Crystal Growth & Design最新文献

This Article revisits the “Definition of the Halogen Bond (IUPAC Recommendations 2013)” [Desiraju, G. R. Pure Appl. Chem. 2013, 85 (8), 1711–1713], recommendations that fail to include the fundamental, underlying concept of (electrophilic) σ- and p-/π-hole theory and orbital-based charge transfer interactions that accompany halogen bond formation. An electrophilic σ-hole, or p-/π-hole, is an electron-density-deficient region of positive polarity (and positive potential) on the electrostatic surface on the side of halogen along, or orthogonal to, a covalently bonded halogen in a molecular entity that leads to the development of a noncovalent interaction─a halogen bond─when in close proximity to an electron-density-rich nucleophilic region on the same or another identical or different molecular entity, with which it interacts. This Article re-examines the characteristic features of the halogen bond and lists a wide variety of donors and acceptors that participate in halogen bonding. We add caveats that are essential for identifying halogen bonding in chemical systems, necessary for the appropriate use of the terminologies involved. Illustrative examples of chemical systems that feature inter- and intramolecular halogen bonds and other noncovalent interactions in the crystalline phase are given, together with a case study of some dimer systems using first-principles calculations. We also point out that the π-hole/belt (or p-hole/belt) that may develop on the surface of a halogen derivative in halogenated molecules may be prone to forming a π-hole/belt (or p-hole/belt) halogen bond when in close proximity to nucleophiles on another similar or different molecular entity.

The all-inorganic metal halide perovskite CsPbBr₃ is a well-known semiconductor which attracts attention from many researchers in the field of optoelectronics. Although CsPbBr₃ in the form of single crystals offers the best charge transport properties, their high cost of fabrication makes them less suitable for large-scale applications. Polycrystalline films, on the other hand, can fill this market gap, and numerous solution- and vapor-based techniques exist to produce them. However, no superior solution has been found yet, and we propose the less explored close space sublimation (CSS), a fast and scalable physical vapor deposition technique, as a viable processing technique for manufacturing CsPbBr₃ films. We show the fabrication of high-quality single-phase CsPbBr₃ films with homogeneous film thicknesses over an area of 3.14 cm². By optimizing the deposition temperature, a growth rate of 10 μm/min can be reached with a material utilization of up to 98%. In addition, the necessary CsPbBr₃ source material is synthesized via ball milling; hence, the whole process is solvent-free. This work aims at rationalizing the CSS process and offering a comprehensive study of the impact of the deposition conditions on the growth of CsPbBr₃.

Crystal nucleation shapes the structure and product size distribution of solid-state pharmaceuticals and is seeded by early-stage molecular self-assemblies formed in host solution. Here, molecular clustering of salicylamide in ethyl acetate, methanol, and acetonitrile was investigated using photon correlation spectroscopy. Cluster size steadily increased over 3 days and with concentration across the range from undersaturated to supersaturated solutions. Solute concentration normalized by solubility provided more sensitive characterization of molecular-level conditions than concentration alone. In saturated solution, cluster size is independent of solvent, while at equal supersaturation, solvent-dependent cluster size increases as methanol < acetonitrile < ethyl acetate, commensurate with increasing nucleation propensity. In ethyl acetate, with largest prenucleation clusters, the driving force required for nucleation is lowest, compared to methanol with smallest clusters and highest driving force. To understand solvent–solute effects, we performed IR spectroscopy supported by molecular simulations. We observe solute–solvent interaction weakening in the same order: methanol < acetonitrile < ethyl acetate, quantifying the weaker solvent–solute interactions that permit the formation of larger prenucleation clusters. Our results support the hypothesis that nucleation is easier in weaker solvents because weak solute–solvent interactions favor growth of large clusters, as opposed to relying solely on ease of desolvation.

Molecular clustering of salicylamide in ethyl acetate, methanol, and acetonitrile was investigated using photon correlation spectroscopy. To understand solvent−solute effects, IR spectroscopy was performed supported by molecular simulations. Nucleation gets easier in weaker solvents because of weak solute−solvent interactions which favor growth of large clusters.

