.04, γ = 89.64° andZ = 2. The structure was refined by block-diagonal least-squares methods to a finalR value of 0.042, including hydrogen atoms. The compound contains a dicarboxymethylethylene ligand coordinated to ruthenium both through a ketonic oxygen and through a metal-β-carbon σ-bond. An intramolecular hydrogen bond is observed. Details of the structure are reported, and the structures of several Ru(0) complexes are compared.

The single-electron reductions of BrO/sub 2/. by Fe(CN)/sub 6//sup 4 -/, phenoxide ion, Mn(II), and phenol have been investigated. The BrO/sub 2/. was produced by pulse radiolysis of aqueous solutions of BrO/sub 3//sup -/ which also contained one of these reductants. All experiments were carried out at pH 6-12. The reductions by Fe(CN)/sub 6//sup 4 -/ and phenoxide ion were rapid and clean and led to the products Fe(CN)/sub 6//sup 3 -/ and phenoxy radical. The rate constants for these reductions were found to be, respectively, (1.9 +- 0.1) x 10/sup 9/ and (2.6 +- 0.2) x 10/sup 9/ M/sup -1/ s/sup -1/. The reductions of BrO/sub 2/. by Mn(II) and phenol were found to be much slower as well as more complex than the reductions by Fe(CN)/sub 6//sup 4 -/ and phenoxide ion. The products were, as expected, Mn(III) and phenoxy radical. However, there was a component of BrO/sub 2/. reduction by Mn(II) whose rate did not depend upon (Mn(II)). Furthermore, the rate of BrO/sub 2/. reduction by phenol did not depend at all upon the concentration of phenol. It is suggested that these slower reductions were complicated by the well-known dimerization equilibrium between BrO/sub 2/. and Br/sub 2/O/submore » 4/. If the rate of reduction of this dimer by Mn(II) or phenol is comparable to or faster than the rate of its return to BrO/sub 2/., then the dimerization process itself will become partially or completely rate determining. 8 figures, 1 table.« less

The product of the reaction of (π-C5 H5)Ru(PPh3)2 Cl and CuC2Ph has been characterized by single-crystal x-ray diffraction techniques and shown to have stoichiometry (π-C5 H5)Ru(PPh3)2Cu(C2Ph)Cl-(CH3)2CO(I). The compound contains a phenylethynyl group σ-bonded to the ruthenium atom and simultaneously π-bonded to a terminal Cu-Cl bond. Crystals of this compound from acetone are monoclinic,P21/c, witha = 12.914, = 22.111,c = 16.534 A, β = 110.77 °, andZ — 4. Full-matrix least-squares refinement constraining the phenyl rings of the triphenylphosphines, the cyclopentadienyl ring, and the solvent of crystallization (acetone) as rigid groups yieldedR and weightedR values of 0.084 and 0.075, respectively.

Using pulse radiolysis with optical detection and high-pressure liquid chromatography techniques it is shown that the isomeric dihydroxycyclohexadienyl radicals formed in aqueous solution by reaction of OH with phenol react with quinones by electron transfer to yield semiquinones and dihydroxybenzenes. The rate constants for these electron-transfer reactions depend on the redox potential of the quinone and on the isomer structure of the dihydroxycyclohexadienyl radical; i.e., the rate constants are large (10/sup 7/-10/sup 9/M/sup -1/s/sup -1/) in the case of the ortho and para isomers and small (less than or equal to 10/sup 7/M/sup -1/s/sup -1/) in the case of the meta and ipso isomers. The isomeric dihydroxycyclohexadienyl radicals differ also with respect to their rates of H/sup +/-catalyzed dehydration to yield phenoxyl radical. It is thus possible to distinguish kinetically between the different dihydroxycyclohexadienyl radicals. On this basis and from the product analysis data the fractions of OH attack at the ipso, ortho, meta, and para position of phenol are 0.08, 0.48, 0.08, and 0.36, respectively. These data show the strong preference of the electrophilic OH radical for attack at the ring positions activated by the phenolic OH group.

