Acta Crystallographica Section C Structural Chemistry最新文献

The crystal structure of the novel Knoevenagel-type indole derivative (2E)-2-(1H-indol-3-ylmethylidene)-4,4-dimethyl-3-oxopentanenitrile, C₁₆H₁₆N₂O, was determined by single-crystal X-ray diffraction and further characterized by NMR, FT-IR and UV-Vis spectroscopy. The compound crystallizes in the monoclinic space group P2₁/c (Z = 4). The molecule has a nearly planar conformation across the indole ring and the adjacent C=C-C[triple-bond]N fragment. In the crystal, molecules are linked by N-H...O hydrogen bonds into chains parallel to the b axis, which are reinforced by inversion-related π-π stacking interactions in a slipped configuration along the a axis; additional C[triple-bond]N...H contacts further stabilize the supramolecular framework. Hirshfeld surface analysis reveals that H...H and H...C contacts dominate the packing, with smaller contributions from H...N and H...O interactions. Pairwise interaction energy calculations highlight the key role of π-π stacking (E_tot = -46.8 kJ mol^-1) and N-H...O hydrogen-bonded chains (E_tot = -43.6 kJ mol^-1), with dispersion identified as the principal stabilizing force.

Two benzamide-based derivatives were synthesized and their structures solved for the first time. The successful syntheses of N-ethyl-4-iodobenzamide (C₉H₁₀INO, NE4IBA) and N-ethyl-4-ethynylbenzamide (C₁₁H₁₁NO, NE4EBA) were achieved via a simple synthetic route. The molecules of NE4IBA in the crystal form one-dimensional double chains with strong hydrogen bonding and weak I...I halogen interactions, while NE4EBA forms two-dimensional hydrogen-bonded layers, including acetylene moieties engaging in C-H...O interactions within a rigid planar layer packing arrangement. Intermolecular N-H...O interactions between the amide groups dominate in both crystal structures. The strong exothermal effect of acetylene-group polymerization was detected immediately after melting NE4EBA using a simultaneous thermal analysis.

Recrystallization of pazufloxacinium mesylate from HCl solutions yielded two previously unknown salts of pazufloxacin. These were characterized by X-ray diffraction and are bis(oxidanium) pentakis[(2S)-6-(1-azaniumylcyclopropyl)-7-fluoro-2-methyl-10-oxo-4-oxa-1-azatricyclo[7.3.1.0^5,13]trideca-5(13),6,8,11-tetraene-11-carboxylic acid] heptachloride decahydrate, 2H₃O⁺·5C₁₆H₁₆FN₂O₄⁺·7Cl^-·10H₂O (1), and (2S)-6-(1-azaniumylcyclopropyl)-7-fluoro-2-methyl-10-oxo-4-oxa-1-azatricyclo[7.3.1.0^5,13]trideca-5(13),6,8,11-tetraene-11-carboxylic acid chloride ethanol hemisolvate 1.75-hydrate, C₁₆H₁₆FN₂O₄⁺·Cl^-·0.5C₂H₆O·1.75H₂O (2), which were obtained from acetonitrile and ethanol, respectively. The compounds crystallize in the noncentrosymmetric triclinic space group P1. Salt 1 contains five independent cations and seven chloride anions, while compound 2 contains eight independent cations and anions. In both, an intramolecular COOH...O=C hydrogen bond is present and the amino group is protonated. The cations, anions and solvent molecules form extensive hydrogen-bonded frameworks. In addition, in both structures, the cations are packed into infinite stacks via π-π interactions, with interplanar distances of approximately 3.2 Å.

