Crystal Growth & Design最新文献

Three racemic ligands (L¹–L³) containing 1,2-dihydroquinazoline units have been designed and synthesized as a continuation of our previous research work. Six Ag(I) coordination polymers, {[AgL¹]BF₄·3MeCN}_n (1), {[Ag₂(L¹)₂](NO₃)₂·MeCN·H₂O}_n (2), {[Ag₂(L²)₂(μ₂–N₂)](NO₃)₂·2H₂O}_n (3), {[Ag₂(L²)₂(μ₂–N₂)](BF₄)₂·2H₂O}_n (4), {[Ag(L³)₂]tosylate·2MeCN·H₂O}_n (5), and {[Ag₂(L³)₄](PF₆)₂·2MeOH}_n (6), were synthesized upon reaction of these ligands with different Ag(I) salts. The structural diversity of the resulting complexes revealed the chiral self-discrimination or self-recognition processes of the racemic ligands when coordinated to Ag(I) ions. More importantly, the pyridyl orientation in the ligands has a crucial effect on the resulting structures of these complexes. In addition, with the combination of the biological activity of the 1,2-dihydroquinazoline derivatives and the redox behaviors of their resulting Ag(I) complexes, we investigated their antibacterial activity against two bacteria (MDREC and MRSA), and the synthesized Ag(I) complexes showed satisfactory antibacterial properties.

Building on the established Ga droplet etching (DE) technique on SiO_x, we report a scalable and reproducible method for the self-catalyzed vapor–liquid–solid growth of GaAs nanowires (NWs) on 2-in. SiO_x/Si(111) wafers using molecular beam epitaxy. By systematically varying only the Ga deposition time during DE, the number density of vertical NWs can be tuned over 2 orders of magnitude (from low-10⁷ to high-10⁸ cm^–2). We identify a threshold Ga deposition time above which uniform, untapered NW arrays with high-density (>10⁸ cm^–2) and near-unity vertical yield (>99%) are obtained, exhibiting low reflectance (<1%) across the visible to near-infrared range, thereby demonstrating a wafer-scale antireflective “black” material. The sample possesses the thinnest GaAs parasitic layer, suggesting sufficient surface modification of the native oxide on the Si substrate enables efficient utilization of incident Ga and As₄ atoms for vertical NW growth. By fine-tuning the Ga deposition time without altering any other growth parameters, this work investigates the role of Ga deposition time in DE and establishes a single in situ calibration protocol that enables reproducible NW growth across different substrate lots.

Stimuli-responsive molecular crystals that exhibit abrupt color changes are commonly observed in Schiff-base organic compounds when exposed to temperature or light irradiation; these alterations are often driven by proton transfer. However, reversible switching involving combined structural and optical changes under pressure remains underexplored, because of the limited understanding of the charge transfer processes and lattice-charge coupling involved. Here, we design a new Schiff-base crystal, 2,5-dichlorosalicylideneaniline-benzonitrile, which undergoes a reversible piezochromic transition from pale yellow to orange-red at ∼0.65 GPa, accompanied by a unit-cell volume collapse of ∼2.7%. High-pressure single-crystal X-ray diffraction data reveal that the enol form undergoes planarization, reducing the dihedral angle between the salicylidene and phenyl rings from 40.15° to nearly 0°. High-pressure infrared spectroscopy and density-functional theory calculations support pressure-induced intramolecular proton transfer from the hydroxyl (−OH) to the imine (−NH) group, ultimately driving enol→cis-keto tautomerization. Moreover, the transformation causes a large band gap reduction of ∼0.70 eV and a photoluminescence peak shift of ∼10 nm. This work establishes an interplay of pressure-induced intramolecular proton transfer, molecular planarization, and large color changes in a new Schiff-base crystal, thereby providing a blueprint for designing piezo-responsive chromic switches operable under extreme environments.

