Part~I: Determination of Quadrupole Couplings via L-Band, B(0) // B(1) EPR. Part~II: Surface Interactions of Perylene Adsorbed on Oxide Powders

Rothenberger, Kurt Summers

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Title

Part~I: Determination of Quadrupole Couplings via L-Band, B(0) // B(1) EPR. Part~II: Surface Interactions of Perylene Adsorbed on Oxide Powders

Author(s)

Rothenberger, Kurt Summers

Issue Date

1988

Doctoral Committee Chair(s)

Belford, R. Linn

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Chemistry, Inorganic
• Chemistry, Physical

Abstract

• Part I. A novel experimental technique, the L-band, B$\sb0$ $\Vert$ B$\sb1$ Electron Paramagnetic Resonance (EPR) spectrometer, is proposed as part of an overall "Multi-Frequency" analysis, as an effective method for the determination of copper quadrupole couplings in disordered samples. In the first phase of the project, an often-studied doped powder sample of Bisacetylacetonato copper(II), $\sp{63}$Cu/Pd(acac)$\sb2$, is used to investigate the technique. The L-band, B$\sb0$ $\Vert$ B$\sb1$ EPR spectra are observed with respect to variation of temperature, concentration, centering in resonator, and microwave power. EPR spectra of the same sample are also recorded at L-band (with B$\sb0$ $\perp$ B$\sb1$), S-band, X-band and Q-band. All results are analyzed with the aid of EPR spectral simulation via computer in a manner consistent with the Multi-Frequency approach.
• The L-band, B$\sb0$ $\Vert$ B$\sb1$ technique is then used to investigate a series of lesser known copper(II) complexes. Two doped powders, Bis(diethyldithiocarbamato) copper(II), $\sp{63}$Cu/Ni(dtc)$\sb2$, and N,N$\sp\prime$-Bis(acetylacetone)ethylenediimine copper(II), $\sp{63}$Cu/Ni(acac$\sb2$en), and three frozen solutions, $\sp{63}$Cu(acac)$\sb2$, $\sp{63}$Cu(acac)$\sb2$/pyridine and $\sp{63}$Cu(acac$\sb2$en)/pyridine are studied. The values reported for QD are: 9 MHz for $\sp{63}$Cu/Pd(acac)$\sb2$, 0 for 6$\sp3$Cu/Ni(dtc)$\sb2$, 3 MHz for $\sp{63}$Cu/Ni(acac$\sb2$en), 8 MHz for $\sp{63}$Cu(acac)$\sb2$ solution, 19 MHz for the $\sp{63}$Cu(acac)$\sb2$/pyridine solution adduct and 14 MHz for the $\sp{63}$Cu(acac$\sb2$en)/pyridine solution adduct.
• Part II. Multi-frequency EPR and complex Electron-Nuclear Double Resonance (ENDOR) spectra are obtained from the perylene radicals formed on activated alumina and silica-alumina powders. A model of nearly isotropic Zeeman (g) and very anisotropic hyperfine (A) splittings is supported by these measurements and ENDOR simulations. All three proton hyperfine interactions of the perylene radical ion are resolved and the absolute values of the principal elements of the hyperfine coupling matrices are obtained. The fact that these values for radicals formed on alumina and silica-alumina are nearly identical implies that the same cation radical forms on both surfaces.
• Nuclei in the environment (matrix) of the radicals were also probed by ENDOR spectroscopy. Depending on the nature of the sample and experimental conditions, signals could be detected from $\sp1$H, $\sp2$D, and $\sp{27}$Al. The source and behavior of these signals are investigated with special attention paid to contrasting the data from the alumina and silica-alumina substrates. The results suggest that the radicals, although themselves similar, occupy sites of significantly different environment.

Graduation Semester

1988

Type of Resource

text

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