Packing Problems: High <i>Z</i>′ Crystal Structures and Their Relationship to Cocrystals, Inclusion Compounds, and Polymorphism

Steed, Kirsty M.; Steed, Jonathan W.

doi:10.1021/cr500564z

Cited by 320 publications

(365 citation statements)

References 289 publications

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“…Com-pound 1 is unusual in exhibiting 17 molecules in the asym-metric unit and can be categorised amongst the small num-ber of molecules with particularly high Z′ numbers. 20 While there are relatively large numbers of structures with Z′ > 4, the numbers decrease significantly for Z′ > 8 and are very rare for Z′ > 16 with just 7 reported structures. 21 In addition, we find 2 is polymorphic and compare the structures of 2α, initially reported by Kisenyi et al,22 with the new polymorph 2 in relation to 1 and other dithia-chloroarsoles.…”

mentioning

confidence: 96%

Supramolecular aggregation in dithia-arsoles: chlorides, cations and N-centred paddlewheels

et al. 2017

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mentioning

confidence: 96%

Supramolecular aggregation in dithia-arsoles: chlorides, cations and N-centred paddlewheels

et al. 2017

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“…In this example, the strongest C=O…C=O are found between the largest faces of the anhydride ring of independent molecules implying that molecules are fitting together to minimise the surface area and emphasising the importance of other factors which are the molecular shape and flexibility. The idea of high Z' structures arising as a consequence of awkward molecular shape has been postulated by several authors [35,36]. From these studies, molecules crystallizing with Z'>1 are more awkward than those crystallizing with Z'=1.…”

Section: Results Of Theoretical Calculations and Comparison With Expementioning

confidence: 99%

Modelling of crystal structure of cis-1,2,3,6 and 3,4,5,6-tetrahydrophthalic anhydrides using lattice energy calculations

Fredj¹,

Day

2015

J Mol Model

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Lattice energy calculations using a model potential have been performed to model the crystal structures of cis-1,2,3,6-and 3,4,5,6-tetrahydrophthalic anhydrides. The optimized molecular models using the DFT method at the B3LYP/6-31G** level were found consistent with the available experimental evidence and allow to reproduce all differences observed in crystal packing between cis-1,2,3,6-and 3,4,5,6-tetrahydrophthalic anhydrides. Calculations provide evidence for the presence of dipole-dipole C=O…C=O intermolecular interactions and support the idea that the molecules distort from their ideal geometries, improving packing in both crystals. The search for minima in the lattice energy of both crystals amongst the more common space groups with Z'=1, using a simulated annealing crystal structure prediction procedure followed by lattice energy minimisation shows that the observed structure of 3,4,5,6-tetrahydrophthalic anhydride (Z'=2) is the thermodynamically most stable and allow us to justify why 3,4,5,6-tetrahydropthalic anhydride crystallises in such complex structure with 16 molecules in the unit cell. The computational model was successful to predict the second observed form at 173 K for cis-1,2,3,6-tetrahydropthalic anhydride as a polymorph and could predict several hypothetical structures with Z'=1 which appear competitive with the observed structures. The results of phonon estimates of zero point intermolecular vibrational energy and entropy suggest that crystal structures of cis-1,2,3,6-tetrahydropthalic anhydride cannot be predicted just on the basis of lattice energy, there are yet, other factors than thermodynamics favoring the observed structures.

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“…The growth in both the incidence and the interest in high Z' structures has been stimulated by improving instrumentation and complementary information from a range of techniques including single crystal and powder X-ray and neutron diffraction, solid-state NMR spectroscopy, computational energy calculations, DSC, and hot stage microscopy. A Recent review on high Z' crystal structures [29] present a holistic overview of the recent startling progress in scientific understanding of crystal packing in general, and attempt to place the phenomenon of crystal structures with Z'>1 firmly into context within the contemporary view of crystal packing phenomena.…”

Section: Crystallographic Parameters To Be Considered In Cspmentioning

confidence: 99%

Crystal Structure Prediction in the Context of Pharmaceutical Polymorph Screening and Putative Polymorphs of Ciprofloxacin

Singh

Chadha

2017

Int J Pharm Pharm Sci

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Molecular simulation is increasingly used by medicinal chemists in the process and product development. Reliable computational predictions are of great value not only for the design of an active pharmaceutical ingredient with novel properties but also for the avoidance of an undesirable change of form in the late stages of development of an industrially important molecule. In the pharmaceutical industry, drug polymorphism can be a critical problem and is the subject of various regulatory considerations. This contribution tried to review the fuzzy frontiers between the chemical structure of the molecule and its crystal energy landscape with a particular focus on the crystal structure prediction (CSP) methodology to complement polymorph screening. A detailed application of CSP in the pharmaceutical industry is illustrated on ciprofloxacin; describing its putative polymorphs. This approach successfully identifies the known crystal form within this class, as well as a large number of other low-energy structures. The performance of the approach is discussed in terms of both the quality of the results and computational aspects. CSP methods are now being used as part of the interdisciplinary range of studies to establish the range of solid forms of a molecule. Moreover, further methodological improvements aimed at increasing the accuracy of the predictions and at broadening the range of molecules i.e. co-crystals, salts and solvates.

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Packing Problems: High Z′ Crystal Structures and Their Relationship to Cocrystals, Inclusion Compounds, and Polymorphism

Cited by 320 publications

References 289 publications

Supramolecular aggregation in dithia-arsoles: chlorides, cations and N-centred paddlewheels

Supramolecular aggregation in dithia-arsoles: chlorides, cations and N-centred paddlewheels

Modelling of crystal structure of cis-1,2,3,6 and 3,4,5,6-tetrahydrophthalic anhydrides using lattice energy calculations

Crystal Structure Prediction in the Context of Pharmaceutical Polymorph Screening and Putative Polymorphs of Ciprofloxacin

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