A series of stiff stilbene macrocycles have been studied to investigate the possible impact of macrocycle ring size on their photo-dynamic properties. The results show that reducing the ring size counteracts the photoisomerization ability of the macrocycles. However, even the smallest macrocycle studied (stiff stilbene subunits linked by a six carbon chain) showed some degree of isomerization when irradiated. DFT calculations of the energy differences between the E- and Z-isomers show the same trend as the experimental results. Interestingly the DFT study highlights that the energy difference between the E- and Z-isomers of even the largest macrocycle (linked by a twelve carbon chain) is significantly higher than that of the stiff stilbene unit itself. In general, it is indicated that addition of even a flexible chain to the stiff stilbene unit may significantly affect its photochemical properties and increase the photostability of the resulting macrocycle.
Keywords: stiff stilbene; photo-switch; ring-strain; photostability; DFT; molecular mechanics;
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Olsson, S.; Benito Pérez, Ó.; Blom, M.; Gogoll, A. Beilstein Arch. 2019, 201930. doi:10.3762/bxiv.2019.30.v1
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