CrystEngComm最新文献

The metastable zone width (MSZW) during the cooling crystallization of sulfamethazine–acetylsalicylic acid (SMZ–ASA) cocrystal system in acetonitrile (ACN) exhibits different patterns with variations in coformer ratios and saturation temperatures. Studies were carried out at a fixed 0.3 °C min⁻¹ cooling rate in 20 mL with three agitation rates (100, 400, and 800 RPM), across a saturation temperature range of 15–35 °C with ASA/SMZ molar ratios ranging from 2.5–9.61. Polynomial surface fitting of the induction time data was employed to assess the dependence of MSZW on solute concentration and saturation temperature, where the concentration range was varied between 30–70 mM for SMZ and 100–400 mM for ASA. The results revealed that both coformers' composition and temperature strongly influence MSZW. Importantly, a non-monotonic trend was observed, with the MSZW broadening at higher saturation temperatures for fixed ASA/SMZ ratios, an atypical behavior compared to conventional cooling crystallization. These findings emphasize the system-specific complexity of cocrystal nucleation and the intertwined influence of solute composition and saturation temperature.

“Bridge-flipped isomers” are pairs of organic molecules differing only in the reversal of a bridge of atoms connecting two major parts of the molecules. Among the benzylideneanilines, the isomerism is R–CHN–R′ vs. R–NCH–R′ (R, R′ = aryl). Isomorphous pairs of bridge-flipped benzylideneanilines are rare. This study is focused on pairs of molecularly centrosymmetric bis-benzylideneanilines to determine whether the tendency of centrosymmetric molecules to be located on crystallographic inversion centers, in combination with their overall similarity in molecular space-filling requirements, may promote their isomorphism. A survey of the Cambridge Structural Database for centrosymmetric bridge-flipped bis-benzylideneaniline pairs of the R–CHN–C₆H₄–NCH–R vs. R–NCH–C₆H₄–CHN–R type identified 23 pairs, only two of which are isomorphous. A survey for bridge-flipped diimine pairs of the R–CHN–NCH–R vs. R–NCH–CHN–R type identified six pairs, none of which are isomorphous. Conformational differences attributed to steric interaction between the bridge C–H hydrogen atom and a ring hydrogen atom account for most of the non-isomorphous cases. From examination of whether similar intermolecular packing motifs involving organic fluorine might promote isomorphism between molecularly centrosymmetric pairs, described here are the crystal structures of three pairs of bridge-flipped bis-benzylideneanilines prepared by reaction of 2-(trifluoromethyl)benzaldehyde, 3-(trifluoromethyl)benzaldehyde, and 4-(trifluoromethyl)benzaldehyde with p-phenylenediamine and by reaction of 2-(trifluoromethyl)aniline, 3-(trifluoromethyl)aniline, and 4-(trifluoromethyl)aniline with terephthalaldehyde. The 3-(trifluoromethyl) isomers, located on inversion centers and nearly planar, are isomorphous. Certain bis-benzylideneanilines assume crystal structures isomorphous with those of the corresponding bis-stilbene or bis-azo compound, although whether they do so more readily than with their bridge-flipped isomer has not been determined.

Structural reproducibility, in terms of ligand conformation and subsequent predictability, has been explored for five-membered imide-based ligands. Three dicarboxylic acids, based on a pyromelliticdiimide core appended with amino acids, have been synthesised, structurally characterised, and used in the (attempted) synthesis of coordination polymers. The diacids differ in steric bulk at the α-carbon by varying the precursor between glycine (2× H), alanine (1× H, 1× CH₃) and aminoisobutyric acid (2× CH₃). Coordination polymers containing the glycine- and alanine-derived dicarboxylates (GlyPmDI²⁻ and AlaPmDI²⁻, respectively) were synthesised, although none could be isolated containing the most sterically encumbered ligand (ibaPmDI²⁻). The glycine-based coordination polymers show close, parallel stacking of the ligands, whereas the alanine-based coordination polymers do not. The conformation of the coordinating group with respect to the core of the ligand was studied by comparison of crystallographic data and computationally minimised structures. The preferred geometry of the ligand is shown to be dependent on the α-carbon substituents. For each ligand the geometry is reasonably predictable despite the ability of the terminal groups to rotate freely in solution.

