Self-assembled coordination cage as a reaction vessel: triplet sensitized [2+2] photodimerization of acenaphthylene, and [4+4] photodimerization of 9-anthraldehyde

Inner cavity of Pd-nanocage has been used as a reaction vessel for performing triplet sensitized 2+2] photodimerization of acenaphthylene using water soluble xanthene dyes (Eosin Y and Rose Bengal) as sensitizers, and 4+4] photodimerization of 9-anthraldehyde. Although the 4+4] photodimerization of 9-anthraldehyde gave similar results to solution reaction, the xanthene dye sensitized 2+2] triplet state photodimerization of acenaphthylene encapsulated within Pd-nanocage yielded the syn dimer in quantitative yield. The results obtained from the triplet state 2+2] photodimerization of acenaphthylene within Pd-nanocage is remarkable given the fact that the photodimerization reaction when performed in methanol in the presence of Eosin Y and Rose Bengal gave the syn and anti dimers in the ratio 0.5 and 0.6, respectively. Preaggregation of molecules encapsulated inside Pd-nanocage in a syn fashion seems to be the governing factor for such a behavior.