We present gas phase vibrational spectra of the trinuclear vanadium oxide
cations V3O6+·He1–4, V3O7+·Ar0,1, and V3O8+·Ar0,2 between 350 and 1200 cm−1.
Cluster structures are assigned based on a comparison of the experimental and
simulated IR spectra. The latter are derived from B3LYP/TZVP calculations on
energetically low-lying isomers identified in a rigorous search of the
respective configurational space, using higher level calculations when
necessary. V3O7+ has a cage-like structure of C3v symmetry. Removal or
addition of an O-atom results in a substantial increase in the number of
energetically low-lying structural isomers. V3O8+ also exhibits the cage
motif, but with an O2 unit replacing one of the vanadyl oxygen atoms. A chain
isomer is found to be most stable for V3O6+. The binding of the rare gas atoms
to V3O6–8+ clusters is found to be strong, up to 55 kJ/mol for Ar, and
markedly isomer-dependent, resulting in two interesting effects. First, for
V3O7+·Ar and V3O8+·Ar an energetic reordering of the isomers compared to the
bare ion is observed, making the ring motif the most stable one. Second,
different isomers bind different number of rare gas atoms. We demonstrate how
both effects can be exploited to isolate and assign the contributions from
multiple isomers to the vibrational spectrum. The present results exemplify
the structural variability of vanadium oxide clusters, in particular, the
sensitivity of their structure on small perturbations in their environment