To assess photoswitching of I-III we used an LED irradiation platform (see supporting information) and initially characterised the photoisomerization behaviour using UV-Vis absorption spectroscopy. In accordance with previous studies on compound I, we irradiated the samples in the visible range at 405 nm and 530 nm to exploit the n→π* absorption bands of the photoresponsive azobenzene moiety. The UV-Vis spectra were recorded after irradiation of 0.01 mM samples for 10 minutes. Blue light (405 nm) was used to produce the E isomer of each compound I-III and green light (530 nm) was used to generate the Z isomer. Upon exposing blue light irradiated samples to green light, the absorption maxima underwent a hypsochromic shift. Upon re-irradiation with blue light, back-switching was achieved as evidenced by the corresponding bathochromic shift of the absorption maxima (Fig. ). For 1 H NMR studies, solutions were prepared in anhydrous deuterochloroform (4 mM) and irradiated with blue light (405 nm) for 10 min and green light (530 nm) for 10 min. H NMR spectra showed evidence of switching via a change of environment for key proton resonances (Fig. ). The ratio of E/Z isomers could be estimated from the integrals of the azobenzene protons, which show characteristic changes in chemical shift (δ) after irradiation. The distribution at the photo-stationary state for compound I was found to be 13:87 Z:E after irradiation at 405 nm and 85:15 Z:E after irradiation at 530 nm, similar to the previously reported values. For compound II the distribution at the photo-stationary state after irradiation at 405 nm was 27:73 Z:E and 71:29