High-resolution gas-phase spectroscopy of a single-bond axle rotary motor

High-resolution laser spectroscopy in combination with molecular beams and mass-spectrometry has been applied to study samples of a prototypical rotary motor. Vibrationally well-resolved excitation spectra have been recorded that are assigned, however, to a structural isomer of the original rotary motor which is formed in situ under the elevated temperatures required experimentally. In this isomer the ‘rotor’ and ‘stator’ parts are to a large extent conjugationally disconnected leading to excited-state properties that are dominantly determined by the ‘rotor’ with the ‘stator’ acting as observer.