Penning spectroscopy

Using UV-visible and IR spectroscopies, thermal analyses and scanning electron microscopes measurements, Young and Slemp studied the performance of several polymeric materials after exposure to an outer-space environment . PEN exhibited good environmental resistance to the oxygen-induced erosion, UV-induced degradation and spacecraft-induced contamination in such an environment [33],... 

In order to allow for a closer approach of the boron centers, the introduction of flat cyclic boryl moieties with reduced steric hindrance has also been pursued. Thus, the reaction of 26 with 9-chloro-9-borafluorene and 5-bromo-10,l 1-di-hydrodibenzo[b,f]borepin resulted in the formation of diboranes 31 and 32 which bear two different boryl moieties at the pen-positions of naphthalene (Scheme 13). " These diboranes have been characterized by multinuclear NMR spectroscopy and X-ray single-crystal analysis. In 31, the boron center of the borafluorenyl moiety is 7i-coordinated by the zp o-carbon of a mesityl group with which it forms a contact of 2.730(3) A (Fig. 8). As a result of this interaction, the boron center involved in this contact is slightly pyramidalized (Xangie = 355.7°). In the case of 32 (Fig. 9), the distance between the boron center of the boracylic moiety and the zpio-carbon of... 

Figure 11. Schematic drawing of experimental setup used for Penning ionization electron spectroscopy using helium metastables.

Reaction of selenoxanthene 9 with bromine affords the selenium addition product 72 (Equation 26) however, selenoxanthone 10 reacts with bromine to form a molecular complex 73 (Equation 27). The explanation of this difference in reactivity is based on the differences in ionization potentials of selenium in these molecules which were determined using penning ionization electron spectroscopy <1998JOC8373>. These results are consistent with ab initio calculations of the electronic states of the precursors (see Section 7.11.2). 

Purify of the crude residue by flash chromatography on silica gel using hexane ethyl acetate (96 4) to obtain pure 1-[2-(phenylmethyl)cyclopropylidene]pen-tanenitrile (39 Z E = 2.1 1) (0.064 g, 73%) as a clear oil. Characterize the product by 1H NMR, IR, MS spectroscopy, and HRMS spectroscopy. 

Block et al.194 examined the effects of trimethylsilyl substitution on the first vertical ionization potentials by photoelectron and Penning ionization electron spectroscopy studies of a range of cyclic and noncyclic sulfides and ethers. It was shown that substitution of oxirane 218 with a trimethylsilyl substituent as in 219 lowered the ionization potential by 0.90 eV (20.8 kcal/mol), while similar substitution of dimethyl ether 220 in 221 lowered the ionization potential by 0.64 eV (14.8 kcal/mol). By comparison, the effects of silyl substitution on sulfur lone-pair ionization potentials was found to be smaller thus the ionization potential of dimethyl sulfide 222 is lowered by 0.37 eV upon trimethylsilyl substitution in 223, and the trimethylsilyl-substituted thiirane 225 is lowered by 0.59 eV relative to thiirane 224. The raising of the energy of the sulfur lone-pair electrons in the thiirane 225 is also apparent from its UV spectrum, where there is a bathochromic shift in the absorption maximum compared to the parent 224. 

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