Self-assembled boronic ester cavitand capsule as a photosensitizer and a guard nanocontainer against photochemical reactions of 2,6-diacetoxyanthracene.

The optical properties of 2,6-diacetoxyanthracene 4 encapsulated in the self-assembled boronic ester cavitand capsule 3 in C(6)H(6) are described. Upon excitation at 285 nm, the encapsulated 4 showed strong fluorescence emission as a result of the energy transfer from the excited 3 to the encapsulated 4, while 4 alone in C(6)H(6) exhibited very weak emission. Upon photoirradiation at 365 nm, the encapsulated 4 also showed strong fluorescence emission and remained almost intact, whereas 4 alone in C(6)H(6) gradually underwent photodimerization and photooxygenation to afford photodimers 5 and 5' and 9,10-anthraquinone 6 via 9,10-endoperoxide 7, respectively. Thus, the capsule 3 serves as a photosensitizer for the encapsulated 4 as well as a guard nanocontainer to protect against the photochemical reactions of 4.