TY - JOUR A1 - Hanopolskyi, Anton I. A1 - De, Soumen A1 - Białek, Michał J. A1 - Diskin-Posner, Yael A1 - Avram, Liat A1 - Feller, Moran A1 - Klajn, Rafal T1 - Reversible switching of arylazopyrazole within a metal–organic cage JF - Beilstein Journal of Organic Chemistry PY - 2019/// VL - 15 SP - 2398 EP - 2407 SN - 1860-5397 DO - 10.3762/bjoc.15.232 PB - Beilstein-Institut JA - Beilstein J. Org. Chem. UR - https://doi.org/10.3762/bjoc.15.232 KW - arylazopyrazoles KW - coordination cages KW - inclusion complexes KW - molecular switches KW - photochromism N2 - Arylazopyrazoles represent a new family of molecular photoswitches characterized by a near-quantitative conversion between two states and long thermal half-lives of the metastable state. Here, we investigated the behavior of a model arylazopyrazole in the presence of a self-assembled cage based on Pd–imidazole coordination. Owing to its high water solubility, the cage can solubilize the E isomer of arylazopyrazole, which, by itself, is not soluble in water. NMR spectroscopy and X-ray crystallography have independently demonstrated that each cage can encapsulate two molecules of E-arylazopyrazole. UV-induced switching to the Z isomer was accompanied by the release of one of the two guests from the cage and the formation of a 1:1 cage/Z-arylazopyrazole inclusion complex. DFT calculations suggest that this process involves a dramatic change in the conformation of the cage. Back-isomerization was induced with green light and resulted in the initial 1:2 cage/E-arylazopyrazole complex. This back-isomerization reaction also proceeded in the dark, with a rate significantly higher than in the absence of the cage. ER -