CrystEngComm最新文献

Bent-shaped compounds are attractive building blocks because they self-assemble into unique two- or three-dimensional structures. We used bent-shaped host molecule (1), which is composed of two nitrophenols linked to adamantane. Vapor diffusion of hexane into a tetrahydrofuran solution of 1 afforded inclusion crystals. The host molecules were assembled into tetrameric H-shaped structures as a motif through the quadruple π-stacking of nitrophenol moieties within a unit cell, in which eight hydroxy groups interacted with eight guests through hydrogen bonds. These assemblies were fabricated to form network structures with channels. In inclusion crystals with 1,4-dioxane, 1 was arranged into layer architectures that were packed into the channel structures. In inclusion crystals with γ-butyrolactone, 1 was aligned into network structures with channels, where cyclic dimeric structures without cavities were formed. These results demonstrate the crucial role of solvent molecules in the creation of tetrameric and dimeric motifs in the crystalline state.

A selection of 10 mono- and dihalopyridines have been used as salt coformers for benzenesulfonic and p-toluenesulfonic acids. In most cases, the resultant halopyridinium cations are bifunctional donors of both charge-assisted hydrogen and halogen bonds to the sulfonate anions.

Designing Dy^III-containing single-ion magnets (SIMs) and single-molecule magnets (SMMs) based on a symmetry strategy has been extensively employed. To date, numerous SIMs and SMMs have exhibited high effective energy barriers (U_eff), high blocking temperatures (T_B) and large coercive fields in the hysteresis loops, with one SIM achieving a T_B (80 K) value above the liquid-nitrogen temperature. Interestingly, the magnetic relaxation behavior of some high-performance SIMs and/or SMMs can also be interpreted from an electrostatic perspective. Although the coordination geometries of Dy^III in most complexes with high SIM/SMM performance exhibit high symmetry, many complexes with Dy^III located in the low symmetrical coordination geometries also exhibit remarkable SIM/SMM performance. This phenomenon can be explained from the electrostatic perspective. However, to the best of our knowledge, few reviews have specifically addressed this aspect. In this review, we first provide an overview of the electrostatic mode, followed by a detailed discussion of representative Dy-SIMs and Dy-SMMs from an electrostatic perspective, and finally, we present conclusions and prospects of the electrostatic strategy for designing Dy-based SIMs and/or SMMs.

In this work, we benchmark quadrupolar NMR crystallography guided crystal structure prediction (QNMRX-CSP) for determining the crystal structures of two zwitterionic organic HCl salts, L-ornithine HCl (Orn) and L-histidine HCl·H₂O (Hist). These salts present an interesting challenge for QNMRX-CSP, as gas-phase geometry optimizations used to generate starting structures for the organic zwitterionic fragments fail to capture their correct solid-state geometries. To overcome this limitation, geometry optimizations using the COSMO water-solvation model are employed to generate initial structural models. Using this approach, QNMRX-CSP yields structural models of the two zwitterionic organic HCl salts that closely match experimentally determined crystal structures. In addition, the application of QNMRX-CSP to Hist represents a further step toward the de novo structural determination of solvated organic HCl salts, as Hist is the first benchmark system of this type to include a water molecule as a component of its crystal structure. This work is significant for its potential application to the structural determination of active pharmaceutical ingredients, which often feature complex organic components and solvated solid forms.

The synthesis of conventional organic primary explosives poses significant safety challenges. A novel strategy for designing primary explosives has been developed, featuring the incorporation of a non-energetic methyl group into a fused ring system. This approach enabled the safe and efficient preparation of 2-methyl-4,7-nitroamino-1H-imidazo[4,5-d]pyridazine (MNIP), a compound demonstrating considerable potential as a primary explosive. MNIP demonstrates good energetic performance and enhanced safety parameters (ν = 7710 m s⁻¹; FS = 120 N), outperforming the classical organic primary explosive DDNP. Theoretical and experimental analyses reveal that the methyl group effectively modulates the aromaticity of the fused ring system and weakens intermolecular hydrogen bonding interactions, resulting in enhanced sensitivity characteristics. Furthermore, energetic salts derived from MNIP were synthesized and characterized, exhibiting favorable thermal stability (T_d ≥ 185 °C) while maintaining appropriate impact sensitivity (<2 J). Synthesis of MNIP is efficient and economical in terms of material costs, suggesting its considerable potential as a next-generation metal-free primary explosive for practical use.

Metformin is a common active pharmaceutical ingredient and is usually administered orally in the solid form as a stable monohydrochloride salt. Herein, we discuss the crystal structure of a recently discovered dihydrochloride metformin salt, which reveals that protonation of the secondary amine in the divalent metformin cation disrupts both the extensive electron delocalisation and N–H⋯N hydrogen bonding found in the known α- and β-polymorphs of the metformin hydrochloride salt; this leads to charge-assisted N–H⁺⋯Cl⁻ hydrogen bonds dominating the solid form, forming a three-dimensional network. Analysis shows that metformin dihydrochloride can be distinguished from the metformin hydrochloride polymorphs by infrared spectroscopy and powder X-ray diffraction. Computational calculations suggest that metformin dihydrochloride has a lower lattice enthalpy than the known metformin hydrochloride phases, indicating a high solubility and lower stability consistent with experimental measurements.

