Switching properties of a spiropyran-cucurbit[7]uril supramolecular assembly: usefulness of the anchor approach

Nilsson, Jesper R.; Carvalho, Cátia Parente; Li, Shiming; Silva, José P. da; Andreasson, Joakim; Pischel, Uwe

http://hdl.handle.net/10400.1/6557

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Authors

Nilsson, Jesper R.

Carvalho, Cátia Parente

Abstract(s)

A nitrospiropyran, which was modified with a cadaverine-derived anchor, was investigated with respect to its thermally induced isomerizations, hydrolytic stability of the merocyanine form, and photochromic ring closure. The hostguest complexation of the anchor by the cucurbit[7]uril macrocycle, evidenced by absorption titration, NMR spectroscopy, and electrospray ionization mass spectrometry, produced significant improvements of the switching properties of the photochrome: 1) appearance of the merocyanine form about 70 times faster, 2) practically unlimited hydrolytic stability of the merocyanine (two and a half days without any measureable decay), and 3) fast, clean, and fatigue-resistant photoinduced ring closure back to the spiro form. The importance of an adequate molecular design of the anchor was demonstrated by including control experiments with spiropyrans with a shorter linker or without such structural asset.