2 mm Electron paramagnetic resonance studies of the new types of imidazoline nitroxide radicals

Abstract

The 2 mm band spectra have been obtained for imidazoline nitroxides, nitronyl and imino nitroxides, containing various substituents in different positions of a radical cycle in frozen toluene solutions. The spectra allowed the determination of all g tensor principal values and the A, , component of the hyperfine interaction tensor with the nitrogen nucleus of ,N-0.1989), pp. 15-57.

First determination of the spin relaxation properties of a nitronyl nitroxide in solution by electron spin echoes at X-band: A comparison with Tempone

“…For short correlation times, T 2 is largely dominated by spin-rotational relaxation, which depends on (Dg:Dg). This term is larger for nitronyl nitroxides (see Table 2 and [70,71]), and this gives a contribution to relaxation which is faster by a factor of 1.6 for PTIO with respect to Tempone. On the other hand, the secular, pseudosecular and non-secular relaxation terms arising from the modulation of the hyperfine 14 N dipolar interaction are larger for Tempone with respect to PTIO due to the smaller principal values of the hyperfine tensors of the latter radical, see Table 2.…”

Characterization of free radicals from vitamin K1 and menadione by 2 mm-band EPR, ENDOR and ESEEM

“…That radical is well characte¡ in liquid solution [10,11] and has a large hyperfine splitting of about 0.8 mT from the methyl protons. If present, such a large splitting would certainly be resolved in either the X-band or the 2 mm-band EPR spectra [34]. Also the magnitude of the isotropic coupling for an OH proton of 0.232 mT from both the ENDOR and the ESEEM lies within the range 0.20--0.24 mT tabulated [35] for naphthoquinone cation radicals but not for the neutral radicals.…”

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

“…The isotropic values of the g and A tensors of these radicals have been reported. , The g and A tensor components of the BzNN radicals should be examined in more detail in the dispersed state to gain insight into the nature of the 4- Y -PhBzNN radicals that can be potentially used as spin probes in the ESR spin probe technique. Details of the ESR spectra of phenyliminonitroxide (PhIN ( 8 ); Z = H; (Figure d)) present in organic matrices and 1D nanochannels have also been reported. , The use of these radicals can help identify suitable probe radicals for further studies. The structures and shapes of the matrices, and the interactions between the matrices and guest radicals should be taken into consideration while selecting the suitable radicals for the studies.…”

“…Several radicals belonging to this group of radicals behave as organic magnets at low temperatures. , Various NN radicals are present in the ligands in magnetic metal complexes − and metal–organic frameworks (MOFs) . Studies on the 2- X -NN radical present in frozen organic matrices, cement, and porous organic films have been rarely conducted using the ESR spectroscopy. − …”