Ternary Cocrystals Research Articles

Isomorphous three-component crystals (pseudopolymorphs of binary cocrystals) based on lattice inclusion of guests with a sterically-rigidified tetraarylpyrene host

Based on structural studies already available for the cocrystals of a sterically-rigidified tetraarylpyrene (TP) host substituted at the periphery by flexible methoxymethyl (MM) groups, i.e., TPMM, with aliphatic guests, formation of ternary or three-component cocrystals was targeted by replacing one of the guest species in the binary cocrystals with a different guest. Ternary cocrystals of TPMM with cyclododecene + cyclodecane, cyclododecene + cyclooctane and cyclododecene + decalin pairs were indeed successfully isolated and characterized by single-crystal X-ray structure determination. The ternary cocrystals, in principle, constitute ‘isomorphous pseudopolymorphs’ of binary cocrystals of TPMM with cyclododecene.

Multicomponent ternary cocrystals of the sulfonamide group with pyridine-amides and lactams.

SMBA was selected as a bifunctional sulfa drug to design ternary cocrystals with pyridine amides and lactam coformers. Supramolecular assembly of five ternary cocrystals of p-sulfonamide benzoic acid with nicotinamide and 2-pyridone is demonstrated and reproducible heterosynthons are identified for crystal engineering.

Hierarchical Ordering in Ternary Co-Crystals of C60, N-Benzyl Ammonium Resorcinarene Bromide and Solvent Molecules

Co-crystallization of C60 together with an N-benzyl ammonium resorcinarene bromide from toluene:1,2-dichloroethane mixture results in ternary co-crystals where the modulated C60 lattice entraps dimeric resorcinarene assemblies, which, in turn, have 149 and 280 Å3 cavities filled with 1,2-dichloroethane molecules.

Combinatorial crystal synthesis: structural landscape of phloroglucinol:1,2-bis(4-pyridyl)ethylene and phloroglucinol:phenazine.

A large number of crystal forms, polymorphs and pseudopolymorphs, have been isolated in the phloroglucinol-dipyridylethylene (PGL:DPE) and phloroglucinol-phenazine (PGL:PHE) systems. An understanding of the intermolecular interactions and synthon preferences in these binary systems enables one to design a ternary molecular solid that consists of PGL, PHE, and DPE, and also others where DPE is replaced by other heterocycles. Clean isolation of these ternary cocrystals demonstrates synthon amplification during crystallization. These results point to the lesser likelihood of polymorphism in multicomponent crystals compared to single-component crystals. The appearance of several crystal forms during crystallization of a multicomponent system can be viewed as combinatorial crystal synthesis with synthon selection from a solution library. The resulting polymorphs and pseudopolymorphs that are obtained constitute a crystal structure landscape.

Combinatorial Crystal Synthesis: Structural Landscape of Phloroglucinol:1,2‐bis(4‐pyridyl)ethylene and Phloroglucinol:Phenazine

AbstractA large number of crystal forms, polymorphs and pseudopolymorphs, have been isolated in the phloroglucinol‐dipyridylethylene (PGL:DPE) and phloroglucinol‐phenazine (PGL:PHE) systems. An understanding of the intermolecular interactions and synthon preferences in these binary systems enables one to design a ternary molecular solid that consists of PGL, PHE, and DPE, and also others where DPE is replaced by other heterocycles. Clean isolation of these ternary cocrystals demonstrates synthon amplification during crystallization. These results point to the lesser likelihood of polymorphism in multicomponent crystals compared to single‐component crystals. The appearance of several crystal forms during crystallization of a multicomponent system can be viewed as combinatorial crystal synthesis with synthon selection from a solution library. The resulting polymorphs and pseudopolymorphs that are obtained constitute a crystal structure landscape.

