scholarly journals Crystal structures of two furazidin polymorphs revealed by a joint effort of crystal structure prediction and NMR crystallography

2020 ◽  
Vol 76 (3) ◽  
pp. 322-335 ◽  
Author(s):  
Marta K. Dudek ◽  
Piotr Paluch ◽  
Edyta Pindelska
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Determination ◽  
Structure Prediction ◽  
Structural Features ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
Crystal Forms ◽  
Space Groups ◽  
Nmr Crystallography

This work presents the crystal structure determination of two elusive polymorphs of furazidin, an antibacterial agent, employing a combination of crystal structure prediction (CSP) calculations and an NMR crystallography approach. Two previously uncharacterized neat crystal forms, one of which has two symmetry-independent molecules (form I), whereas the other one is a Z′ = 1 polymorph (form II), crystallize in P21/c and P 1 space groups, respectively, and both are built by different conformers, displaying different intermolecular interactions. It is demonstrated that the usage of either CSP or NMR crystallography alone is insufficient to successfully elucidate the above-mentioned crystal structures, especially in the case of the Z′ = 2 polymorph. In addition, cases of serendipitous agreement in terms of 1H or 13C NMR data obtained for the CSP-generated crystal structures different from the ones observed in the laboratory (false-positive matches) are analyzed and described. While for the majority of analyzed crystal structures the obtained agreement with the NMR experiment is indicative of some structural features in common with the experimental structure, the mentioned serendipity observed in exceptional cases points to the necessity of caution when using an NMR crystallography approach in crystal structure determination.

scholarly journals Crystal structure determination of an elusive methanol solvate – hydrate of catechin using crystal structure prediction and NMR crystallography

CrystEngComm ◽  
2020 ◽  
Vol 22 (30) ◽  
pp. 4969-4981 ◽  
Author(s):  
Marta K. Dudek ◽  
Piotr Paluch ◽  
Justyna Śniechowska ◽  
Karol P. Nartowski ◽  
Graeme M. Day ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Structure Prediction ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
Molecular Conformations ◽  
Nmr Crystallography

A useful short-cut was developed to limit the number of molecular conformations that need to be regarded in crystal structure prediction calculations, which led to the crystal structure determination of new methanol solvate – hydrate of catechin.

New similarity index for crystal structure determination from X-ray powder diagrams

2005 ◽  
Vol 38 (6) ◽  
pp. 861-866 ◽  
Author(s):  
Detlef Walter Maria Hofmann ◽  
Ludmila Kuleshova
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Structure Prediction ◽  
Similarity Index ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Organic Pigments ◽  
Structure Solution ◽  
Similarity Indices

A new similarity index for automated comparison of powder diagrams is proposed. In contrast to traditionally used similarity indices, the proposed method is valid in cases of large deviations in the cell constants. The refinement according to this index closes the gap between crystal structure prediction and automated crystal structure determination. The opportunities of the new procedure have been demonstrated by crystal structure solution of un-indexed powder diagrams of some organic pigments (PY111, PR181 and Me-PR170).

COMPACK: a program for identifying crystal structure similarity using distances

2005 ◽  
Vol 38 (1) ◽  
pp. 228-231 ◽  
Author(s):  
James Alexander Chisholm ◽  
Sam Motherwell
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Prediction ◽  
Structural Features ◽  
Crystal Structure Prediction ◽  
Blind Test ◽  
Interatomic Distances ◽  
Structure Similarity ◽  
Measure Of Similarity ◽  
Orientation Of Molecules

A method is presented for comparing crystal structures to identify similarity in molecular packing environments. The relative position and orientation of molecules is captured using interatomic distances, which provide a representation of structure that avoids the use of space-group and cell information. The method can be used to determine whether two crystal structures are the same to within specified tolerances and can also provide a measure of similarity for structures that do not match exactly, but have structural features in common. Example applications are presented that include the identification of an experimentally observed crystal structure from a list of predicted structures and the process of clustering a list of predicted structures to remove duplicates. Examples are also presented to demonstrate partial matching. Such searches were performed to analyse the results of the third blind test for crystal structure prediction, to identify the frequency of occurrence of a characteristic layer and a characteristic hydrogen-bonded chain.

Polymorphism of 7-dimethylaminocyclopenta[c]coumarin: packing analysis and generation of trial crystal structures

1996 ◽  
Vol 52 (1) ◽  
pp. 201-208 ◽  
Author(s):  
A. Gavezzotti
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
Acta Cryst ◽  
Structure Generation ◽  
Space Groups ◽  
Energy Hypersurface ◽  
Packing Analysis ◽  
Potential Energy Hypersurface

The crystal structures of two polymorphs of the title compound [Pbca and Pna21; Jasinski & Woudenberg (1995). Acta Cryst. C51, 107–109] were analysed. Packing energies and indices were compared. Molecules in the two forms show a slight conformational difference; both conformers were packed in some of the most frequent space groups for organic molecules (P21, P21/c, P212121 and Pna21) using a computer program for crystal structure generation and prediction (PROMET3). The results of such calculations are used to provide tentative explanations for the preference of the two conformers for centrosymmetric and non-centrosymmetric space groups. Several comments on general problems encountered in crystal structure prediction are also presented, concerning in particular the multi-minima structure of the potential energy hypersurface.

Crystal structure determination by combined synchrotronpowder X-ray diffraction and crystal structure prediction: 1 : 1 l-ephedrined-tartrate

CrystEngComm ◽  
2013 ◽  
Vol 15 (10) ◽  
pp. 1853-1859 ◽  
Author(s):  
Han Wu ◽  
Matthew Habgood ◽  
Julia E. Parker ◽  
Nik Reeves-McLaren ◽  
Jeremy K. Cockcroft ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Structure Prediction ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals Minimizing Polymorphic Risk Through Cooperative Computational and Experimental Exploration

2020 ◽  
Author(s):  
Christopher R. Taylor ◽  
Matthew T. Mulvee ◽  
Domonkos S. Perenyi ◽  
Michael R. Probert ◽  
Graeme Day ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Structure Prediction ◽  
Experimental Approach ◽  
Significant Risk ◽  
Free Energy Calculations ◽  
Crystal Structure Prediction ◽  
Crystal Forms ◽  
Wide Range ◽  
Solid Form

<div> <p>We combine state-of-the-art computational crystal structure prediction (CSP) techniques with a wide range of experimental crystallization methods to understand and explore crystal structure in pharmaceuticals and minimize the risk of unanticipated late-appearing polymorphs. Initially, we demonstrate the power of CSP to rationalize the difficulty in obtaining polymorphs of the well-known pharmaceutical isoniazid and show that CSP provides the structure of the recently discovered, but unsolved, Form III of this drug despite there being only a single known form for almost 70 years. More dramatically, our blind CSP study predicts a significant risk of polymorphism for the related iproniazid. Employing a wide variety of experimental techniques, including high-pressure experiments, we experimentally obtained the first three known non-solvated crystal forms of iproniazid, all of which were successfully predicted in the CSP procedure. We demonstrate the power of CSP methods and free energy calculations to rationalize the observed elusiveness of the third form of iproniazid, the success of high-pressure experiments in obtaining it, and the ability of our synergistic computational-experimental approach to “de-risk” solid form landscapes.</p> </div>

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