X-band ENDOR and S-band ESEEM of paramagnetic disordered solids

X-band ENDOR and S-band ESEEM have been employed in this study to measure weak electron-nuclear hyperfine and nuclear electric quadrupole couplings in paramagnetic disordered solids. In the X-band ENDOR investigation, radicals generated from perylene adsorbed on catalytically active alumina and silica-alumina surfaces were studied. Complex ENDOR spectra were obtained. The magnitudes of the principal elements of the anisotropic hyperfine matrix for each chemically distinct type of proton could be determined by means of a computer simulation analysis. The hyperfine parameters for radicals on both of the surfaces studied are found to be nearly identical and the radicals are assigned as the perylene cation radical. In addition, matrix ENDOR signals are found to reveal distinct differences between the surface adsorption sites on the two oxides studied. Most notably, a matrix peak attributed to $\sp{27}$Al nuclei is detected from samples prepared with alumina. However, this peak was not detected from samples prepared with the silica-alumina.A description of the world's first S-band ESE spectrometer is presented. The use of lower microwave frequencies (fields) to enhance the modulation depth from weakly coupled nuclei has been investigated with this instrument. Also, an S-band ESEEM investigation of an adduct formed between pyridine and bis(1-phenyl-1,3-butanedianto) copper(II) exemplifies the importance of multi-frequency ESEEM. The investigation also further demonstrates that weak nuclear electric quadrupole coupling information from nuclei such as $\sp{14}$N can be obtained through ESEEM.U of I OnlyETDs are only available to UIUC Users without author permissio