In this study, we have investigated the photochemical properties and photodynamic effects of
ruthenium phthalocyanine (RuPc(
CO)(Py)) and naphthalocyanine (RuNc(
CO)(Py)) complexes. When a nanosecond-
pulsed laser is used, the photodecarbonylation of our Ru complexes efficiently proceeds via stepwise two-photon excitation, while the reaction yields are negligibly small when a continuous-wave (CW)
laser is employed. The
pulsed laser selective photodecarbonylation decreases the Q-band absorbance, which satisfies what the
photodynamic therapy (
PDT) requires of the photobleaching. For RuPc(
CO)(Py), the photochemical reactions including both the photodecarbonylation and just photobleaching occur in HeLa cells in vitro. Toxicity and
phototoxicity tests indicate that our RuPc(
CO)(Py) and RuNc(
CO)(Py) complexes in concentrations of 0.3-1 microM and 1-2 microM, respectively, are applicable as
PDT agents. The
phototoxicity is consistent with the photochemical properties of these complexes, namely, excited triplet lifetimes (10 and 4.8 micros for the Pc and Nc complexes, respectively) and
singlet oxygen yields (0.48 and 0.35 for the Pc and Nc complexes, respectively). On the basis of these results, we propose a novel concept for achieving a greater depth of
necrosis in
PDT as follows: (1)
PDT of upper cellular layers using CW-
laser irradiation; (2) efficient photobleaching in upper cellular layers using
pulsed dye-laser irradiation, which results in an increase in the therapeutic depth of red light; (3)
PDT directed toward deeper
tumor tissues using CW
laser irradiation. In addition, these Ru complexes are promising as CO release agents for investigative biochemistry.