Gas phase chemistry of pyrene and related cations with molecules and atoms of interstellar interest

The chemistry of the pyrene radical cation C(16)H(10)(+) acid its derivatives C(16)H(9)(+) and C(16)H(11)(+) has been investigated in the gas phase using a flowing afterglow-selected ion flow tube. Rate coefficients have been determined for reactions between C(16)H(n)(+) (n = 9, 10, 11) and H(2), CO, H(2)O and NH(3) molecules as well as H, O, and N atoms. These studies supplement previous investigations on the smaller benzene and naphthalene cations. It is found that C(16)H(10)(+) and C(16)H(11)(+) display consistent, predictable chemistry with reactivities very similar to those of benzene and naphthalene cations. On the other hand, the striking reactivity of C(16)H(9)(+) toward atoms, compared to the relative unreactivity of phenylium and naphthylium cations, is believed to result from the triplet nature of this ion in its ground state. Ab initio calculations have been carried out to validate this hypothesis in conjunction with experimental evidence. (Int J Mass Spectrom 185/186/187 (1999) 949-959) (C) 1999 Elsevier Science B.V.