432
H. Kobayashi
The principal axes of the g tensor of the PhIN radical are assumed to be similar
to those of the 4-XPNN radical and also consistent with NN due to the higher spin
density on the NO group [44]. However, it should be noted that A 1 = A 2 for IN
radicals ((A 1 ) iso > (A 2 ) iso ), [44, 67] where A 1 is the hyperfine tensor of the NO
nitrogen of the IN groups and A 2 is that of the 3-position nitrogen. Since the xx and
yy components of A 1 and A 2 are much smaller than the zz component, the principal
axes of the g, A 1 , and A 2 tensors for the IN radicals are also assumed to be coincident
to allow for simplified calculations, similar to the procedure for 4-XPNN radicals.
12.2.3.2 Calculation Procedure
To the determine the molecular orientations and dynamics of guest radicals in 1D
nanochannels, the ESR spectra of isolated radicals must be reproduced in detail,
because these spectra provide information concerning the principal values of the
g and A tensors. Such spectra can be generated based on theoretical calculations.
EasySpin program is a component of the MATLAB software package (MathWorks,
Natick, MA, USA), developed by Stoll and intended for the simulation and fitting
of a wide range of ESR spectra (EasySpin 5.2.20, ETH Zürich) [46, 47]. EasySpin
program provides extensive ESR-related functionality, ranging from spin physics
to data analysis. This software also contains routines for the simulation of liquidand solid-state ESR and electron-nuclear double resonance data. The programming
language of MATLAB is based on matrices and very efficient matrix algorithms, and
EasySpin program consists of over 80 MATLAB functions that perform a variety of
ESR-related tasks. Functions from the larger and more basic category provide the
core functionality necessary for computational ESR. Building on this foundation,
a small number of general, robust high-level functions for spectral simulation are
provided.
This sub-subsection references a number of programs. These include the Pepper,
which is used to produce the field-swept and frequency-swept solid-state cw ESR
spectra of powders and crystals; Chili, which simulates field- and frequency-swept
cw ESR spectra in the slow-motion regime on the ESR time scale; and Garlic,
which produces the isotropic or anisotropic fast-motion cw ESR spectra of radicals
in solution or nanospaces. Calculations for 4-XPNN and PhIN radicals with two
14 N atoms (I = 1) based on the interactions of electron spins can be performed
using a PC with more than 8 GB of RAM. Chili requires more memory to
generate spectral reproductions for 4-XPNN or PhIN radicals, and so the allocation
function of Opt within the program parameters, as an example, should be set to
Opt.Allocation = [4e7 2e5] [47].
12.2.3.3 Rigid-Limit ESR Spectra
Figure 12.2 presents typical rigid-limit ESR spectra for nitroxide, NN, and IN
radicals as simulated using the EasySpin Pepper program to calculate solid-state
H. Kobayashi
The principal axes of the g tensor of the PhIN radical are assumed to be similar
to those of the 4-XPNN radical and also consistent with NN due to the higher spin
density on the NO group [44]. However, it should be noted that A 1 = A 2 for IN
radicals ((A 1 ) iso > (A 2 ) iso ), [44, 67] where A 1 is the hyperfine tensor of the NO
nitrogen of the IN groups and A 2 is that of the 3-position nitrogen. Since the xx and
yy components of A 1 and A 2 are much smaller than the zz component, the principal
axes of the g, A 1 , and A 2 tensors for the IN radicals are also assumed to be coincident
to allow for simplified calculations, similar to the procedure for 4-XPNN radicals.
12.2.3.2 Calculation Procedure
To the determine the molecular orientations and dynamics of guest radicals in 1D
nanochannels, the ESR spectra of isolated radicals must be reproduced in detail,
because these spectra provide information concerning the principal values of the
g and A tensors. Such spectra can be generated based on theoretical calculations.
EasySpin program is a component of the MATLAB software package (MathWorks,
Natick, MA, USA), developed by Stoll and intended for the simulation and fitting
of a wide range of ESR spectra (EasySpin 5.2.20, ETH Zürich) [46, 47]. EasySpin
program provides extensive ESR-related functionality, ranging from spin physics
to data analysis. This software also contains routines for the simulation of liquidand solid-state ESR and electron-nuclear double resonance data. The programming
language of MATLAB is based on matrices and very efficient matrix algorithms, and
EasySpin program consists of over 80 MATLAB functions that perform a variety of
ESR-related tasks. Functions from the larger and more basic category provide the
core functionality necessary for computational ESR. Building on this foundation,
a small number of general, robust high-level functions for spectral simulation are
provided.
This sub-subsection references a number of programs. These include the Pepper,
which is used to produce the field-swept and frequency-swept solid-state cw ESR
spectra of powders and crystals; Chili, which simulates field- and frequency-swept
cw ESR spectra in the slow-motion regime on the ESR time scale; and Garlic,
which produces the isotropic or anisotropic fast-motion cw ESR spectra of radicals
in solution or nanospaces. Calculations for 4-XPNN and PhIN radicals with two
14 N atoms (I = 1) based on the interactions of electron spins can be performed
using a PC with more than 8 GB of RAM. Chili requires more memory to
generate spectral reproductions for 4-XPNN or PhIN radicals, and so the allocation
function of Opt within the program parameters, as an example, should be set to
Opt.Allocation = [4e7 2e5] [47].
12.2.3.3 Rigid-Limit ESR Spectra
Figure 12.2 presents typical rigid-limit ESR spectra for nitroxide, NN, and IN
radicals as simulated using the EasySpin Pepper program to calculate solid-state