The nonclassical [Rh(CO)(4)](+) cation is luminescent at low temperature with a peak maximum at 19640 cm(-1) and a full-width at half-maximum of 2900 cm(-1). Both the solution absorption and low-temperature solid-state luminescence spectra of the [Rh(CO)(4)](1-Et-CB11F11) salt are reported. The cesium salt of the [1-Et-CB11F11]counterion is also luminescent (with a peak maximum at 22650 cm(-1)), but the emission maximum of [Rh(CO)(4)](+) is lower in energy. The Rh-C bond length changes of similar to0.07 Angstrom in the excited state are calculated. The calculated bond length changes in the nonclassical [Rh(CO)(4)](+) ion are not very different from those in classical complexes.