Computer simulation, ESR spectra

Figure 4.12 [E] Computer-simulated ESR spectra for a hypothetical low-spin Mn(n) radical with g = (2.100, 2.050, 2.000), AMn = (150, 25, 25) x 10-4 cm-1, for various values of / , the Euler angle between the g-matrix and hyper-...

Figures 1.23a and b illustrate computer simulated ESR spectra of positive polaron P+ and C "0 signals in two frequency ranges, (a) 9.5 GHz and (b) 95 GHz with identical components of the -tensors, line width and amplitudes. The signals that overlap at 9.5 GHz can be clearly separated at 95 GHz, and coincide with the experimental ones in one important aspect the (/-anisotropy can be clearly resolved.

Spin trapping with PMNB was applied to the radicals derived from initiator decomposition (formula 3) and their subsequent reactions with the model compounds (formula 5). Both initiator radicals could be trapped and identified. When model compounds were present during UV-irradiation, new radicals were identified from the ESR spectra. For dihydrocyclopentadiene (DHCPD) only one trapped radical was found and for ethylidene norbornane (ENB) two radicals. By comparison with computer simulated ESR spectra, it is concluded that the radicals of these model compounds are all allyl radicals (formula 8 and 9) formed by hydrogen abstraction from the models. Radical (8 a) has two stereoisomers but they have closely the same ESR spectra when trapped and cannot be separated. Radical (8 b) has two resonance structures (shift of double bond in the ethylidene group) but only one radical (8 b) is trapped, probably due to steric hinderance for trapping the methin radical. The DHCPD radical (formula 9) has two steric forms because the two allylic hydrogens are not identical. Once they are formed, the spin trap can only approach from one side and only one of the steric forms is trapped as shown in the ESR spectrum. 

Figure 4. Computer-simulated ESR spectra due to Kramers doublet with three g values typical of low-spin Fe. = 183, gy = 2.25, g. = 2.575 line widths w —1 mT, Wy = 2 mT,...

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See also in sourсe #XX -- [ ]

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