Hydrogen bonding of the naphthalene radical cation to water and methanol and attachment of the naphthalene ion to extended hydrogen bonding chains

The binding energies of water and methanol to the naphthalene radical cation (7.8 and 8.3 kcal/mol, respectively) are reported. The naphthalene ion forms unconventional carbon-based ionic hydrogen bonds with H2O and CH3OH (CHδ+⋯OH2 and CHδ+⋯OHCH3, respectively) which can be extended to hydrogen bonding chains with additional solvent molecules. Both water and methanol molecules show a strong tendency for the external solvation of the naphthalene cation. These structures allow the PAH ion to reside on the surface of ice grains in interstellar medium where reactions with incoming organic molecules could take place to produce a variety of complex organics in space.