Zum Ligandenaustausch an TcNX4−-Komplexen (X = Cl,Br)

Ligand-Exchange Reactions on TcNX₄^? Complexes (X = Cl, Br) Ligand exchange reactions on the nitridotechnetium(VI) compounds (Bu₄N)TcNCl₄ and (Bu₄N)TcNBr₄ are reported. The use of various organic ligands having different donor atom sets produces Tc^V nitrido complexes. The reaction of (Bu₄N)TcNCl₄ with (Bu₄N)TcNBr₄ is characterized by the formation of Tc^VI complex species with mixed Cl/Br coordination spheres. EPR detection of the mixed-ligand complexes results in a well-defined dependence of the EPR parameters on the composition of the first coordination sphere of the complexes.     

A note on invariant sets of iterated function systems

We prove that the family of all invariant sets of iterated systems of contractions R ^N → R ^N is a nowhere dense F _σ type subset in the space of the nonempty compact subsets of R ^N equipped with the Hausdorff metric.     

A synthesis of licofelone using Fenton’s reagent

An efficient synthesis of licofelone, an anti-inflammatory drug currently undergoing phase-III clinical studies, based on Fenton-type radical alkylation of 2,3-dihydro-1H-pyrrolizine 3 with iodoacetonitrile or iodoacetates is reported. The iodoacetates can be replaced by NaI and by the corresponding bromoacetate.     

ERP-Untersuchungen an Oxovanadium(IV)-Bis-Komplexen mit 1,2-Dithioliganden

EPR Studies on Oxovanadium(IV) Bis-Complexes of 1,2-Dithio Ligands EPR investigations on oxovanadium(IV) bis-complexes containing the ligands 1,3-dithiol-2-thione-4,5-dithiolate, dmit^2?, 1,2-dithiol-3-thione-4,5-dithiolate, dmt^2?, and 1,2-dithiooxalate are reported. The parameters of the spin-Hamiltonian are used to characterize the bonding properties, and are compared with those obtained for the corresponding VOS₄ chelates containing four-membered chelate rings. According to this a successful characterization of VOS₄ type mixed-ligand complexes should be possible.     

DFT calculation of structures and NMR chemical shifts of simple models of small diameter zigzag single wall carbon nanotubes (SWCNTs)

Linearly conjugated benzene rings (acenes), belt‐shape molecules (cyclic acenes) and model single wall carbon nanotubes (SWCNTs) were fully optimized at the unrestricted level of density functional theory (UB3LYP/6‐31G*). The models of SWCNTs were selected to get some insight into the potential changes of NMR chemical shift upon systematic increase of the molecular size. The theoretical NMR chemical shifts were calculated at the B3LYP/pcS‐2 level of theory using benzene as reference. In addition, the change of radial breathing mode (RBM), empirically correlated with SWCNT diameter, was directly related with the radius of cyclic acenes. Both geometrical and NMR parameters were extrapolated to infinity upon increase in the studied systems size using a simple two‐parameter mathematical formula. Very good agreement between calculated and available experimental CC bond lengths of acenes was observed (RMS of 0.0173 Å). The saturation of changes in CC bond lengths and ¹H and ¹³C NMR parameters for linear and cyclic acenes, starting from 7–8 conjugated benzene rings, was observed. The ¹³C NMR parameters of individual carbon atoms from the middle of ultra‐thin (4,0) SWCNT formed from 10 conjugated cyclic acenes differ by about 130 ppm from the corresponding open end carbon nuclei. Copyright © 2011 John Wiley & Sons, Ltd.     

Polymerization Kinetics of Water-Soluble N-Vinyl Monomers in Aqueous and Organic Solution

Summary: Free-radical batch polymerization (FRP) of N-vinyl pyrrolidone (NVP) and N-vinyl formamide (NVF) monomers in aqueous solution as well as NVP polymerization in organic (n-butanol) solution has been studied. The differences found in rate of monomer conversion with monomer and solvent choice correlates well with the differences in values of the propagation rate coefficients (k_p) and their variation with monomer concentration measured in independent pulsed-laser polymerization studies, a result demonstrating that a generalized understanding of water-soluble vinyl monomers can be obtained once their k_p differences have been accounted for. A reasonable representation of polymer molecular mass averages and the complete molecular mass distributions for the three systems was obtained by assuming that the rate coefficient for transfer to monomer, polymer, and organic solvent also vary as a function of monomer concentration.     

Combining Topology and Sequence Design for the Discovery of Potent Antimicrobial Peptide Dendrimers against Multidrug‐Resistant Pseudomonas aeruginosa

Multidrug‐resistant opportunistic bacteria, such as Pseudomonas aeruginosa, represent a major public health threat. Antimicrobial peptides (AMPs) and related peptidomimetic systems offer an attractive opportunity to control these pathogens. AMP dendrimers (AMPDs) with high activity against multidrug‐resistant clinical isolates of P. aeruginosa and Acinetobacter baumannii were now identified by a systematic survey of the peptide sequences within the branches of a distinct type of third‐generation peptide dendrimers. Combined topology and peptide sequence design as illustrated here represents a new and general strategy to discover new antimicrobial agents to fight multidrug‐resistant bacterial pathogens.     

Mathematical foundation of a global strategy for searching reaction paths

For the determination of reaction paths and critical points on the potential energy hypersurface of chemical reactions, a rigorous mathematical background for the theory of a global searching procedure based on the catchment regions of the gradient field is given.