Crystalline inclusion compounds of lower rim propyl substituted calix[4]arenes featuring different number and positions of the modifying groups

Three lower rim n-propyl substituted calix[4]arenes (1–3) with varied number and position of the modifying groups have been prepared. Inclusion compounds (five species) involving different kinds of guest solvents have been isolated. Their X-ray crystal structures were determined and comparatively discussed using isostructurality calculations. Two of the inclusion compounds obtained (1a and 1b) are polymorphs containing the same host and guest molecules in equal stoichiometric ratio but different Z′ values caused by a phase transition around 140 K. The inclusion compounds 2a and 2b refer to the interesting case of a mixed solvent complex while 3a allows studying the effect of full lower rim n-propyl substitution.     

Kinetische Untersuchungen zur Hydrierung von Kohlendioxid zu Ameisensäure mit einem Rhodiumkomplex als Katalysator

Kinetic Studies on the Hydrogenation of Carbon Dioxide to Formic Acid using a Rhodium Complex as Catalyst A detailed kinetic analysis has been performed on the hydrogenation of carbon dioxide with the complex [(dppp)₂RhH] (dppp = 1,3‐bis(diphenyl‐phosphino)propane in DMSO using stopped‐flow techniques. Activation parameters including the activation volume for this reaction as well as for the related reaction of the formation of the dihydrogen complex [(dppp)₂RhH₂]HCO₂ were obtained and thus allowed the formulation of a mechanism for this reaction cycle.     

Synthesis of an Iron(IV) Aqua–Oxido Complex Using Ozone as an Oxidant

The iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclo‐tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H₂O)(tmc)Fe=O)](OTf)₂ could be prepared. This complex is important in regard to a better understanding of the reactivity of Fe^IV oxido complexes. Mössbauer measurements using the solid compound showed an isomer shift of δ=0.19 mm s^?1 and a quadrupole splitting ΔE_Q=1.38 mm s^?1, confirming the high‐valent Fe^IV state. DFT calculations were performed and led to an assignment of triplet spin multiplicity. Crystallographic characterization of [(H₂O)(tmc)Fe=O)](OTf)₂ as well as of starting materials [(tmc)Fe(CH₃CN)](OTf)₂ and [(tmc)Fe(OTf)]OTf together with previous results strongly suggest that [(H₂O)(tmc)Fe=O)](OTf)₂ was formed similar to the oxido–hydroxido tautomerism analogous to heme systems.     

Functionalized cyclopentanes via Sc(III)-catalyzed intramolecular enolate alkylation

We report herein the intramolecular α-tert-alkylation of unsaturated β-ketoesters which gives rise to highly functionalized cyclopentanes. This transformation is characterized by its operational simplicity, mild reaction conditions and the use of scandium (III) triflate as a Lewis acid catalyst. Of interest, cyclopentanes bearing heterocycles, sites for post reaction functionalization and spirocyclic architectures are accessible with this strategy.     

Imaging single-molecule dichroism

Video-enhanced optical fluorescence microscopy has been used to determine the direction of the transition dipole moment of individual molecules. Fast electro-optical switching of the polarization of the excitation allowed us to detect the linear dichroism of single fluorophores in solid phospholipid membranes. Quantitative analysis of the fluorescence signal showed that rotational mobility is absent in solid biomembranes.     

The unique Jordan-Hahn decomposition property

We show that a finite orthomodular poset with a strong section of states (probability measures) is distributive if and only if has the unique Jordan-Hahn decomposition property(UJHDP). That this result does not extend to infinite orthomodular posets is shown by the projection lattices of von Neumann algebras without direct summand of typeI ₂, for which the set of completely additive states is strong and has theUJHDP. There also exist nondistributive -classes for which the set of countably additive states has theUJHDP.Research supported by Schweizerischer Nationalfonds/Fonds National Suisse under grant number 2.445-0.87.