7-Selenabicyclo[2.2.1]heptane

Thermolysis of a benzene solution of N-[4-(p-(methoxybenzyl)seleno)cyclohexanoyl]-N,S-dimethyldithiocarbonate affords the hitherto unknown 7-selenabicyclo[2.2.1]heptane in 48% conversion and in 20% yield after chromatography. G3(MP2)-RAD calculations predict a rate constant of 5 × 10(4) s(-1) at 80 °C (3.8 × 10(6) s(-1) at 200 °C) for the intramolecular homolytic substitution process involved in this cyclization.     

Chemical repercussions of orbital interactions through bond and through space The reactivity of the double bond in unsaturated cyclic sulphones towards aziridine formation and epoxidation

The ease of formation of aziridine and/or epoxides from a series of bicyclic olefins, where distant sulphonyl groups are present, is very variable. There is some correlation between reactivity of the vinyl group and its π-ionisation potential which is high in the present molecules relative to comparison olefins. This increase is thought to be due to the presence of orbital interactions through bonds and/or through space between the sulphone group and the double bond, making the latter electron deficient. The ionisation potentials were determined by UV-photoelectron spectroscopy and the assignments made by recourse to ab initio configuration interaction methods.     

Bonding in HNO-myoglobin as characterized by X-ray absorption and resonance raman spectroscopies

The EXAFS and resonance Raman spectra on the HNO-myoglobin adduct, 1, are consistent with the presence of HNO bound to a heme center. The three-dimensional structure about the heme center of 1 obtained from multiple-scattering (MS) analysis of the EXAFS of the heme protein yielded an Fe-N-O bond angle of 131 degrees and an Fe-N bond length of 1.82 A, which compare well with published values for model complexes containing RNO ligands. Resonance Raman spectra identified the nu(N=O) stretch at 1385 cm-1 (confirmed by 15N labeling), which corresponds well with those reported for small molecule HNO complexes. The wavelength of the nu(Fe-N) at 636 cm-1 of 1 is significantly higher than those of MbIINO and MbIIINO (554 and 595 cm-1, respectively). The XAFS, XANES, and resonance Raman data are all consistent with the structure deduced from the NMR experiments, providing more detail on the bonding between HNO and the metal center.     

Thermal analysis of poly(p-xylylene) and poly(α,α,α′,α′-tetrafluoro-p-xylylene)

The TG(DTG) and DTA of poly(p-xylylene) and poly(α,α,α′,α′-tetrafluoro-p-xylylene) are reported. The degradation was performed from ambient temperature to 900°C in both air and nitrogen. Both polymer degrade faster in air than under nitrogen but the fluorinated polymer eventually decomposed at higher temperature in air than in nitrogen atmosphere. The activation energies of the degradation processes is given.     

Infrared multiphoton spectra from metal dication complexes in the gas phase

Infrared multiphoton spectra have been recorded for the first time from metal dication complexes held in an ion trap. The photofragmentation of [M(pyridine)4]2+ complexes has been observed in the range 920-1090 cm(-1) and for M=Cu2+, Mg2+ and Zn2+. The narrow absorption features are identified as vibrational modes of the pyridine molecule and comparisons with calculations suggest that the Mg2+ and Zn2+ ion complexes have D2d (compressed tetrahedron) structures, and that the Cu2+ complex is probably square-planar (D4h).