Obtaining Synthon Modularity in Ternary Cocrystals with Hydrogen Bonds and Halogen Bonds

Design of ternary cocrystals based on synthon modularity is described. The strategy is based on the idea of extending synthon modularity in binary cocrystals of 4-hydroxybenzamide:dicarboxylic acids and 4-bromobenzamide:dicarboxylic acids. If a system contains an amide group along with other functional groups, one of which is a carboxylic acid group, the amide associates preferentially with the carboxylic acid group to form an acid–amide heterosynthon. If the amide and the acid groups are in different molecules, a higher multicomponent molecular crystal is obtained. This is a stable pattern that can be used to increase the number of components from two to three in a multicomponent system. Accordingly, noncovalent interactions are controlled in the design of ternary cocrystals in a more predictable manner. If a single component crystal with the amide–amide dimer is considered, modularity is retained even after formation of a binary cocrystal with acid–amide dimers. Similarly, when third component halogen a...

Incorporation of the Similarly Sized Molecules, Diiodine and Carbon Disulfide, into Cocrystals Formed with the Fullerenes, C60 or C70

Cocrystallization of diiodine and carbon disulfide with the two common fullerenes, C60 and C70, has been examined. The binary cocrystal, C70·I2, readily formed when a solution of diiodine in diethyl ether was layered over C70 dissolved in toluene, chlorobenzene, or 1,2-dichlorobenzene, but no binary cocrystal of diiodine and C60 could be obtained despite persistent efforts. The ternary cocrystal, C70·0.85I2·0.15CS2, which was grown from a carbon disulfide solution of C70 and a benzene solution of diiodine, is isostructural with C70·I2 but has 15% of the diiodine sites replaced with carbon disulfide. In contrast, C70·0.68I2·0.32CS2, which was obtained from diffusion of a cyclohexane solution of diiodine into a carbon disulfide solution of C70, is a unique ternary cocrystal that is not related to any binary cocrystal of C70 with diiodine or carbon disulfide. Crystals of 2C60·2.46CS2·0.54I2 were obtained from a saturated carbon disulfide solution of diiodine and C60. Black crystals of 2C60·2.46CS2·0.54I2 form in a different space group from those of the solvate 2C60·3CS2 but have a very similar structure. Remarkably, diiodine molecules fractionally replace carbon disulfide in only two of the three independent sites within this crystal.

Halogen bonds in crystal engineering: like hydrogen bonds yet different.

The halogen bond is an attractive interaction in which an electrophilic halogen atom approaches a negatively polarized species. Short halogen atom contacts in crystals have been known for around 50 years. Such contacts are found in two varieties: type I, which is symmetrical, and type II, which is bent. Both are influenced by geometric and chemical considerations. Our research group has been using halogen atom interactions as design elements in crystal engineering, for nearly 30 years. These interactions include halogen···halogen interactions (X···X) and halogen···heteroatom interactions (X···B). Many X···X and almost all X···B contacts can be classified as halogen bonds. In this Account, we illustrate examples of crystal engineering where one can build up from previous knowledge with a focus that is provided by the modern definition of the halogen bond. We also comment on the similarities and differences between halogen bonds and hydrogen bonds. These interactions are similar because the protagonist atoms-halogen and hydrogen-are both electrophilic in nature. The interactions are distinctive because the size of a halogen atom is of consequence when compared with the atomic sizes of, for example, C, N, and O, unlike that of a hydrogen atom. Conclusions may be drawn pertaining to the nature of X···X interactions from the Cambridge Structural Database (CSD). There is a clear geometric and chemical distinction between type I and type II, with only type II being halogen bonds. Cl/Br isostructurality is explained based on a geometric model. In parallel, experimental studies on 3,4-dichlorophenol and its congeners shed light on the nature of halogen···halogen interactions and reveal the chemical difference between Cl and Br. Variable temperature studies also show differences between type I and type II contacts. In terms of crystal design, halogen bonds offer a unique opportunity in the strength, atom size and interaction gradation; this may be used in the design of ternary cocrystals. Structural modularity in which an entire crystal structure is defined as a combination of modules is rationalized on the basis of the intermediate strength of a halogen bond. The specific directionality of the halogen bond makes it a good tool to achieve orthogonality in molecular crystals. Mechanical properties can be tuned systematically by varying these orthogonally oriented halogen···halogen interactions. In a further development, halogen bonds are shown to play a systematic role in organization of LSAMs (long range synthon aufbau module), which are bigger structural units containing multiple synthons. With a formal definition in place, this may be the right time to look at differences between halogen bonds and hydrogen bonds and exploit them in more subtle ways in crystal engineering.

