D030 Structure determination from powder diffraction data of some moisture-sensitive, network coordination compounds

2006 ◽  
Vol 21 (2) ◽  
pp. 172-172
Author(s):  
P. S. Whitfield ◽  
A. Abouimrane ◽  
I. Davidson
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Coordination Compounds ◽  
Powder Diffraction Data ◽  
Network Coordination ◽  
Moisture Sensitive

Challenging structure determination from powder diffraction data: two pharmaceutical salts and one cocrystal with Z′ = 2

2019 ◽  
Vol 234 (4) ◽  
pp. 257-268 ◽  
Author(s):  
Carina Schlesinger ◽  
Michael Bolte ◽  
Martin U. Schmidt
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Real Space ◽  
Powder Diffraction Data ◽  
The Real ◽  
Pharmaceutical Salts ◽  
Structure Solution ◽  
Space Method

Abstract Structure solution of molecular crystals from powder diffraction data by real-space methods becomes challenging when the total number of degrees of freedom (DoF) for molecular position, orientation and intramolecular torsions exceeds a value of 20. Here we describe the structure determination from powder diffraction data of three pharmaceutical salts or cocrystals, each with four molecules per asymmetric unit on general position: Lamivudine camphorsulfonate (1, P 21, Z=4, Z′=2; 31 DoF), Theophylline benzamide (2, P 41, Z=8, Z′=2; 23 DoF) and Aminoglutethimide camphorsulfonate hemihydrate [3, P 21, Z=4, Z′=2; 31 DoF (if the H2O molecule is ignored)]. In the salts 1 and 3 the cations and anions have two intramolecular DoF each. The molecules in the cocrystal 2 are rigid. The structures of 1 and 2 could be solved without major problems by DASH using simulated annealing. For compound 3, indexing, space group determination and Pawley fit proceeded without problems, but the structure could not be solved by the real-space method, despite extensive trials. By chance, a single crystal of 3 was obtained and the structure was determined by single-crystal X-ray diffraction. A post-analysis revealed that the failure of the real-space method could neither be explained by common sources of error such as incorrect indexing, wrong space group, phase impurities, preferred orientation, spottiness or wrong assumptions on the molecular geometry or other user errors, nor by the real-space method itself. Finally, is turned out that the structure solution failed because of problems in the extraction of the integrated reflection intensities in the Pawley fit. With suitable extracted reflection intensities the structure of 3 could be determined in a routine way.

Organa– a program package for structure determination from powder diffraction data by direct-space methods

2005 ◽  
Vol 38 (4) ◽  
pp. 688-693 ◽  
Author(s):  
V. Brodski ◽  
R. Peschar ◽  
H. Schenk
Keyword(s):  
Potential Energy ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Energy Function ◽  
Potential Energy Function ◽  
Van Der Waals Interactions ◽  
Powder Diffraction Data ◽  
Trial Structure ◽  
The Cost

A new software package has been developed, namedOrgana, forab initiosolution of crystal structures from powder diffraction data by direct-space methods. The package contains energy-guiding Monte Carlo and grid-search algorithms and is based on a combined global minimization of theRfactor and a potential energy function of the system with the option of local minimization of the cost function for each generated trial structure. Basically, the potential energy function consists of van der Waals interactions, but harmonic potentials can be added to impose soft distance restraints. The program was successfully applied to the structure determination of a series of melamine phosphate compounds. The program is freely available (for all Windows platforms) from the correspondence author upon request.

Structure Determination of CaH2P2O7 From In Situ Powder Diffraction Data

2000 ◽  
Vol 321-324 ◽  
pp. 374-379 ◽  
Author(s):  
J. Trommer ◽  
M. Schneider ◽  
H. Worzala ◽  
Andrew N. Fitch
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Powder Diffraction Data
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