Vibrational Spectroscopy of Intermediates in Benzene-to-Pheno Conversion by FeO+

Gas-phase FeO+ can convert benzene to phenol under thermal conditions. Two key intermediates of this reaction are the [HO-Fe-C6H5](+) insertion intermediate and Fe+(C6H5OH) exit channel complex. These intermediates are selectively formed by reaction of laser ablated Fe+ with specific organic precursors and are cooled in a supersonic expansion. Vibrational spectra of the sextet and quartet states of the intermediates in the O-H stretching region are measured by infrared multiphoton dissociation (IRMPD). For Fe+ (C6H5OH), the O-H stretch is observed at 3598 cm(-1). Photodissociation primarily produces Fe+ + C6H5OH; Fe+(C6H4) + H2O is also observed. IRMPD of [HO-Fe-C6H5](+) mainly produces FeOH+ + C6H5 and the O-H stretch spectrum consists of a peak at similar to 3700 cm(-1) with a shoulder at similar to 3670 cm(-1). Analysis of the experimental results is aided by comparison with hybrid density functional theory computed frequencies. Also, an improved potential energy surface for the FeO+ + C6H6 reaction is developed based on CBS-QB3 calculations for the reactants, intermediates, transition states, and products. (J Am Soc Mass Spectrom 2010, 21, 750-757) (C) 2010 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry