Acta Crystallographica Section C Structural Chemistry最新文献

The synthesis, crystal structure, and [2+2] cycloaddition photoreactivity of a halogen-bonded mixed cocrystal is reported. The cocrystal solid solution contains two isosteric donors, namely, 1,4-diiodoperchlorobenzene (C₆I₂Cl₄) and iodoperchlorobenzene (C₆ICl₅), along with trans-1,2-bis(pyridin-4-yl)ethylene (BPE, C₁₂H₁₀N₂) which behaves as a ditopic reactant molecule. The mixed cocrystal, namely, (C₆I₂Cl₄)_0.75·(C₆ICl₅)_0.25·(BPE), is achieved since both halogen-bond donors are similar in shape and are interchangeable at equivalent crystallographic positions. The combination of I...N and Cl...N halogen bonds generates one-dimensional chains that engage in homogeneous π-stacks, thereby positioning a pair of reactant molecules in a suitable location to photoreact. Notably, the overall yield for the solid-state photoreaction is influenced by the initial molar ratio of the isosteric halogen-bond donors within the mixed cocrystal.

To date there are very few examples of crystallographically well-documented racemic mimics. The original discovery of this class of crystals occurred at a time when crystallography was in its infancy, data collection and processing were tedious and limited by X-ray equipment, and computing power was indeed limited. Therefore, this interesting class of crystalline molecules, potentially having useful biological uses, is today one of those scientific orphans largely ignored in the crystallographic realm. As proof of this, to date, you cannot systematically search for this class in databases. Thus, for the time being, there are few satisfactory examples of high-quality crystal structures of both members of such pairs which have been highlighted in the literature. Finally, being largely undocumented, there are no useful clues to guide you as to how to guess the classes of compounds likely to produce such pairs. The question then is, how do we go about searching for potential cases of such crystallization modes using information already in print? Herein, we provide some suggestions we believe are useful, and to the extent possible with such data, to illustrate the possibilities offered by such an approach.

Three multicomponent systems, namely, 2,4-diamino-6-phenyl-1,3,5-triazine-nicotinic acid (DAPT-NA), C₉H₉N₅·C₆H₅NO₂, (I), 2,4-diamino-6-phenyl-1,3,5-triazin-1-ium hydrogen malonate (DAPT-MMA), C₉H₁₀N₅⁺·C₃H₃O₄^-, (II), and 2,4-diamino-6-phenyl-1,3,5-triazin-1-ium hydrogen (+)-dibenzoyl-D-tartarate (DAPT-DBTA), C₉H₁₀N₅⁺·C₁₈H₁₃O₈^-, (III), have been synthesized and characterized via single-crystal X-ray diffraction, and their supramolecular interactions have been analysed. The formation of cocrystal (I) and salts (II) and (III) was confirmed through the widening of the C-N-C bond angle of the triazine moiety of 2,4-diamino-6-phenyl-1,3,5-triazine and the difference in the C-O bond distances between the carboxyl and carboxylate groups of the respective carboxylic acids. Cocrystal (I) and salt (II) form robust homomeric and heteromeric R₂²(8) ring motifs through primary acid-base interactions and complementary base pairing. In cocrystal (I), the complementary base pair exists as wave-like supramolecular strands, whereas in salt (II), it exists as a discrete pair. Salt (II) exhibits DDDAAD sextuple and DADA quadruple hydrogen-bonded arrays (D is donor and A is acceptor) through acid-base interactions and generates a supramolecular rosette-like architecture. In salt (III), the presence of carboxyl-carboxylate interactions and acid-base interactions led to the development of a supramolecular sheet and tunnel-like architecture. Cocrystal (I) and salt (III) are stabilized through offset aromatic π-π stacking interactions and C-H...π interactions, and salts (II) and (III) are stabilized via weak carbonyl-π and C-H...O hydrogen bonds. Macrocyclic R₁₂¹²(64) and R₃³(24) motifs are present in salts (II) and (III), respectively. Hirshfeld surface analysis of (I)-(III) reinforces the fact that N...H/H...N, O...H/H...O and C...H/H...C interactions contribute to the crystal packing and stability.

