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This study aimed to address the issue of the low solubility in the model drug probenecid (PRO) and its impact on bioavailability. Two salts of probenecid (PRO), 4-aminopyridine (4AMP), and 4-dimethylaminopyridine (4DAP) were synthesized and characterized by PXRD, DSC, TGA, FTIR, and SEM. The crystal structures of the two salts were determined by SCXRD, demonstrating that the two salts exhibited different hydrogen bond networks, stacking modes, and molecular conformations of PRO. The solubility of PRO and its salts in a phosphate-buffered solution (pH = 6.8) at 37 °C was determined, the results showed that the solubility of PRO salts increased to 142.83 and 7.75 times of the raw drug, respectively. Accelerated stability experiments (40 °C, 75% RH) showed that the salts had good phase stability over 8 weeks. Subsequently, Hirshfeld surface (HS), atom in molecules (AIM), and independent gradient model (IGM) were employed for the assessment of intermolecular interactions. The analyses of salt-forming sites and principles were conducted using molecular electrostatic potential surfaces (MEPs) and pKa rules. The lattice energy (EL) and hydration-free energy (EHF) of PRO and its salts were calculated, and the relationships between these parameters and melting points and the solubility changes were analyzed. [ABSTRACT FROM AUTHOR]

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]

The preparation of a cocrystal is one of the effective strategies to tune the luminescence properties of organic crystals. In this work, four charge transfer cocrystals were constructed with isomeric substances of amino substituted dimethyl phthalates as the donors and 1,2,4,5-tetracyanobenzene as the acceptor. The emission range of the individual electron donors is from 400 nm to 505 nm, while all cocrystals have their emission redshift exceeding 100 nm. The tunable emission range of the charge transfer cocrystals is from 573 nm to 640 nm. All the obtained four cocrystals contain π–π stacking structures with the presence of π–π and C–H⋯π interactions. Fourier transform infrared spectroscopy and UV-vis spectroscopy demonstrated the presence of charge transfer interactions in the cocrystals. The tuning of the luminescence properties of the cocrystals was explained by the analysis of the crystal packing structure and the intermolecular interaction, and the distribution of frontier orbitals was obtained by DFT calculation. We believe our work is helpful to understand the relationship between the crystal structure and luminescence properties in the charge transfer cocrystals and provide guidance for the modulation of the luminescence properties. [ABSTRACT FROM AUTHOR]

Flexible crystals with unique mechanical properties have presented enormous applications in optoelectronics, soft robotics and sensors. However, there have been no reports of low-temperature-resistant flexible crystals with second-order nonlinear optical properties (NLO). Here, we report the flexible chiral Schiff-base crystals capable of efficient second harmonic generation (SHG). Both enantiomers and racemic modifications of these crystals are mechanically flexible in two directions at both room temperature and at -196 °C, although their mechanical responses differ. The enantiomers display SHG with an intensity of up to 12 times that of potassium dihydrogenphosphate (KDP) when pumped at 980 nm, and they also have high laser-induced damage thresholds (LDT). Even when bent, the crystals retain strong second harmonic generation, although with a different intensity distribution depending on the polarization, compared to when they are straight. This work describes the first instance of flexible organic crystal with NLO properties and lays the foundation for the development of mechanically flexible organic NLO materials., (© 2024 Wiley‐VCH GmbH.)

Various mechanical effects have been reported with molecular materials, yet organic crystals capable of multiple dynamic effects are rare, and at present, their performance is worse than some of the common actuators. Here, we report a confluence of different mechanical effects across three polymorphs of an organic crystal that can efficiently convert light into work. Upon photodimerization, acicular crystals of polymorph I display output work densities of about 0.06-3.94 kJ m -3 , comparable to ceramic piezoelectric actuators. Prismatic crystals of the same form exhibit very high work densities of about 1.5-28.5 kJ m -3 , values that are comparable to thermal actuators. Moreover, while crystals of polymorph II roll under the same conditions, crystals of polymorph III are not photochemically reactive; however, they are mechanically flexible. The results demonstrate that multiple and possibly combined mechanical effects can be anticipated even for a simple organic crystal., (© 2024. The Author(s).)