The Photochemistry of Polydonor-Substituted Phthalimides: Curtin-Hammett-Type Control of Competing Reactions of Potentially Interconverting Zwitterionic Biradical Intermediates

The results of studies designed to obtain information about the factors that control the chemical efficiencies/regioselectivities and quantum yields of single electron transfer (SET)-promoted reactions of acceptor−polydonor systems are reported. Photochemical and photophysical investigations were carried out with bis-donor tethered phthalimides and naphthalimides of general structure N-phthalimido- and N-naphthalimido-CH2CH2-D-CH2CH2-NMsCH2-E (E = SiMe3 or CO2NBu4 and D = NMs, O, S, and NMe). These substrates contain common terminal donor groups (NMsCH2SiMe3 or NMsCH2CO2NBu4) that have known oxidation potentials and cation radical fragmentation rates. Oxidation potentials and fragmentation rates at the other donor site in each of these substrates are varied by incorporating different heteroatoms and/or substituents. Photoproduct distribution, reaction quantum yield, and fluorescence quantum yield measurements were made. The results show that photocyclization reactions of α-trimethylsilylmethansulfonamide ...