Infrared photodissociation spectroscopy of mass selected homoleptic copper carbonyl cluster cations in the gas phase.

Infrared spectra of mass-selected homoleptic copper carbonyl cluster cations including dinuclear Cu2(CO)6(+) and Cu2(CO)7(+), trinuclear Cu3(CO)7(+), Cu3(CO)8(+), and Cu3(CO)9(+), and tetranuclear Cu4(CO)8(+) 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 Cu2(CO)6(+) cation is characterized to have an unbridged D3d structure with a Cu-Cu half bond. The Cu2(CO)7(+) cation is determined to be a weakly bound complex involving a Cu2(CO)6(+) core ion. The trinuclear Cu3(CO)7(+) and Cu3(CO)8(+) cluster cations are determined to have triangle Cu3 core structures with C2 symmetry involving two Cu(CO)3 groups and one Cu(CO)x group (x = 1 or 2). In contrast, the trinuclear Cu3(CO)9(+) cluster cation is determined to have an open chain-like (OC)3Cu-Cu(CO)3-Cu(CO)3 structure. The tetranuclear Cu4(CO)8(+) cluster cation is characterized to have a tetrahedral Cu4(+) core structure with all carbonyl groups terminally bonded.