Ring Centroid Research Articles

Structural elucidation of the dichloridodioxido-[(4,7-dimethyl)-1,10-phenanthroline]molybdenum(VI) (C14H12Cl2MoN2O2)

In this work, the synthesis, characterization, and X-ray powder diffraction data for dichloridodioxido-[(4,7-dimethyl)-1,10-phenanthroline]molybdenum(VI) are reported. The crystal structure of this compound was solved from powder diffraction data using the simulated annealing method with a subsequent refinement using the Rietveld method. The dioxo-molybdenum (VI) complex C14H12Cl2MoN2O2 crystallizes in a monoclinic system with space group C2/c (N° 15) with refined unit-cell parameters a = 12.9495 (5) Å, b = 9.7752 (4) Å,c = 12.0069 (6) Å, β = 101.702 (3) °, unit-cell volume V = 1488.27 (11) Å3, and values of Z′ = 0.5 and Z = 4. The molecules are organized into chains diagonally along the a and c axis. Parallel polyhedra are observed along these axes formed by the interactions of Mo, Cl, O, and N atoms present in the coordination sphere. The crystalline packing of this dioxo-molybdenum (VI) complex is dominated by five intermolecular hydrogen bonds, two intramolecular hydrogen bonds, and the four interactions between the centroids (CgI⋯CgJ) of the aromatic rings. An analysis of the Hirshfeld surface revealed that the greatest contributions of the attractive forces are given by H⋯Cl/Cl⋯H, H⋯C/C⋯H, H⋯O/O⋯H, and H⋯H interactions.

Single-Crystal Structure Analysis of Dicarboxamides: Impact of Heteroatoms on Hydrogen Bonding of Carboxamide Groups

This research examines how heteroatoms in a six- or five-membered pyridine, thiophene or furan ring spacer between two carboxamide groups influence the hydrogen bonding for advancements in supramolecular chemistry and drug development. The solvent-free crystal structures of 3,5-pyridinedicarboxamide (PDC), 2,5-thiophenedicarboxamide (TDC) and 2,5-furandicarboxamide (FDC-subl, crystallized by sublimation), and the monohydrate structure of FDC-solv (crystallized from methanol) are described with the hydrogen-bonding analyzed by the Etter graph-set notation. The carbon atoms of the amide groups form an angle of 121° in PDC, 151° in TDC, 137° in FDC-solv and 135° in FDC-subl with the ring centroid. Only in the structure of PDC does the heteroatom act as an H-bond acceptor as part of a C11(6) chain. In TDC and FDC, the heteroatoms do not interact with the amide -NH2 groups.

Synthesis and crystal structures of N,2,4,6-tetra-methyl-anilinium tri-fluoro-methane-sulfonate and N-iso-propyl-idene-N,2,4,6-tetra-methyl-anilinium tri-fluoro-methane-sulfonate.

Two 2,4,6-tri-methyl-aniline-based trifuloro-methane-sulfonate (tri-fluoro-methane-sulfonate) salts were synthesized and characterized by single-crystal X-ray diffraction. N,2,4,6-Tetra-methyl-anilinium tri-fluoro-methane-sulfonate, [C10H14NH2 +][CF3O3S-] (1), was synthesized via methyl-ation of 2,4,6-tri-methyl-aniline. N-Iso-propyl-idene-N,2,4,6-tetra-methyl-anilinium tri-fluoro-meth-ane-sulfonate, [C13H20N+][CF3O3S-] (2), was synthesized in a two-step reaction where the imine, N-iso-propyl-idene-2,4,6-tri-methyl-aniline, was first prepared via a dehydration reaction to form the Schiff base, followed by methyl-ation using methyl tri-fluoro-methane-sulfonate to form the iminium ion. In compound 1, both hydrogen bonding and π-π inter-actions form the main inter-molecular inter-actions. The primary inter-action is a strong N-H⋯O hydrogen bond with the oxygen atoms of the tri-fluoro-methane-sulfonate anions bonded to the hydrogen atoms of the ammonium nitro-gen atom to generate a one-dimensional chain. The [C10H14NH2 +] cations form dimers where the benzene rings form a π-π inter-action with a parallel-displaced geometry. The separation distance between the calculated centroids of the benzene rings is 3.9129 (8) Å, and the inter-planar spacing and ring slippage between the dimers are 3.5156 (5) and 1.718 Å, respectively. For 2, the [C13H20N+] cations also form dimers as in 1, but with the benzene rings highly slipped. The distance between the calculated centroids of the benzene rings is 4.8937 (8) Å, and inter-planar spacing and ring slippage are 3.3646 (5) and 3.553 Å, respectively. The major inter-molecular inter-actions in 2 are instead a series of weaker C-H⋯O hydrogen bonds [C⋯O distances of 3.1723 (17), 3.3789 (18), and 3.3789 (18) Å], an inter-action virtually absent in the structure of 1. Fluorine atoms are not involved in strong directional inter-actions in either structure.

