Crystal Growth & Design最新文献

Extending our previous work on cocrystallization of roseolumiflavin (R), the rational design approach with various N-heterocyclic coformers has been explored to systematically tune photophysical properties of the chromophore. A series of binary and, for the first time, ternary flavin cocrystals was systematically synthesized and analyzed with particular focus on the modification of spectroscopic behavior. Structural analyses based on obtained single crystal data reveal distinct molecular packing patterns, with binary cocrystals maintaining either face-to-face or slipped stacking motifs, while ternary systems demonstrate acid-mediated protonation effects and modified π-stacking arrangements. The original hydrogen-bonded R dimer is replaced by a donor–acceptor–donor (DAD) motif and, in the case of the ternary systems, further stabilized through hydrogen bonds with acid molecules. The structural modifications directly correlate with the photophysical behavior, as all cocrystals exhibit blue-shifted fluorescence relative to R. The most pronounced influence on the spectral behavior occurs in ternary cocrystals with the emission band shifts of up to 158 nm. This work expands on to this date scarcely available knowledge of flavin cocrystallization and highlights the role of hydrogen bonding, stacking interactions and coformer selection in fine-tuning its optical properties.

This work uses bis(2-methyl-3-amino-1,2,4-triazolyl)-furoxan (1) and bis(2-methyl-3-nitroamino-1,2,4-triazolyl)-furoxan (2) as platforms to construct five new energetic ionic salts, with the goal of tuning the physicochemical profiles of the parent frameworks and testing salt formation as a general route to performance enhancement in energetic materials. Across the series, the salts show higher densities (Δρ = +0.01 to +0.08 g cm^–3 for most cases), faster detonation velocities (ΔD = +0.61–0.73 km s^–1), and lower mechanical sensitivities (IS = 14–29 J) relative to their precursors, corroborating the effectiveness of the ionic-salt strategy. Particularly noteworthy are the ammonium and hydroxylammonium salts derived from precursor 2, which deliver detonation velocities of 8.83 and 8.75 km s^–1, respectively, while retaining moderate sensitivities (IS = 29 and 25 J). The combination of elevated detonation performance and improved safety metrics identifies these salts as competitive candidates for high-energy explosive applications. The observed, systematic links between ionic structure and property gains substantiate molecular salt formation as a rational design principle for next-generation energetic materials.

The rational design of mechanochromic luminescent copper(I) coordination polymers (CPs) via the strategic incorporation of fluorophore ligands presents a promising approach for developing robust and efficient stimuli-responsive materials. In this work, three distinct CPs were synthesized by reacting CuI with 9-(pyrimidin-5-yl)-9H-carbazole (5-CzPm) under varied solvent systems and stoichiometric conditions. The reaction in acetonitrile, under different CuI and ligand ratios, led to the formation of one-dimensional (1D) [Cu₂(μ₃-I)₂(5-CzPm)₂]_n CP1 and [Cu₄(μ₃-I)₄(μ₂-5-CzPm)(CH₃CN)₂]_n CP2, while the use of an acetonitrile and dichloromethane mixed solvent system yielded the two-dimensional (2D) [Cu₄(μ₃-I)₄(μ₂-5-CzPm)]_n CP3. The synthesized CPs incorporate structurally diverse secondary building units (SBUs): CP1 features a Cu₂I₂ chain motif, CP2 contains a Cu₄I₄ staircase-type cluster, and CP3 adopts a Cu₄I₄ cubane-type SBU. All three CPs were found to be emissive, with CP1 showing a reversible mechanochromic response. CP3 also displays a mechanochromic response; however, the changes are irreversible. Detailed studies suggest that mechanical stimulation induces a phase transformation: CP1 undergoes a reversible amorphous–crystalline cycle, whereas CP3 irreversibly converts into a mixture of CP1 and CP2 upon acetonitrile exposure.

