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Isostructural crystals are crucial for the development of high-performance functional materials and precise control over physicochemical properties, whereas the design of isostructural crystals is extremely challenging. In this work single-component isostructural crystals were obtained with the substitution of side-chain groups. High-quality single crystals of isostructural crystals methyl 2-amino-5-methylbenzoate (MAMB) and methyl 2-amino-5-methoxybenzoate (MAMOB) were harvested through sublimation crystallization. Their crystal structures were determined by single-crystal X-ray diffraction (SCXRD). Similar intermolecular interactions and packing modes suggested that MAMB and MAMOB are 3D isostructural, and the quantitative similarity parameters were calculated via the XPac program. Furthermore, these two obtained isostructural crystals exhibited similar blue light emission behaviors and solvation effects. [ABSTRACT FROM AUTHOR]

Dynamic molecular crystals are thought to be an emerging functional material with enormous tunability in physicochemical properties. Here, a smart crystal, 6‐Chloronicotinic acid (6‐CNA), is reported, responding to heat stimulus by bending, splitting‐to‐self‐healing, and jumping, induced thermally by a reversible single‐crystal‐to‐single‐crystal phase transition. This phase transition proceeds by a well‐organized migration of the habit plane, which is reproducible after more than twenty phase transition cycles. The temperature function introduced externally can realize a reversible migration of the habit plane and also act as a jump switch. A comprehensive analysis of the microscopic observations demonstrates that the heterogeneity of phase transition and the homogeneity of self‐driven orientations account for the splitting‐to‐self‐healing. Utilization of the reversible phase transition of 6‐CNA single crystal can generate a pushing force that is > 104 times the gravitational force of the crystal, thus making 6‐CNA an actuator to drive the reversible movement of a glass plate. Both forms of these crystal materials are mechanically compliant in two dimensions and can be twisted in terms of requirement. This excellent actuation performance, reversibility of the phase transition, and soft nature make it a prospective candidate for robust single‐crystal actuators. [ABSTRACT FROM AUTHOR]

In this study, curcumin 1,4-dioxane solvates (CUR–DIO) were obtained in two molecular ratios of 1 : 1.5 (CUR–DIO-1.5) and 1 : 1 (CUR–DIO-1) at different temperatures. In the two single crystal structures, the molecular conformation of curcumin is a planar structure and a curved structure, respectively. Moreover, the length of the hydrogen bond between the curcumin molecule and the 1,4-dioxane molecule indicates that with the increase in the system temperature, the difficulty of solvate formation increases, the solvent ratio decreases, and the inter-molecular hydrogen bond energy increases. In addition, with the increase in temperature, the crystal morphology changes from spherulites to rod-shaped crystals. The hollow spherulites of CUR–DIO-1 were obtained at 25 °C, and based on the ReactRaman data and microscope recording, a new formation mechanism of hollow spherulites was proposed. The formation mechanism and preparation method of organic small molecule hollow spherulites will play an important role in promoting the application of the hollow spherulite structures in the fields of drug loading, slow release and multifunctional drugs. [ABSTRACT FROM AUTHOR]

Boscalid, a commonly used fungicide, is mainly used for controlling gray mold, powdery mildew, and sclerotia. The aim of this study was to investigate the solid forms of boscalid systematically. The powder production of two anhydrous polymorphs (form I and form II) and monohydrate (H1) has been reported in the literature, while three novel solvates, i.e. S1 (1,4-dioxane solvate), S2 (N-methyl pyrrolidone solvate) and S3 (dimethyl sulfoxide solvate) have been obtained for the first time. The physicochemical properties of these six solid forms were fully characterized including power X-ray diffraction, scanning electron microscopy, Fourier transform-infrared spectroscopy, solid-state NMR, and thermal analysis. The crystal structures of all the six solid forms were determined from the single crystal data. The molecule conformations and packing arrangements in the crystal structures were analyzed and compared. Hirshfeld surface analysis was applied to reveal the intermolecular interactions. The packing coefficients of the crystal forms have been calculated to explain the formation of solvates. Finally, the desolvation process of solvates and the transformation relationship between different phases were explored. Meanwhile, the desolvation of solvate S2 leads to form II suitable for practical applications. [ABSTRACT FROM AUTHOR]

Levofloxacin is a fluoroquinolone and bears a broad-spectrum antibacterial effect. The polymorphism of levofloxacin was intensively studied, nevertheless, the landscape of polymorphs is not fully understood. Herein we reported for the first time the fully solved crystal structure of an anhydrous α form and three newly discovered solvates including n-propanol solvate, ethylene glycol solvate and acetic acid solvate. The successfully solved crystal structure of the anhydrous α form by single crystal X-ray diffraction was found to be in good agreement with the reported data by the SDPD (structure determination from powder X-ray diffraction data) method, but is significantly different from the one by the crystal structure prediction (CSP) approach. The comparison results suggest the wrong solved crystal structure of the α form using the CSP method. The newly reported n-propanol solvate, ethylene glycol solvate and acetic acid solvate of levofloxacin were fully characterized by powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and single crystal X-ray diffraction (except for the acetic acid solvate). It was found that the solvent molecules of the n-propanol solvate fill the channels and interact weakly with the active pharmaceutical ingredient (API) molecules, while they play crucial roles in the stability of the crystal structure. Further, the phase transformations among different solid-state crystal forms of levofloxacin were investigated in detail by variable-temperature powder X-ray diffraction. The results reveal that all of the newly discovered solvates can be directly dehydrated to an anhydrous γ form, which eventually converted into an anhydrous α form during subsequent heating. [ABSTRACT FROM AUTHOR]

• The kind, chain length and concentration of polymers are key factors in regulating the crystal habit of PABA. • PVP-K17 at low concentrations showed the best control effect which regulated PABA crystal from rodlike to blocklike. • The regulation mechanism of PVP-K17 on the crystal habit of PABA was proposed by combining experiments and molecular simulation. This study focuses on how polymers regulate the crystal habit of p -aminobenzoic acid (PABA) from long rodlike to blocklike. To propose the regulation mechanism of polymers on the crystal habit of PABA, experiments include cooling crystallization and single crystal growth as well as molecular simulation have been carried out. Firstly, crystal form of PABA from cooling crystallization was determined as α form. Secondly, among four 1.0 wt% polymers, polyvinylpyrrolidone (PVP) played a more significant role in regulating crystal habit, which inhibited the growth of long axis resulting the growth rates of the long axis from 92.1 μm/h down to 6.7 μm/h. Furthermore, the effect of PVP chain length and concentration on crystal habit has also been studied, 0.2 wt% PVP-K17 regulated the crystal habit of PABA from long rodlike to blocklike but the effect of PVP was weakened with increasing chain length and decreasing concentration. Molecular simulation results show that the interaction between PVP-K17 and (1 1 0)/(0 1 1) face, which determines the axial growth rate, is stronger compared with other crystal faces. The mechanism of PVP-K17 regulating crystal habit was that it can be selectively adsorbed on (1 1 0) and (0 1 1) faces, hindering the diffusion and adsorption of solute molecules, inhibiting the growth of the long axis of PABA crystals, so the crystal habit of obtained crystal is blocklike. [ABSTRACT FROM AUTHOR]