170,185 research outputs found
Weak interactions in crystals: an integrated approach
No full textChiara Massera and Helen Stoeckli-Evans introduce this special issue of Acta Crystallographica Section E on 'Weak interactions in crystals: an integrated approach' where the contributions serve as an excellent introduction to the importance and the interest these have been acquiring in the scientific arena over the last two decades or so
Structural characterization of the supramolecular complex between a tetraquinoxaline-based cavitand and benzonitrile
No full textThe structural characterization is reported of the supramolecular complex between the tetraquinoxaline-based cavitand 2,8,14,20-tetrahexyl-6,10:12,16:18,22:24,4-O,O′-tetrakis(quinoxaline-2,3-diyl)calix[4]resorcinarene (QxCav) with benzonitrile. The complex, of general formula C84H80N8O8·2C7H5N, crystallizes in the space group P\overline{1} with two independent molecules in the asymmetric unit, displaying very similar geometrical parameters. For each complex, one of the benzonitrile molecules is engulfed inside the cavity, while the other is located among the alkyl legs at the lower rim. The host and the guests mainly interact through weak C—H...π, C—H...N and dispersion interactions. These interactions help to consolidate the formation of supramolecular chains running along the crystallographic b-axis direction
Partial functionalisation of C4-symmetric tetramethoxyresorcinarenes
No full textInvestigations into the distal-functionalisation of the phenols of racemic C-4-symmetric tetramethoxyresorcinarene has led to a simple, single-step procedure that allows the isolation of gram quantities of partially silylated derivatives, with the targeted distally silylated resorcinarene being obtained in a yield of 31%. These partially silylated derivatives would serve as versatile intermediates for the selective functionalisation of this elegant architecture. The solid-state structures of many of these derivatives have been determined by single crystal X-ray crystallography.[GRAPHICS]
Crystal structure of a host–guest complex between mephedrone hydrochloride and a tetraphosphonate cavitand
No full textA new supramolecular complex (I) between the tetraphosphonate cavitand Tiiii[C3H7,CH3,C6H5] [systematic name: 2,8,14,20-tetrapropyl-5,11,17,23-tetramethyl-6,10:12,16:18,22:24,4-tetrakis(phenylphosphonato-O,O′)resorcin[4]arene] and mephedrone hydrochoride {C11H16NO+·Cl−; systematic name: methyl[1-(4-methylphenyl)-1-oxopropan-2-yl]azanium chloride} has been obtained and characterized both in solution and in the solid state. The complex of general formula (C11H16NO)@Tiiii[C3H7,CH3,C6H5]Cl·CH3OH or C11H16NO+·Cl−·C68H68O12P4·CH3OH, crystallizes in the monoclinic space group P21/c with one lattice methanol molecule per cavitand, disordered over two positions with occupancy factors of 0.665 (6) and 0.335 (6). The mephedrone guest interacts with the P=O groups at the upper rim of the cavitand through two charge-assisted N—H...O hydrogen bonds, while the methyl group directly bound to the amino moiety is stabilized inside the π basic cavity via cation...π interactions. The chloride counter-anion is located between the alkyl legs of the cavitand, forming C—H...Cl interactions with the aromatic and methylenic H atoms of the lower rim. The chloride anion is also responsible for the formation of a supramolecular chain along the b-axis direction through C—H...Cl interactions involving the phenyl substituent of one phosphonate group. C—H...O and C—H...π interactions between the guest and adjacent cavitands contribute to the formation of the crystal structure
Lo sport e il principio della parità delle armi, tra politiche antidoping e diritto della concorrenza
No full textL’articolo si propone di analizzare le modalità di compatibilità tra l’ordinamento sportivo e il diritto dell’Unione europea con specifico riferimento ai rapporti tra politiche antidoping e diritto della concorrenza. Ripercorrendo la giurisprudenza e la dottrina sulla giuridicità dell’ordinamento sportivo come sistema autonomo e separato, viene messa in evidenza la progressiva valorizzazione delle sue forme di comunicazione con l’ordinamento statale e quello dell’Unione, con riguardo sia al diritto sostanziale che al diritto processuale. In questo contesto generale, assumono specifica rilevanza le politiche antidoping come strumento per garantire la concorrenzialità delle attività sportive nel più ampio ambito dell’ordinamento dell’Unione europea. Nella misura in cui presentino caratteristiche economiche, infatti, anche le attività sportive devono essere sottoposte ai principi e alla disciplina europea in materia di concorrenza (Meca Medina, C-519/04 P
Regolazione e concorrenza nelle telecomunicazioni e nei servizi postali: convergenze e divergenze nell'ordinamento delle comunicazioni tra fallimenti della regolazione e fallimenti del mercato