Crystalline materials capable of responding to multiple external stimuli have garnered considerable attention in recent years due to their promising potential for various applications in smart materials, sensing, and actuation. In this paper, we report the synthesis and characterization of two developed linker-based Schiff base molecular crystals, designated as 1 and 2, both of which exhibit two distinct reversible stimuli-responsive behaviors: (i) a thermal expansion–contraction response during repeated heating and cooling cycles and (ii) a reversible acidochromic color change upon sequential exposure to acidic and basic vapors. Importantly, these two reversible responses are governed by entirely distinct underlying processes. The thermal expansion–contraction behavior is driven by a martensitic phase transition, from a low-temperature phase to a high-temperature phase, which involves rapid and reversible lattice displacive rearrangements. In contrast, the acidochromic color change arises from a disruption in the electronic conjugation within the molecular framework, where the system undergoes a transformation from an A−π–D−π–A (acceptor−π–donor−π–acceptor) configuration to an A−π–A−π–A (acceptor−π–acceptor−π–acceptor) configuration upon protonation, manifested by a distinct shift in optical absorption properties. The unique combination of these two reversible phenomena─thermal expansion-contraction and acidochromic responses─within a single material system offers significant potential for advanced applications, particularly in the development of acid-sensitive sensors and thermally responsive microactuators.

A copper(II)-based MOF, designated as PCP-7 and chemically formulated as ([Cu₂(L)(H₂O)₂]·2DMF), was synthesized using a nitrogen-rich cyclotriphosphazene-derived tetracarboxylate ligand (H₄L). The three-dimensional framework, constructed from paddlewheel-type {Cu₂(COO)₄} secondary building units (SBUs), exhibited remarkable photocatalytic efficiency in the visible-light irradiation toward the degradation of organic dyes such as methylene blue (MB), rhodamine B (RhB), and methyl orange (MO). Detailed mechanistic investigations revealed that superoxide radicals (O₂^•–) serve as the primary reactive species responsible for photocatalytic degradation. Under visible-light irradiation, PCP-7 achieved over 90% degradation efficiency of MB, RhB, and MO and maintained excellent structural stability over five consecutive cycles. Electrochemical analysis further confirmed its capacitive behavior, redox activity, and photoactive nature. Ideal Adsorbed Solution Theory (IAST) analysis revealed that PCP-7 exhibits favorable gas separation performance, achieving CO₂/N₂ selectivity values of up to 41.9 at 298 K (and theoretically infinite at 323 K), together with a CO₂/CH₄ selectivity of 29.4 at 273 K, underscoring its strong potential for efficient and selective CO₂ capture.

This study investigates the hierarchical self-assembly of ring-banded spherulites formed from phthalic acid (PA) crystallized in a 50:50 wt % water ethanol binary solvent system. At elevated crystallization temperatures (≥70 °C), PA forms highly ordered double ring-banded spherulites with a distinct eye-like nucleus, where edge-on lamellae cross-hatch from flat-on lamellae. Morphological analysis reveals eye-like cores that undergo a radial, orientation-dependent lamellar transformation: edge-on lamellae gradually reorient into flat-on alignment, and flat-on lamellae reinitiate edge-on growth beyond a characteristic radial distance, corresponding to the observed periodic band spacing. AFM and SEM imaging confirm a ridge─valley periodicity and height modulation (∼250 nm), while microbeam X-ray diffraction mapping identifies alternating crystallographic textures associated with edge-on and flat-on lamellae. These features are preserved both radially and vertically, reflecting a three-dimensional, spatially coherent hierarchical assembly.

Phthalic acid crystallized from a 50:50 wt % water−ethanol mixture forms temperature-dependent spherulites, transitioning from dendritic, nonbanded structures at low temperatures to double ring-banded spherulites with an eye-like nucleus at ≥70 °C. Microbeam XRD mapping reveals a hierarchical, grating-like lamellar self-assembly with alternating edge-on and flat-on lamellae, radial and vertical coherence, and a characteristic periodicity of ∼18 μm, challenging classical helicoidal models.

