Photoinduced Homolysis of Alkyl–Cobalt(III) Bonds in a Cyclodextrin Cage

Photodecomposition of methyl– and ethyl–Co III complexes of meso ‐tetrakis(4‐sulfonatophenyl)porphyrin (CH 3 – and C 2 H 5 –Co III TPPSs) was used as a reaction probe to study the cage effect of cyclodextrin capsules formed by two per‐ O ‐methylated β‐cyclodextrin (TMe‐β‐CD) molecules and their covalently linked dimer, Ph2CD. The photodecomposition of CH 3 –Co III TPPS under aerobic conditions was markedly suppressed in the presence of TMe‐β‐CD and Ph2CD, while C 2 H 5 –Co III TPPS was less affected. Alkyl–Co III TPPS formed two types of inclusion complex with Ph2CD, the alkyl groups in Type 1 being located at the opposite side of the phenyl linker of Ph2CD and those in Type 2 being located at the same side. The photodecomposition of C 2 H 5 –Co III TPPS in Type 1 proceeded via an ethylperoxo complex, while that in Type 2 occurred via a radical pair generated in a narrow, rigid cage to form ethylene and Co II TPPS.