A new class of quasi-one-dimensional quantum magnetic materials, BiAO₂Cu₂(SO₄)₂ (A = K, Rb, Cs), were successfully synthesized via a conventional hydrothermal method. Systematic characterization of their structural and magnetic properties reveals that the radius of alkali metal cation A⁺ plays a critical role in structural tuning. Structurally, the K and Rb compounds are isostructural, crystallizing in the monoclinic system (P2₁/m). The Cu1O₅ square pyramids and Cu2O₄ square planes form a uniform chain via μ₂-O bridges. In contrast, substitution with the larger Cs⁺ ions at the A-site reduces the crystal symmetry to the triclinic system (P-1). Specifically, the pronounced steric effect induced by the Cs⁺ ions causes a relative rotation of the SO₄ tetrahedra. This rotation consequently modifies the coordination geometry of the Cu²⁺ ions, resulting in a five-coordinate, distorted square-pyramidal configuration for each copper site and thereby transforming the copper chain into an alternating chain. Magnetic measurements indicate a nonmagnetic spin-singlet ground state for all compounds. The formation of this spin-singlet ground state may originate from the presence of significant antiferromagnetic next-nearest-neighbor interactions along the chain direction.

The selective detection of phosphate ions (PO₄^3–) remains a challenge in fluorescence sensing. This work reveals the underlying mechanism of a unique fluorescence enhancement response in a Zr-MOF constructed with a pyrazinoquinoxaline-based tetracarboxylate linker. The MOF exhibits high selectivity for PO₄^3– over other anions, with a strong binding affinity (K = 1.02 × 10⁵ M^–1). Combined experimental and theoretical studies demonstrate that PO₄^3– preferentially adsorbs at the Zr₆O₄(OH)₄ clusters via strong hydrogen bonding. Crucially, density functional theory calculations indicate that PO₄^3– acts as an efficient electron donor, injecting electrons into the ligand’s antibonding orbitals. This injection narrows the HOMO–LUMO gap from 0.913 to 0.312 eV, thereby facilitating charge transfer and enhancing radiative transition. The fluorescence enhancement efficiency correlates with the phosphate protonation state (PO₄^3– > HPO₄^2– > H₂PO₄^–), and both noncoordinative adsorption and direct coordination to Zr(IV) yield similar electronic effects. This study provides an electronic-structure basis for the rational design of MOF-based sensors.

Hydrogen-bond-directed self-assembly of organophosph(on)ates represents a versatile strategy for constructing functional supramolecular frameworks. To clarify how organophosph(on)ate anions direct urea-based assemblies, a mono(urea) ligand, 1,3-bis(4-nitrophenyl)urea (L), was coordinated with organophosph(on)ate salts to afford three crystalline structures (1–3). Single-crystal X-ray diffraction revealed that 1 and 2 exhibit a tendency to form anion–anion dimers, which assemble with the mono(urea) ligand into A₂L₂-type (A = anion, L = ligand) units. In contrast, controlled deprotonation in MeCN with trace water generated 3, in which a deprotonated phenylphosphonate (PhPO₃^2–) forms an eight-hydrogen-bond coordination loop comprising three L donors and two water molecules. This multidentate environment resembles the dense hydrogen-bond network found in PTP1B–phosphate complexes. Comparative structural analysis demonstrates a protonation-controlled transition from self-dimerization to multipoint encapsulation, modulated by counter-cations and solvent interactions. These findings provide a molecular-level understanding of organophosph(on)ate-directed hydrogen-bond assembly and establish a readily accessible small-molecule platform for emulating phosphate-mediated recognition motifs relevant to both biomolecular regulation and functional material design.

Organic–inorganic hybrids demonstrate UV-induced fluorochromic behavior, with both Zn-1 and Zn-2 crystallized as discrete zero-dimensional coordination units. Single-crystal X-ray diffraction revealed that Zn-1 features an isolated Zn center coordinated by photosensitive ligands in a relatively loose packing arrangement, whereas Zn-2 exhibits a denser molecular packing with stronger intermolecular π–π stacking and hydrogen-bonding interactions. Upon UV irradiation, both compounds display distinct fluorochromic responses; however, Zn-2 shows superior UV detection sensitivity and more pronounced coloration, thereby establishing its potential as a promising UV dosimeter material. Furthermore, Electron Paramagnetic Resonance (EPR) and Hirshfeld surface analyses were conducted to elucidate the underlying UV-induced fluorochromic mechanism, revealing how the different intermolecular interactions of the photosensitive ligands in Zn-1 and Zn-2 modulate their respective photoresponsive sensitivities.

