UV photochemistry of a
polycyclic aromatic hydrocarbon model,
coronene (C(24)H(12)), has been investigated when it is in interaction with water in
argon cryogenic matrices, adsorbed on amorphous water
ice films, and embedded in solid water. Photoprocessing, carried out
at 10 K and λ > 235 nm by means of a high-pressure Hg
arc lamp, results in the oxidation and reduction of
coronene. These species have been tentatively identified as being the 1,10-dihydroxycoronene and the 1,10-coroquinone by FTIR spectroscopy with the support of isotopic experiments and DFT calculations. These photochemical products most likely form, after hydrogen bonding between C(24)H(12) and H(2)O, through ionization of the PAH and subsequent reactivity with water upon irradiation.
Cations, thus generated, react subsequently with water yielding the production of
oxygen containing
coronene compounds. Such species are of particular interest as they may form in interstellar and early Solar System ices, and are also of astrobiological significance as they could play an important role in processes taking place in most of the living organisms.