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Crystal structure and photo-physical properties in a perovskite–type semiconducting hybrid phase: {(m-C6H7N2O2)2CdCl4}n
No full textA new intercalation crystalline polymer compound of bis m-nitroanilinium tetrachlorocadmate (II) {(m-C6H7N2O2)2CdCl4}n was synthesized and analyzed using single crystal SXRD, differential scanning calorimetry (DSC), DFT analysis, thermal gravimetric analysis (TGA) and FT-IR, Raman, UV–Vis, fluorescence spectroscopy techniques. X-ray diffraction analyses (SXRD, PXRD) show a layered structure consisting of alternating organic bilayers and two-dimensional inorganic sheets in which each CdCl6 octahedron shares four corners with adjacent octahedra. The crystal packing is consolidated by means of classic and non-classic hydrogen bonds and π-π interactions. At room temperature photoluminescence spectra of {(m-C6H7N2O2)2CdCl4}n yield broad peaks in the 469–770 nm range with full width at half maximum (FWHM) values up to 153 nm. Besides, this compound exhibits a semiconducting behavior with bright red-light under 360 nm ultraviolet photoexcitation and possesses a large Stokes shift and direct band gap of 2.69 eV which overlaps well with solar spectrum. The CIE chromaticity coordinates of {(m-C6H7N2O2)2CdCl4}n are (x = 0.4704 and y = 0.4523). The color rendering index CRI and the low correlated color temperature CCT are 84 and 2861 K, respectively. Electronic structure (BS, DOS and PDOS), and optical properties (dielectric constant ε(ω), refractive index n(ω), reflectivity R(ω), absorption coefficient α(ω), optical conductivity σ(ω) and energy loss function L(ω) with the incident photon energy) were determined using (DFT) calculations by CASTEP code
5,5′-Dibenzoimidazole as building block for a new 3D Co(II) coordination polymer: A combined EPR and DFT study using UB3LYP model
No full textA new Co(II) three-dimensional coordination polymer, [Co(L)(L')](n) (1) [where L = 5,5'-dibenzoimidazole, and L' = doubly deprotonated terephthalic acid] has been synthesized hydro(solvo)thermally and its molecular and crystal structure have been elucidated through single crystal X-ray diffraction analysis. Each Coal) ion displays a slightly distorted trigonal bipyramidal geometry, the apical positions being occupied by the nitrogen atoms of two symmetry-related dibenzoimidazole ligands, while the oxygen atoms from three distinct terephthalic acids are in the equatorial plane. Considering the Co2C2O6 dimeric moieties as nodes, and the ancillary ligands as connectors, the structure can be simplified as a 8-c uninodal net of the type bcu, body centered cubic, with point symbol 4(24).6(4) and vertex symbol [4.4.4.4.4.4.4.4.4.4.4.4.4(3).4(3).4(3).4(3).4(3).4(3).4(3).4(3).4(3).4(3).4(3).4(3).*.*.*.*]. The EPR spectra for 1 have been reported, showing g(parallel to) = 2.176 and g(perpendicular to) = 2.052 at RT (room temperature), and g(parallel to) = 2.172 and g(perpendicular to) = 2.060 at LNT (liquid nitrogen temperature). Finally, the electronic nature of the molecular geometry of 1 has been explored by DFT computation applying the UB3LYP/def2-TZVP level of theory, showing the energy difference between the high spin and low spin configurations. (C) 2019 Elsevier Ltd. All rights reserved
Nitrosonium complexation by the tetraphosphonate cavitand 5,11,17,23-tetramethyl-6,10:12,16:18,22:24,4-tetrakis(phenylphosphonato-κ2O,O)resorcin(4)arene
No full textThe crystal structure of a new supramolecular complex between the tetraphosphonate cavitand 5,11,17,23-tetramethyl-6,10:12,16:18,22:24,4-tetrakis(phenylphosphonato-κ2O,O′)resorcin(4)arene and the nitrosyl cation NO+, as the BF4− salt, is reported. The complex, of general formula [(C56H44P4O12)(NO)]BF4·CH2Cl2 or NO@Tiiii[H, CH3, C6H5] BF4·CH2Cl2, crystallizes in the space group P-1. The nitrosyl cation is disordered over two equivalent positions, with occupancies of 0.503 (2) and 0.497 (2), and interacts with two adjacent P=O groups at the upper rim of the cavitand through dipole–charge interactions. In the lattice, the cavitands are connected through a series of C—H...π interactions involving the methyl and methylenic H atoms and the aromatic rings of the macrocycle. The structure is further stabilized by the presence of C—H...F interactions between the hydrogen atoms of the cavitands and the F atoms of the tetrafluoridoborate anion. As a result of the disorder, the lattice dichloromethane molecules could not be modelled in terms of atomic sites, and were treated using the PLATON SQUEEZE procedure [Spek (2015). Acta Cryst. C71, 9–18]. The complexation process has also been studied in solution through NMR titrations
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