Photodimerization-induced transition of helixes to vesicles based on coumarin-12-crown-4

Rational construction of fine-tuning and precisely controllable topological nanostructures based on supramolecular self-assembly system remains a challenge. Herein, coumarin-12-crown-4 (1) as a building block was synthesized by one-pot method and showed reversible high stereo-selective photodimerization (anti-head-to-head dimer (anti-HH-1): syn-head-to-head dimer (syn-HH-1) = 10.8:1) and photocleavage. Helical nanobelts were formed by the self-assembly of 1 through asymmetrical H-bonds, which were in concordance with the crystal state superstructure. Upon irradiation with 365 nm light, these nanobelts transformed into nanoballs which were constructed by three building blocks. Further, we investigated the photoreaction of 1 and got two pure covalent dimers (anti-HH-1 and syn-HH-1). The anti-HH-1 self-assembled into hollow micro-vesicles. The transformation of superstructures based on photo-controlled multiple blocks shines a light to the research on the relationship between molecules and superstructures.