scholarly journals Nicotinamide: Seven New Polymorphic Structures Revealed by Melt Crystallization and Crystal Structure Prediction

2020 ◽  
Author(s):  
Xizhen Li ◽  
Xiao Ou ◽  
Bingquan Wang ◽  
Haowei Rong ◽  
Bing Wang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
Melt Crystallization ◽  
Efficient Tool ◽  
Single Crystal Structures ◽  
Solution Crystallization

<p>Here, we reported nicotinamide (NIC), a long-known vitamin, was revealed in fact to be a highly polymorphic compound with nine solved single-crystal structures by performing melt crystallization. A CSP calculation successfully identified all six Z’ = 1 and 2 experimental structures. Melt crystallization has turned out to be an efficient tool for exploring polymorphic landscape, especially in regions inaccessbile by solution crystallization.</p>

scholarly journals Nicotinamide: Seven New Polymorphic Structures Revealed by Melt Crystallization and Crystal Structure Prediction

2020 ◽  
Author(s):  
Xizhen Li ◽  
Xiao Ou ◽  
Bingquan Wang ◽  
Haowei Rong ◽  
Bing Wang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
Melt Crystallization ◽  
Efficient Tool ◽  
Single Crystal Structures ◽  
Solution Crystallization

<p>Here, we reported nicotinamide (NIC), a long-known vitamin, was revealed in fact to be a highly polymorphic compound with nine solved single-crystal structures by performing melt crystallization. A CSP calculation successfully identified all six Z’ = 1 and 2 experimental structures. Melt crystallization has turned out to be an efficient tool for exploring polymorphic landscape, especially in regions inaccessbile by solution crystallization.</p>

scholarly journals Rich polymorphism in nicotinamide revealed by melt crystallization and crystal structure prediction

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Xizhen Li ◽  
Xiao Ou ◽  
Bingquan Wang ◽  
Haowei Rong ◽  
Bing Wang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Structure Prediction ◽  
Calculation Model ◽  
Crystal Structure Prediction ◽  
Melt Crystallization ◽  
Efficient Tool ◽  
Single Crystal Structures ◽  
Solution Crystallization ◽  
Theoretical Predictions

Abstract Overprediction is a major limitation of current crystal structure prediction (CSP) methods. It is difficult to determine whether computer-predicted polymorphic structures are artefacts of the calculation model or are polymorphs that have not yet been found. Here, we reported the well-known vitamin nicotinamide (NIC) to be a highly polymorphic compound with nine solved single-crystal structures determined by performing melt crystallization. A CSP calculation successfully identifies all six Z′ = 1 and 2 experimental structures, five of which defy 66 years of attempts at being explored using solution crystallization. Our study demonstrates that when combined with our strategy for cultivating single crystals from melt microdroplets, melt crystallization has turned out to be an efficient tool for exploring polymorphic landscapes to better understand polymorphic crystallization and to more effectively test the accuracy of theoretical predictions, especially in regions inaccessible by solution crystallization.

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 Powder diffraction and crystal structure prediction identify four new coumarin polymorphs

2017 ◽  
Vol 8 (7) ◽  
pp. 4926-4940 ◽  
Author(s):  
Alexander G. Shtukenberg ◽  
Qiang Zhu ◽  
Damien J. Carter ◽  
Leslie Vogt ◽  
Johannes Hoja ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Structure Prediction ◽  
Prediction Method ◽  
Crystal Structure Prediction ◽  
Free Energies ◽  
Structure Prediction Method

Crystal structures of four new coumarin polymorphs were solved by crystal structure prediction method and their lattice and free energies were calculated by advanced techniques.

scholarly journals The Consistent Hexameric Paddle-Wheel Crystallisation Motif of a Family of 2,4-Bis(n-Alkylamino)Nitrobenzenes: Alkyl = Pentyl, Hexyl, Heptyl and Octyl

2017 ◽  
Vol 41 (4) ◽  
pp. 235-238 ◽  
Author(s):  
M. John Plater ◽  
William T.A. Harrison ◽  
Laura M. Machado de los Toyos ◽  
Lewis Hendry
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Paddle Wheel ◽  
Alkyl Chains ◽  
Single Crystal Structures ◽  
Hydrogen Bonded

Three examples of 2,4-bis(n-alkylamino)nitrobenzenes have been crystallised (alkyl = pentyl, hexyl and heptyl) and the single crystal structures were determined. The three structures are similar and adopt a cyclic hydrogen bonded hexameric motif. n-Octyl alkyl chains prevented a crystal structure determination owing to disorder.

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.

Modelling the crystal structure of the 2-hydronitronylnitroxide radical (HNN): observed and computer-generated polymorphs

1999 ◽  
Vol 55 (4) ◽  
pp. 543-553 ◽  
Author(s):  
G. Filippini ◽  
A. Gavezzotti ◽  
J. J. Novoa
Keyword(s):  
Crystal Structure ◽  
Force Field ◽  
Crystal Structures ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Narrow Energy Range ◽  
Coulomb Type ◽  
Atomic Coordinates ◽  
Hydrogen Bonded

The crystal structures of two polymorphs of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide (the 2-hydronitronylnitroxide radical, HNN) are analyzed by packing energy criteria. Other unobserved polymorphic crystal structures are generated using a polymorph predictor package and three different force fields, one of which is without explicit Coulomb-type terms. The relative importance of several structural motifs (hydrogen-bonded dimers, shape-interlocking dimers or extended hydrogen-bonded chains) is discussed. As usual, many crystal structures within a narrow energy range are generated by the polymorph predictor, confirming that ab initio crystal-structure prediction is still problematic. Comparisons of powder patterns generated from the atomic coordinates of the X-ray structure and from computational crystal structures confirm that although the energy ranking depends on the force field used, the X-ray structure of the \alpha polymorph was found to be among the most stable ones produced by the polymorph predictor, even using the chargeless force field.

scholarly journals Validation of a search technique for crystal structure prediction of flexible molecules by application to piracetam

2005 ◽  
Vol 61 (5) ◽  
pp. 558-568 ◽  
Author(s):  
Harriott Nowell ◽  
Sarah L. Price
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Crystal Structures ◽  
Gas Phase ◽  
Intermolecular Interactions ◽  
Structure Prediction ◽  
Low Energy ◽  
Crystal Structure Prediction ◽  
New Approach ◽  
Flexible Molecules

A new approach to the crystal structure prediction of flexible molecules is presented. It is applied to piracetam, whose conformational polymorphs exhibit a variety of hydrogen-bond motifs but lack the intramolecular hydrogen bond found in the gas-phase ab initio optimized conformer. Stable crystal packing can result when favourable intermolecular interactions are made possible when the molecule distorts from the gas-phase conformation. If the resulting intermolecular lattice energy is sufficiently favourable to compensate for the intramolecular energy penalty associated with the suboptimal gas-phase conformation, then the crystal structure may be experimentally feasible. The new approach involves searching for low-energy crystal structures using a large number of rigid conformers, firstly to systematically explore which regions of conformational space could give rise to low-energy hydrogen-bonded crystal structures, and then to refine the search using crystallographic insight to optimize particular intermolecular interactions. The timely discovery of a new polymorph (form IV) by an independent experimental team allowed this approach to be validated by way of a `blind test' of crystal structure prediction. Form IV was successfully identified as the most favourable computed crystal structure with a conformation very distinct from that in the previously known polymorphs.

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