Infrared Multiphoton Dissociation of Transition Metal Containing Ions: MCnH2n+ (M = Fe, Co, Ni; n = 2−5)

The infrared multiphoton dissociation (IRMPD) processes of groups 8−10 (Fe, Co, Ni) transition metal ion complexes containing acetylene and alkenes were investigated. Of the 30 ions studied, all but four were found to be photoactive at 944 cm - 1, the wavelength of the CO 2 infrared laser employed. Most of the ions were observed to yield one photodissociation product, as is typical for IRMPD. Ironacyclopentane, nickelacyclopentane, Co(isobutene) +, and Ni(isobutene) +, however, were observed to give multiple products. This observation is a result of kinetic and thermodynamic factors, and it gives information about the potential energy surface of the dissociating ion. More specifically, activation barrier heights leading to the product ions can be probed. Sustained off-resonance irradiation, an experiment designed to mimic infrared activation, was also performed on these ions, yielding results in good agreement with the infrared results.