The transformation of a thiocarbonyl compound into an alkene by stepwise treatment with a diazo compound and triphenylphosphane is known as Barton-Kellogg olefination. As a model reaction, 4,4'-dimethoxythiobenzophenone and diazocyclohexane were used to prepare [bis(4-methoxyphenyl)methylidene]cyclohexane, C₂₁H₂₄O₂. The crystal structure of the latter, as well as that of the intermediate thiirane, 2,2-bis(4-methoxyphenyl)-1-thiaspiro[2.5]octane, C₂₁H₂₄O₂S, have been determined and their molecular conformations and geometries are generally consistent with those of related structures in the literature. Variations in the influence of four substituents on crowded thiirane rings are minimal and the main differences are noted in the presence of bulky tert-butyl substituents. The conformation of the intermediate thiirane is influenced by weak intramolecular C-H...S interactions. A three-dimensional supramolecular structure of the methylene cyclohexane compound results from the combination of three distinct weak C-H...π interactions. Under similar reaction conditions, 5-phenyl-3H-1,2-dithiole-3-thione has been transformed into 3-[bis(4-methoxyphenyl)methylidene]-5-phenyl-3H-1,2-dithiole, C₂₄H₂₀O₂S₂, by treatment with bis(4-methoxyphenyl)diazomethane. The crystal structure of the 1,2-dithiole product reveals a molecule with an all-trans 2,4-hexadiene core, in which the Csp²-Csp² bond lengths display an alternating character that suggests little delocalization of the double bonds. The 1,2-dithiole ring is nearly planar, with just a slight puckering into an envelope form. Two weak C-H...π and one C-H...O interaction link the molecules into thick two-dimensional supramolecular layers.

The newly obtained compound 7-(4-chlorophenyl)-1-hydroxy-5-methylpyrido[3,4-d]pyridazin-4(3H)-one (CPM) was crystallized as two new variable solvates, namely, the dimethyl sulfoxide monosolvate, C₁₄H₁₀ClN₃O₂·C₂H₆SO (I), and the sesquisolvate, C₁₄H₁₀ClN₃O₂·1.5C₂H₆SO (II), and their structures were confirmed by single-crystal X-ray diffraction analysis. In previous work, 1-hydroxy-5-methyl-7-phenylpyrido[3,4-d]pyridazin-4(3H)-one (PM) was found to display anticancer activity. In the next step of our studies, we synthesized a new derivative of PM, introducing a Cl atom into the PM structure, obtaining CPM, which showed not only anticancer but also anti-inflammatory activity. CPM and the new semi-products of each step of the synthesis were examined by ¹H NMR, ¹³C NMR and FT-IR spectroscopic analyses, and mass spectrometry. CPM forms (I) and (II) crystallize in the triclinic P1 and monoclinic C2/c space groups, respectively, and differ in the stoichiometry of the CPM and DMSO molecules in the crystal lattice, being 1:1 and 1:1.5 for (I) and (II), respectively. A powder X-ray diffraction analysis was performed only for solvate (I) due to the lack of stability of solvate (II). The potential cytotoxicity of CPM was evaluated against the normal cell lines L929 and RPTEC, as well as the cancer cell lines A172, AGS, CACO-2 and HepG2. The anti-inflammatory activity of CPM was also evaluated using colorimetric assay for the inhibition of COX-1 and COX-2. The same biological tests were carried out for PM to compare the activities of both compounds. The biological studies revealed that CPM does not exhibit more activity than PM. Moreover, in silico analysis of the bioavailability and molecular docking were performed.

Noncovalent interactions have received much attention in the fields of supramolecular chemistry and crystal engineering. Hydrogen bonding and weak interaction forces affect crystal stacking. Crown-ether-based host-guest inclusion compounds with hydrogen bonding and weak intermolecular interaction forces deserve our attention. In addition, Xiong and co-workers have proposed a molecular design strategy of H/F substitution. Based on this H/F substitution strategy, it is possible to develop halogen substitution, also known as the halogenation effect. Here, using benzylamine as an organic parent, the molecular design strategy of the halogenation effect was used. That is, halogen atoms (F, Cl, Br and I) were used to replace H atoms at the para site of the aromatic ring, and four halogenated benzylamine compounds were obtained, namely, 4-fluorobenzylaminium di(methanesulfonyl)amidate-18-crown-6 (1/1), C₇H₉FN⁺·C₂H₆NO₄S₂^-·C₁₂H₂₄O₆ or [(4-FBA)(18-crown-6)][DMSA], 1; 4-chlorobenzylaminium di(methanesulfonyl)amidate-18-crown-6 (1/1), C₇H₉ClN⁺·C₂H₆NO₄S₂^-·C₁₂H₂₄O₆ or [(4-ClBA)(18-crown-6)][DMSA], 2; 4-bromobenzylaminium di(methanesulfonyl)amidate-18-crown-6 (1/1), C₇H₉BrN⁺·C₂H₆NO₄S₂^-·C₁₂H₂₄O₆ or [(4-BrBA)(18-crown-6)][DMSA], 3; and 4-iodobenzylaminium di(methanesulfonyl)amidate-18-crown-6 (1/1), C₇H₉IN⁺·C₂H₆NO₄S₂^-·C₁₂H₂₄O₆ or [(4-IBA)(18-crown-6)][DMSA], 4. Clathrate 1 crystallizes in the space group P2₁, while 2-4 crystallize in the space group P2₁/n. In these compounds, extensive intermolecular interactions have been utilized for the self-assembly of diverse supramolecular architectures.