Designing Ternary Co-crystals with Stacking Interactions and Weak Hydrogen Bonds. 4,4′-Bis-hydroxyazobenzene

Three ternary co-crystals of the title compound are reported. The design strategy hinges on the identification of a robust synthon with O-H center dot center dot center dot N hydrogen bonds in a binary co-crystal. Construction of this module allows the tuning of pi center dot center dot center dot pi stacking interactions and weak hydrogen bonds to incorporate the third component into the crystal structure. Screening of various co-formers showed that a delicate balance of electrostatics is required for stacking to favor the formation of ternaries. A C-H center dot center dot center dot N hydrogen-bonded motif was also found to occur repetitively in the ternary co-crystals. The directional nature of weak hydrogen bonds allows them to be used effectively in this study.

A robust two-dimensional hydrogen-bonded network for the predictable assembly of ternary co-crystals of furosemide

Identification of a two-dimensional hydrogen-bonded network leads to a new family of ternary co-crystals of furosemide.

Olanzapinium Salts, Isostructural Solvates, and Their Physicochemical Properties

Solubility and dissolution play a crucial role in the activity and efficacy of an oral drug. Olanzapine is an antipsychotic drug of the Biopharmaceutics Classification System (BCS) class II category. Several solvates, cocrystals, salts, and amorphous forms of olanzapine have been prepared to study materials properties and its X-ray crystal structures were classified. We report herein a few salts, solvates, and solvate polymorphs of olanzapine to improve the physicochemical properties and study novel structural motifs. Olanzapinium dimaleate monofumaric acid is the first case of a ternary cocrystal of an active pharmaceutical ingredients (API) in the CSD database with maleate ion and fumaric acid coformers. The olanzapine disalts, olanzapinium dipicrate, dimaleate, and dimaleate monofumaric acid, contain a novel structural motif, different from the dimer motif characteristic of the four structural categories reported in the literature.

Creation of Ternary Multicomponent Crystals by Exploitation of Charge‐Transfer Interactions

Four new ternary crystalline molecular complexes have been synthesised from a common 3,5-dinitrobenzoic acid (3,5-dnda) and 4,4'-bipyridine (bipy) pairing with a series of amino-substituted aromatic compounds (4-aminobenzoic acid (4-aba), 4-(N,N-dimethylamino)benzoic acid (4-dmaba), 4-aminosalicylic acid (4-asa) and sulfanilamide (saa)). The ternary crystals were created through the application of complementary charge transfer and hydrogen-bonding interactions. For these systems a dimer was created through a charge-transfer interaction between two of the components, while hydrogen bonding between the third molecule and this dimer completed the construction of the ternary co-crystal. All resulting structures display the same acid⋅⋅⋅pyridine interaction between 3,5-dnba and bipy. However, changing the third component causes the proton of this bond to shift from neutral OH⋅⋅⋅N to a salt form, O(-) ⋅⋅⋅HN(+) , as the nature of the group hydrogen bonding to the carboxylic acid was changed. This highlights the role of the crystal environment on the level of proton transfer and the utility of ternary systems for the study of this process.

Novel solid forms of the anti-tuberculosis drug, Isoniazid: ternary and polymorphic cocrystals

Novel cocrystals of an anti-tuberculosis drug, Isoniazid (INH), with pharmaceutically acceptable coformers such as nicotinamide (NA), 4-hydroxybenzoic acid (HBA), fumaric acid (FA), and succinic acid (SA) are reported. Cocrystallization experiments involving INH and HBA produced two polymorphs of a novel hydrate of the INH·HBA cocrystal. Similarly, cocrystallization of INH and FA produced a novel polymorph of the reported INH·FA cocrystal. We have successfully explored the idea of designing ternary cocrystals involving INH with NA and FA or SA. All the novel solids were thoroughly characterized and their crystal structures determined. All the crystal structures feature an acid–pyridine heterosynthon involving INH and the carboxylic acid. Stability of the novel cocrystals was evaluated by slurry experiments and dynamic vapor sorption studies. In addition, stability of the cocrystals at accelerated test conditions (40 °C, 75% RH) was also tested. Anhydrous INH·HBA cocrystal and Form I of INH·HBA cocrystal hydrate were found to convert to Form II of the INH·HBA hydrate, and Form II of INH·FA cocrystal converted to Form I of the INH·FA cocrystal. Ternary cocrystals remain stable at all test conditions. Solubility and dissolution experiments revealed a greater solubility of the INH·NA·SA cocrystal and its dissolution rate is comparable to the dissolution rate of the native INH. All other cocrystals showed lower solubility and dissolution rate compared to INH.