Halide-bridged polymers are a type of coordination polymer whereby halide ligands act as bridging ligands between the metal centres. The crystal structures of three halide-bibridged polymers of the formula [Hg(μ-X)₂(4-Etpy)]_n, namely, catena-poly[[(4-ethylpyridine)mercury(II)]-di-μ-halido], obtained through the combination of the organic ligand 4-ethylpyridine (4-Etpy, C₇H₉N) and HgX₂ (X = Cl, Br or I), were determined. In these structures, abbreviated as 4epHgCl, 4epHgBr and 4epHgI, respectively, the Hg^II ion exhibits a coordination number of five. All three structures were found to display a similar one-dimensional scalloped polymeric chain with halide ligands bridging pairs of Hg^II ions in a bidentate fashion; however, 4epHgI differs from the other two structures in terms of the packing arrangement of the polymer. The change of the halide ligand to the larger iodide ligand disrupts the formation of the regular halide-bibridged polymeric chain observed in the chloride and bromide analogues, with 4epHgI displaying pseudo-bridging in the polymer chain.

The structures of three doubly-acylated 4-aminoantipyrine (AP) compounds where the aryl substituent is varied are reported and analysed in terms of their relative conformation, intermolecular interactions and overall packing; these are N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-4-methyl-N-[(4-methylphenyl)carbonyl]benzamide, C₂₇H₂₅N₃O₃, N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-N-[(furan-2-yl)carbonyl]furan-2-carboxamide, C₂₁H₁₇N₃O₅, and N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-N-[(thiophen-2-yl)carbonyl]thiophene-2-carboxamide, C₂₁H₁₇N₃O₃S₂. The compounds were crystallized using the encapsulated nanodroplet crystallization (ENaCt) protocol. Where previous singly-acylated AP compounds produced structures with obvious classical hydrogen-bonding motifs, the doubly-acylated derivatives lack classical donors and therefore exhibit weak C-H hydrogen bonds and interactions involving the π-system. All three AP compounds form bifurcated C-H...O interactions having either dimer or chain motifs, with the other structure-directing interactions being dependant on the nature of the aryl substituent.

Deprotonation of the Schiff base 2,6-dimethyl-N-(1-phenylethylidene)aniline, C₁₆H₁₇N or [MeC(Ph)=N(2,6-Me₂C₆H₃)], 1, with one equivalent of lithium diisopropylamide (LDA) and subsequent reaction with half an equivalent of SiPh₂Cl₂ gave a new diimine, N-[2-({2-[(2,6-dimethylphenyl)imino]-2-phenylethyl}diphenylsilyl)-1-phenylethylidene]-2,6-dimethylaniline, C₄₄H₄₂N₂Si, 2. Further treatment of 2 with LDA in the presence of tetrahydrofuran (THF) yielded the target binuclear ansa-bis(1-azaallyl) lithium compound {μ-N-[2-({2-[(2,6-dimethylphenyl)azanidyl]-2-phenylethyl}diphenylsilyl)-1-phenylethylidene]-2,6-dimethylanilinido}bis[(tetrahydrofuran)lithium], [Li₂(C₄₄H₄₀N₂Si)(C₄H₈O)₂], 3. Both 2 and 3 were characterized by ¹H and ¹³C NMR spectroscopy and elemental analysis, and the structures of 1, 2 and 3 were confirmed by X-ray crystallography. Density functional theory (DFT) calculations were carried out for compounds 1-3. In addition, the catalytic properties of 3 towards the ring-opening polymerization of ϵ-caprolactone were investigated and the compound showed good catalytic activity.

