Acta Crystallographica Section C Structural Chemistry最新文献

Hirshfeld atom refinement (HAR) has so far been explored almost exclusively for the determination of accurate and precise H-atom positions from X-ray diffraction experiments, neglecting other features of the resulting crystal structures and molecular wavefunctions. In contrast, here we compare the applicability of the HAR and transferable aspherical atom model (TAAM) approaches for the structure refinement, as well as for the reconstruction of electron-density distribution in a series of quinoic compounds, known for their pronounced single-double bond alternation. A set of five quinone-like compounds has been crystallized and investigated using single-crystal X-ray diffraction at standard resolution and subjected to various structure refinement approaches, namely, 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione (Cl4Q), C₆Cl₄O₂, 2,3,5,6-tetrafluorocyclohexa-2,5-diene-1,4-dione (F4Q), C₆F₄O₂, 2-[4-(dicyanomethylidene)cyclohexa-2,5-dien-1-ylidene]propanedinitrile (TCNQ), C₁₂H₄N₄, 2-[4-(dicyanomethylidene)-2,5-difluorocyclohexa-2,5-dien-1-ylidene]propanedinitrile (F2TCNQ), C₁₂H₂F₂N₄, and 2-[4-(dicyanomethylidene)-2,3,5,6-tetrafluorocyclohexa-2,5-dien-1-ylidene]propanedinitrile (F4TCNQ), C₁₂F₄N₄. The HAR results quantitatively reproduce the alternating electron-density effects in the studied compounds, while the electron densities from the TAAM approach, utilizing pseudoatom parameters averaged over a large number of chemical compounds, do not perform as well in capturing bond alternation. As a consequence of the differences in the electron-density models, the two refinement approaches also yield distinct atomic displacement parameters (ADPs).

Salcaprozate sodium (SNAC) is a clinically approved oral permeation enhancer, notably used in the formulation of oral semaglutide. Despite its pharmaceutical importance, the crystallographic information of SNAC or its free acid form, salcaprozoic acid {systematic name: 8-[(2-hydroxyphenyl)formamido]octanoic acid, C₁₅H₂₁NO₄, denoted HNAC}, has not been reported previously. Here, we present the first crystallographic and physicochemical characterization of HNAC using single-crystal X-ray diffraction and complementary analytical techniques. The structure reveals the molecular conformation, hydrogen-bonding network and packing features of HNAC, supported by a complementary solid-state dataset. These findings provide fundamental insights into the structural and physicochemical properties of this physiologically relevant form of SNAC.

With the aim of producing an extended bridging ligand for the assembly of coordination polymers, a terphenyl ligand incorporating carboxyl and phenol functionalities, namely, 4''-hydroxy-1,1':4',1''-terphenyl-4-carboxylic acid (H₂htpa, C₁₉H₁₄O₃, 1), was prepared. Within the structure, complementary hydrogen bonding between carboxylic acid groups leads to dimer formation with additional hydrogen bonding between phenolic groups, resulting in the formation of a 2D network. Following the addition of Na₂CO₃, mono- and dianionic forms of the ligand are generated within a compound of composition Na₃(Hhtpa)(htpa)·hydrate or {[Na₃(C₁₉H₁₃O₃)(H₂O)₉](C₁₉H₁₂O₃)}_n (2). The addition of tetraethylammonium hydroxide (NEt₄OH) solution to the acid leads to the formation of (Et₄N)Hhtpa·2(dioxane) or C₈H₂₀N⁺·C₁₉H₁₃O₃^-·2C₄H₈O₂ (3) and (Et₄N)₅(Hhtpa)₂(H_0.5htpa)₂·hydrate or 5C₈H₂₀N⁺·[H(C₁₉H₁₂O₃)₂]^3-·2C₁₉H₁₃O₃^-·17.522H₂O (4), with hydrogen-bonded chains a feature of both. Compound 4 contains both the Hhtpa^- anion, and pairs of htpa^2- dianions linked by a single proton between phenolate O atoms to generate a trianionic unit, [H(htpa)₂]^3-. A ladder-shaped anionic coordination polymer of composition (NEt₄)₄[Zn₄(htpa)₃Cl₆] or {(C₈H₂₀N)₄[Zn₄(C₁₉H₁₂O₃)₃Cl₆]}_n (5) was obtained when Zn^II was combined with htpa^2- in the presence of NEt₄⁺ and chloride. Finally, an anionic coordination polymer with the formulation (Et₄N)[Zn(htpa)(OAc)]·1.5(dioxane) or {(C₈H₂₀N)[Zn(C₃H₃O₂)(C₁₉H₁₂O₃)]·1.5C₄H₈O₂}}_n (6) was generated with both OAc^- (acetate) and htpa^2- serving as bridging ligands between Zn^II centres in a 2D network.

