72
J. Abe et al.
Fig. 4.11 Photochromic reaction schemes of 3H-NP, 8H-PQ, bis-NP, and bis-PQ
(Fig. 4.11). The two pyran units are perpendicularly connected to the central dihydroanthracene moiety through a spiro carbon of each pyran rings. Because the two
pyran units are electronically separated in the closed-closed form and the closedopen form, the energy transfer from the closed form to the open form can be negligible. Moreover, the substitution of a n-butoxy group to the 1-position of the 8H-PQ
units can increase the thermal decoloration rate of the transient open-ring form and
reduces the generation ratio of the long-lived TT form [56]. Therefore, bis-PQ is a
potential candidate to realize fast-switchable stepwise photochromism by controlling
excitation light conditions.
The X-ray crystallographic analysis of the crystal of bis-NP revealed that the two
pyran units are arranged perpendicularly against the central dihydroanthracene unit.
Figure 4.12 shows the UV-vis absorption spectra of bis-NP, bis-PQ, and 3H-NP in
Fig. 4.12 a UV-vis absorption spectra of bis-NP, bis-PQ, and 3H-NP in toluene and b molecular
structure of bis-NP obtained by the X-ray crystallography
J. Abe et al.
Fig. 4.11 Photochromic reaction schemes of 3H-NP, 8H-PQ, bis-NP, and bis-PQ
(Fig. 4.11). The two pyran units are perpendicularly connected to the central dihydroanthracene moiety through a spiro carbon of each pyran rings. Because the two
pyran units are electronically separated in the closed-closed form and the closedopen form, the energy transfer from the closed form to the open form can be negligible. Moreover, the substitution of a n-butoxy group to the 1-position of the 8H-PQ
units can increase the thermal decoloration rate of the transient open-ring form and
reduces the generation ratio of the long-lived TT form [56]. Therefore, bis-PQ is a
potential candidate to realize fast-switchable stepwise photochromism by controlling
excitation light conditions.
The X-ray crystallographic analysis of the crystal of bis-NP revealed that the two
pyran units are arranged perpendicularly against the central dihydroanthracene unit.
Figure 4.12 shows the UV-vis absorption spectra of bis-NP, bis-PQ, and 3H-NP in
Fig. 4.12 a UV-vis absorption spectra of bis-NP, bis-PQ, and 3H-NP in toluene and b molecular
structure of bis-NP obtained by the X-ray crystallography