On
reacting laser-ablated manganese or iron difluorides with O2 or O3 during codeposition in solid neon or argon,
infrared absorptions of several new metal oxo-fluoride molecules,
including OMF2, (η1-O2)MF2, (η2-O3)MF2, (η1-O2)2MF2 (M = Mn and Fe),
and O2MnF, have been observed. Quantum chemical density
functional and multiconfiguration wavefunction calculations have been
applied to characterize these new products by their geometric and
electronic structures, vibrations, charges, and bonding. The assignment
of the main vibrational absorptions as dominant symmetric or antisymmetric
M–F or M–O stretching modes is confirmed by oxygen isotopic
shifts and quantum chemical calculations of frequencies and thermal
stabilities. The tendency of Fe to form polyoxygen complexes in lower
oxidation states than the preceding element Mn is affirmed experimentally
and supported theoretically. The M–F stretching frequencies
of the isolated metal oxo-fluorides may provide a scale for the local
charge on the MF2 sites in active energy conversion systems.
The study of these species provides insights for understanding the
trend of oxidation state changes across the transition-metal series.