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

Abstract

Phenol +–Kr cations (PhOH +–Kr) generated by photoionization (REMPI) of the neutral complex and in an electron ionization (EI) source were assayed by their infrared (IR) spectra in the OH stretch ( ν OH) range. Two isomers are identified in the EI–IR spectrum by their Δ ν OH complexation shifts: the more stable H-bound global minimum (Δ ν OH = −123 cm −1) and the less stable π-bound local minimum (Δ ν OH = +1 cm −1). The REMPI–IR spectrum reveals ν OH absorptions assigned to cold π-bound complexes and hot H-bound dimers. The latter are generated via π → H isomerization after the ionization of neutral π-bound dimers. EI–IR spectra are also presented for PhOH +–Kr 2. Quantum chemical calculations support the interpretation of the spectroscopic data.