458
H. Kobayashi
72]. The average molecular orientation of TEMPO in TPP nanochannel by rotational
diffusion provides homogeneous interaction between unpaired electrons in adjacent
TEMPOs. This scenario produces a large exchange integral, thus increasing the
efficiency of exchange narrowing. The exchange integral in this system may be
calculated based on the wavefunction perturbed by molecular motion of guest
radicals in TPP nanochannel. For these reasons, 1a/2a is a remarkable material,
as the dimensionality of the exchange interactions changes from 1D to 3D with
increasing temperature (compare this result to that in CLPOT above).
In other [TPP-(4-X-TEMPO)], a few interesting experimental results are known.
[(TPP) 2 -(DTBN) 1.3 ] (1a/2e) exhibits a similar effect of temperature on ΔB pp
to 1a/2a [42]. However, the ΔB pp
D value for 1a/2e estimated from Eq. (12.8)
(approximately 9 mT) is significantly larger than that for 1a/2a. Therefore, the
line width of 1a/2e is thought to be much narrower than that for 1a/2a. In
addition, the ESR line profiles for [(TPP) 2 -(DTBN) 1.3 ] (1a/2e) are also temperaturedependent, but 1D spin diffusion behavior is observed around room temperature
[42], while [TPP-TEMPONE] (1a/2b) shows temperature-dependent anisotropic
exchange interaction even in the vicinity of 4.2 K. Thus, [TPP-(4-X-TEMPO)] is
unique among the various 1D OIC-OR.
12.7 Concluding Remarks and Outlook
In CLPOT and TPP nanochannels, incorporated organic radicals form 1D organic
radical chain. To examine the 1D or 3D exchange interactions in 1D organic radical
chain, molecular dynamics of organic radicals in the nanochannels were assessed
by experimental and theoretical ESR analyses.
It was found that molecular dynamics of 4-X-TEMPO radical in CLPOT
nanochannel is independent of the substituent groups of the guest radicals and/or
the type of spacer. From ESR adsorption line profiles and the molecular dynamics
of 4-X-TEMPO radicals in CLPOT nanochannels, it was found that [CLPOT(4-X-TEMPO)] exhibits temperature-independent 3D exchange interactions. The
existence of 3D exchange interaction in [CLPOT-(4-X-TEMPO)] may be the first
step to express magnetic phase transition in 1D OIC-OR.
On the other hand, [TPP-(4-X-TEMPO)] exhibited temperature-dependent
anisotropic exchange interaction. It may be correlated with temperature dependency
on molecular dynamics of guest radical in TPP nanochannel with a small pore
diameter. These different exchange interaction in CLPOT and TPP nanochannels
will be a key to design and develop a new organic magnet.
The molecular dynamics of 4-XPNN and PhIN radicals in CLPOT or TPP
nanochannels was clarified using ESR analyses. These results may be available
to the development of a new ESR spin probe technique using NN or IN radicals
for the clarification of the structure of nanospaces in polymer, liquid crystal, and
membrane. It is expected that spin system based on 4-XPNN or PhIN radicals will
be formed in 1D OIC-OR by the increase of the guest inclusion amount.
H. Kobayashi
72]. The average molecular orientation of TEMPO in TPP nanochannel by rotational
diffusion provides homogeneous interaction between unpaired electrons in adjacent
TEMPOs. This scenario produces a large exchange integral, thus increasing the
efficiency of exchange narrowing. The exchange integral in this system may be
calculated based on the wavefunction perturbed by molecular motion of guest
radicals in TPP nanochannel. For these reasons, 1a/2a is a remarkable material,
as the dimensionality of the exchange interactions changes from 1D to 3D with
increasing temperature (compare this result to that in CLPOT above).
In other [TPP-(4-X-TEMPO)], a few interesting experimental results are known.
[(TPP) 2 -(DTBN) 1.3 ] (1a/2e) exhibits a similar effect of temperature on ΔB pp
to 1a/2a [42]. However, the ΔB pp
D value for 1a/2e estimated from Eq. (12.8)
(approximately 9 mT) is significantly larger than that for 1a/2a. Therefore, the
line width of 1a/2e is thought to be much narrower than that for 1a/2a. In
addition, the ESR line profiles for [(TPP) 2 -(DTBN) 1.3 ] (1a/2e) are also temperaturedependent, but 1D spin diffusion behavior is observed around room temperature
[42], while [TPP-TEMPONE] (1a/2b) shows temperature-dependent anisotropic
exchange interaction even in the vicinity of 4.2 K. Thus, [TPP-(4-X-TEMPO)] is
unique among the various 1D OIC-OR.
12.7 Concluding Remarks and Outlook
In CLPOT and TPP nanochannels, incorporated organic radicals form 1D organic
radical chain. To examine the 1D or 3D exchange interactions in 1D organic radical
chain, molecular dynamics of organic radicals in the nanochannels were assessed
by experimental and theoretical ESR analyses.
It was found that molecular dynamics of 4-X-TEMPO radical in CLPOT
nanochannel is independent of the substituent groups of the guest radicals and/or
the type of spacer. From ESR adsorption line profiles and the molecular dynamics
of 4-X-TEMPO radicals in CLPOT nanochannels, it was found that [CLPOT(4-X-TEMPO)] exhibits temperature-independent 3D exchange interactions. The
existence of 3D exchange interaction in [CLPOT-(4-X-TEMPO)] may be the first
step to express magnetic phase transition in 1D OIC-OR.
On the other hand, [TPP-(4-X-TEMPO)] exhibited temperature-dependent
anisotropic exchange interaction. It may be correlated with temperature dependency
on molecular dynamics of guest radical in TPP nanochannel with a small pore
diameter. These different exchange interaction in CLPOT and TPP nanochannels
will be a key to design and develop a new organic magnet.
The molecular dynamics of 4-XPNN and PhIN radicals in CLPOT or TPP
nanochannels was clarified using ESR analyses. These results may be available
to the development of a new ESR spin probe technique using NN or IN radicals
for the clarification of the structure of nanospaces in polymer, liquid crystal, and
membrane. It is expected that spin system based on 4-XPNN or PhIN radicals will
be formed in 1D OIC-OR by the increase of the guest inclusion amount.