Royal Society of Chemistry, Physical Chemistry Chemical Physics, 6(14), p. 1865-1875
DOI: 10.1039/c1cp22146a
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Time-resolved vibrational spectroscopy is used to investigate the inter-component motion of an ultraviolet-triggered two-station molecular shuttle. The operation cycle of this molecular shuttle involves several intermediate species, which are observable in the amide I and amide II regions of the mid-IR spectrum. Using ab initio calculations on specific parts of the rotaxane, and by comparing the transient spectra of the normal rotaxane with that of the N-deuterated version, we can assign the observed vibrational modes of each species occurring during the shuttling cycle in an unambiguous way. The complete time- and frequency-dependent data set is analyzed using singular value decomposition (SVD). Using a kinetic model to describe the time-dependent concentrations of the transient species, we derive the absorption spectra associated with each stage in the operation cycle of the molecular shuttle, including the recombination of the charged species.