Crystal Growth & Design最新文献

Crystals are integral to a variety of industrial applications, such as the development of pharmaceuticals and advancements in material science. To anticipate crystal behavior and pinpoint effective crystallization techniques, a thorough investigation of crystal structures, properties, and the associated processes is essential. However, conventional methods like experimental procedures and quantum mechanics calculations, while crucial, can be expensive and time-consuming. In response, machine learning has risen as an effective alternative, complementing the traditional approaches based on quantum mechanics and classical force fields. In the recent years, the deployment of machine learning in the realm of crystallization has yielded notable progress. This review offers a concise overview of the application of machine learning techniques in crystallization, focusing on the past five years. Our analysis of the literature indicates that machine learning has accelerated the prediction of crystal structures by streamlining the generation and evaluation of structures. Additionally, it has facilitated the prediction of key crystal properties such as solubility, melting point, and habit. The review further explores the role of machine learning in refining the control and optimization of crystallization processes, highlighting the restrictions of conventional algorithms and sensing technologies. The advantages of end-to-end processing for enhancing the accuracy of predictions and the combination of data-driven with mechanism-based models for robustness are also considered. In summary, this review provides insights into the current state of machine learning in the field of intelligent crystallization and suggests pathways for future research and development.

In this study, we examine the experimental and theoretical capabilities of two perhalogenated anilines, 2,3,5,6-tetrafluoro-4-bromoaniline (btfa) and 2,3,5,6-tetrafluoro-4-iodoaniline (itfa) as hydrogen and halogen bond donors. A series of 11 cocrystals derived from the two anilines and selected ditopic nitrogen-containing acceptors (4,4′-bipyridine, 1,2-bis(4-pyridyl)ethane, and 1,4-diazabicyclo[2.2.2]octane) in 1:1 and 2:1 stoichiometries were prepared by liquid-assisted grinding and crystallization from solution. Crystallographic analysis revealed bifunctional donor properties in both anilines. The dominant supramolecular interaction in four cocrystals of btfa is the N–H···N_acceptor hydrogen bond between btfa and acceptor molecules, while in the one remaining cocrystal, donor and acceptor molecules are connected via the N–H···N_acceptor hydrogen bond and the Br···N_acceptor halogen bond. In two cocrystals of itfa, the dominant supramolecular interaction is the I···N_acceptor halogen bond between itfa and acceptor molecules, while in the remaining four cocrystals, donor and acceptor molecules are additionally connected by the N–H···N_acceptor hydrogen bond. Periodic density-functional theory (DFT) calculations have been conducted to assess the formation energies of these cocrystals and the strengths of the established halogen and hydrogen bonds. Molecular DFT calculations on btfa and itfa indicate that the differences in electrostatic potential between the competing sites on the molecules are 261.6 and 157.0 kJ mol^–1 e^–1, respectively. The findings suggest that itfa, with a smaller electrostatic potential difference between donor sites, is more predisposed to act as a bifunctional donor.

The experimental and theoretical capability of two perhalogenated anilines, 2,3,5,6-tetrafluoro-4-bromoaniline and 2,3,5,6-tetrafluoro-4-iodoaniline, as hydrogen and halogen bond donors have been explored by cocrystallization with 4,4′-bipyridine, 1,2-bis(4-pyridyl)ethane, and 1,4-diazabicyclo[2.2.2]octane.

Mono- and bis-carbonyl hypoiodites incorporating the tertiary amines quinuclidine (1a–e) or 1,4-diazabicyclo[2.2.2]octane (DABCO; 2a, 2b, and 2e), respectively, have been synthesized and represent the first examples of hypoiodites stabilized by alkyl amines rather than aromatic Lewis bases (e.g., pyridine derivatives). These highly reactive complexes have been characterized in the solid state by SCXRD and DFT calculations. The DABCO hypoiodite derivatives are rare examples of ditopic bis(O–I–N) complexes and were found to display unexpected bonding parameters relative to iodine(I) complexes in which the DABCO is coordinating in a monotopic manner.

Mono- and bis-carbonyl hypoiodites incorporating the tertiary amines quinuclidine or 1,4-diazabicyclo[2.2.2]octane have been synthesized and represent the first examples of hypoiodites stabilized by alkyl amines rather than aromatic Lewis bases.

