As previously described for the photoisomerisation experiments, an in-situ UV-Vis action plot was performed, while each sample was simultaneously irradiated with an identical photon flux at different excitation wavelengths. No evidence of any cis-PyChal formation was observed for these molecules, so experiments were performed without degassing. The results are shown in Figure for molecules D2 to D4, with the initial linear rate of conversion for each excitation wavelength shown. Here, the rate of conversion is seen to closely resemble the molar absorptivity spectrum of trans-PyChal, suggesting that the most important factor in conversion is the wavelengthdependent absorption of light by the molecule. There is a clear difference between the reactivity for the monomer in free solution, and for the tethered series of monomers, with the mismatch in reactivity not nearly as present in the D2-4 molecules, while a difference of 50 nm is seen for the trans-PyChal monomers in solution (Figure ).