Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Robert A. Jacobson

Abstract

A Fourier deconvolution method was employed to estimate the grain size from a recorded pattern. The usefulness of the method is shown to be very dependent on effects of noise and sampling discontinuities in the recorded patterns, and the treatment of data with a least squares spline smoothing method to ease their effects is discussed. A computer program incorporating a fast Fourier transform technique was written and is discussed. The FWHM's of the peaks thus obtained were used individually for the calculation of the grain size by Scherrer's equation. The advantages of Fourier deconvolution methods over those methods in the popular Rietveld refinement programs are discussed. The grain size results obtained by this program are compared with those obtained by Rietveld refinements and by transmission electron microscope investigations;X-ray structure determinations of single crystals of compounds I: benzo-(2,3) -4-methyl-thiophene, C[subscript]9H[subscript]10S-Ir( C[subscript]5(CH[subscript]3)[subscript]5], and II: dibenzothiophene, C[subscript]12H[subscript]10S-Ir-( C[subscript]5(CH[subscript]3)[subscript]5] were performed. It has been expected that in the two compounds the Ir d-orbitals would be associated with the whole p-system of the complexing benzo - group, implying that all carbon atoms in this group would remain aromatic. The X-ray structure determinations and NMR [superscript]1H results indicate that both I and II can be best described as complexes in which two carbon atoms of a benzo-group of the ligand have been converted from sp[superscript]2 to sp[superscript]3 character. In order to gain further evidence for the reasonableness for these structural results, molecular mechanics calculations were employed to generate the corresponding sp[superscript]2 and sp[superscript]3 configurations of both the complexes and their minimized total energies compared. The structural results of the X-ray determinations and those of molecular mechanics are also compared and discussed;An optical alignment procedure making use of ordinary optical telescopes was developed which provides an easy-to-use alignment operation for the first stage of diffractometer alignment. It avoids some of the radiation hazards associated with previous procedures. Details regarding a combination of the optical and X-ray alignment procedure to align a Hilger-Watts diffractometer on the RIGAKU Rotating Anode X-ray generator are discussed on a step-by-step basis.

DOI

https://doi.org/10.31274/rtd-180813-11910

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Yingzhong Su

Language

en

Proquest ID

AAI9223969

File Format

application/pdf

File Size

151 pages

Share

COinS