We report the effect of the countercations in three crystalline networks based on a mixed-valence hexavanadate fragment containing 3 V^IV and 3 V^V centers and functionalized with three molecules of tris(hydroxymethyl)aminomethane, giving the polyanion [V₃^IVV₃^VO₁₀{(OCH₂)₃CNH₂}₃]^2–. The mixed-valence hexavanadate is crystallized using three different cations, obtaining [H₃O]₂[V₃^IVV₃^VO₁₀{(OCH₂)₃CNH₂}₃]·6H₂O, 1, Na₂[V₃^IVV₃^VO₁₀{(OCH₂)₃CNH₂}₃]·9H₂O, 2, and [n-Bu₄N]₂[V₃^IVV₃^VO₁₀{(OCH₂)₃CNH₂}₃]·(H₂O)(DMF), 3. The structural characterization shows that 1–3 present perfect equilateral arrangements of the paramagnetic triangles of V^IV, thus showing structural spin frustration. The supramolecular interaction modulates the studied magnetic properties depending on the size and distribution of the cations around the hexavanadate fragment. Theoretical calculations demonstrated that the three studied compounds present the ground state doublets degenerated. Compound 3 shows a plateau below 16 K in the χ_mT(T) plot, showing the S = 1/2 ground state due to the antiferromagnetic interactions in the triangle, whereas in compounds 1 and 2, the plateau is absent and the χ_mT product decreases near zero at 2 K. In 1 and 2, the magnetic moment decreases at low temperatures due to antiferromagnetic interactions of the spin triangles in the tetrahedral supramolecular arrangement.

The sustainable development of nuclear energy urgently requires the development of appropriate materials for the effective adsorption of radioiodine. Electron-donating group-functionalized layered metal–organic frameworks (MOFs) can not only enhance the host–guest interactions but also avoid the reduction of free pore voids benefit by the flexible interlayer spacing, supposed to have excellent I₂ adsorption ability. Herein, by rational selection of methyl-decorated aromatic 4,4′,4″-(2,4,6-trimethylbenzene-1,3,5-triyl)tribenzoic acid (H₃TMTB) and Zn(NO₃)₂·6H₂O as the building units, a three-blade-paddlewheel unit-based layered [Zn₂(TMTB)(H₂O)₂]·(OH^–)·guest (1), possessing rare [Zn₂(COO)₃(H₂O)₂]⁺ unit, was successfully synthesized and systematically characterized. I₂ adsorption study indicated that 1 is recyclable and the maximum adsorption in organic solution and vapor phase is 77.7 mg g^–1 and 2.00 g g^–1, respectively. Grand Canonical Monte Carlo simulations revealed that the layered structure in synergy with the coexistence of −CH₃, π-electron-rich phenyl, and [Zn₂(COO)₃(H₂O)₂]⁺ contribute to the excellent performance. This work may provide a new way for the development of advanced I₂ adsorption MOF-based materials.

Balancing detonation performance and sensitivity has always been a challenge in the field of energetic materials. Herein, we present the synthesis of 2-(1H-pyrazol-3-yl)-2H,2′H-5,5′-bistetrazole (4) followed by the introduction of C-NO₂, resulting in the formation of 2-(4-nitro-1H-pyrazol-3-yl)-2H,2′H-5,5′-bistetrazole (5) characterized by low sensitivity, high energy content, and good thermal stability. Characterization of these compounds was conducted via NMR and IR spectroscopy, with the structures of compounds 4a, 5, and 5a elucidated through single-crystal X-ray diffraction. The energetic properties of these compounds were studied, and all new compounds had detonation velocities (7384–9111 m s^–1) higher than trinitrotoluene (TNT). Particularly noteworthy is compound 5b (D_v = 9111 m s^–1, impact sensitivity (IS) = 13 J, friction sensitivity (FS) = 144 N), which exhibits superior detonation velocity and reduced sensitivity compared to Research Department eXplosive (RDX), presenting a promising avenue for the development of novel energetic materials.

