Photochemical and photophysical aspects of (1) triplet energy transfer (TET
) from triplet benzophenone (BP) to naphthalene derivatives (NpD) and (2) f
ormation and decay processes of triplet exciplexes between (NpD)-Np-3* and
BP have been studied by 355-nm laser photolysis techniques in the liquid ph
ase. As an initial event, TET occurs from (BP)-B-3* to NpD competing with H
-atom transfer (HT), electron transfer (ET), and induced quenching (IQ) on
the nanosecond time scale. The TET rate constant increases with an increase
of solvent polarity while that of HT decreases, indicating that the (3)(n,
pi*) state of BP is slightly mixed with (1)(pi, pi*) in polar media. After
formation of 3NpD* by TET from 3BP*, chemical reactions via triplet excipl
exes between (NpD)-Np-3* and BP having loose sandwich-like structures with
weak charge transfer character take place in the microsecond time scale, de
pending on the substituent groups of NpD. (1) HT from triplet 2-naphthylamm
oniun ion and triplet naphthol to BP occurs efficiently to yield the 2-naph
thylamine cation radical and naphthoxy radical plus the benzophenone ketyl
radical, respectively. The more protic H-atom in NpD is the more reactive i
n HT. (2) The proton-induced ET from triplet methoxynaphthalene to BP takes
place effectively via the protonated triplet exciplex to give the methoxyn
aphthalene cation and benzophenone ketyl radical. (3) Hydrogen bonding-indu
ced ET from triplet N, N-dialkyl-1-naphthylamine to BP occurs to yield the
N-dialkyl-1-naphthylamine cation radical and benzophenone anion radical in
the presence of protic solvents.