Coordination and Spin
States in Vanadium Carbonyl Complexes (V(CO)<sub><i>n</i></sub><sup>+</sup>, <i>n</i> = 1–7) Revealed with
IR Spectroscopy
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Abstract
The vibrational spectra of vanadium carbonyl cations
of the form V(CO)<sub><i>n</i></sub><sup>+</sup>, where <i>n</i> = 1–7, were obtained via mass-selected infrared
laser photodissociation spectroscopy in the carbonyl stretching region.
The cations and their argon and neon “tagged” analogues
were produced in a molecular beam via laser vaporization in a pulsed
nozzle source. The relative intensities and frequency positions of
the infrared bands observed provide distinctive patterns from which
information on the coordination and spin states of these complexes
can be obtained. Density functional theory is carried out in support
of the experimental spectra. Infrared spectra obtained by experiment
and predicted by theory provide evidence for a reduction in spin state
as the ligand coordination number increases. The octahedral V(CO)<sub>6</sub><sup>+</sup> complex is the fully coordinated experimental
species. A single band at 2097 cm<sup>–1</sup> was observed
for this complex red-shifted from the free CO vibration at 2143 cm<sup>–1</sup>