Adolf Gogoll

Directing protonation in [FeFe] hydrogenase active site models by modifications in their second coordination sphere

Subtle changes in the second coordination sphere of [Cl(2)bdtFe(2)(CO)(4)(Ph(2)P-CH(2)-X-CH(2)-PPh(2))] (bdt = benzene-1,2-dithiolate, X = NCH(3), NCH(2)CF(3), CH(2)) that do not influence the electronic character of the Fe(2) center can however direct protonation to three different sites: the N in the bis-phosphane, the Fe-Fe bond or the bdt-S.

Evidence for (π-allyl)palladium(II)(quinone) complexes in the palladium-catalyzed 1,4-diacetoxylation of conjugated dienes

Evidence for a coordination of p-benzoquinone to palladium in [4-acetoxy-η3-(1,2,3)-cyclohexenyl]-palladium(II) complexes was provided by changes of the 1H NMR chemical shift values of the π-allyl ...

Characterization of phosphorus in sequential extracts from lake sediments using 31P nuclear magnetic resonance spectroscopy

Phosphorus (P) compounds in three different lake surface sediments were extracted by sequential P extraction and identified by P-31 nuclear magnetic resonance (P-31 NMR) spectroscopy. The extractio ...

Diffusion and ionic conductivity in Li(CF3SO3)PEG10 and LiN(CF3SO2)2PEG10

Self-diffusion of the cation, the anion and the polymer chain in the low-molecular-weight polymer electrolyte systems Li(CF3SO3)PEG10 and LiN(CF3SO2)2PEG10 has been studied as a function of temperature using nuclear magnetic resonance spectroscopy. The diffusion behaviour is very similar in the two systems, where the cation is diffusing attached to the polymer chain, while the anion is moving slightly decoupled. However, all species are slightly more mobile in LiN(CF3SO2)2PEG10 than in Li(CF3SO3)PEG10, due to the plasticizing effect of the N(CF3SO2)2− ion, which also explains the higher conductivity for the LiN(CF3SO2)2PEG10 system. The temperature dependence of the diffusion coefficients is of Arrhenius type while the ionic conductivity follows the Vogel-Tammann-Fulcher relation. The diffusion has been compared with the conductivity by applying the Nernst-Einstein relation: a slight discrepancy is found for Li(CF3SO3)PEG10, while the agreement is very good for LiN(CF3SO2)2PEG10. Spin-lattice relaxation experiments have shown that the polymer chains undergo local conformational transformations, providing an additional diffusion mechanism for the ions.

Release of Organic P Forms from Lake Sediments

The effects of different physical and chemical conditions on the decomposition and release of organic and inorganic P compound groups from the sediment of Lake Erken were investigated in a series of laboratory experiments. Conditions investigated were temperature, oxygen level, and the effects of additions of carbon substrate (glucose) and poison (formalin). The effects on the P compound groups were determined by measurements with (31)P NMR before and after the experiments, as well as analysis of P in effluent water throughout the experiment. Phosphate analysis of the effluent water showed that oxygen level was the most influential in terms of release rates, with the sediments under anoxic conditions generally releasing more phosphate than the other treatments. (31)P NMR showed that the various treatments did influence the P compound group composition of the sediment. In particular, the addition of glucose led to a decrease in orthophosphate and polyphosphate while the addition of formalin led to a decrease in phosphorus lipids, DNA-phosphate and polyphosphate. Oxic conditions resulted in an increase in polyphosphates, and anoxic conditions in a decrease in these. Temperature did not seem to affect the composition significantly.

Synthesis of cyclopent[b]indolones

A number of cyclopent[b]indol-1-ones as well as -3-ones have been synthesized, using a new methodology involving intramolecular ring closure of α,β-unsaturated acylindoles. In some cases 1,2,3,4-tetrahydrocarbazol-4-ones were obtained. This methodology was used in the syntheses of the indole alkaloid yuehchukene and the carbazole alkaloid analogue demethoxycarbazomycin B.

On the Use of C2-Symmetric Aziridines as Chiral Auxiliaries

Abstract A systematic study has been made of the utility of readily available C 2 -symmetric aziridines as auxiliaries for asymmetric alkylation and aldol rea

Palladium–hydroquinone catalysed electrochemical 1,4-oxidation of conjugated dienes

The mediator system palladium(II)–hydroquinone was shown to catalyse the anodic oxidation of cyclohexa-1,3-diene in acetic acid to produce selectively either trans- or cis-1,4-diacetoxycyclohex-2-ene (1) depending on the conditions.

Air- and Light-Stable P4 and As4 within an Anion-Coordination-Based Tetrahedral Cage

In contrast to the stable dinitrogen molecule, white phosphorus (P4) and yellow arsenic (As4) are very reactive allotropic modifications of these two heavier pnictogen elements, which has greatly hampered the study of their properties and applications. Thus, the safe storage and transport of them is imperative. Supramolecular caged structures are one of the most efficient approaches for the encapsulation and stabilization of reactive species; however, their use in the P4 and As4 chemistry is very rare. In the current work, we demonstrate a new design strategy for constructing finite cages and including guests based on anion coordination chemistry. The phosphate-coordination-based tetrahedral cages can readily accommodate the tetrahedral guests P4 and As4, which is facilitated by the shape and size complementarity as well as favorable σ-π and lone-pair-π interactions. Moreover, the latter case represents the first example of As4 inclusion in a well-defined tetrahedral cage.

Synthesis, receptor binding affinities and conformational properties of cyclic methylenedithioether analogues of angiotensin II.

Cyclic 12-, 13- and 14-membered ring angiotensin II analogues related to disulfides but encompassing methylene-dithioether bridges have been prepared. The affinity data from these derivatives were compared to those from the disulfides. The methylenedithioether analogues displayed good binding affinities to rat liver AT1 receptors although in most cases somewhat lower than their disulfide counterparts. One of the methylenedithioethers with a 13-membered ring system demonstrated the highest binding affinity among the thioethers. Theoretical conformational analysis of model compounds of the two series were performed suggesting a similarity between the disulfide and the corresponding methylenedithioether analogues and also between the ring size homologues. This analysis also suggested that some of the model compounds were prone to adopt inverse gamma-turn conformations, which was further supported by use of NMR spectroscopy of the 12-membered ring analogue in the series. The easily executed methylenedithioether cyclization should constitute a valuable complement to the common disulfide methodology for fine-tuning and for probing the bioactive conformation of peptides.