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Combinatorial selection of molecular conformations and supramolecular synthons in quercetin cocrystal landscapes: a route to ternary solids.

Dubey R, Desiraju GR - IUCrJ (2015)

Bottom Line: The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons.Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event.In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560 012, India.

ABSTRACT
The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons. The crystal structures are characterized by distinctive O-H⋯N and O-H⋯O based synthons and are classified as nonporous, porous and helical. Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event. This space is the crystal structure landscape of the compound and is explored by fine-tuning the experimental conditions of crystallization. In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin. The absence of concomitant polymorphism in this study highlights the selectivity in conformation and synthon choice from the virtual combinatorial library in solution.

No MeSH data available.


Related in: MedlinePlus

Helical molecular arrangements in quercetin cocrystal landscapes. Compounds are color coded: green – quercetin; blue – coformer.
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fig5: Helical molecular arrangements in quercetin cocrystal landscapes. Compounds are color coded: green – quercetin; blue – coformer.

Mentions: Let us now consider the anhydrates. By altering the experimental conditions, we found that crystallization of a 1:1 ratio of QUE and DPE-I provides two forms: the first has a 1:1 QUE:DPE-I stoichiometry with Conf 1B and synthon H, while the other is a 1:2 QUE:DPE-I cocrystal with Conf 7B and synthon G. The latter illustrates a new helical structure type illustrated in Fig. 5 ▸, which shows different molecular and supramolecular features from the previously described nonporous and porous structure types and correspondingly enhances the domain of the structural space available. Similar to the pseudopolymorphs, the anhydrates also follow the same trend after coformer replacement of DPE-I by DPE-II or 44AP and hints about the robustness of conformation and synthon selection during crystallization. Changing the experimental conditions for QUE:TMP, QUE:44BP and QUE:DPE-I allows one to move within a landscape from nonporous to porous and thereafter to helical crystal structures. In most cases the corresponding DPE-I, DPE-II and 44AP cocrystal structures are isomorphous. However, in the 2:1 QUE:DPE-II cocrystal there is a different synthon C despite the same conformation Conf 6B. There are a number of structures lying within a small energy window, all with the same conformation but different synthon possibilities. We did not observe any instance of concomitant polymorphism so selectivity in synthon choice is clearly present. The crystallographic details of the crystal structures are given in the supporting information.


Combinatorial selection of molecular conformations and supramolecular synthons in quercetin cocrystal landscapes: a route to ternary solids.

Dubey R, Desiraju GR - IUCrJ (2015)

Helical molecular arrangements in quercetin cocrystal landscapes. Compounds are color coded: green – quercetin; blue – coformer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491312&req=5

fig5: Helical molecular arrangements in quercetin cocrystal landscapes. Compounds are color coded: green – quercetin; blue – coformer.
Mentions: Let us now consider the anhydrates. By altering the experimental conditions, we found that crystallization of a 1:1 ratio of QUE and DPE-I provides two forms: the first has a 1:1 QUE:DPE-I stoichiometry with Conf 1B and synthon H, while the other is a 1:2 QUE:DPE-I cocrystal with Conf 7B and synthon G. The latter illustrates a new helical structure type illustrated in Fig. 5 ▸, which shows different molecular and supramolecular features from the previously described nonporous and porous structure types and correspondingly enhances the domain of the structural space available. Similar to the pseudopolymorphs, the anhydrates also follow the same trend after coformer replacement of DPE-I by DPE-II or 44AP and hints about the robustness of conformation and synthon selection during crystallization. Changing the experimental conditions for QUE:TMP, QUE:44BP and QUE:DPE-I allows one to move within a landscape from nonporous to porous and thereafter to helical crystal structures. In most cases the corresponding DPE-I, DPE-II and 44AP cocrystal structures are isomorphous. However, in the 2:1 QUE:DPE-II cocrystal there is a different synthon C despite the same conformation Conf 6B. There are a number of structures lying within a small energy window, all with the same conformation but different synthon possibilities. We did not observe any instance of concomitant polymorphism so selectivity in synthon choice is clearly present. The crystallographic details of the crystal structures are given in the supporting information.

Bottom Line: The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons.Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event.In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560 012, India.

ABSTRACT
The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons. The crystal structures are characterized by distinctive O-H⋯N and O-H⋯O based synthons and are classified as nonporous, porous and helical. Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event. This space is the crystal structure landscape of the compound and is explored by fine-tuning the experimental conditions of crystallization. In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin. The absence of concomitant polymorphism in this study highlights the selectivity in conformation and synthon choice from the virtual combinatorial library in solution.

No MeSH data available.


Related in: MedlinePlus