IR spectra of resorcinol +–Ar n cluster cations ( n = 1, 2): Evidence for photoionization-induced π → H isomerization

Abstract

Resorcinol +–Ar n cations (Rs +–Ar n , n = 1,2) generated by resonant multiphoton ionization (REMPI) and electron ionization (EI) were assayed by their infrared (IR) photodissociation spectra in the OH stretch ( ν OH) range. Several isomers distinguished by their Ar ligand binding sites and their Rs + isomeric cores are identified by characteristic Δ ν OH complexation shifts. Neutral Rs–Ar n complexes prefer intermolecular π-bonding of Ar to the aromatic ring, whereas cationic Rs +–Ar n clusters show predominant H-bonding to the acidic OH groups. The REMPI-IR spectra of Rs +–Ar 2 reveal ν OH absorptions assigned to cold π-bound complexes and hot H-bound complexes. The latter are generated via ionization-induced intermolecular π → H isomerization.