Among the various methods for removing carbon monoxide (CO) from hydrogen-rich (H₂-rich) gases, carbon monoxide selective methanation (CO-SMET) has become one of the most effective ones, bringing considerable advantages in terms of performance, environmental sustainability and cost. A bimetallic NiRu/η-Al₂O₃ catalyst with Ni–Ru alloy phases was prepared and its performance in the removal of CO through a selective methanation process was examined in this study. Also, a comparison was made with the NiRu/γ-Al₂O₃ catalyst. The NiRu/η-Al₂O₃ catalyst demonstrated excellent CO-SMET performance, reducing the CO concentration to below 10 ppm with over 50% selectivity between 215 and 300 °C. Its excellent catalytic performance can be ascribed to numerous Ni active sites, increased oxygen vacancies, and more acidic sites. Additionally, the NiRu/η-Al₂O₃ catalyst had the ability to resist sintering because of the formation of Ni–Ru alloy on it. Moreover, it also exhibited good catalytic stability.

The Schiff base ligand, N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH₂), was initially employed in both homometallic Cu^II and heterometallic Mn^II/Cu^II coordination chemistry. A 1-D helical chain, [Cu^II₂(sacb)₂(MeOH)]_n (1), and a decanuclear 0-D heterometallic cluster, [Cu^II₈Mn^II₂(OH)₄(sacb)₈(H₂O)₂] (2), were synthesized and fully characterized. Complex 2 is one of the two highest nuclearity Mn^II/Cu^II complexes reported to date and exhibits a unique {Cu₈Mn₂(μ₃-OH)₄(μ-OR)₆(μ₃-OR)₂(μ-O₂CR)₂}⁶⁺ core composed of two oppositely oriented pentanuclear {Cu₄Mn} units, each featuring two vertex-sharing {Cu₂Mn} triangles. The presence of the {Cu₂(sacb)₂} fragment in both species suggests a templating role of the preformed chain 1 in the assembly of molecular cluster 2. Variable-temperature dc magnetic susceptibility studies reveal predominant antiferromagnetic interactions between Cu^II⋯Mn^II and Cu^II⋯Cu^II centers, with exchange coupling constants: J₁ = −16.5(1) cm⁻¹, J₂ = −35.1(5) cm⁻¹ and J₃ = +0.7(3) cm⁻¹. These findings highlight the utility of preformed oligonuclear and polymeric 3d-metal species as building blocks for the preparation of heterometallic 3d/3d′ polynuclear complexes with novel architectures and tailored physicochemical properties.

Aluminum nitride (AlN) crystals, as a typical representative of wide bandgap semiconductor materials, are being widely used in high-performance power electronics and optoelectronics devices. However, the high-power density of the devices poses new challenges for thermal management, therefore, there is an urgent need to enhance the study of thermal properties of AlN crystals, especially for crystals with different orientations. In this work, (0001) and (10−11) oriented AlN crystals are taken as examples for comparative study. Thermal conductivity is measured from room temperature to 300 °C using a laser flash method. The data within the tested temperature range are fitted, revealing the functional forms of thermal diffusivity and thermal conductivity as a function of temperature. It is found that thermal conductivity is proportional to T⁻ⁿ, where 1 < n < 2, consistent with observations in 4H-SiC and 6H-SiC. The temperature dependent thermal properties are evaluated in both orientations revealing weak anisotropy in thermal conductivity. In addition, various factors affecting the thermal properties of AlN crystals are discussed. These findings provide valuable insights for the development of AlN-based devices.

