Water Clusters in Interaction with Corannulene in a Rare Gas Matrix: Structures, Stability and IR Spectra

Abstract

The interaction of polycyclic aromatic hydrocarbons (PAHs) with water is of paramount importance in atmospheric and astrophysical contexts. We report here a combined theoretical and experimental study of corannulene-water interactions in low temperature matrices and of the matrix’s influence on the photoreactivity of corannulene with water. The theoretical study was performed using a mixed density functional based tight binding/force field approach to describe the corannulene-water clusters trapped in an argon matrix, together with Born-Oppenheimer molecular dynamics to determine finite-temperature IR spectra. The results are discussed in the light of experimental matrix isolation FTIR spectroscopic data. We show that in the solid phase, π isomers of (C20H10)(H2O)n, with n = 2 or 3, are energetically favored. These π complexes are characterized by small shifts in corannulene vibrational modes and large shifts in water bands. These π structures, particularly stable in the case of the water trimer where the water cluster is trapped “inside” the corannulene bowl, may account for the difference in photoreactivity of non-planar–compared to planar–PAHs with water. Indeed, planar PAHs such as pyrene and coronene embedded in H2O:Ar matrices form σ isomers and react with water to form alcohols and quinones under low energy UV irradiation, whereas no photoreactivity was observed for corannulene under the same experimental conditions.

Addressing electronic and dynamical evolution of molecules and molecular clusters: DFTB simulations of energy relaxation in polycyclic aromatic hydrocarbons

“…Let us finally mention the growing interest in the environmental topic of oxygenated-PAHs and biomass burning, 228,229 a research field that has already started to be investigated through force fields 230 and DFTB potentials. 231,232 Regarding the description of electronic structures, the DFTB framework seems to offer a relevant frame for medium and larger size molecules and species. Nevertheless, advances still remain to be achieved to provide a general and unified electronuclear coupling scheme for all geometrical situations and time-scales.…”

“…Let us finally mention the growing interest in the environmental topic of oxygenated-PAHs and biomass burning, 228,229 a research field that has already started to be investigated through force fields 230 and DFTB potentials. 231,232…”

Optical Studies of Thin Films of Cryocondensed Mixtures of Water and Admixture of Nitrogen and Argon

“…When water molecules dissolve in matrices of simple molecules at low temperatures, very clear discrete bands of monomeric, dimeric, and polymeric water appear. The infrared spectrum of water, in various solid matrices of simple molecules, has been the subject of several studies [ 17 , 18 , 19 , 20 , 21 , 22 , 23 ].…”