| Autor: |
Hai-Chuan Liu, Xin-Hao Zhang, Changsheng WangPermanent address: Department of Chemistry, Liaoning Normal University, Dalian, People’s Republic of China., Yun-Dong Wu, Shihe Yang |
| Zdroj: |
Physical Chemistry Chemical Physics (PCCP); Jan2007, Vol. 9 Issue 5, p607-615, 9p |
| Abstrakt: |
Gas phase complexes Mg˙+(2,6-difluoropyridine) (1) and Mg˙+(pentafluoropyridine) (2) have been subjected to photodissociation in the spectral range of ∼230–440 nm. Except for the evaporative photofragment Mg˙+, the primary photoproduct for 1 is C5H3N˙+, which is associated with the rupture of two C–F bonds by the photoexcited Mg˙+, forming very stable MgF2. In contrast, the direct loss of MgF+ is more favorable for 2 due to fluorine substitution. Given enough energy, C5H3N˙+ can undergo decomposition to form C4H2˙+ and HCN. These results are very different from those for Mg˙+(2-fluoropyridine), highlighting the significance of the additional F at C6 of 1 and 2. Density functional theory (DFT) calculations have been employed to examine the geometries and energetics of the complexes as well as relevant reaction mechanisms. All of the complexes feature the direct attachment of Mg˙+ to the N atom. The key intermediate is found to be FMg+(C5HxF4−xN) (x = 3 or 0), which can lead to the formation of MgF+ directly or MgF2 through activation of another C–F bond adjacent to N, producing the pyridyne radical cations. However, hydrogen-transfer prior to the rupture of the second C–F bond followed by ring-opening of C5H3N˙+ may result in the formation of chain forms of C5H3N˙+. The influence of the fluorine substitution on the competition of the two routes have been demonstrated. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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