Abstract:
A long-standing challenge in photoinduced electron
transfer research is the design of compact donor−acceptor dyads
that can generate long-lived charge-separated (CS) states for use as
sensitizers in solar energy harvesting. Reports of dyads exhibiting CS
state lifetimes in the microsecond time domain are very rare. Herein,
we report two compact donor−bridge−acceptor dyads exhibiting
lifetimes in the microsecond domain. We employed an adamantane
moiety as a bridge, and the lifetimes obtained are nearly 1000-fold
larger when compared to those of the same donor−acceptor dyads bridged through C3-alkyl chains. In addition to long-lived CS
state decays, slow formation of acceptor triplets was also observed via nanosecond flash photolysis. The long lifetime of the CS state
is attributed to the extremely small value of the electronic coupling matrix element for the charge recombination compared to charge
separation.
