Fluorinated methyl cation (CF(3)(+), CFH(2)(+))-alkyl nitrile cluster ions

Area of Science:

• Physical Chemistry
• Chemical Physics
• Mass Spectrometry

Background:

• Ion-molecule reactions are fundamental to chemical processes.
• Understanding cluster ion structures is crucial for reaction mechanism elucidation.
• Previous studies on cation-bound dimers provide a basis for comparison.

Purpose of the Study:

• To investigate the structures of product cluster ions formed from ion-molecule reactions.
• To explore the binding interactions within dimeric complexes of acetonitrile and butyronitrile with fluorinated methyl cations.
• To reconcile experimental fragmentation data with theoretical models of ion complex formation.

Main Methods:

• Collision-induced dissociation (CID) using a multi-quadrupole mass spectrometer.
• Ab initio calculations to model potential energy surfaces and complex structures.
• Collision energy dependence studies.
• Quasi-equilibrium theory (QET) calculations for data interpretation.

Main Results:

• Formation of cluster ions involving CF(3)(+) or CFH(2)(+) with acetonitrile-butyronitrile mixtures.
• Unexpected inverse correlation between fragment ion abundance and proton affinity of alkyl nitriles.
• Evidence for non-symmetrical dimeric complexes with a significant internal energy barrier, rather than simple cation-bound dimers.
• Ab initio and QET calculations support the formation of complexes within potential energy wells on a symmetrical surface.

Conclusions:

• The fragmentation behavior indicates complex structural arrangements beyond simple cation-bound dimers.
• The findings suggest a pair of non-symmetrical dimeric complexes are formed, separated by a large internal barrier.
• The results are analogous to those observed for methyl cation-bound heterodimers, highlighting a common theme in such systems.