Photochromic materials have significant application value in the field of anti-counterfeiting, with viologen-based compounds being particularly noteworthy due to their superior properties. In this study, two cadmium-based coordination polymers Cd (CPB) L1 (1) and [Cd₂(CPB)₂(L2)₂(H₂O)]·2H₂O (2) were synthesized using a solvothermal method (L1 = trimesic acid, L2 = 5-methylisophthalic acid and HCPB·Cl = 1-(4-carboxyphenyl)-4,4′-biphenyl chloride). Both compounds exhibit a two-dimensional wave-like layered structure, with the key difference being that the layers of compound 1 are parallel and cross-hatched, whereas those of compound 2 are parallel without interpenetration. Both compounds display reversible color changes under light or electrical stimulation. The two compounds have similar color change behavior and different fluorescence behavior, with compound 2 showing visible fluorescence. Additionally, we explored the applications of these materials in inkless printing and anti-counterfeiting.

Controlling the crystal packing of perfluorophenyl-substituted aryl molecules (Ar–Ar^F-type molecules) is crucial for their properties. Herein, we investigated the crystal structures of perfluorophenyl-substituted thiophene derivatives bearing three different trialkylsilyl groups: trimethylsilyl, tert-butyldimethylsilyl, and triisopropylsilyl. Single-crystal X-ray diffraction analysis revealed that the compounds exhibited distinct head-to-tail stacking patterns depending on the length and degree of branching of the alkyl chains on the trialkylsilyl groups. Notably, the photophysical properties of the crystals differed, despite being similar in solution. Specifically, the trimethylsilyl and tert-butyldimethylsilyl derivatives exhibited a larger red shift in their excitation and emission wavelengths, as well as higher photoluminescence quantum yields. These results indicate that trialkylsilyl groups can effectively modulate molecular packing to enhance the solid-state properties of these compounds.

Vapochromic luminescent organic crystals have attracted significant attention in recent years for their potential in environmental monitoring and solvent sensing. Restoring the original emission color after vapor-induced changes typically requires additional stimuli such as heating, vacuum treatment, or prolonged exposure to air. Herein, three types of microcrystals obtained by reprecipitation of an organic luminophore exhibit two-solvent-mediated vapochromic luminescence, in which their emission color can be reversibly modulated by sequential exposure to two distinct organic solvent vapors. Interconversion between a chloroform-including green-emissive crystal and a solvent-free yellow-emissive crystal is achieved by exposure to ethyl acetate and chloroform vapors, respectively. Yellow- and orange-emissive solvent-free crystals that share the same crystal structure but differ in preferred orientation convert to green-emissive crystals upon exposure to chloroform vapor. Notably, both crystals revert to their original states upon exposure to ethyl acetate vapor, indicating retention of the initial crystal memory.

In order to rationally design MOFs with predictable and reproducible structures, the effect of varying a metal ion on MOF topology while keeping the ligand constant is explored. In this study, a triptopic ligand with more than one type of coordination site is investigaed, namely 4′-(1H-imidazo[4,5-f]imidazo[1,10]phenanthrolin-2-yl)-[1.1′]biphenyl]-3,5-dicarboxylic acid) (H₂NCCPP = H₂L1). H₂L1 was synthesised and used to form HNCP type MOFs with non-default topologies revealing five new MOFs: Cu·L1(α) [Cu₃(L1)₂(H₂O)₃](NO₃)₂, Cu·L1(β) [Cu₃(L1)₂(H₂O)₃](NO₃)₂, Mg·L1 [Mg₂(L1)₂H₂O], Ca·L1 ([Ca₂(L1)₂(H₂O)₂], and Gd·L1 [Gd₄(L1)₆H₂O]. All five structures were based around at least one dinuclear SBU related to the well known paddlewheel geometry with the ‘cap’ showing increasing coordination as the size and malleability of the metal ion increased. Cu·L1(α) and Cu·L1(β) were polymorphic structures showing large square channels and based around both a traditional paddlewheel and a rarely seen semi-paddlewheel, both capped by a single solvent water. Mg·L1 and Ca·L1 each contained a single, dinuclear SBU capped by a phenanthroline, and a phenanthroline and water, respectively, due to the increase in size of the metal ion. Gd·L1 contained four distinct dinuclear SBUs, all capped by a phenanthroline, water and carboxylate as a result of the increased size and coordination of the lanthanide ion. Mg·L1 and Ca·L1 both showed adsorption of CO₂ peaking at 38.4 cm³ g⁻¹ and 26.1 cm³ g⁻¹, respectively, at 273 K.