Abstract. 3-pyridylmethaniminoxyl has been generated by '-irradiation of the parent oxime in the solid state and by incorporation of 3-pyridinealdoxime into the channels of thermally activated pentasil zeolite ZSM-5. The radical formed by both methods exhibits an electron paramagnetic resonance (EPR) spectrum with a characteristic powder pattern. The assignment of the hyperfine structure of the anisotropic spectra to the couplings with "N and 'H nuclei of Z geometrical isomer of 3-pyridylmethaniminoxy radical has been aided significantly by comparison with the coupling parameters calculated with the density functional theory (DFT). It has been found that 3-and 4-pyridylmethaniminoxyls generated in the oxime matrices, in contrast to the radicals derived from 2-pyridinealdoxime, have a possibility to isomerize. The EPR spectra of y-irradiated 3-and 4-pyridinealdoximes show a distinct temperature dependence of particular isomer contributions which have been correlated with the relative energies of the isomers derived from DFT calculations. Hybrid density functional methods have been also used to determine the structure of transition states for isomerization (via inversion at nitrogen) and rotation (of pyridyl ring) as well as to predict the appropriate energy barriers.

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Radiation reduction of binuclear [Rh2(OAc)2(phen)2(H20)2](OAc)2, [Rh2(OAc)(tpy)2C12]C1.2H20 and [Rh2C12(HCOO)2(bpy)2].4H20 complexes in aqueous-methanol solution have been studied. The reduction yields as equal to ca. 6 equiv/100 eV and the rate constants of reactions: complex+esolv as equal to 2.9.1010, 3.2.10 l~ and 3.7.10 l~ M 1.s 1, respectively, have been determined. On the basis of electronic spectra it has been shown that Rh(II) compounds were reduced giving several Rh(I) complexes being in equilibrium. The mechanism of the processes has been discussed.

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