Expected and unexpected photoreactions of 9-(10-)substituted anthracene derivatives in cucurbit[]uril hosts.

By arranging substrates in a "reaction ready" state through noncovalent interactions, supramolecular nanoreactors/catalysts show high selectivity and/or rate acceleration features. Herein, we report the host-guest complexation of 9-(10-)substituted anthracene derivatives () with cucurbit[]uril (CB[], = 8, 10), and the photoreactions of these derivatives in the presence of CB[] hosts. Both CB[10] and CB[8] showed no obvious effects on the photoreaction of 9,10-disubstituted derivative . For and , CB[10] operated as either a nanoreactor or catalyst (10%) for the photodimerization of two compounds with high selectivity and high yield. However, although CB[8] formed a 1 : 2 complex with , as also observed with CB[10], the photosolvolysis product (9-anthracenemethanol) was obtained quantitatively after photoirradiation of the CB[8]·2 complex. This unexpected photosolvolysis was rationalized by a plausible catalytic cycle in which anthracene acts as a photoremovable protecting group (PPG) and the carbonium ion intermediate is stabilized by CB[8].