In this study, two series of energetic salts derived from distinct triazole-linked tetrazole systems were designed and synthesized by connecting 1,2,4-triazole and tetrazole groups via C–C or C–N bonds. Their energetic properties─including detonation performance (calculated by EXPLO5 6.05.02 software), sensitivity, and thermal stability─were comprehensively characterized. Physicochemical analysis revealed that the C–C bonded triazole–tetrazole system (compound 5) exhibited optimal detonation performance (D_v = 8725 m s^–1, P = 31.7 GPa), comparable to that of RDX. Notably, compound 6 demonstrated the most balanced overall performance, combining suitable detonation performance (D_v = 8556 m s^–1, P = 27.9 GPa) with remarkable thermal stability (T_d = 203.7 °C) and stable mechanical sensitivities (IS > 40 J, FS > 360 N), surpassing that of ADN. In contrast, the C–N bonded triazole-tetrazole system (compounds 14 and 16) showed comparatively lower detonation performance (D_v = 7707–8396 m s^–1, P = 24.2–27.9 GPa), reduced thermal stability (T_d = 146.6–182.5 °C), and poorer mechanical sensitivities.

A strategy to modulate the mechanical and optical properties of 9,10-dicyanoanthracene (DCA) through subtle structural modification is reported. The cyanomethyl-substituted DCA derivative CCMA forms blue- and green-emitting polymorphs that exhibit face-selective elastic and plastic bending. Crystallographic analyses revealed that intercolumnar interactions along the deformation axis are responsible for the elastic response. Furthermore, the methylene unit suppresses excimer formation, resulting in a shorter-wavelength emission of CCMA, compared to that of DCA in the pristine and ground phases.

Stacking transition metal dichalcogenide (TMDs) monolayers into van der Waals heterostructures enables interfacial charge transport and interface excitons, deepening our understanding of strong correlations and spin-valley coupling in low-dimensional materials. The exfoliation of large-scale TMD monolayers is crucial for constructing van der Waals heterostructures and for further exploring their unique properties. Extending the gold-assisted mechanical exfoliation method, we develop a polymer-assisted method combined with a novel hemispherical handle (HH) for the high-efficiency, large-area exfoliation, transfer, and stacking of MoS₂, WS₂, and other TMDs monolayers. The exfoliated monolayers exhibit lateral dimensions ranging from hundreds of micrometers to millimeters, maintaining clean interfaces and preserving structural integrity after transfer and stacking. This work presents an efficient, low-damage strategy for exfoliating and transferring large-area TMDs monolayers, facilitating their integration into optoelectronic devices and advancing related research.

Pentoxifylline (PTX) is a xanthine drug that acts as a nonspecific inhibitor of phosphodiesterase with rapid dissolution and absorption in the body, given its high solubility in aqueous media. Due to that, PTX requires modulation of its release through sustained dosage forms. However, none of these formulations cater to reducing the solubility, controlling the dissolution rate, and giving rise to a longer half-life of PTX, extending the in vivo retention time. This work employs crystal engineering to systematically investigate how coformer selection governs PTX’s dissolution behavior through structure–property relationships. Five novel solid forms were produced by mechanochemical activation (PTX with caffeic, citric, glutaric, and vanillic acid). The new structures were elucidated by X-ray diffraction techniques and were characterized by spectroscopic and thermal methods. The physicochemical (solubility and melting point) and structural (crystal packing) properties were carefully investigated. Combined with two reproduced reported systems (salicylic/benzoic acids), we identify key structural motifs─particularly R₂²(8) carboxylic acid···N-heterocycle synthons─that correlate with solubility modulation and dissolution assays. While one novel cocrystal showed reduced solubility, the results provide design criteria for tuning PTX formulations, with mechanistic insights applicable to xanthine derivatives.

This image explores pentoxifylline (left) cocrystals with diverse coformers (middle), correlating molecular interactions with dissolution profiles (right). Coformer colors match their respective cocrystal solubility curves, demonstrating how structural modifications govern drug release. Mechanochemical synthesis and thermal/diffraction characterization reveal structure−property relationships for optimized pharmaceutical performance. The systematic approach provides design guidelines for solubility-modulated xanthine derivatives.