We introduce a Hirshfeld-volume-driven equation of state (EoS) to resolve atomistic compression mechanisms in diopside (CaMgSi₂O₆) under high pressure (0–10.16 GPa). Our approach integrates topological electron density partitioning via Hirshfeld surface analysis with third order Birch–Murnaghan EoS, achieving <2% error in Hirshfeld volume (V_H) predictions versus experimental benchmarks. Critically, this method visualizes and quantifies how interatomic contacts and crystal packing evolve under compression. Hirshfeld analysis reveals a stark differential atomic compressibility: Mg atoms dominate strain absorption (ΔV_atom/V_atom = −16.2% at 10.16 GPa), followed by Ca (−12.7%), Si (−8.54%), and O (−4.60%). This hierarchy arises from the flexible coordination environments of Mg/Ca–O polyhedra (bulk modulus B₀ ≈ 85 GPa) accommodating compression via bond shortening, while the rigid SiO₄ tetrahedra (B₀ > 150 GPa) preserve the supramolecular architecture. Calibrated Hirshfeld volume-EoS parameters (V_H = 438.72 ų, B₀ = 119.0 GPa, = 3.44) align with experiments (ΔV_H < 0.03%), providing a profound link between microscopic interactions and macroscopic properties. This work establishes the Hirshfeld-driven EoS as a transformative tool for decoding structure–property relationships in molecular crystals and designing pressure-resilient functional materials.

We demonstrate the structural, thermal, spectroscopic and laser performance of a novel Er³⁺-doped LuGSGG mixed crystal grown using the Cz method. The crystal possesses a garnet structure with a lattice parameter of 12.51 Å. The thermal conductivity is 4.3 W m⁻¹ K⁻¹ and the thermal expansion coefficient is 8.5 × 10⁻⁶ K⁻¹. The spectral analysis identifies a prominent absorption peak centered at 966 nm with an absorption coefficient of 4.7 cm⁻¹, corresponding to an absorption cross-section of 1.3 × 10⁻²¹ cm² and a full width at half maximum (FWHM) of 21 nm. The absorption and fluorescence spectra of Er:LuGSGG are broadened slightly. The level lifetimes are 1.19 ms for ⁴I_11/2 and 5.06 ms for ⁴I_13/2. Under 973 nm LD end-pumping, a continuous-wave laser power of 396 mW with a slope efficiency of 10% at 2.79 μm is achieved, yielding a high beam quality with M_x²/M_y² = 1.38/1.42. The laser spectrum reveals a narrow linewidth at 2795.6 nm with an FWHM of 0.097 nm. These findings confirm significant potential of Er:LuGSGG as a gain medium for solid-state tunable and short pulse laser applications.

High pressure studies have a long history, yet they have been a rather specialized niche activity. The availability of commercial high pressure chambers and the progress in optical and structural probes are changing all this, and an increasing number of papers is appearing. This highlight focuses on the effect of pressure on the physical properties and phase transitions of low-dimensional molecular crystals, a class of materials where the role of weak intermolecular interactions has yet to be fully understood. To illustrate the relevance of spectroscopic and structural studies under pressure, three classes of organic molecular crystals are considered, with the common ground of high anisotropy and low-dimensionality, namely: charge transfer (CT) co-crystals exhibiting valence instabilities, quasi-one-dimensional di-substituted anthracenes, and high mobility organic thin-film transistors.

Metal–organic coordination polymers (CPs), with the advantages of a simple preparation process and tunable optical properties, provide an ideal platform for constructing high-performance room temperature phosphorescence (RTP) systems. Here, by using the pyridine derivative tri(pyridin-3-yl)amine (TPA), a series of Cd-based compounds namely [Cd₂Cl₄(TPA)(DMA)] (1), [Cd₃Cl₆(TPA)₂] (2), [Cd(NO₃)₂(TPA)(DMF)] (3) and [Cd₂(NO₃)₄(TPA)₂(DMA)₂] (4) have been assembled. In the crystal structure of 1, the inorganic [Cd₄Cl₈] units are alternately connected with the organic N-donor TPA, forming a 3D framework. Each Cd²⁺ ion in 2 is bridged by μ₂-coordinated Cl ions to form an infinite inorganic chain, which is further coordinated with TPA to generate a different 3D structure with 1. 2D layers of compounds 3 and 4 are fabricated from the infinite linkage of Cd²⁺ and TPA ligands, with NO₃⁻ and solvent molecules serving as the terminally coordinated species. Owing to the restriction of molecular vibration/rotation of organic luminogens (TPA) and the heavy-atom effect, the title compounds 1–4 exhibit RTP characteristics with yellow afterglow. Moreover, the photochromic behaviors of compounds 3 and 4, which are based on the electron transfer process, have also been investigated.