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High‐energy collisional activation of the molecular ions of thiophene‐2‐one with different target gases
Author(s) -
Gerbaux Pascal,
Sciamanna Valérie,
Flammang Robert,
Nguyen MinhTho
Publication year - 2001
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.108
Subject(s) - chemistry , excited state , ground state , ab initio , ion , dissociation (chemistry) , thiophene , density functional theory , molecular orbital , bond dissociation energy , radical ion , computational chemistry , atomic physics , photochemistry , molecule , organic chemistry , physics
Collisional activation of keV thiophene‐2‐one radical cations 1 +· with O 2 or NO · as the target gas leads to a desulfuration reaction. This peculiar reaction is insignificant or absent with other targets such as helium, argon, methane or nitrogen. The radical cations produced in this desulfuration reaction are most probably vinylketene ions, as indicated by a triple mass spectrometric (MS/MS/MS) experiment performed on a ‘hybrid’ tandem mass spectrometer of sector–quadrupole–sector configuration. Tentatively, it is proposed that population of an excited state accounts for the non‐ergodic behavior of 1 +· upon collision with oxygen or nitric oxide. Ab initio molecular orbital calculations using molecular orbital theory (UMP2, UCCSD(T)) and density functional theory (B3LYP) with 6–31G(d,p) and 6–311++G(d,p) basis sets were used to evaluate the relative energy of the excited quartet state of 1 +· radical cations. This quartet state is calculated to lie about 3.6 eV above the 2 A ″ ground state and 0.9 eV above the C 4 H 4 O +· +S dissociation products. It is proposed that the quartet ion serves as the precursor for the spontaneous desulfuration. Copyright © 2001 John Wiley & Sons, Ltd.