Isolation and characterization of a peroxo manganese (III) dioxygen reaction intermediate using cryogenic ion vibrational predissociation spectroscopy

We apply cryogenic ion vibrational predissociation (CIVP) spectroscopy to characterize the O-2 attachment motif in a prototypical peroxo manganese (III) reaction intermediate. In this approach, species are extracted from solution using electrospray ionization and cooled in a 30 K ion trap. The infrared spectrum is then obtained by monitoring the photoinduced evaporation of a single, weakly bound N-2 molecule as a function of laser wavelength. Because the resulting CIVP action spectrum is linear in laser fluence, the pattern of well-resolved transitions can be directly compared with harmonic spectra calculated for predicted local minima using density functional theory (DM. The assignment of the O-O stretching band derived from the activated O-2 ligand is established by following the evolution of the bands with (18)Q(2) substitution, and the energy of this transition indicates that O-2 is bound side-on to the Mn center. The successful application of CIVP to this class of compounds opens the way for sensitive spectroscopic characterization of weakly abundant species in complex solution environments. (C) 2013 Elsevier B.V. All rights reserved.