Synthesis of Crystallographically Characterizable Bis(cyclopentadienyl) Sc(II) Complexes: (C5H2tBu3)2Sc and {[C5H3(SiMe3)2]2ScI}1.

The synthesis of previously unknown bis(cyclopentadienyl) complexes of the first transition metal, i.e., Sc(II) scandocene complexes, has been investigated using C5H2(tBu)3 (Cpttt), C5Me5 (Cp*), and C5H3(SiMe3)2 (Cp″) ligands. Cpttt2ScI, 1, formed from ScI3 and KCpttt, can be reduced with potassium graphite (KC8) in hexanes to generate dark-red crystals of the first crystallographically characterizable bis(cyclopentadienyl) scandium(II) complex, Cpttt2Sc, 2. Complex 2 has a 170.6° (ring centroid)-Sc-(ring centroid) angle and exhibits an eight-line EPR spectrum characteristic of Sc(II) with Aiso = 82.6 MHz (29.6 G). It sublimes at 200 °C at 10-4 Torr and has a melting point of 268-271 °C. Reductions of Cp*2ScI and Cp″2ScI under analogous conditions in hexanes did not provide new Sc(II) complexes, and reduction of Cp*2ScI in benzene formed the Sc(III) phenyl complex, Cp*2Sc(C6H5), 3, by C-H bond activation. However, in Et2O and toluene, reduction of Cp*2ScI at -78 °C gives a dark-red solution, 4, which displays an eight-line EPR pattern like that of 1, but it did not provide thermally stable crystals. Reduction of Cp″2ScI, in THF or Et2O at -35 °C in the presence of 2.2.2-cryptand, yields the green Sc(II) metallocene iodide complex, [K(crypt)][Cp″2ScI], 5, which was identified by X-ray crystallography and EPR spectroscopy and is thermally unstable. The analogous reaction of Cp*2ScI with KC8 and 18-crown-6 in Et2O gave the ligand redistribution product, [Cp*2Sc(18-crown-6-κ2O,O')][Cp*2ScI2], 6, as the only crystalline product. Density functional theory calculations on the electronic structure of these compounds are reported in addition to a steric analysis using the Guzei method.

Synthesis and crystal structure of bis-(tert-butyl isocyanide-κC)[5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinato-κ4N]iron(II).

In the title compound, [FeII(C44H24Cl4N4)(C5H9N)2] or [FeII(TClPP)(t-BuNC)2] [where TClPP and t-BuNC are 5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinate and tert-butyl isocyanide ligands, respectively], the metal ion lies on an inversion center and is octa-hedrally coordinated by the N atoms of the porphyrin ring in the equatorial plane and by carbon atoms of the trans t-BuNC ligands in the axial sites. The Fe-N bond length of 2.0074 (14) Å suggests a low-spin complex (S = 0). The crystal packing of the title compound is sustained by C-H⋯Cl, C-H⋯N and C__H⋯Cg (Cg = the centroid of a pyrrole ring of the TClPP porphyrinate) inter-actions, leading to a three-dimensional network. The Hirshfeld surface (HS) analysis indicates that 61.4% of the inter-molecular inter-actions are from H⋯H contacts while other contributions are from C⋯H/H⋯C, O⋯H/H⋯O and N⋯H/H⋯N inter-actions, which comprise 21.3%, 13.3% and 3.6% of the HS, respectively.

Strong structuring arising from weak cooperative O-H···π and C-H···O hydrogen bonding in benzene-methanol solution

Weak hydrogen bonds, such as O-H···π and C-H···O, are thought to direct biochemical assembly, molecular recognition, and chemical selectivity but are seldom observed in solution. We have used neutron diffraction combined with H/D isotopic substitution to obtain a detailed spatial and orientational picture of the structure of benzene-methanol mixtures. Our analysis reveals that methanol fully solvates and surrounds each benzene molecule. The expected O-H···π interaction is highly localised and directional, with the methanol hydroxyl bond aligned normal to the aromatic plane and the hydrogen at a distance of 2.30 Å from the ring centroid. Simultaneously, the tendency of methanol to form chain and cyclic motifs in the bulk liquid is manifest in a highly templated solvation structure in the plane of the ring. The methanol molecules surround the benzene so that the O-H bonds are coplanar with the aromatic ring while the oxygens interact with C-H groups through simultaneous bifurcated hydrogen bonds. This demonstrates that weak hydrogen bonding can modulate existing stronger interactions to give rise to highly ordered cooperative structural motifs that persist in the liquid phase.

