Acta Crystallographica Section C Structural Chemistry最新文献

Dissymmetric ligands have garnered interest due to their ability to simultaneously coordinate to multiple different acceptors. Herein, we report the synthesis of a dissymmetric thioether N,N'-bidentate ligand, namely, 2-[(6-chloropyrimidin-4-yl)sulfanyl]pyrimidine-4,6-diamine (C₈H₇ClN₆S, L1), along with its hydrated form (C₈H₇ClN₆S·H₂O). In addition, we describe the structure of a nitrate salt of the protonated ligand {4,6-diamino-2-[(6-chloropyrimidin-4-yl)sulfanyl]pyrimidin-1-ium nitrate, C₈H₈ClN₆S⁺·NO₃^-} and a cobalt(II) complex of L1 (dichlorido{2-[(6-chloropyrimidin-4-yl-κN³)sulfanyl]pyrimidine-4,6-diamine-κN³}cobalt(II), [CoCl₂(C₈H₇ClN₆S)]). The structures of all four compounds were determined by single-crystal X-ray diffraction and Hirshfeld surface analyses were performed. These analyses reveal unengaged hydrogen-bond donors and acceptors in both the neutral ligand and its water solvate, while protonation or metal coordination induces a conformational change that enables full engagement of hydrogen-bond donors. These structural insights have implications for the molecular design of ligands in ion-sensing applications.

In the presence of 4-[4-(1H-imidazol-1-yl)phenyl]pyridine (ipp), the self-assembly reaction of 2-methoxyterephthalic acid (H₂mta) with Co^II ions produced the complex poly[[{μ-4-[4-(1H-imidazol-1-yl)phenyl]pyridine}(μ-2-methoxyterephthalato)cobalt(II)] monohydrate], {[Co(C₉H₆O₅)(C₁₄H₁₁N₃)]·H₂O}_n or {[Co(mta)(ipp)]·H₂O}_n (denoted as HU29). The complex was structurally characterized by thermogravimetric analysis, elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Single-crystal structure analysis revealed that the mta^2- anions and ipp ligands are connected according to AABB and ABAB modes to form four distinct helical chains. These helical chains further construct a three-dimensional (3D) framework. Owing to the similar geometries of mta^2- and ipp, combined with the low coordination numbers of the Co^II centres, the resulting 3D framework exhibits a fivefold interpenetrating structure. Topological analysis indicates that HU29 can be simplified as a four-connected dia net. UV-Vis absorption spectroscopy shows a broad absorption band in the UV-Vis region and a band gap of 2.72 eV based on the Kubelka-Munk method, indicating semiconductor behaviour. Moreover, a magnetic study reveals that antiferromagnetic interactions occur in HU29 between 300 and 2 K.

The structure of the 1:1 gallic acid (3,4,5-trihydroxybenzoic acid)-N-methylurea cocrystal, C₇H₆O₅·C₂H₆N₂O, (I), has been determined by single-crystal X-ray diffraction. In the crystal, molecules of both components form O-H...O and N-H...O hydrogen-bonded complexes. These complexes are further linked by O-H...O, N-H...O and C-H...O hydrogen bonds, together with aromatic π-π stacking interactions, to generate a triperiodic supramolecular network. Energy framework analysis shows that electrostatic contributions predominate over dispersive ones in (I). Quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses indicate that the O-H...O and N-H...O interactions are strong, with homonuclear hydrogen bonds being stronger than heteronuclear ones. Stabilization of the carboxylic acid-urea complexes arises primarily from charge transfer resulting from orbital interactions between the lone electron pairs of hydrogen-bond acceptors (O atoms) and the empty antibonding orbitals of the hydrogen-bond donor [LP(O) → BD*(D-H)].

Four new crystal structures of the salts of N-[(2,3-dimethylphenoxy)alkyl]aminoalkanol derivatives with anticonvulsant activity are reported. Bis{D,L-trans-N-[(2,3-dimethylphenoxy)ethyl]-1-hydroxycyclohexan-2-aminium} succinate, 2C₁₆H₂₆NO₂⁺·C₄H₄O₄^2-, 1, and its polymorph 1p, crystallize in the monoclinic space group P2₁/n, 1 with two cations and one anion, and 1p with four cations and two anions in the asymmetric unit. The other two salts, D,L-trans-N-[(2,3-dimethylphenoxy)ethyl]-1-hydroxycyclohexan-2-aminium 6-carboxypyridine-2-carboxylate, C₁₆H₂₅NO₂⁺·C₇H₄O₄^-, 2, and N-[(2,3-dimethylphenoxy)propyl]-3-hydroxypiperidinium pyridine-2-carboxylate, C₁₆H₂₆NO₂⁺·C₆H₄O₂^-, 3, crystallize in the monoclinic space group P2₁/c, with one cation and one anion in each asymmetric unit. The geometry of the created polymorphs indicates the main differences in the conformation of the linker between the two rings. The arrangement of the ether O atom and the N atom shows an unusual antiperiplanar conformation for the cations of 1p. The crystal packing of all four salts is dominated by charge-assisted hydrogen bonding between the protonated N atom and the carboxylate group of the corresponding acid. Structural studies have been enriched by quantum chemical calculations.

The crystal structure of bis[μ-3,5-bis(pyridin-2-yl)pyrazolato-κ⁴N²,N³:N¹,N⁵]bis[bis(methanol-κO)cobalt(II)] dinitrate methanol disolvate, [Co₂(C₁₃H₉N₄)₂(CH₄O)₄](NO₃)₂·2CH₄O (I), was solved by X-ray diffractometry in order to gain insights into its electronic and catalytic properties because of its relevance to an analogous cobalt(II) dimer (V) which was shown to be highly active for CO₂ reduction. The geometrical and electronic properties are also discussed in relation to other reported Co^II dimers having analogous structures (compounds II-IV and VI). Interestingly, I was found to possess quite similar structural features compared with the five other reported analogues (II-VI). The similarly elongated coordinate bond lengths in I-VI further implied a consistency in their spin states at the metal centres. By analogy to a report on V, all these compounds were suggested to possess a high-spin septet state (S = 3), previously evidenced for V by measuring its magnetic susceptibility data. The validity of these considerations was also confirmed by examining the density functional theory (DFT)-based structures, together with the energies of three possible spin states (S = 3, 1 and 0).

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.