Inter-spin Interactions of Organic Radical Chains in Organic 1D Nanochannels: An ESR Study of the Molecular Orientations and Dynamics of Guest Radicals

Investigation of Various Organic Radicals Dispersed in Polymethylmethacrylate Matrices Using the Electron Spin Resonance Spectroscopy Technique

“…The lowest component of the g tensor should be observed perpendicular to the molecular plane of the BzNN group, that is , along the principal z axis . It should be approximately 2.0023. ,, As g xx > g yy > g zz for the 4- Y -PhBzNN radical, the intensity of the g xx component is observed at the region of the lowest magnetic field.…”

“…The Hamiltonian functions reported in the literature were used to describe the free radicals dispersed in the organic matrices and 1D nanochannels. ,,− Previously reported calculation methods were followed to describe the system where PMMA was used as the organic matrix. NO, 2- X -NN, 4- Y -PhBzNN, and 2- Z -IN radicals in the matrices were characterized as follows using the spin Hamiltonian: where β e , B , g , A (N i ), A (H j ), β n , g n (N i ), g n (H j ), Ŝ , and Î denote the Bohr magneton; laboratory magnetic flux density vector; electron spin g tensor; hyperfine tensor for the i th 14 N nucleus of the NO, 2- X -NN, 4- Y -PhBzNN, and 2- Z -IN radicals ( i = 1 or 2); superhyperfine tensor of j th 1 H nucleus of 4- Y -PhBzNN ( j = α, β, o , m , or p ; the protons at α and α′, β and β′, o and o ′, or m and m ′ are equivalent due to molecular symmetry; Figure c); nuclear magneton; nuclear spin g tensor of the i th 14 N nucleus of the NO, 2- X -NN, 4- Y -PhBzNN, and 2- Z -IN radicals; nuclear spin g tensor of the j th 1 H nucleus of 4- Y -PhBzNN; electron spin operator; and nuclear spin operator, respectively.…”

“…The principal axes of the g tensor of the NO, 2- X -NN, and 2- Z -IN radicals were defined following previous reports. ,,,, The g tensor corresponding to the 4- Y -PhBzNN radical was then determined. The unpaired electron present in the BzNN group was present in the π orbital.…”

“…The A (N i ) tensor (NO, 2- X -NN, and 2- Z -IN radicals) was defined following previously reported protocols. ,,,, The A (N i ) tensor corresponding to the 4- Y -PhBzNN radical was determined following the protocol used to determine the A (N i ) tensor corresponding to the 2- X -NN radical. Unpaired electrons of 4- Y -PhBzNN occupy the π orbital (2p z orbitals of the nitrogen atoms).…”

“…The superhyperfine patterns of the 4- Y -PhBzNN radicals associated with the hydrogen atoms at α (or α′), β (or β′), o (or o ′), m (or m ′), and/or p -position further split the hyperfine interaction lines ( A zz (N i ) ≈ 10 A kk (H j ) ( k = x , y , or z )) associated with the equivalent nitrogen atoms present in the 4- Y -PhBzNN radicals (Figure c). The hydrogen at the p -position was considered only when Y = H. If the molecular motions of the 4- Y -PhBzNN radicals dispersed in PMMA are assumed to be frozen, the solid-state ESR spectra recorded for the radicals can be reproduced using the principal values of the g and A tensors of the unpaired electrons, and the line width parameters and signal amplitudes. ,, The zz components of the g and A (N 1 ) tensors of the 4- Y -PhBzNN radicals were estimated by visually inspecting the ESR spectra ( A (N 1 ) is equal to A (N 2 ) for the 2- X -NN and 4- Y -PhBzNN radicals). It was difficult to guess the values of g xx , g yy , A xx (N 1 ) , A yy (N 1 ), and A (H j ) from the solid-state ESR spectra for the 4- Y -PhBzNN radicals.…”