Does the valence state index reflect the stability of neutral boron subhalide clusters?

The numbers of valence structures (NVS) and the valence state indexes (VSI) have been determined for a series of 2n framework electron clustersviz. polyhedral boron subhalides B _n X _n (n=6–12) and compared with those obtained for the parent B _n H _n ^2– dianions. The VSI does not reflect the experimental stabilities.     

Polarized emission of individual self-assembled oligo(p-phenylenevinylene)-based nanofibers on a solid support

We have prepared 5 nm diameter, micrometer long tetra(p-phenylenevinylene) (OPV)-based nanofibers on a graphite surface. The fluorescence emission of an individual fiber shows a profound polarization over its entire length that directly corresponds to its orientation on the substrate. Quantitative analysis of the fluorescence polarization, including the depolarizing effect of the underlying graphite, evidences the high degree of organization within chiral fibers with the OPV molecules perpendicular to the fiber axis. The control of the internal order within self-assembled fibers, and the ability to measure it, is a crucial step to obtain uniform organic fibers that can be applied in nanosized electronics at room temperature.     

Solid‐state 119Sn NMR and antitumor activity of bis [1,3‐bis (3‐oxapentamethylenecarbamoylthioacetato)‐1,1,3,3‐tetrabutyl‐1,3‐distannoxare], and the crystal structure of its bis‐ethanol solvate

The ¹¹⁹Sn cross polarization‐magic angle spinning NMR spectrum of bis[1,3‐bis(3‐oxapentamethylenecarbamoylthioacetato)‐1,1,3,3‐tetrabutyl‐1,3‐distannoxane], {[(C₄H₉)₂SnO₂CCH₂SC(O)N(CH₂CH₂)₂O]₂O}₂, which consists of two resonances of similar chemical shifts and symmetry (δ_iso = −152, −202 ppm; asymmetry, κ = 0.38), implies the existence of two five‐coordinate tin sites in the centrosymmetric dimer. The assignment has been corroborated by X‐ray diffraction analysis on the compound that has been crystallized from ethanol; the crystal structure shows two tin atoms in cis‐C₂SnO₃ trigonal‐bipyramidal coordination [C‐Sn‐C = 131.5(1), 131.3(2) °]. The analysis also reveals the presence of two lattice ethanol molecules that are hydrogen‐bonded to the dimer [OO = 2.779(5) Å]. When exposed to air, the distannoxane loses ethanol. The unsolvated distannoxane is more active than cis‐platin when screened against MCF‐7 (mammary cancer), EVSA‐T (mammary cancer), WiDr (colon cancer), IGROV (ovarian cancer), M19 MEL (melanoma), A498 (renal cancer) and H226 (lung cancer) cell lines. Copyright © 2000 John Wiley & Sons, Ltd.     

M. Nath,S. Phokaria,X. Song,G. Eng,M. Gielen,M. Kemmer,M. Biesemans,R. Willem and D. de Vos, ‘New organotin(IV) derivatives of dipeptides as models for metal–protein interactions: in vitro anti‐tumour activity’ Applied Organometallic Chemistry 2003; 17(5): 305–314

The original article to which these Errata refer was published in the journal Applied Organometallic Chemistry 2003; 17 (5): 305–314. Copyright © 2003 John Wiley & Sons, Ltd.     

Preparation and characterization of MgB2 superconductor

The MgB₂ superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been determined using magnetization data. The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB₂ is sensitive to atmospheric degradation.     

A spectroscopic determination of ferrous iron content in glasses

A comparison is given between a Mössbauer spectroscopy determination and the classical chemical analysis of the Fe²⁺ content in SiO₂Na₂OFe₂O₃ glass systems, for different iron concentrations, and for 16.0 and 24.0 wt% Na₂O respectively. The agreement between Mössbauer analysis and chemical analysis is good only for large Fe₂O₃ contents, while for small Fe₂O₃ contents the Mössbauer analysis gives a much larger Fe²⁺/(Fe²⁺ + Fe³⁺) ratio than the chemical analysis: a physical reason is given for this fact. The Fe₂O₃ content below which Fe²⁺ becomes predominant in glass is rather sharply defined, and a qualitative explanation is proposed to account for this rapid transition from Fe³⁺ to Fe²⁺.     

The reaction of di‐n‐butyltin oxide with hexafluoro‐2,2‐bis(4‐carboxyphenyl)propane

The reaction of hexafluoro‐2,2‐bis(4‐carboxyphenyl)propane with tetrabutyldipropoxydistannoxane, formed in situ from dibutyltin oxide and n‐propanol in benzene, yields a compound the structure of which is a strained macrocycle with a single dicarboxylate moiety. Copyright © 1999 John Wiley & Sons, Ltd.     

Mechanisms for the cleavage of carbon-tin bonds : VI. A kinetic and stereochemical study of the halodemetallation of cyclopropyltrialkyltins: the solvent effect

The bimolecular halodemetallation of substituted cyclopropyltrialkyltins is stereospecific, and proceeds with retention of the configuration at carbon in methanol, acetic acid and chlorobenzene. The kinetic study confirms the hypothesis which was based on results for the R′SnR₃ series, and shows the participation of the ring orbitals in the rate determining step of the reaction.