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Stability of Odd‐ Versus Even‐Electron Gas‐Phase (Quasi)Molecular Ions Derived from Pyridine‐Substituted N‐Heterotriangulenes
Author(s) -
Hitzenberger Jakob F.,
Dral Pavlo O.,
Meinhardt Ute,
Clark Timothy,
Thiel Walter,
Kivala Milan,
Drewello Thomas
Publication year - 2017
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201600416
Subject(s) - chemistry , ion , fragmentation (computing) , molecule , protonation , dissociation (chemistry) , singlet state , collision induced dissociation , ab initio , density functional theory , radical ion , excitation , heteroatom , pyridine , quadrupole , computational chemistry , mass spectrometry , atomic physics , tandem mass spectrometry , ring (chemistry) , physics , organic chemistry , chromatography , computer science , excited state , operating system , quantum mechanics
Electrospray ionisation of N‐heterotriangulenes (i.e., dimethylmethylene‐bridged triphenylamines) with up to three pyridyl groups at their periphery, produces the true radical cation ([ M ] + . ) and the protonated molecule ([ M +H] + ) simultaneously. These ions are studied as model systems to illustrate the stability alternation of odd‐ versus even‐electron ions in energy‐dependent collision‐induced dissociation (CID) experiments. All ions show the same fragmentation pattern, the consecutive loss of three methyl radicals ( . CH 3 ) from the dimethylmethylene bridges of the central triangulene core. [ M ] + . ions dissociate at much lower collision energies than their [ M +H] + counterparts. The radical cation forms a singlet fragment with an extended aromatic system that is energetically favoured. Ab initio and density functional theory calculations support this interpretation and allow the assignment of the electronic structure of the fragment ions. Consecutive collision‐induced dissociations provide a better match with theory when studied with an ion trap, rather than a linear quadrupole. This is attributed to the resonant nature of the excitation of intermediate ions.