A modern definition for whole powder pattern decomposition WPPD methods would be that they simultaneously have to refine the unit-cell parameters and extract the best estimations of the Bragg peak intensities from a complete diffractogram. This is done very fast nowadays, irrespective of the number of Bragg peaks present in a powder diffraction pattern, but we did not attain this comfortable situation without some past efforts. The WPPD methods’ introduction occurred slowly and progressively thanks to the increase in computer power, the improvements in graphical user interfaces, the diffractometer data digitalization, the availability of synchrotron and neutron radiation, and last but not least, the proposition of new algorithms. Innovations were not instantly accepted this being true for all the whole powder pattern fitting methods including the Rietveld and the decomposition methods or could not be applied immediately to every radiation source or diffractometer the hardware before adaptations made by an essential category of crystallographers being conceivers and developers of the software. Ancestors of the WPPD methods extracted peak intensities without the cell restraint, so that each peak position was a parameter to be refined as well as the peak intensity, the peak shape and its width. This is still useful if the aim is the search for the peak positions for indexing, though derivative methods can make that peak-position-hunting job faster. Taking advantage of the indexing see a recent review paper by Bergmann et al. 2004, new WPPD methods, applying cell restraint to the peak position, opened the door to a long list of new possibilities and applications including first indexing confirmation which are detailed in this paper. However, only some selected application references will be provided because the number of papers involved is quite high and increasing more than 2000 texts specify the use of WPPD methods. Contributions from Rennes by Louer’s group from 1987 to 1993 will be especially enlightened, not forgetting the other players during that same time, restraining generally to the structure determinations by powder diffractometry SDPD applications published in the early stages of this retrospection because the subsequent activity increased too considerably, by more than 850 SDPDs in the last ten years. If only a partial review of applications can be given, the evolution of the methods will be discussed as completely as possible.

/pdf/whole-powder-pattern-decomposition-methods-and-applications-597bm0bp60.pdf

Whole powder pattern decomposition methods and applications: A retrospection

Structure Determination from Powder Diffraction Data

Recent developments in the chemistry of early transition metal porphyrin compounds

The reaction of trimethylsilyl-substituted 2-aminopyridines with mixed chloro(dialkylamido)metal complexes (titanium and zirconium) leads via amine elimination to octahedral group 4 metal complexes that contain amine, amido, and aminopyridinato ligands. The X-ray crystal structure analyses of (4-Me-TMS-APy)(NMe2)(HNMe2)TiCl2 (1) (crystallographic data:  P21/c (No. 14), monoclinic, a = 16.754(2) A, b = 14.395(2) A, c = 17.890(3) A, β = 110.28(1)°, Z = 8) and (6-Me-TMS-APy)(NEt2)(HNEt2)ZrCl2 (2) (crystallographic data:  P21/n (No. 14) monoclinic, a = 10.125(1) A, b = 16.331(1) A, c = 15.276(2) A, β = 93.90(1), Z = 4) prove the compounds to be mononuclear with a cisoid arrangement of the two chloro ligands embedded in a reactive pocket determined by the steric demand of the three nitrogen containing ligands. Oligo- and polymerization studies with propene and 1-butene reveal the following results. First, 1 is a remarkably active precatalyst in contrast to the very low activity of 2. Second, MAO, a 1:1 mixture...

Octahedral Group 4 Metal Complexes That Contain Amine, Amido, and Aminopyridinato Ligands: Synthesis, Structure, and Application in alpha-Olefin Oligo- and Polymerization.

The hydrothermal reactions of lead(II) acetate with carboxylic acids gave solids of composition [Pb(C4H4O4)] 1 (C4H4O4 = succinate); [Pb6O2(C14H9O3)8] 2 (C14H9O3 = benzoylbenzoate), [Pb(C8H4NO4)2(H2O)] 4 (C8H4NO4 = 2-nitrobenzoate) and [Pb(C8H3N2O6)2(H2O)] 5 (C8H3N2O6 = 3,5-dinitrobenzoate). The reaction of lead monoxide with trichloroacetic acid in hot wet toluene followed by filtration and cooling gave a solid of composition [Pb3(C2Cl3O2)6(H2O)3] 3. The compounds were characterised by X-ray single crystal structure determinations. Compounds 1, 3, 4 and 5 are polymeric whereas 2 is monomeric. The lead co-ordination number ranges from 5 to 8. Compound 2 is a novel hexanuclear lead(II) distorted octahedron containing two bridging oxide ligands.

Synthesis and characterisation of polymeric and oligomeric lead(II) carboxylates

/pdf/a-crystal-structure-determination-of-pbc2o4-from-synchrotron-2erk958upl.pdf

A Crystal Structure Determination of PbC2O4 from Synchrotron X-Ray and Neutron Powder Diffraction Data.

/pdf/some-complex-structures-built-up-of-modules-obtained-from-209kto6x31.pdf

Some complex structures built up of modules obtained from the R-Nb2O5 structure through chemical twinning

/pdf/a-synchrotron-x-ray-powder-diffraction-study-of-the-54r2eqo6bi.pdf

A synchrotron X-ray powder diffraction study of the structure of trans-dichlorotitanium(IV) tetraphenylporphyrin

X-ray synchrotron powder data were collected from a capillary sample of a small-molecule organic peptide compound, glycylglycine (NH2CH2CONHCH 2COOH) by step-scanning at 1 ° intervals with a linear position-sensitive detector covering an angular range of 2"7 ° in order to test the feasibility of recording a high-resolution pattern and using the data for Rietveld analysis. Appropriate corrections for detector linearity and position were implemented, and comparison with a diagram recorded with a single scintillation detector and a crystal analyser system showed similar quality for the two sets of data. A detailed comparison of the refined atomic coordinates and those of an earlier X-ray single-crystal study showed the estimated standard deviations to be significantly underestimated in both refinements. A linear detector should be particularly useful for small samples and capillary specimens of moderately absorbing materials.

High-Resolution Synchrotron X-ray Powder Diffraction with a Linear Position-Sensitive Detector

/pdf/bisignate-n-pi-cotton-effects-in-the-circular-dichroism-5dtc1a92tk.pdf

Bisignate n -> pi* Cotton Effects in the Circular Dichroism Spectra of 2- and 3-Substituted N-Nitrosopyrrolidines.

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