The molecular structures of two novel cobalt aminodiphosphine (PNP) complexes (1 and 2) are reported, namely, bis[bis(diphenylphosphanyl)(pentyl)amine-κ²P,P']chloridocobalt(III) di-μ-chlorido-bis[dichloridocobalt(II)], [CoCl(C₂₉H₃₁NP₂)₂][Co₂Cl₆], and bis[bis(diphenylphosphanyl)(propan-2-yl)amine-κ²P,P']chloridocobalt(III) di-μ-chlorido-bis[dichloridocobalt(II)], [CoCl(C₂₇H₂₇NP₂)₂][Co₂Cl₆], featuring variation in the N-atom substituent, i.e. n-pentyl in complex 1 and isopropyl in complex 2. The asymmetric unit of complex 1 contains a five-coordinated cationic [CoCl{κ²-P,P-(N)-C₅H₁₁}₂]²⁺ species and a [Co₂(μ₂-Cl)₂Cl₄]^2- anion, while complex 2 includes a five-coordinated cation [CoCl{κ²-P,P-(N)-C₃H₇}₂], half a [Co₂(μ₂-Cl)₂Cl₄]^2- anion, and disordered diethyl ether and dichloromethane solvent molecules. The impact of ligand-induced strain, particularly due to the small bite angles of the PNP aminodiphosphine ligands, was examined in the context of geometric constraints and their influence on stability and reactivity. A Cambridge Structural Database (CSD) survey, along with a noncovalent interaction (NCI) analysis of the analogous [TMCl_n(PNP)₂] (where TM = transition metal and n = 1 or 2) core, revealed an inverse correlation between P-TM-P bite angles and N...TM contact distances. This correlation is attributed to the influence of the van der Waals radius of the metal: smaller metals allow wider bite angles and stronger N...TM contacts, whereas larger metals favour narrower bite angles and longer N...TM distances. NCI analysis indicated significant steric repulsion at the TM...N contacts, reflecting strain imposed by ligand geometry. A comparison of sign(λ₂)ρ eigenvalues suggests that Mo-P bonds exhibit weaker attractive interactions relative to Co-P and Ru-P bonds, with Cr-P bonds being the weakest. These findings provide pointers to structural and electronic factors governing coordination in PNP-ligated transition-metal complexes, offering rational design and catalytic and material applications.

Our laboratory recently explored a highly stereospecific rearrangement of epoxides into tetrahydrofurans. To unambiguously determine the stereochemical outcome of this rearrangement, single crystals of one of the products, (2R*,3R*)-2-(2-phenoxyethyl)tetrahydrofuran-3-yl acetate, C₁₄H₁₈O₄, were grown and analyzed. Based on the crystal structure data, we were able to show that the contiguous stereocenters of this molecule are in a syn configuration, and we now suggest with confidence a plausible mechanism for the rearrangement reaction. The syn configuration of the ring may also account for the inability of most members of this class to crystallize, as it imparts a kink in the structure reminiscent of low-melting unsaturated fatty acids.

The structural chemistry of selenourea ligands is quite diverse, though examples of their coordination to cobalt are rare. In this study, the solid-state structures of the selenourea 1,3-diethylimidazole-2-selone, C₇H₁₂N₂Se, and the cobalt complexes dichloridobis(1,3-diethylimidazole-2-selone-κSe)cobalt(II), [CoCl₂(C₇H₁₂N₂Se)₂] (1), and dichloridobis(1,3-diisopropylimidazole-2-selone-κSe)cobalt(II), [CoCl₂(C₉H₁₆N₂Se)₂] (2), are presented. Two crystallization methods for the coordination complexes are utilized. The structures of complexes 1 and 2 are compared with the few existing examples in the literature, revealing a similar trend for terminal binding modes, rather than bridging modes which are often seen for late d-block metal complexes. Density functional theory calculations reveal a trend in cobalt-selenium bond strengths for 1,3-dialkyl-substituted imidazole-2-selones of Me ≃ Et < ⁱPr.

The ternary boride MgNi₂B₆ (magnesium dinickel hexaboride) crystallizes as a new representative of the CeCr₂B₆ structure type. The Mg and Ni atoms occupy sites with mmm and mm2 symmetry, respectively. The B atoms occupy two sites with m.. and m2m symmetry. The 14-membered polyhedron around the Mg atom is a hexagonal prism, with two adjacent lateral faces centred by Mg atoms. The Ni atoms are encapsulated in 10-vertex polyhedra. The trigonal prismatic coordination is typical for both B atoms. The electronic structure was calculated by the tight-binding linear muffin-tin orbital atomic spheres approximation (TB-LMTO-ASA) method. The electron concentration is higher around the B atoms, which form eight-membered channels along b, which are filled with Mg and Ni atoms. The maximum hydrogen absorption is up to 2.38 wt% H₂.