Chemical substitutions electron diffraction studies

Two-coordinate Compounds. - X-Ray diffraction studies, together with quantum-chemical calculations, have been used to explain peculiarities in the molecular and electronic structures of halogen-substituted phosphaalkenes. ... 

Stucki JW, Roth CB, Baitinger WE (1976) Analysis of iron-bearing clay minerals by electron spectroscopy from chemical analysis (ESCA). Clays Clay Minerals 24 289-292 Swope J (1997) Single crystal X-ray and neutron diffraction studies of the crystal chemical effects of OH=0 substitution in mantle ratile and of Cl-OH substitution in biotite, and the crystal chemistry of IM ferromagnesian trioctahedral micas. PhD dissertation, Dept Geological Sciences, University of Colorado, Botrlder, 85 p... 

In crystallography, heavy atom derivatives are required to solve the phase problem before electron density maps can be obtained from the diffraction patterns. In nmr, paramagnetic probes are required to provide structural parameters from the nmr spectrum. In other forms of spectroscopy a metal atom itself is often studied. Now many proteins contain metal atoms, but even these metal atoms may not be suitable for crystallographic or spectroscopic purposes. Thus isomorphous substitution has become of major importance in the study of proteins. Isomorphous substitution refers to the replacement of a given metal atom by another metal that has more convenient properties for physical study, or to the insertion of a series of metal atoms into a protein that in its natural state does not contain a metal. In each case it is hoped that the substitution is such that the structural and/or chemical properties are not significantly perturbed. 

The molecular and electronic structure of P- and C-halogen-substituted phosphaalkenes have been studied using quantum-chemical calculations together with X-ray diffraction data. The introduction of an electronegative... 

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