The unusual (syn-/anti-)2 conformation of a di-meth-oxy-pyrimidyl-based tennimide.

The tennimide macrocycle, (I) (C52H40N16O16.0.167H2O), was synthesized from 2-amino-4,6-di-meth-oxy-pyrimidine and pyridine-2,6-dicarbonyl dichloride. Compound (I) represents the first tennimide incorporating pyridine rings in the macrocycle scaffold. In the macrocycle ring, the carbonyl groups at each successive dicarbon-yl(pyridine) moiety adopt the (syn/anti)2 conformation. This contrasts with all previously reported tetra-imide macrocycles, which exhibit the (syn)4 conformation. The effect is to close any potential cavity or niche by having two of the central pyridine C5N rings aligned close to each other [with closest pyridine Cg⋯Cg ring centroid separations of 3.5775 (19) Å; closest C⋯C = 3.467 (5) Å]. A partial occupancy water mol-ecule (with s.o.f. = 0.167), resides with its oxygen atom on a twofold axis at hydrogen-bonding distances to the carbonyl O atom, in a mol-ecular niche between two pyridine rings. Macrocyles of (I) have all six C=O groups and all eight meth-oxy O atoms present on the macrocycle surface. However, all twelve N atoms are effectively shielded on steric grounds from any potential inter-molecular inter-actions. The remaining two C=O O atoms inter-act with the partial occupancy water mol-ecule via two O-H⋯O=C hydrogen bonds. Macrocycles of (I) stack as one-dimensional chains along the b-axis direction with primary inter-molecular inter-actions involving weak C-H⋯O=C/OCH3/H2O contacts. Chains inter-lock weakly via meth-oxy-meth-oxy C-H⋯O inter-actions into two-dimensional sheets.

Cu(II) complex of S-benzyl-β-N-(2-methoxybenzylmethylene)dithiocarbazate: Synthesis, DFT calculations, cell cytotoxicity assay and DNA binding studies

A copper(II) complex (CuL2) containing bidentate N,S-donor Schiff base ligands (S-benzyl-β-N-(2-methoxybenzylmethylene) dithiocarbazate, HL) was synthesised and characterised using physicochemical and spectroscopic methods. This work comprehensively includes the single crystal X-ray diffraction analysis of HL, revealing that the centroid of the phenyl ring was engaged in the intermolecular CH interactions that stabilised the three-dimensional (3D) molecular structure. The Hirshfeld surface analysis was used to measure the intermolecular interactions of HL. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations of HL and CuL2 were carried out using B3LYP with the LanL2DZ pseudopotential and 6–311G(d, p) basis set for all the other atoms. The selected calculated frequencies (v(C = N), v(NN), v(C = S)) correlated well with the experimental data obtained, except v(NH). Due to the intra- and intermolecular hydrogen bondings between molecules in solid, some deviation of this band was observed in the calculated gas phase system. The calculated structures and UV–vis results also concur with the experimental findings. It was discovered through cytotoxicity studies that CuL2 had promised good activity against extremely aggressive breast cancer cells (MDA-MB-231). In order to investigate the interactions between cytoactive CuL2 and calf thymus-DNA (DNA), electronic absorption titrations were performed, which revealed moderate binding through groove binding mode with a binding constant (Kb) of 1.75 × 105 M−1. Additionally, the binding capacity of CuL2 with DNA was investigated using molecular docking simulations. The results are comparable with the experimental data, in which CuL2 is bound to the DNA groove via hydrogen bonds and hydrophobic interactions. DNA binding studies have shown that sulfur, nitrogen, and aromatic rings is very important, in terms of the interactions between the lone pairs and π-aromatic ring with nucleobases of DNA.