We report the preparation and crystal structure of potassium hafnium pentafluoride, KHfF₅, obtained by the hydrothermal technique. The compound crystallizes in the orthorhombic noncentrosymmetric space group P2₁2₁2₁, with the unit-cell parameters a = 6.2843 (3), b = 7.8063 (3) and c = 15.8286 (7) Å. Hf atoms are coordinated by eight F atoms, forming square antiprismatic polyhedra. Bonding in pairs, HfF₈ antiprisms are interconnected via common F-atom edges and form a double chain of hafnium polyhedra. A comparison of the structure of KHfF₅ with other complex fluorides of alkali metals and hafnium, zirconium or terbium(IV) revealed that this compound has no isostructural analogue among the known phases of general composition M^IM^IVF_5.

Isoguanine nucleosides constructed by different heterocyclic skeletons play a significant role in the context of genetic code expansion, as well as for purine-purine base pairing. However, with respect to structure analysis, only limited information is available on this class of nucleosides. In this study, the single-crystal X-ray structure of 8-ethynyl-2'-deoxyisoguanosine, C₁₂H₁₃N₅O₄·C₁₂H₁₃N₅O₄·2H₂O (1), has been investigated. In the crystal of 1, the N1-H and N3-H tautomers exist together. They are connected by O3'-H to O3' hydrogen bonds. The conformation at the glycosylic bond is syn for both tautomeric forms. This conformation is stabilized by intramolecular hydrogen bonds from N3 or N3-H of the pyrimidine ring to the 5'-OH group of the sugar residue. For both tautomers, the sugar conformation adopts a C2'-endo-C3'-exo twist (²T₃; S-type), with P = 165.0 and 163.9°. A synclinal orientation is observed around the C4-C5' bond. Crystal packing is controlled by a tridentate purine-purine pair of 8-ethynyl-2'-deoxyisoguanosine that is enabled by a tautomeric shift of the proton from N1 to N3 of the nucleobase. Additional stability to the 3D network is contributed by water molecules connecting different layers in the solid state. A Hirshfeld surface analysis was performed confirming the existence of the purine-purine pair and the impact of the water molecules on hydrogen bonding. To the best of our knowledge, this is the first X-ray analysis on a nucleoside with two different tautomeric forms in the crystal unit that form a purine-purine base pair.

The crystal structure of capsaicin (C₁₈H₂₇NO₃), or trans-8-methyl-N-vanillylnon-6-enamide, the natural product responsible for the spiciness of chilli peppers, was determined using low-temperature single-crystal X-ray diffraction. The reported crystal structure is in good agreement with previous determinations based on powder X-ray diffraction data. The localization and free refinement of all H atoms revealed that each capsaicin molecule is hydrogen bonded to four other molecules, with the O-H and N-H groups acting as hydrogen-bond donors, and the C=O group serving as a bifurcated hydrogen-bond acceptor.

The reaction of Ni(NO₃)₂·6H₂O with the thio-modified nucleoside 2'-deoxy-6-thioguanosine (d-tG, C₁₀H₁₃N₅O₃S) in methanol in a 1:1.3 stoichiometric ratio deposited the title compound, [Ni(d-tG)₃](NO₃)₂·2H₂O, as green crystals. Despite the <1:3 Ni-ligand ratio used in the synthesis, the deoxy-thioguanosine binds to form three N⁷,S⁶-coordinated five-membered chelate rings with individual Ni^II ions in mononuclear complexes rather than bridge metal centres into more extended oligomeric or polymeric structures.