MCs+ secondary ion and sputtering yields of oxygen-exposed semiconductors and glasses

The emission of MCs⁺ molecular ions sputtered by Cs⁺ ion impact from a variety of elemental (Si and Ge) and compound (GaAs, InP, InSb, ZnSe, CdS, CdSe, CdTe and CdZnTe) semiconductors and a selection of glass samples of different composition has been investigated. For the glass samples a set of relative sensitivity factors has been determined which are largely composition-independent and provide the possibility of a reliable quantification of glasses by MCs⁺ SIMS. For the semiconductors fractional ion yields (i.e. the number of detected MCs⁺ ions per sputtered M atom) range from 10^?6 to some 10^?4 and exhibit little variation with the oxygen surface coverage of the specimen. Depending on M, the emission of MOCs⁺ molecular species becomes prominent (or even dominating) at high oxygen concentrations. Furthermore, total sputtering yields for 5.5 keV Cs⁺ impact and different oxygen partial pressures have been determined from sputtered craters.     

The development of analytical methods for the determination of ions and acidity in individual raindrops

Summary In this publication the first results of a microanalytical investigation of individual rain droplets are given. Analytical methods for a sampling procedure as well as analysis in the ultra trace level with volumes less than 1 l have been developed. Because of the small volumes chromatographic methods are to be preferred.     

The synthesis of 6-deoxyanthracyclinones: (±)α-citromycinone and (±)4-demethoxy-6-deoxydaunomycinone

Two synthetic approaches have been explored to prepare 6-deoxyanthracyclinones in general and α-citromycinone in particular. The first approach employed as starting materials 1,4,5-trimethoxynaphthalene and the Diels-Alder product from butadie regioselective carbon acylation of 4-hydroxy-l,5-dimethoxynaphthalene with the half-ester acid chloride of cis-4,5-dicarboxycyclohexene. The resulting product was converted to 7,10-dideoxy-α-citromycinone; however, even the C-7—OH group required for glycosylation could not be introduced satisfactorily into this product. The second strategy employed as the key step the coupling of a highly functionalized metallated quinol equivalent with the monoketal of a benzocyclobutenedione. This route gave (± )-α-citromycinone and (±)-4-demethoxy-6-deoxydaunomycinone in quantities suitable for biological testing.     

Die komplexchemie polyfunktioneller liganden : XXVIII. Über die selektive spaltung von arsenphenyl-bindungen mit jodwasserstoff in nichtwässrigen systemen

The phenylalkyl arsines (CH₃)₂AsC₆H₅, CH₃As(C₆H₅)₂, C₂H₅As(C₆H₅)₂, (CH₂)_n [As(C₆H₅)₂]₂ (n = 1, 2), and C[CH₂As(C₆H₅)₂]₄ react with liquid or gaseous HI in nonaqueous solvents by selective cleavage of the arsenicphenyl bonds yielding (CH₃)₂AsI, CH₃AsI₂, C₂H₅AsI₂, (CH₂)_n(AsI₂)₂ and C(CH₂AsI₂)₄. The latter forms the tetradentate ligand C[CH₂As(CH₃)₂]₄ with CH₃MgI. The electron impact mass spectra of these compounds show clear fragmentation patterns resulting mainly from the formation of fragments with AsAs bonds or (As)_n clusters (_n = 3, 4). From CH₃AsI₂ and C₂H₅AsI₂ the iodine-free cycloarsines (AsCH₃)₃, (AsC₂H₅)₃, (AsC₂H₅)₄, As₃(C₂H₅)₂CH₃ and As₄(C₂H₅)₃CH₃ are formed by thermal secondary reactions in the high temperature inlet systems of the mass spectrometer. The fragmentations of the cycloarsines and the other compounds are discussed. The infrared spectral absorptions of all the alkyl iodoarsines can be completely assigned in the range of 4000 – 250 cm^?1. The IR data of C₂H₅AsI₂ indicate the existence of trans and gauche rotational isomers.     

Dendrimers and hyperbranched polymers as high-loading supports for organic synthesis

Polymeric supports have become a big necessity for automated synthesis and combinatorial chemistry, yet, the loading capacities of most polystyrene resins are very limited (typically < 1.5 mmol x g(-1)). Dendrimers and hyperbranched polymers have been discussed for this application and now became readily available. These soluble polymers can either be used directly as high-loading supports for substrates, reagents, and catalysts or alternatively in hybrid polymers linked to conventional polystyrene resins.     

Highly regioselective synthesis of amino-functionalized dendritic polyglycerols by a one-pot hydroformylation/reductive amination sequence

[reaction: see text] Dendritic architectures with neutral core structures and amines groups in the shell are a synthetic challenge, and there is a need for an efficient access. In this paper, highly selective Rh-catalysts are used for sequential hydroformylation/reductive amination of dendritic perallylated polyglycerols 1 with various amines in a one-pot procedure to give dendritic polyamines 3a-e in high yields (73-99%). In all cases, complete conversion of the allyl ether and aldehyde intermediate has been observed. Furthermore, the use of protected amines provides reactive core-shell-type architectures after deprotection. These soluble but membrane filterable multifunctional dendritic polyamines are of high interest as reagents in synthesis or as supports in homogeneous catalysis as well as nonviral vectors for DNA-transfection.