Crystal and molecular structure of Michler’s ketone as a pure phase

The pure phase crystals of Michler’s ketone, [4-(CH3)2NC6H4]2CO, are reported herein as monoclinic in the space group P21/c with Z’ = 2 by single-crystal X-ray diffraction. The data collection of the title compound proved quite difficult, which could explain why the structure has not been reported previously. The crystallographically independent molecules in the asymmetric unit differ by dihedral angles of 24.60/30.34° and 25.25/27.20° between the essentially planar 4-dimethylaminophenyl (DMAP) rings and the central C2C=O plane of the ketone and dihedral angles of 52.14 and 47.41°, respectively, between the DMAP planes. A DMAP ring of each molecule overlaps in the lattice with a methyl ring that overlays the ring centroid of the opposite number (CMe-Cg distances of 3.452 and 3.505 Å), describing sets of trifurcated CAr-acceptor hydrogen bond interactions (HBIs). The trifurcated HBIs possess H∙∙∙CAr distances of 2.90, 2.75, and 2.86 Å; CMe∙∙∙Car distances of 3.554(5), 3.798(5) and 3.881(5) Å; and ÐCMe-H∙∙∙CAr of 115.0, 121.3 and 167.7°, respectively. Stabilization of the asymmetric unit in the title compound is further achieved by supramolecular synthons such as CMe-H∙∙∙CAr (2.831 Å), CAr-H∙∙∙O (2.561 Å) and CAr-H∙∙∙H-CAr (2.290 Å) and coulombic CMe-Ocontact (3.209 Å). The structures of the two independent molecules in the asymmetric unit of the title compound were compared with the same molecule as found in the following co-crystals, adducts or salts: a halogen-bonded adduct with 1,4-diiodotetrafluorobenzene; a hydrogen-bonded adduct with a fluorinated phenol; a coordination complex between the ketone and a trimeric mercury acceptor; and two salts from protonation or methylation at one of the amino nitrogen atoms.

Isolation and crystal and molecular structures of [(C5H2Br3)2Fe], [(C5HBr4)2Fe] and [(C5Br5)(C5Br4HgBr)Fe

The reaction of [(C5H3Br2)2Fe] with lithium tetramethylpiperidinide (LiTMP) in a 1:10 molar ratio in tetrahydrofuran yields, after quenching with C2H2Br4, a mixture of the polybromoferrocenes [C10H10-nBrnFe] with n= 4-9, from which single crystals of bis(1,2,3-tribromocyclopentadienyl)iron(II), [Fe(C5H2Br3)2], and bis(1,2,3,4-tetrabromocyclopentadienyl)iron(II), [Fe(C5HBr4)2Fe], were obtained by a combination of chromatography and fractional crystallization. Treatment of `[C10(HgOAc)10Fe]' with KBr3 yields a mixture of polybromoferrocenes [C10H10-nBrnFe] with n= 8-10 and bromomercurioferrocenes [C10H9-nBrn(HgBr)Fe] with n= 7-9, from which single crystals of (1-bromomercurio-2,3,4,5-tetrabromocyclopentadienyl)(1,2,3,4,5-pentabromocyclopentadienyl)iron(II), [FeHgBr(C5Br4)(C5Br5)], were obtained by fractional crystallization. The crystal structures of all the compounds show Br...Br, Br...H and sometimes Br...Cp...π (Cp is a ring centroid) interactions, as well as π-π interactions. The findings are supported by Hirshfeld analyses.

Crystal structure of 4,5-dimethyl-1,3-dioxol-2-one.

The planar title compound 4,5-dimethyl-1,3-dioxol-2-one, C5H6O3, 1, crystallizes with its mol-ecular C 2 axis coincident with a crystallographic mirror plane in space group P21/m. In the plane defined by the b axis and an ac face diagonal, anti-parallel linear strands of 1, formed by simple translation, associate to form sheets with close H⋯H and O⋯O inter-molecular contacts. Between the sheets, parallel strands of 1 place the carbonyl O atom near the five-membered ring centroid of a neighboring mol-ecule with close O⋯O and O⋯C contacts.

Designing polyoxometalate-based metal-organic framework for oxidation of styrene and cycloaddition of CO2 with epoxides

A photoactive polyoxometalate-based metal−organic framework (POMOF), NiW-DPNDI, was synthesized by combination of Ni(II) ions, [ZnW12O40]6‒ anions, and N,N'-bis(4-pyridylmethyl)naphthalene diimide (DPNDI) molecules into one single framework. NiW-DPNDI displays a three-dimensional structure by the strong anion⋅⋅⋅π interactions between the trapped [ZnW12O40]6‒ anions and the electron-deficient naphthalenic ring centroids and the π−π stacking interactions between DPNDI moieties. NiW-DPNDI displayed a highly efficient hole-electron separation and ordered electron transfer under irradiation, thus ensuing its excellent photocatalysis in oxidation of styrene to produce benzaldehyde. In addition, it gave a high efficiency for styrene oxide under thermocatalytic conditions. Because the carbonic anhydrase (CA)-mimicking Ni sites and the negative electron-enriched [ZnW12O40]6‒ anions are well aligned in the pores, it can promote the cycloaddition of CO2 with epoxides under mild conditions.