Coordination polymers serve as an important platform to promote highly selective solid-state reactions between organic struts. A new class of amide-containing cyclobutane molecules has been synthesized using a [2 + 2] photodimerization reaction in coordination polymers (CPs) of rigid and linear diene 3,3′-(1,4-phenylene)bis(N-(3-pyridyl)acrylamide), 4PMA, with rigid as well as flexible dicarboxylates as coligands. Four Co(II) CPs studied here produce 2D layers with rhomboidal grids (isophthalate (CP-1) and p-carboxy cinnamate (CP-2)), while p-phenylene acrylate (CP-3) yields a 3D framework with cds topology and p-phenylene diacetate forms 2D layers with a bimetallic secondary building unit (SBU). The [2 + 2] cycloaddition reaction upon exposure to 365 nm UV light on the methanol solvate of 4PMA remained elusive despite a favorable polymeric alignment in its crystal structure. Single crystals of CPs upon irradiation resulted in photodimerization; however, the crystal structure suggests polymerization (CP-1 and CP-2) or no reaction (CP-3). This unusual behavior is attributed to deviations in geometrical parameters from the ideal, serving as the driving force behind the photodimerization reaction. Nevertheless, the 2D CP of CP-4 exhibited resilience during dimerization, leading to the formation of a 3D coordination polymer of the fsc net of CP-4P through a single-crystal-to-single-crystal structural transformation. The separated dimer product displays quenched photoluminescence and blue-shifted spectra compared with the monomer.

Epitaxial thin films of the La_1–xSr_xMnO₃ system, spanning a wide range of compositions (0.5 ≤ x ≤ 0.65), have been prepared, using the polymer-assisted deposition method, on SrTiO₃ (100) substrates. The primary objective was to achieve the highly stable A-type antiferromagnetic (AF) phase associated with x = 0.5. However, the electronic and magnetic properties of the samples, with different substitution levels of La with Sr, exhibit deviations from the anticipated behavior according to the bulk phase diagram. Employing X-ray absorption spectroscopy, we demonstrate that the effective 0.5:0.5 ratio of Mn³⁺:Mn⁴⁺ is actually attained in the sample with x = 0.65, suggesting the presence of an alternative charge compensation mechanism. High oxygen pressure annealing processes allow us to demonstrate that oxygen vacancies, generated to accommodate the epitaxial structural strain, are responsible for the partial charge compensation and the observed deviations from the bulk phase diagram.

Epitaxial thin films of the La_1−xSr_xMnO₃ system (0.5 ≤ x ≤ 0.65) have been prepared by PAD to achieve the A-type antiferromagnetic (AF) phase (x = 0.5). However, the samples show deviations from the bulk phase diagram, and this AF phase is found for x = 0.65, according to XAS. The presence of oxygen vacancies can justify these results.

Azo-pyridinic derivatives are renowned for their ability to undergo reversible molecular switching when exposed to light. By combining the photoresponsive properties of azo-benzene with the supramolecular capabilities of pyridyl groups, azo-pyridines offer a route to develop multifunctional responsive materials through noncovalent interactions or reversible chemical reactions. Although azo-pyridine and its derivatives are commonly used in crystal engineering, their spectroscopic characterization is typically limited in solution and only poor attention has been given to their photoresponsive behavior in the solid state. Here, we present a library of azo-pyridinic derivatives designed as potential photoresponsive compounds with different spectroscopic behaviors based on the chemical decoration of the phenyl ring. Comprehensive characterization, including crystal structure, thermal analysis, and spectroscopic analysis, was performed for all compounds. Finally, their trans-to-cis isomerization propensity in the solid state is correlated with their crystal structures.

Detailed crystallographic and computational analysis of solvates of dasatinib (DAS), an inhibitor of multiple tyrosine kinases, was performed by confirming the high structural similarity of most of the DAS crystal structures and identifying the differences in molecular conformation, hydrogen bonding, and molecular packing. The crystal structures of 14 new DAS solvates are presented, allowing the crystallographic analysis of 23 DAS solvates and one nonsolvated phase. The analysis of molecular conformation revealed that in most of the structures DAS adopts three slightly different conformations, even though computational analysis indicated the existence of alternative energetically competitive conformations. In almost all structures, DAS molecules form identical hydrogen-bonded layers. The lack of structural variation is believed to be the result of the limited ways for efficient packing of the large sized and specifically shaped DAS molecules. Detailed analysis, however, revealed three similar but somewhat different ways these layers are packed, resulting in the classification of DAS solvates in three structure groups I, II, and III. The different arrangements of the layers result in different hydrogen bonds formed by O1–H and the space available for the solvent, but, interestingly, this is not linked with the exact DAS conformation or solvent functionality, properties, or bonding with DAS molecules.

