Use of a Fourier deconvolution method in particle size determination and use of molecular mechanics in crystal structure determinations

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. 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, C9H10S-Ir-(C5(CH3))), and II: dibenzothiophene, C12H10S-Ir-(C5CH)5 were performed. It was 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 H-1 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(sup 2) to sp(sup 3) character. 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.