The crystal structure of the metastable form of S-ibuprofen-nicotinamide cocrystals, C₁₃H₁₈O₂·C₆H₆N₂O, was solved from powder X-ray diffraction. This form was obtained by melting a molar mixture of S-ibuprofen and nicotinamide at 100 °C, and then cooling. The high-resolution powder X-ray diffraction pattern of this new phase was recorded at room temperature using synchrotron radiation at SOLEIL Synchrotron (France). A hypothetical structure was obtained from the Monte-Carlo simulated annealing method and confirmed by Rietveld refinement. The symmetry is monoclinic (space group P2₁, No. 4) and the unit cell contains four molecules, two of nicotinamide and two of S-ibuprofen. Density functional theory (DFT) energy minimization simulation was performed in order to locate the H atoms. The determination of the crystallographic structure of this metastable form allowed an explanation of the main mechanisms at the origin of the relative stability of the two forms of the S-ibuprofen-nicotinamide cocrystals. This also made it possible to explain the transition mechanism between the two forms with temperature.

The reaction of decafluorobenzophenone [perfluorobenzophenone, (C₆F₅)₂CO] with AsF₅ in anhydrous HF yields the protonated salt [bis(2,3,4,5,6-pentafluorophenyl)methylidene]oxidanium hexafluoridoarsenate, (C₆F₅)₂COH⁺[AsF₆]^-, whereas its reaction with AsF₅ in SO₂ affords the Lewis acid-base adduct decafluorobenzophenone-arsenic pentafluoride, (C₆F₅)₂CO·AsF₅. In both compounds, the decafluorobenzophenone moiety exhibits an elongated C=O bond [1.274 (2) and 1.2526 (15) Å in the salt and adduct, respectively]. The crystal structure of (C₆F₅)₂COH⁺[AsF₆]^- features a short O-H...F hydrogen bond between the cation and the anion, and the crystal structure of (C₆F₅)₂CO·AsF₅ represents a rare example of a ketone coordinated to the strong Lewis acid AsF₅.