Designing ternary cocrystals with hydrogen bonds and halogen bonds

A graded selection of hydrogen bonds and halogen bonds allows for the isolation of 2 : 1 : 1 ternary cocrystals of the general form 4-nitrobenzamide : diacid : 1,4-dihalogenated benzene, which are mediated by the amide-acid and I···O2N supramolecular synthons.

Porous Organic Alloys

Another brick in the wall: Porous ternary cocrystals were prepared by chiral recognition between organic cage modules. One module, CC1, is ordered on 50 % of the lattice positions with respect to two other modules, CC3 and CC4, that are disordered across the other 50 % of sites (see picture). There is a linear relationship between relative module composition and the cocrystal lattice parameters.

An Investigation of the Hydrogen-Bond Preferences and Co-crystallization Behavior of Three Didonor Compounds.

We assess the suitability of the three didonor compounds as building blocks for ternary co-crystals of the type (didonor)(monoacceptor)2. A Cambridge Structural Database (CSD) survey was carried out to analyze the hydrogen-bond connectivity and develop a strategy for the preparation of the desired co-crystal. Six specific compounds were selected and crystals were grown from 1:1 and 1:2 solutions of didonor compounds (m-hydroxybenzoic acid, p-hydroxybenzoic acid, and racemic mandelic acid) and acceptor compounds (acridine, triphenylphosphine oxide, and nicotinamide) leading to three co-crystals (m-hydroxybenzoic acid)·(triphenylphosphine oxide)2 (1), ((RS)-mandelic acid)·(acridine) (2) and (p-hydroxybenzoic acid)·(nicotinamide) (3). Characterization by single-crystal structure determination confirms the success of this design strategy.

Shape and size mimicry in the design of ternary molecular solids: towards a robust strategy for crystal engineering

2- and 5-methylresorcinol form co-crystals with 4,4'-bipyridine in which some of the bipyridine molecules are loosely bound. These molecules can be replaced with other molecules of a similar shape and size to give a general method for the engineering of a ternary co-crystal.

Engineering of ternary co-crystals based on differential binding of guest molecules by a tetraarylpyrene inclusion host

Tetraarylpyrene host TP exhibits remarkable differential binding of guest molecules in the solid state to include aromatic and aliphatic guests in different domains to permit synthesis of ternary co-crystals in a predictable manner.

Controlling hydrogen-bond preferences in bipyridines with competing binding sites

The design and synthesis of a family of supramolecular reagents (SRs) based on ethynyl-spaced substituted bipyridines are described, and their potential use as molecular ‘hubs’ for the predictable construction of binary and ternary co-crystals is explored. Each SR was synthesized in good yields through consecutive Pd-catalyzed Sonogashira cross-coupling reactions. Crystal structures of three binary co-crystals are presented with each structure clearly illustrating how accurate supramolecular assembly control can be achieved by increasing/decreasing the strength of the participating hydrogen-bond interactions.

2-Amino-benzothia-zolium 2,4-dicarboxy-benzoate monohydrate.

Cocrystallization of 2-amino­benzothia­zole with benzene-1,2,4-tricarboxylic acid in a mixed solvent affords the title ternary cocrystal, C7H7N2S+·C9H5O6 −·H2O, in which one of the carboxyl groups of the benzene­tricarboxylic acid is deproton­ated and the heterocyclic N atom of the 2-amino­benzothia­zole is protonated. In the crystal, inter­molecular N—H⋯O and O—H⋯O hydrogen-bonding inter­actions stabilize the packing.