Molecular crystals with desirable structures and tunable photoluminescence are highly important for multiscenario field applications as lasers, sensors, and light-emitting devices. However, purposeful controls on the photoluminescence are still challenging because of the high sensitivity of molecular stackings to molecular structures and surroundings. Herein, solid-state assembly and photoluminescent behavior of nine 5-(9H-carbazol-9-yl) isophthalic acid (CzIp)-based molecular crystals have been crystallographically, spectroscopically, and theoretically investigated by incorporation with electron-deficient acceptors and polar solvent molecules. As compared to the self-aggregation of green-emissive CzIp, methanol-solvated CzIp-CH₃OH and hydrated CzIp-H₂O exhibit tailorable structural overlaps for the π-stacked CzIp–CzIp dimers, emitting high-energy cyan and blue fluorescence upon excitation by UV light. These blue-shifted emissions are from different local excited states of the π-stacked dimers. By contrast, six cocrystals with 1:1 and 2:1 stoichiometry and/or cocrystallized solvent are constructed, respectively, from the π–π stacked CzIp-acceptor or CzIp–CzIp pairs, which are assembled into one-dimensional ribbons (for CzIp-OFN, CzIp-TCNB, CzIp-DCTFB, and CzIp-TCNQ, OFN = octafluoronaphthalene, TCNB = 1,2,4,5-tetracyanobenzene, DCTFB = 2,3,5,6-tetrafluoro-1,4-dicyanobenzene, and TCNQ = 7,7,8,8-tetracyanoquinodimethane), two-dimensional sheet (for CzIp-DITFB, DITFB = 1,4-diiodotetrafluorobenzene), and discrete cyclic tetramer (for CzIp-TND, TND = 1,4,5,8-naphthalenetetracarboxdiimide) through intermolecular hydrogen- and halogen-bonding interactions. These cocrystals emit switchable emissions from quenched fluorescence to intense blue, green, orange, and near-infrared photoluminescence. Further structural comparisons and theoretical calculations demonstrate that the wide-range multicolor luminescence is either from the local excited state or from the charge transfer, in which the π-stacked donor–acceptor pair, suitable energy levels, and band gap, as well as rational hole–electron distributions, manipulate synergistically the charge transfer-induced photoluminescence. These findings offer in-depth insights into the relationships of molecular stackings and photoluminescence, advancing the development of organic luminescence crystals with desirable optoelectronic properties.

The synthesis and solid-state structures of four structurally diverse i-mnt-based anionic complexes and coordination polymers are described (i-mnt = iso-maleonitrile dithiolate). (ⁿPr₄N)₄[Pb₂(i-mnt)₄] is dimeric, containing a five-coordinate distorted square pyramidal Pb(II) center with a stereochemically active lone pair. The isoelectronic (ⁿPr₄N)[Bi(i-mnt)₂] is a distorted six-coordinate complex that crystallizes in the polar P2₁ space group and forms a 2D coordination polymer via intermolecular Bi–N interactions; the d¹⁰s² Bi(III) center also has a hemidirectional coordination sphere with a stereochemically active lone pair. Using the more compact (Me₄N)⁺ cation, (Me₄N)₂[Pb(i-mnt)₂] contains eight-coordinate holodirectional Pb(II) centers that form 1D chains via bridging Pb–S bonding. These anionic complexes could provide the foundation to incorporate stereochemically active lone pairs into heterometallic coordination polymers. As a comparison, (ⁿPr₄N)₃Cr(i-mnt)₃·H₂O was also prepared and has a propeller structure with a typical octahedral Cr(III) center.

The physicochemical properties of chemical compounds can be altered and optimized by cocrystallization with a suitable coformer. However, discovering suitable coformers is a difficult and expensive process. Link prediction is one of the several techniques developed to predict suitable new coformers computationally. Link prediction uses a network of known coformers extracted from, e.g., the Cambridge Structural Database (CSD) to predict new cocrystals. We have investigated link prediction methods and were able to improve the performance of these methods using a scoring function called “multi-steps resource allocation”. Further improvements were obtained by examining the local structure of the network to remove imperfections and by using an algorithm previously designed by us to bipartise the network, thus removing imperfections on a global scale. By repeatedly predicting and synthesizing new cocrystals and adding them to the network to predict more new cocrystals, we obtain more and better predictions, but saturation of the local network eventually leads to diminishing returns. We demonstrate this for praziquantel (PZQ), a drug used to treat schistosomiasis. We discovered 11 new cocrystals for this compound, one of which is a racemic conglomerate that could be used to improve the medical efficacy of PZQ, and present 6 new cocrystal structures.

Link prediction for the CSD cocrystal network is optimized and iteratively applied to praziquantel.