Supramolecular triplet photosensitizer.: Effects of the cation binding mode on E-Z isomerization of 1,2-dichloroethylene

Effects of metal cation recognition on photosensitized E-Z isomerization of 1,2-dichloroethylene have been investigated with two types of m,p- and o,o'-podand (oligo-oxyethylene unit) benzophenones 2 and 3. With increasing cation size, the %Z ratio at the photostationary state was changed from 67 to 91% for 2 but remained almost unchanged (86-88%) for 3. These results were interpreted in terms of the variation of excited triplet energy, E-T, associated with the cation complexation of these photosensitizers 2 and 3.