Infrared Photodissociation Spectroscopy of Mass Selected
Homoleptic Copper Carbonyl Cluster Cations in the Gas Phase
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Abstract
Infrared spectra of mass-selected
homoleptic copper carbonyl cluster
cations including dinuclear Cu<sub>2</sub>(CO)<sub>6</sub><sup>+</sup> and Cu<sub>2</sub>(CO)<sub>7</sub><sup>+</sup>, trinuclear Cu<sub>3</sub>(CO)<sub>7</sub><sup>+</sup>, Cu<sub>3</sub>(CO)<sub>8</sub><sup>+</sup>, and Cu<sub>3</sub>(CO)<sub>9</sub><sup>+</sup>, and
tetranuclear Cu<sub>4</sub>(CO)<sub>8</sub><sup>+</sup> are measured
via infrared photodissociation spectroscopy in the carbonyl stretching
frequency region. The structures are established by comparison of
the experimental spectra with simulated spectra derived from density
functional calculations. The Cu<sub>2</sub>(CO)<sub>6</sub><sup>+</sup> cation is characterized to have an unbridged <i>D</i><sub>3<i>d</i></sub> structure with a Cu–Cu half bond.
The Cu<sub>2</sub>(CO)<sub>7</sub><sup>+</sup> cation is determined
to be a weakly bound complex involving a Cu<sub>2</sub>(CO)<sub>6</sub><sup>+</sup> core ion. The trinuclear Cu<sub>3</sub>(CO)<sub>7</sub><sup>+</sup> and Cu<sub>3</sub>(CO)<sub>8</sub><sup>+</sup> cluster
cations are determined to have triangle Cu<sub>3</sub> core structures
with <i>C</i><sub>2</sub> symmetry involving two Cu(CO)<sub>3</sub> groups and one Cu(CO)<sub><i>x</i></sub> group
(<i>x</i> = 1 or 2). In contrast, the trinuclear Cu<sub>3</sub>(CO)<sub>9</sub><sup>+</sup> cluster cation is determined
to have an open chain-like (OC)<sub>3</sub>Cu–Cu(CO)<sub>3</sub>–Cu(CO)<sub>3</sub> structure. The tetranuclear Cu<sub>4</sub>(CO)<sub>8</sub><sup>+</sup> cluster cation is characterized to have
a tetrahedral Cu<sub>4</sub><sup>+</sup> core structure with all carbonyl
groups terminally bonded