The structural and electronic properties of bibenzyl (1,2-diphenylethane) are investigated as a function of pressure using single-crystal X-ray diffraction (SC-XRD) and two-photon-induced fluorescence. Bibenzyl is an appealing pseudostilbene compound for the high-pressure synthesis of mixed carbon nanothreads with tunable optical properties, due to its fully saturated linking group. Crystal structures are refined from ambient pressure up to 37 GPa by synchrotron XRD, and the appearance of pseudosymmetry traits at 13 GPa reveals a phase transition that consists of molecular distortions leading to the tripling of the a axis and asymmetric unit while maintaining the unit cell's point group symmetry. Two-photon-induced fluorescence up to 18 GPa provides insights into the structural changes where the strengthening of π–π interactions at the phase transition stabilizes the electronic ground state and drives the molecular distortions that occur at that pressure. Coupling structural and electronic properties rationalizes the high-pressure reactivity compared to other pseudostilbenes, showing that the molecular evolution from the added torsional degree of freedom and establishment of π–π interactions at the phase transition lead the molecular conformation to an unfavorable state for pressure-induced polymerization.

The solid forms of three new diastereomeric quinine-based salts (two hydrated naproxen salts (S-Nap_RS-Quin_W and R-Nap_RS-Quin_W) and one anhydrous ibuprofen salt (S-Ibu_RS-Quin) were investigated using a combination of experimental techniques (e.g., X-ray diffraction, thermal analyses, infrared spectroscopy) and in silico methods. Additionally, the solid-state form of a naproxen-cinchonine salt (S-Nap_SR-Cinch) was studied, and for comparison, the crystal structure of a related quinine-based salt with flurbiprofen (R-Fbu_RR-Quin) was included. Structural characterization and phase stability studies, including hydration and dehydration behavior, offered valuable insights into the stability profiles of these compounds. Detailed in silico analyses further clarified the molecular interactions and packing arrangements underlying the solid-state structures. Together, these results provide a structural explanation for the enantioselective crystallization observed, highlighting the superior intrinsic stability of the S-Nap_RS-Quin_W crystal packing as a key factor driving chiral discrimination. This integrated approach advances our understanding of the molecular determinants that govern selective salt formation, with potential implications for the design of improved chiral separation strategies in pharmaceutical development.

Hollow-structured MFI zeolite exhibits great potential as a high-performance catalyst, adsorbent, and low-k material. For the construction of interior voids in silicalite-1 (pure silica MFI-type) zeolite, alkaline etching by TPAOH aqueous solution is a typical top-down approach. However, tough conditions like high temperature (around 170 °C) and high pressure (generated in autoclave), which are unfavorable for the safety operation and large-scale application, are necessary for the creation of a hollow structure in the zeolite. In this work, alkaline etching at mild conditions of typically 80 °C and atmospheric pressure by using TMAOH, TEAOH, and TBAOH as etchants is comparatively investigated in detail on the basis of the preliminary study that concentrated on the TPAOH etchant. Hierarchical hollow silicalite-1 zeolites are successfully obtained at different processing times for TEAOH-/TBAOH-etching, while TMAOH-etching only leads to the formation of plate-like crystals even at relatively harsh treatment conditions. The thinning trend of the wall thickness of hollow silicalite-1 against etching time varies depending on the employed etchant. The adsorption affinity of organocations on the zeolite surface of silicalite-1 decreases in the order TMA⁺ > TEA⁺ ≥ TBA⁺ > TPA⁺. The protection-dissolution etching mechanism associated with different etchants is analyzed. Two more detailed routes of protection-dissolution^internal (p-dⁱⁿ) and protection-dissolution^external (p-d^ex) are, for the first time, identified for TEAOH/TPAOH/TBAOH and TMAOH, respectively. The zeolite film layers prepared from the hollow silicalite-1 seeds possess internal cavities, exhibiting good anticorrosion ability and low dielectric constant k values.