448
H. Kobayashi
The 1a/2e/3d spectra at 214 K shown in Fig. 12.8 were accurately simulated
based on rotation around the axis defined by (θ , φ) = (86 ◦ , 89 ◦ ) in the principal
axis system of the g and A tensors in Table 12.3. These simulations assumed that
R || /R ⊥ had a value of approximately 1000, τ R was approximately 7.5 × 10 −9
s and that the line widths of the Gaussian and Loretzian components were 0.08
and 0.15 mT, respectively (see Sect. 12.2.3.4). The direction of the rotational axis
was estimated to be almost parallel to the principal y-axis (θ = 90 ◦ , φ = 90 ◦ ).
That is, the nitroxide groups of uniaxially rotating DTBN molecules confined in
TPP nanochannels are considered to be almost perpendicular to the rotational axis,
which in turn can be assumed to be parallel to the channel axis. When TEMPO or
TEMPONE are dispersed in TPP nanochannels, both the temperature dependency
of the ESR spectra and the molecular orientations of the guest radicals in the TPP
nanochannels are similar [40, 41]. In the range of 85–106 K, the ESR spectra were
reproduced by the superposition of a rigid component and an axially rotational
diffusion component, though it was not reproduced by simple rigid or axially
rotational diffusion components. These results provide evidence for the coexistence
of low- and high-temperature phases, in which the molecular motion of the guest
molecules is frozen out and unfrozen, respectively.
When TEMPOL is included as guest radical in TPP nanochannel, molecular
orientations and dynamics were quite different from DTBN and other 4-X-TEMPO.
Figure 12.9 shows the variable-temperature experimental and simulated ESR spectra
for a powdered sample of [(TPP) 2 -(TEMPOL) 0.004 /(TEMP) 1.2 ] (1a/2c/3a) [43]. At
55 K, the ESR spectrum of 1a/2c/3a demonstrates a rigid-limit for the nitroxide
radical that is similar to those of other radicals in the TPP and CLPOT nanochannels
(see Figs. 12.5 and 12.8 and Sect. 12.2.3.3). In addition, the principal components
of the g and A tensors in this case are comparable to those of other nitroxide radicals
(see Table 12.3). However, the spectra of 1a/2c/3a in the higher temperature region
(e.g., at 288 K in Fig. 12.9) are quite different from those in Figs. 12.5 or 12.8.
According to the spectral simulation, the rotational axis of the TEMPOL molecules
in the TPP nanochannels are tilted by (θ , φ) = (19 ◦ , 66 ◦ ) in the principal axis system
of the g and A tensors. These values are close to the principal z-axis of the g tensor
(corresponding to θ = 0 ◦ and an arbitrary φ; see Sect. 12.2.3.4). Thus, it appears that
the molecular orientations of guest radicals in TPP nanochannels can be adjusted by
the proper selection of guest radicals and spacer molecules, or the co-inclusion of
other radicals.
In addition, a rare example of the inclusion of IN or NN radicals in TPP
nanochannels has been demonstrated. Figure 12.10 presents the temperaturedependent ESR spectra for [(TPP) 2 -(PhIN) 0.002 /(N-PhMI) 1.0 ] (1a/2h/3e) [44]. Here,
green, yellow, and red lines indicate the rotational diffusion and rigid-limit components of PhIN in 1a/2h/3e as reproduced using EasySpin program and their
superposition. The spectra acquired at less than 165 K were well-reproduced
based on a rigid-limit powder pattern for isolated PhIN (see Sect. 12.2.3.3) [68].
The spectrum for 1a/2h/3e at 56 K shown in Fig. 12.10 was simulated using
the g and A tensor components in Table 12.3, and the respective Gaussian and
Lorentzian line width components were 0.31 and 0.30 mT. The values of the g
H. Kobayashi
The 1a/2e/3d spectra at 214 K shown in Fig. 12.8 were accurately simulated
based on rotation around the axis defined by (θ , φ) = (86 ◦ , 89 ◦ ) in the principal
axis system of the g and A tensors in Table 12.3. These simulations assumed that
R || /R ⊥ had a value of approximately 1000, τ R was approximately 7.5 × 10 −9
s and that the line widths of the Gaussian and Loretzian components were 0.08
and 0.15 mT, respectively (see Sect. 12.2.3.4). The direction of the rotational axis
was estimated to be almost parallel to the principal y-axis (θ = 90 ◦ , φ = 90 ◦ ).
That is, the nitroxide groups of uniaxially rotating DTBN molecules confined in
TPP nanochannels are considered to be almost perpendicular to the rotational axis,
which in turn can be assumed to be parallel to the channel axis. When TEMPO or
TEMPONE are dispersed in TPP nanochannels, both the temperature dependency
of the ESR spectra and the molecular orientations of the guest radicals in the TPP
nanochannels are similar [40, 41]. In the range of 85–106 K, the ESR spectra were
reproduced by the superposition of a rigid component and an axially rotational
diffusion component, though it was not reproduced by simple rigid or axially
rotational diffusion components. These results provide evidence for the coexistence
of low- and high-temperature phases, in which the molecular motion of the guest
molecules is frozen out and unfrozen, respectively.
When TEMPOL is included as guest radical in TPP nanochannel, molecular
orientations and dynamics were quite different from DTBN and other 4-X-TEMPO.
Figure 12.9 shows the variable-temperature experimental and simulated ESR spectra
for a powdered sample of [(TPP) 2 -(TEMPOL) 0.004 /(TEMP) 1.2 ] (1a/2c/3a) [43]. At
55 K, the ESR spectrum of 1a/2c/3a demonstrates a rigid-limit for the nitroxide
radical that is similar to those of other radicals in the TPP and CLPOT nanochannels
(see Figs. 12.5 and 12.8 and Sect. 12.2.3.3). In addition, the principal components
of the g and A tensors in this case are comparable to those of other nitroxide radicals
(see Table 12.3). However, the spectra of 1a/2c/3a in the higher temperature region
(e.g., at 288 K in Fig. 12.9) are quite different from those in Figs. 12.5 or 12.8.
According to the spectral simulation, the rotational axis of the TEMPOL molecules
in the TPP nanochannels are tilted by (θ , φ) = (19 ◦ , 66 ◦ ) in the principal axis system
of the g and A tensors. These values are close to the principal z-axis of the g tensor
(corresponding to θ = 0 ◦ and an arbitrary φ; see Sect. 12.2.3.4). Thus, it appears that
the molecular orientations of guest radicals in TPP nanochannels can be adjusted by
the proper selection of guest radicals and spacer molecules, or the co-inclusion of
other radicals.
In addition, a rare example of the inclusion of IN or NN radicals in TPP
nanochannels has been demonstrated. Figure 12.10 presents the temperaturedependent ESR spectra for [(TPP) 2 -(PhIN) 0.002 /(N-PhMI) 1.0 ] (1a/2h/3e) [44]. Here,
green, yellow, and red lines indicate the rotational diffusion and rigid-limit components of PhIN in 1a/2h/3e as reproduced using EasySpin program and their
superposition. The spectra acquired at less than 165 K were well-reproduced
based on a rigid-limit powder pattern for isolated PhIN (see Sect. 12.2.3.3) [68].
The spectrum for 1a/2h/3e at 56 K shown in Fig. 12.10 was simulated using
the g and A tensor components in Table 12.3, and the respective Gaussian and
Lorentzian line width components were 0.31 and 0.30 mT. The values of the g