The reaction of polycyclic aromatic hydrocarbon anions with hydrogen Original Research Article

The reaction of naphthalene anion with an H atom to produce 1-hydronaphthalene anion is exothermic by about 50 kcal/mol. The exothermicity for the formation of 2-hydronaphthalene anion is 4.7 kcal/mol smaller. The 1-hydronaphthalene anion reacts with a second hydrogen atom to restore the naphthalene anion and produce H2. This reaction has no barrier and is exothermic by 53.3 kcal/mol. Similar energetics are found for the analogous coronene and circumcoronene reactions. Thus the polycyclic aromatic hydrocarbon (PAH) anions can catalyse the formation of H2, using a mechanism analogous to the PAH cations. This could have important consequences in several problems of astrophysical interest.