Low-energy electron-induced dissociation in gas-phase nicotine, pyridine, and methyl-pyrrolidine

Abstract

Dissociative electron attachment to nicotine, pyridine, and N-methyl-pyrrolidine was studied in the gas phase in order to assess their stability with respect to low-energy electron interactions. Anion yield curves for different products at electron energies ranging from zero to 15 eV were measured, and the molecular fragmentation pathways were proposed. Nicotine does not form a stable parent anion or a dehydrogenated anion, contrary to other biological systems. However, we have observed complex dissociation pathways involving fragmentation at the pyrrolidine side accompanied by isomerization mechanisms. Combining structure optimization and enthalpy calculations, performed with the Gaussian09 package, with the comparison with a deuterium-labeled N-methyl-d3-pyrrolidine allowed for the determination of the fragmentation pathways. In contrast to nicotine and N-methylpyrrolidine, the dominant pathway in dissociative electron attachment to pyridine is the loss of hydrogen, leading to the formation of an [M-H] anion. The presented results provide important new information about the stability of nicotine and its constituent parts and contribute to a better understanding of the fragmentation mechanisms and their effects on the biological environment.

DFT study of low-energy electron interaction with pyridine, pyrazine and their halo derivatives

“…It should be noted here that the σ * state for all molecules is deformed below the π * -σ * intersection distance, due to the diffuse functions inclusion. According to calculations with B3LYP/6-31+G*, B3LYP/aug-cc-pVTZ and MP2/6-31+G*, separation of one of the hydrogens from pyridine requires around 3.30 -3.75 eV, depending on the position (see Table 4), which is in a good agreement with the results of Ryszka et al [29], obtained with cbs-qb3 method. However, they observed a weak signal for the formation of [Py-H] − anion by DEA at 2.5, 5.3, 7.0 and 9.0 eV, so the first peak is much below the reaction threshold.…”

“…Pyridine [23][24][25][26][27][28][29][30][31] and pyrazine [27,28,[32][33][34] are fairly well studied for its interaction with electrons, both experimentally and theoretically. Pyridine has negative electron affinity and displays three π * resonances in the low-energy regime, which has B 1 , A 2 (shape resonances) and B 1 (mixed-type resonance) symmetry, from the lowest to highest energy.…”

Cross sections for electron collision with pyridine [C5H5N] molecule

“…Worth noting is also some flattening of the TCS curve between 7 and 9.5 eV. In this energy regime, the transmission spectrum [11] and anion yield curves [25] also suggested B. Comparative studies…”

“…Examination of the measured electron energy-loss spectra allowed to observe and assign the triplet excited states of pyridine [24]. Recently, the formation of anionic species resulting from the dissociative attachment of low-energy electrons to pyridine has been investigated [25]. Just in the course of the present experiment, the absolute TCS data have been published [26]; measured in the transmission experiment from 13 to 902 eV and computed between 1 and 1000 eV.…”

Selecting and identifying gas-phase protonation isomers of nicotineH+ using combined laser, ion mobility and mass spectrometry techniques

“…The photo-stability and absorption properties of neutral (S)-nicotine have been subjected to several studies over several decades, including IR, 37 electron-induced dissociation 38 and UV absorption spectra of solution phase (S)-nicotine in various protonated forms. [39][40][41] To our knowledge, there are no reported UV photodissociation studies of singly protonated (S)nicotine in the literature.…”