| Abstract
| - The reactivity ofPFn+ (n = 1, 2)cations toward n-type bases, such as H2O,CH3OH, and NH3, has beeninvestigatedusing Fourier-transform ion cyclotron resonance (FT-ICR) massspectrometry. Both phosphorus ionsattack then-center of the selected bases, yielding the corresponding excitedonium intermediates, which undergo extensiveprototropic rearrangements before fragmenting with formal losses of Hand HF (with H2O and NH3) or HF,CH3,and CH3F (with CH3OH). Ab initiomolecular orbital calculations at the G2 level of theory have been usedtostudy the structures, the relative stability, and the proton lossenergies of the ionic species involved in thesereactions. The G2 [PF, H2O]+ and [PF,NH3]+ potential energy profiles conform wellwith the FT-ICR reactionkinetics. Unequivocal assignment of the structure and themultiplicity of several ionic species obtained from thetitle reactions and potentially involved in the formation ofphosphorus-containing molecules in outer space, i.e.(PO)H+, (FPO)H+,(PNH)H+, and (FPNH)H+, is allowedby a comparison of their G2-calculated proton lossenergies with the experimental protonation enthalpies, measured in theFT-ICR instrument with the bracketingtechnique. The emerging picture has been compared with previoustheoretical data concerning strictly relatedspecies wherein the phosphorus atom is replaced bynitrogen.
- The gas-phase reactions ofPFn+ (n = 1, 2) ionswith water, methanol, and ammonia represent convenient routes to somephosphorus ions, i.e. (PO)H+, (PNH)H+,(FPO)H+, and (FPNH)H+, potentially involvedin the formation of phosphorus molecules detected in the atmosphere ofsome planets and in the interstellar clouds. Their structure,multiplicity, and relative stability are unequivocally assigned by thecoincidence of mass spectrometric (FT-ICR) kinetic measurements with abinitio G2 theoreticalpredictions.
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