The structures of six triperiodic CuCN network structures with conjugate acids of four N-alkylethanolamines as guest cations are described, namely, poly[2-hydroxyethan-1-aminium [μ₃-cyanido-di-μ₂-cyanido-dicuprate(I)]], {(C₂H₈NO)[Cu₂(CN)₃]}_n, 1, poly[bis(2-hydroxy-N-methylethan-1-aminium) [di-μ₃-cyanido-tri-μ₂-cyanido-tricuprate(I)] monohydrate], {(C₄H₁₂NO)₂[Cu₃(CN)₅]·H₂O}_n, 2, poly[tetrakis[N-(2-hydroxyethyl)ethan-1-aminium] [chloridotetra-μ₃-cyanido-penta-μ₂-cyanido-tricuprate(I)]], {(C₄H₁₂NO)₄[Cu₆(CN)₉Cl]}_n, 3, poly[tetrakis[N-(2-hydroxyethyl)ethan-1-aminium] [penta-μ₃-cyanido-hepta-μ₂-cyanido-octacuprate(I)]], {(C₄H₁₂NO)₄[Cu₈(CN)₁₂]}_n, 4, poly[2-hydroxy-N,N-diisopropylethan-1-aminium [μ₃-cyanido-μ₂-cyanido-dicuprate(I)] monohydrate], {(C₈H₂₀NO)[Cu₃(CN)₄]·H₂O}_n, 5, and poly[2-hydroxy-N,N-diisopropylethan-1-aminium [μ₃-cyanido-di-μ₂-cyanido-dicuprate(I)]], {(C₈H₂₀NO)[Cu₂(CN)₃]}_n, 6. In five of the structures (1-5), the CuCN network includes Cu atoms occurring in pairs, linked by cuprophilic interactions. Analysis with the intent of exploring the `template effect' of the cations on the CuCN network structure indicated five separate CuCN topologies. The two different crystal structures involving cations from N-ethylethanolamine have the same basic topology, whereas the two crystal structures involving cations from N,N-diisopropylethanolamine have different topologies, contrary to what might be expected from a template effect. Thermogravimetric analysis of the compounds usually shows loss of HCN(g) and the free base by 200 °C, with a CuCN(s) residue, but decomposition of one of the structures is more complex.

Bis[bis(ethylenedithio)tetraselenafulvalene(0.5+)] dibromidoaurate(I) and its chloride analogue, (C₁₀H₈S₄Se₄)₂[AuX₂] or BETS₂AuX₂ (X = Cl and Br), were synthesized to examine their crystal and band structures. The crystal structures are new in that they have both structural features of different types of organic Dirac electron systems (ODES), i.e. α- and α'-type iodine-centred trihalide (IX₂^-) salts of BETS-related electron-donor molecules. The former often produces zero-gap semiconductors, while the latter is related to nodal-line semimetals, i.e. classes of ODES different from each other. The band structure calculation suggests that BETS₂AuX₂ are close to zero-gap semiconductors, indicating that the α-type structural feature governs the band structures in these salts. Although the dimensions and geometries of the constituents are close to each other between BETS₂IX₂ and BETS₂AuX₂, the strength of the BETS-anion interaction resulted in a difference in the crystal structures between the α- and α'-type molecular arrangements. Our findings show that the crystal and band structures are affected by the electronic states of the constituents sometimes more than one would expect based on their geometrical features.

This article focuses on a specific real-space methodology for solving and refining molecular organic crystal structures, developed by the authors and collaborators. It outlines a practical route from polycrystalline samples to refined crystal structures, emphasizing efficient global optimization by DASH and the robust refinement capabilities of TOPAS. The approach prioritizes laboratory-to-laboratory reproducibility via a standardized workflow that addresses key challenges in molecular organic crystal structure determination.

Stimuli-responsive crystalline materials have demonstrated significant potential for developing multifunctional systems. Achieving precise structural modulation in non-porous crystalline phases remains a critical challenge, particularly in correlating molecular-level conformational changes with macroscopic properties. Here, we report a solvatomorphic crystalline system, (1-azabicyclo[2.2.2]octane-κN){4,4',6,6'-tetra-tert-butyl-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato-κ⁴O,N,N',O'}zinc(II) acetonitrile monosolvate, [Zn(C₃₆H₄₆N₂O₂)(C₇H₁₃N)]·CH₃CN or [Zn(saloph)](quinuclidine)](acetonitrile) (1·solvent), which exhibits a reversible single-crystal-to-single-crystal transformation during acetonitrile adsorption/desorption. Structure analysis reveals that solvation dynamics induce a pronounced variation in the dihedral angle of the [Zn(saloph)] coordination centre, accompanied by a luminescence red shift of approximately 10 nm. This work establishes a strategy for modulating optoelectronic properties in non-porous crystalline materials through solvent-mediated structural reorganization, advancing the development of stimuli-responsive functional materials.