4
H. Miyasaka et al.
experimental results by the two-color stepwise excitation and simultaneous twophoton excitation.
As the second topic, we show the one-color control of fluorescence activation,
deactivation, and excitation of a fluorescent diarylethene derivative. In this system,
a one-color laser light takes various roles through the synergetic interaction between
the material and the light and enables the long-term fluorescence imaging with superresolution.
In the third topic, we introduce the mesoscopic motion of nano- to micron-sized
materials under the laser trapping, which is controlled by the photochromic reactions
of molecules inside the materials. Integration of lasers with the photochemical reaction demonstrates the controlled mesoscopic motion which can amplify the chemical
reaction in molecular levels into the mesoscopic translational movements.
1.2 Multiphoton-Gated Cycloreversion Reaction at Higher
Excited States of 6π Electron Systems
Cyclization and cycloreversion between 1,3,5-hexatriene and 1,3-cyclohexadiene are
typical reactions of 6π electron systems, where the relation between the structure of
the product and the orbital symmetry of the reactant is regulated by the Woodward–
Hoffmann rules [1]. Diarylethene and fulgide derivatives are typical photochromic
molecules undergoing photoinduced cyclization and cycloreversion, which can be
regarded as 6π electrocyclic reactions in principle [2–4]. From viewpoints of the
elucidation of fundamental photochemical reactions as well as the application to
photofunctional molecular materials, these photochromic systems have been long
investigated.
We reported that the cycloreversion reaction of these derivatives in solution,
polymer matrices, and in crystalline phase takes place very efficiently in higher
excited state attained by the visible stepwise two-photon excitation under the pulsed
laser excitation [5–12]. For derivatives with the low cycloreversion reaction yield of
place by the one-photon excitation whose photon energy is almost the same with
that of the two-photon of the visible light, as shown in Fig. 1.1. This result strongly
suggested that the excited state accessible only by the two-photon absorption takes
an important role in the drastic enhancement of the cycloreversion reaction. This
multiphoton-gated reaction is one of the rare responses in polyatomic molecules
depending on the specific high electronic state that are not easily accessible by the
one-photon absorption. The elucidation of the mechanism is quite important for
the control of the photochemical reaction by the multiple laser excitations [13–17]
and development of the photo-function of these molecular materials. In this project,
we applied femtosecond two-color two-pulse excitation to precisely elucidate the
mechanism of this specific reaction channel.
H. Miyasaka et al.
experimental results by the two-color stepwise excitation and simultaneous twophoton excitation.
As the second topic, we show the one-color control of fluorescence activation,
deactivation, and excitation of a fluorescent diarylethene derivative. In this system,
a one-color laser light takes various roles through the synergetic interaction between
the material and the light and enables the long-term fluorescence imaging with superresolution.
In the third topic, we introduce the mesoscopic motion of nano- to micron-sized
materials under the laser trapping, which is controlled by the photochromic reactions
of molecules inside the materials. Integration of lasers with the photochemical reaction demonstrates the controlled mesoscopic motion which can amplify the chemical
reaction in molecular levels into the mesoscopic translational movements.
1.2 Multiphoton-Gated Cycloreversion Reaction at Higher
Excited States of 6π Electron Systems
Cyclization and cycloreversion between 1,3,5-hexatriene and 1,3-cyclohexadiene are
typical reactions of 6π electron systems, where the relation between the structure of
the product and the orbital symmetry of the reactant is regulated by the Woodward–
Hoffmann rules [1]. Diarylethene and fulgide derivatives are typical photochromic
molecules undergoing photoinduced cyclization and cycloreversion, which can be
regarded as 6π electrocyclic reactions in principle [2–4]. From viewpoints of the
elucidation of fundamental photochemical reactions as well as the application to
photofunctional molecular materials, these photochromic systems have been long
investigated.
We reported that the cycloreversion reaction of these derivatives in solution,
polymer matrices, and in crystalline phase takes place very efficiently in higher
excited state attained by the visible stepwise two-photon excitation under the pulsed
laser excitation [5–12]. For derivatives with the low cycloreversion reaction yield of
place by the one-photon excitation whose photon energy is almost the same with
that of the two-photon of the visible light, as shown in Fig. 1.1. This result strongly
suggested that the excited state accessible only by the two-photon absorption takes
an important role in the drastic enhancement of the cycloreversion reaction. This
multiphoton-gated reaction is one of the rare responses in polyatomic molecules
depending on the specific high electronic state that are not easily accessible by the
one-photon absorption. The elucidation of the mechanism is quite important for
the control of the photochemical reaction by the multiple laser excitations [13–17]
and development of the photo-function of these molecular materials. In this project,
we applied femtosecond two-color two-pulse excitation to precisely elucidate the
mechanism of this specific reaction channel.