12 Inter-spin Interactions of Organic Radical Chains in Organic 1D. . .
443
as generated using the EasySpin program (see Sect. 12.2.3.2) [46, 47], and their
superpositions, respectively. The spin concentration for each sample remained
unchanged after the temperature-dependent ESR analyses. The ESR spectra below
102 K for 1b/2d/3b were reproduced on the basis of a rigid-limit powder pattern
showing an isolated nitroxide radical (see Sect. 12.2.3.3). The ESR spectra in this
figure do not include fine structure peaks originating from the formation of radical
clusters [37] in the CLPOT nanochannels. Therefore, at these low temperatures,
the MeO-TEMPO radicals in 1b/2d/3b were evidently adequately isolated and
did not exhibit molecular motion on the ESR time scale (i.e., τ R > 10 −6 s). The
experimental 1b/2d/3b ESR spectra in Fig. 12.5 were generated using the g and
A tensor components in Table 12.3. The Gaussian and Lorentzian line widths of
these components were 0.56 and 0.24 mT, respectively. The values for the g and
A tensors for 1b/2d/3b were estimated using the Pepper program within EasySpin
program (see Sect. 12.2.3.2 and Table 12.3) and were consistent with values reported
previously for different 4-X-TEMPO compounds under other conditions (see Table
12.3).
The ESR spectra for 1b/2d/3b shown in Fig. 12.5 evidently change with
increasing temperature, in accordance with a model for the anisotropic rotational
diffusion of nitroxide radicals within the slow-motion region relative to the ESR
time scale (10 −9 < τ R <10 −6 ) (see Sect. 12.2.3.4). Over the range of 255–290 K,
these spectra can be simulated using the Chili program within EasySpin. The
ESR spectra at 290 K were reproduced by assuming rotational diffusion around
an axis tilted by (θ , ϕ) = (65 ◦ , 42 ◦ ) relative to the principal g tensor system,
with Gaussian and Lorentzian line width components of 0.011 and 0.19 mT,
respectively, and τ R equal to 6.5 × 10 −9 s. The spectra for temperatures above
255 K were also accurately simulated based on the anisotropic rotational diffusion
model around the same rotation axis applied in the case of the 290 K data. The
results obtained for CLPOT nanochannel incorporated 4-X-TEMPO with a spacer
other than TEMP gave similar (θ , ϕ) values [51, 52]. These results demonstrate that
the molecular orientations of guest 4-X-TEMPO molecules in CLPOT nanochannels
are independent of the specific 4-position substituent group or spacer molecules.
In contrast, the 1b/2d/3b spectra obtained in the intermediate-temperature range
(153–231 K) were reproduced using a superposition of rigid and anisotropic
rotational diffusion (i.e., mobile) components (yellow and green, respectively, in
Fig. 12.5). The mobile components in this temperature range were based on the
rotational diffusion model previously discussed, around the same rotational axis as
had been applied when working with the 290 K data, but with longer τ R values (Fig.
12.5). With increasing temperature, the peak intensities of the rigid components
were reduced, whereas those of the mobile components were increased due to the
wide distribution of τ R resulting from the local inhomogeneity of the host structure
and/or guest packing in these ICs.
The procedure applied for 1b/2d/3b are also available for 4-XPNN radicals,
of which molecular orientations and dynamics in nanospaces were not adequately
known before [66]. Figure 12.6 presents the temperature-dependent ESR spectra
for [(CLPOT) 2 -(p-NPNN) 0.04 /(N-PhMI) 0.5 ] (1b/2g/3e) over the temperature range
from 255 to 398 K [27]. The red lines in Fig. 12.6 indicate simulated 1b/2g/3e
443
as generated using the EasySpin program (see Sect. 12.2.3.2) [46, 47], and their
superpositions, respectively. The spin concentration for each sample remained
unchanged after the temperature-dependent ESR analyses. The ESR spectra below
102 K for 1b/2d/3b were reproduced on the basis of a rigid-limit powder pattern
showing an isolated nitroxide radical (see Sect. 12.2.3.3). The ESR spectra in this
figure do not include fine structure peaks originating from the formation of radical
clusters [37] in the CLPOT nanochannels. Therefore, at these low temperatures,
the MeO-TEMPO radicals in 1b/2d/3b were evidently adequately isolated and
did not exhibit molecular motion on the ESR time scale (i.e., τ R > 10 −6 s). The
experimental 1b/2d/3b ESR spectra in Fig. 12.5 were generated using the g and
A tensor components in Table 12.3. The Gaussian and Lorentzian line widths of
these components were 0.56 and 0.24 mT, respectively. The values for the g and
A tensors for 1b/2d/3b were estimated using the Pepper program within EasySpin
program (see Sect. 12.2.3.2 and Table 12.3) and were consistent with values reported
previously for different 4-X-TEMPO compounds under other conditions (see Table
12.3).
The ESR spectra for 1b/2d/3b shown in Fig. 12.5 evidently change with
increasing temperature, in accordance with a model for the anisotropic rotational
diffusion of nitroxide radicals within the slow-motion region relative to the ESR
time scale (10 −9 < τ R <10 −6 ) (see Sect. 12.2.3.4). Over the range of 255–290 K,
these spectra can be simulated using the Chili program within EasySpin. The
ESR spectra at 290 K were reproduced by assuming rotational diffusion around
an axis tilted by (θ , ϕ) = (65 ◦ , 42 ◦ ) relative to the principal g tensor system,
with Gaussian and Lorentzian line width components of 0.011 and 0.19 mT,
respectively, and τ R equal to 6.5 × 10 −9 s. The spectra for temperatures above
255 K were also accurately simulated based on the anisotropic rotational diffusion
model around the same rotation axis applied in the case of the 290 K data. The
results obtained for CLPOT nanochannel incorporated 4-X-TEMPO with a spacer
other than TEMP gave similar (θ , ϕ) values [51, 52]. These results demonstrate that
the molecular orientations of guest 4-X-TEMPO molecules in CLPOT nanochannels
are independent of the specific 4-position substituent group or spacer molecules.
In contrast, the 1b/2d/3b spectra obtained in the intermediate-temperature range
(153–231 K) were reproduced using a superposition of rigid and anisotropic
rotational diffusion (i.e., mobile) components (yellow and green, respectively, in
Fig. 12.5). The mobile components in this temperature range were based on the
rotational diffusion model previously discussed, around the same rotational axis as
had been applied when working with the 290 K data, but with longer τ R values (Fig.
12.5). With increasing temperature, the peak intensities of the rigid components
were reduced, whereas those of the mobile components were increased due to the
wide distribution of τ R resulting from the local inhomogeneity of the host structure
and/or guest packing in these ICs.
The procedure applied for 1b/2d/3b are also available for 4-XPNN radicals,
of which molecular orientations and dynamics in nanospaces were not adequately
known before [66]. Figure 12.6 presents the temperature-dependent ESR spectra
for [(CLPOT) 2 -(p-NPNN) 0.04 /(N-PhMI) 0.5 ] (1b/2g/3e) over the temperature range
from 255 to 398 K [27]. The red lines in Fig. 12.6 indicate simulated 1b/2g/3e