The spectra and kinetics of formation and decay of radical anions of a number of retinyl polenes have been studied in methanol and 2-propanol at room temperature, using pulse radiolysis and kinetic spectrophotometry. The bimolecular rate constants for the attachment of solvated electrons, e/sup -//sub MeOH/, to the retinyl polyenes are in the diffusion-controlled limit (8.6 x 10/sup 9/-1.6 x 10/sup 10/ M/sup -1/ s/sup -1/). The radical anions of retinol and retinol acetate have their spectral maxima at 370 to 390 nm, and undergo decay very slowly with second-order kinetics. On the other hand, the radical anions of retinal, retinal n-butylamine Schiff base, and retinoic acid/ester have spectral maxima at 430 to 510 nm, and decay by first-order kinetics in methanol with rate constants in the range 1 x 10/sup 4/ - 1 x 10/sup 6/ s/sup -1/. The decay rates of radical anions of retinal and retinoic acid/ester become considerably longer on going from methanol to less acidic alcohol, 2-propanol, suggesting that protonation by sovent is the major mode of their decay in protic media. In the case of retinal Schiff base, an additional slow process with bimolecular rate constant 9.0 x 10/sup 7/ M/sup -1/ s/sup -1/more » in methanol is observed for the formation of radical anion and is ascribed to the electron-transfer reaction from the methanol radical, CH/sub 2/OH. 6 figures.« less

In contrast to a related iron—copper compound, the complex (π-C5H5)Ru(PPh3)2(C2Ph)CuCl is shown to be monomeric, and contains linear dicoordinate copper(I); the reactions of this and similar complexes with metal carbonyls are sources of new mixed-metal clusters, such as (π-C5H5)Fe2 Ru(C2Ph)(CO)6 (PPh3).

The reaction between hexafluoroacetone and Ru(PPh3)2(π-C5H5)[σ-C2(CO2Me)2H] affords a 1 1 adduct, containing a coordinated ester group and an intramolecular hydrogen bond; formal insertion of (CF3)2CO into a CH bond of the cyclopentadienyl group has also occurred.

Using pulse radiolysis with optical detection and high-pressure liquid chromatography (HPCL), it has been shown that reaction of OH radicals with cinnamic acid (CA in aqueous solutions leads to addition to both the ring and the olefinic group. The relative extent of the above two pathways was estimated as 3:7, respectively. Benzyl- and hydroxycyclohexadienyl-type radicals were observed with absorption maxima at 320 (310) and 370 (365) nm depending on the pH of the solution. In the pH region 4.9 to 5.7 the absorption at 305 to 315 nm decays during the first 5 ..mu..s after the pulse. The dependence of the rate constants and absorption spectra on pH suggests that this decay is due to an equilibration process between acid-base forms of benzyl-type radicals formed through OH addition to te olefinic group.

The structure of myoglobin as determined from x-ray diffraction data was first reported by Kendrew et al. (1). More recently, Takano (2) described the acidmet and deoxy forms, and Phillips (3) described the oxy form. In these x-ray structures, the positions of the hydrogen atoms cannot be described, but they are important factors in determining the interactions of the heme with its environment. Neutron diffraction work, done in this laboratory, has demonstrated that hydrogen and deuterium positions can be located (4). In addition to the localization of H and D, neutron diffraction provides a unique method for studying the water structure because of the strong scattering ability of D2O. The scattering factor of deuterium is nearly twice as large as that of hydrogen, and it increases the visibility of water molecules in Fourier maps, so that in a neutron map a water molecule appears about three times as strong as in an equivalent electron-density map. Detailed results of the neutron diffraction analysis of carbonmonoxy myoglobin (5) and oxymyoglobin (6), and the initial results on acid metmyoglobin (7) have been reported. The reciprocal-space refinement of acid metmyoglobin and in particular the details of the water structure and hydrogen exchange are presented here.

Reactions between the O/sub 2//sup -/. have been investigated in the transition-metal complexes, ..mu..-amino-..mu..-superoxo-bis(bisethylenediamine cobalt(III)) and ..mu..-superoxo-bis(pentacyano)cobalt(III). After production of the superoxide ion by pulse radiolysis of aqueous solutions, saturated with oxygen, containing 0.1M sodium formate, the reaction with the complex was followed by monitoring the formation of the peroxo complex using spectrometric pulse radiolysis techniques. Results of these studies indicate that the coordination of the superoxide with cobalt(III) has the same effect as the hydrogen ion in the superoxide dismutation reaction: 2O/sub 2//sup -/. + 2H/sup +/ ..-->.. O/sub 2/ + H/sub 2/O/sub 2/. (BLM)

Cadmium(I) has been observed to reduce the µ-amido-µ-superoxo-bis(bisethylenediamine)cobalt(III) cation by an inner-sphere electron transfer process.