428
H. Kobayashi
developing a new ESR spin probe technique based on NN groups [27, 44]. For the
reasons described above, 1D OIC-OR represent an important new type of magnetic
material.
Both organic porous materials and metal organic frameworks [11, 13] can
be used as molecular templates for the array of guest radicals. In addition, 0D,
2D, or 3D porous materials may be employed to produce magnetic inclusion
compounds instead of those having 1D nanochannels. As an example, 2,4,6tris(4-bromophenoxy)-1,3,5-triazine (BRPOT: Scheme 12.1c) [50], one possible
derivative of 2,4,6-tris(4-halophenoxy)-1,3,5-triazine (XPOT: Scheme 12.1b–d),
can contain several different guest molecules, including Buckminsterfullerenes [54–
56]. However, the cavities of XPOT derivatives other than CLPOT do not necessarily
have 1D structures. These difference in morphology originate from the inter-atom
interactions between halogen atoms in the XPOT crystals [50].
In this review, the molecular orientations and dynamics of various guest radicals, as an example, 4-X-TEMPO, 4-XPNN, or PhIN, in CLPOT or TPP 1D
nanochannels are described based on the ESR analyses. In addition, the interspin interactions of 4-X-TEMPO radical chains formed in the CLPOT or TPP
nanochannels are explained in relation to the molecular dynamics of 4-X-TEMPO in
the nanochannels. In Sect. 12.2, theoretical background of ESR and the calculation
method in ESR simulation using EasySpin program [46, 47] are introduced. Sample
preparation and characterization of 1D OIC-OR are noted in Sect. 12.3. The
molecular dynamics of guest radicals in CLPOT- or TPP-based 1D OIC-ORs are
explained in Sects. 12.4 and 12.5, respectively. Remarkable exchange interaction
in CLPOT- or TPP-based 1D OIC-ORs with 4-X-TEMPO chains are explained in
Sect. 12.6. Finally, in Sect. 12.7, the conclusion and outlooks in the future of this
study are described.
12.2 Theoretical Background and ESR Simulation
12.2.1 Electron Spin Resonance
In ICs, magnetic resonance spectroscopy is a powerful means of elucidating the
molecular structures of host materials and the molecular orientations and the
dynamics of guest radicals in host nanochannels, in addition to assessing interspin interactions and magnetism of guest radical chains. When the researchers tune
into the unpaired electrons in guest radicals or the electric properties of 1D OICORs (as examples, conductivity, dielectric or magnetism), they may use electron
spin resonance (ESR) spectroscopy, whereas nuclear magnetic resonance (NMR)
spectroscopy is available for the study when they are interested in the molecular
structures or the dynamics of non-radical compounds. The reader is referred to
several texts that provide detailed discussions of magnetic resonance spectroscopy
[57–60].
H. Kobayashi
developing a new ESR spin probe technique based on NN groups [27, 44]. For the
reasons described above, 1D OIC-OR represent an important new type of magnetic
material.
Both organic porous materials and metal organic frameworks [11, 13] can
be used as molecular templates for the array of guest radicals. In addition, 0D,
2D, or 3D porous materials may be employed to produce magnetic inclusion
compounds instead of those having 1D nanochannels. As an example, 2,4,6tris(4-bromophenoxy)-1,3,5-triazine (BRPOT: Scheme 12.1c) [50], one possible
derivative of 2,4,6-tris(4-halophenoxy)-1,3,5-triazine (XPOT: Scheme 12.1b–d),
can contain several different guest molecules, including Buckminsterfullerenes [54–
56]. However, the cavities of XPOT derivatives other than CLPOT do not necessarily
have 1D structures. These difference in morphology originate from the inter-atom
interactions between halogen atoms in the XPOT crystals [50].
In this review, the molecular orientations and dynamics of various guest radicals, as an example, 4-X-TEMPO, 4-XPNN, or PhIN, in CLPOT or TPP 1D
nanochannels are described based on the ESR analyses. In addition, the interspin interactions of 4-X-TEMPO radical chains formed in the CLPOT or TPP
nanochannels are explained in relation to the molecular dynamics of 4-X-TEMPO in
the nanochannels. In Sect. 12.2, theoretical background of ESR and the calculation
method in ESR simulation using EasySpin program [46, 47] are introduced. Sample
preparation and characterization of 1D OIC-OR are noted in Sect. 12.3. The
molecular dynamics of guest radicals in CLPOT- or TPP-based 1D OIC-ORs are
explained in Sects. 12.4 and 12.5, respectively. Remarkable exchange interaction
in CLPOT- or TPP-based 1D OIC-ORs with 4-X-TEMPO chains are explained in
Sect. 12.6. Finally, in Sect. 12.7, the conclusion and outlooks in the future of this
study are described.
12.2 Theoretical Background and ESR Simulation
12.2.1 Electron Spin Resonance
In ICs, magnetic resonance spectroscopy is a powerful means of elucidating the
molecular structures of host materials and the molecular orientations and the
dynamics of guest radicals in host nanochannels, in addition to assessing interspin interactions and magnetism of guest radical chains. When the researchers tune
into the unpaired electrons in guest radicals or the electric properties of 1D OICORs (as examples, conductivity, dielectric or magnetism), they may use electron
spin resonance (ESR) spectroscopy, whereas nuclear magnetic resonance (NMR)
spectroscopy is available for the study when they are interested in the molecular
structures or the dynamics of non-radical compounds. The reader is referred to
several texts that provide detailed discussions of magnetic resonance spectroscopy
[57–60].