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Low‐energy (0.1 eV) electron attachment SS bond cleavage assisted by Coulomb stabilization
Author(s) -
Sawicka Agnieszka,
BerdysKochańska Joanna,
Skurski Piotr,
Simons Jack
Publication year - 2005
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.20449
Subject(s) - chemistry , endothermic process , crystallography , protonation , antibonding molecular orbital , ion , bond dissociation energy , dissociation (chemistry) , electron , computational chemistry , photochemistry , atomic orbital , organic chemistry , physics , adsorption , quantum mechanics
Electron capture by the ion H 3 C–S–S–CH 2 –CH 2 –NH + 3at either the −NH + 3site (to form the Rydberg radical H 3 C–S–S–CH 2 –CH 2 –NH 3 ) or into the S–S antibonding σ* orbital is shown to be able to produce the same S–S bond fragmentation products H 3 C–S and HS–CH 2 –CH 2 –NH 2 , albeit by very different pathways. Capture into the S–S σ* orbital is, in the absence of the nearby positive site, endothermic by approximately 0.9 eV and leads to an electronically metastable anion that can undergo dissociation or autodetachment. In contrast, in the presence of the stabilizing Coulomb potential provided by the nearby NH + 3site, electron attachment into the S–S σ* orbital is rendered exothermic. As a result, as we have shown in this paper, the effective cross sections for forming the H 3 C–S and HS–CH 2 –CH 2 –NH 2 products via attachment at the −NH + 3and S–S σ* sites are predicted to be comparable for our model compound. Moreover, we predict that the σ* site will become more amenable to electron attachment compared with the −NH + 3site for compounds in which the distance between the S–S bond and the protonated amine is larger than in our cation. These findings and insights should be of substantial value to workers studying bond cleavage rates and fragmentation patterns in gaseous positively charged samples of peptides and proteins. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005