The pharmaceutical industry is increasingly exploring cocrystals as a solution to provide improved material properties for otherwise intractable active pharmaceutical ingredients (APIs). Researchers have attempted to streamline the experimental process of screening for cocrystals by developing in silico predictive tools. These tools use intermolecular interactions, primarily hydrogen bonding, as well as other molecular descriptors to quickly assess the likelihood of cocrystal formation between an API and a set of small-molecule coformers. We have developed a web-based application using three such predictive tools to help us prioritize experimental screening against a library of nearly 300 individual coformers. In order to validate our predictive algorithms, three API molecules from our compound library were screened, experimentally and with our application, against a subset of 40 coformers. Here, we present the design of the web-based app, the experimental work used to validate its predictions, and the relative success of our techniques.

A web-based application incorporating three in silico predictive tools was created to prioritize experimental screening of a large coformer database against target APIs. The application was validated by screening 3 APIs against 40 coformers both experimentally and with the app. We determined that the combination of three predictive tools severely limits correct prediction and that the Hydrogen Bond Propensity tool most accurately predicts cocrystallization outcome.

The Cambridge Structural Database (CSD) played a key role in the recently established crystal isometry principle (CRISP). The CRISP says that any real periodic crystal is uniquely determined as a rigid structure by the geometry of its atomic centers without atomic types. Ignoring atomic types allows us to study all periodic crystals in a common space whose continuous nature is justified by the continuity of real-valued coordinates of atoms. Our previous work introduced structural descriptors pointwise distance distributions (PDD) that are invariant under isometry defined as a composition of translations, rotations, and reflections. The PDD invariants distinguished all nonduplicate periodic crystals in the CSD. This paper presents the first continuous maps of the CSD and its important subsets in invariant coordinates that have analytic formulas and physical interpretations. Any existing periodic crystal has a uniquely defined location on these geographic-style maps. Any newly discovered periodic crystals will appear on the same maps without disturbing the past materials.

For the Cambridge Structural Database (CSD), the paper describes the first projections of the crystal isometry space of all periodic structures defined as equivalence classes under rigid motion. The coordinates in the resulting maps are invariant descriptors (based on interatomic distances and measured in Angstroms), which continuously change under atomic displacements and distinguish all real periodic crystals in the CSD.

Blatter radicals are extremely stable organic electron-deficient paramagnets having good potential as a spin-bearing building block in diverse applications. The packing mode and molecular conformation of such radicals are appropriate for attaining distinctive magnetic and electronic properties. Herein, within the framework of systematic exploration of the “structure–property” correlations inherent in fluorinated Blatter radicals, 1-(2,3,4-trifluorophenyl)-(2a) and 1-(2,3,5,6-tetrafluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (2b) were synthesized and completely characterized. The crystal structure of both radicals 2a and 2b was found to consist of two different centrosymmetric dimers with relatively short intermolecular distances between atoms of the benzotriazinyl moieties. SQUID magnetometry in the range of 2–300 K revealed that crystals of the two radicals, just as crystals of previously synthesized 1-(pentafluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (2c), are dominated by rather strong antiferromagnetic interactions. For the two dimer types, spin-unrestricted broken-symmetry DFT calculations predicted similar parameters J differing by less than 20%. Subsequent fitting of χT vs T dependences using theoretically predicted magnetic motifs resulted in equal values of J for two types of dimers and yielded the following best-fit J/k_B parameters: −156.4 ± 0.8 K for 2a, −230 ± 3 K for 2b, and −58.3 ± 0.6 K for 2c. For comparison, in the corresponding nonfluorinated radical (1a), only weak intermolecular interactions were observed (J/k_B = −2.2 ± 0.2 K). By contrast, previously studied radicals 1b and 1c (containing two fluorine atoms) are dominated by strong antiferromagnetic interactions (J/k_B = −292 ± 10 and −222 ± 17 K, respectively). The reason for the difference in magnetic properties of 1a and fluorinated radicals is that the introduction of fluorine atoms into the phenyl substituent in 1a has a considerable effect on its electrostatic potential, thereby leading to changes in the crystal structure and in bulk magnetic properties.