Photo-responsive catenanes: synthesis and properties†
A series of novel dithienylethene-based macrocycles containing ammonium moieties has been synthesized. They have been employed as templates to construct catenanes showing their photoisomerization properties by means of a dynamic covalent chemistry approach. Their structures have been reliably confirmed by NMR, ESI-MS or MALDI-QTOF-MS, and elemental analysis, and their energy-minimized structures of open- and closed-ring isomers were investigated by the theoretical calculation. Investigation of the photochromic properties of these dithienylethene-based catenanes has revealed good reversibility and excellent fatigue resistance upon irradiation with UV or visible light. Notably, formation of the catenanes enhanced the photochromic properties compared with those of the corresponding macrocyclic ammonium salt, implying that the non-covalently interacting components of the catenanes could affect the photoswitchable properties.