Paracyclophanes
(PCPs), which exhibit interesting properties due
to their transannular interactions, have been employed as a spacer
in various electron transfer (ET) systems. In the present work, we
investigated ET processes in dyads and triads containing [2.2]PCP
or [3.3]PCP as donors to study their properties in multistep ET processes.
The dyad molecules of PCP and 1,8-naphthalimide (NI) as a photosensitizing
electron acceptor exhibited charge separation (CS) upon excitation
of NI. In addition, triads of NI, PCP, and carbazole showed charge
shift after an initial CS, thus confirming multistep ET. In this study,
we demonstrated that use of [3.3]PCP in place of [2.2]PCP enhanced
the initial CS rate. Lower oxidation potentials and a smaller reorganization
energy for [3.3]PCP are shown to be key factors for this enhanced
CS rate. Both of these properties are closely related to the strained
structure of PCP; hence, the present results demonstrate the importance
of strain in ET chemistry.