A bibliographic survey of the supramolecular architectures sustained by delocalised C–I⋯π(arene) interactions in metal-organic crystals

Abstract A survey of the crystallographic literature of metal-organic crystal structures for the presence of C–I···π(arene) interactions where the iodide atom occupies a position close to plumb to the ring centroid, corresponding to a delocalised interaction, and is within the assumed sum of the van der Waals radii, i.e. 3.88 Å, has been undertaken. The majority of the 26 identified examples feature supramolecular chains of varying topology whereby C–I···π(arene) contacts are readily identified and apparently operating independently of other obvious supramolecular synthons. The next most prevalent supramolecular aggregate was zero-dimensional, containing up to a maximum of three molecules. While there were three examples of two-dimensional arrays among a series of isostructural crystal structures, no examples of three-dimensional structures largely sustained by C–I···π(arene) interactions were noted. This distribution of supramolecular aggregation patterns matched that noted for all-organic systems. In terms of the overall adoption rate, delocalised C–I···π(arene) interactions were found in 3% of crystals of metal-organic species where they could form, a percentage lower than 4% noted for all-organic crystals.

A combined experimental and theoretical study on the synthesis, spectroscopic characterization of Magnesium(II) porphyrin complex with DMAP axial ligand and antifungal activity

We report in the present paper the synthesis, the spectroscopic, structural, and electrochemical properties of a new magnesium(II) coordination compound namely the bis(4-dimethylaminopyridine)[meso-tetra(p-tolyl)porphyrinato)]magnesium(II) dichloromethane disolvate complex with the formula [Mg(TTP)(DMAP)2]•2CH2Cl2 (I). This species crystallizes in the triclinic crystal system with the centrosymmetric space group P-1. The crystal lattice of (I) is stabilized by C__H…Cg (Cg is the centroid of a phenyl ring) and C__H…Cl intermolecular interactions. Further insights on these weak intermolecular contacts are provided by the Hirshfeld surface analysis. This new Mg(II) porphyrin species was characterized by 1H NMR, IR, fluorescence, UV/Vis spectroscopy and ESI-HRMS mass spectrometry. A cyclic voltammetry investigation of this new metalloporphyrin was also reported. Furthermore, the bioactivity of the H2TTP free base porphyrin, the [Mg(TTP)] starting material and [Mg(TTP)(DMAP)2]•2CH2Cl2 (I) was evaluated in vitro, by examining their inhibitory effect against three strains of Candida viz. C. albicans, C. glabrata and C. tropicalis with MIC values in the range 2.5 to 10 μg.mL−1. The screening of the susceptibility of M. canis and T. rubrum clinical strains on the three porphyrinic derivatives is also reported.

Study on the synthesis, physicochemical, electrochemical properties, molecular structure and antifungal activities of the 4-pyrrolidinopyridine Mg(II) meso-tetratolylporphyrin complex

A novel magnesium(II) metalloporphyrin namely the bis(4-pyrrolidinopyridine)[meso-tetra(p-tolyl)porphyrinato)]magnesium(II) dichloromethane desolate complex with the formula [Mg(TTP)(4-pypo)2]·CH2Cl2 (I) has been synthetized and fully characterized by UV–Vis, fluorescence, IR, 1H NMR spectroscopy and mass spectrometry. The X-ray molecular structure shows that I presents two molecules (1 and 2) [Mg1(TTP)(4-pypo)2] and [Mg2(TTP)(4-pypo)2] in the asymmetric unit while the Hirshfeld surface analysis on this hexacoordinated Mg(II) porphyrin species indicates that the crystal lattice is mainly sustained by C__H…C, C__H…Cg (Cg is the centroid of a phenyl ring) and C__H…Cl intermolecular interactions. The cyclic voltammetry data of I is also reported. The bioactivity of the H2TTP, the [Mg(TTP)] starting material and [Mg(TTP)(4-pypo)2]·CH2Cl2 (I) was evaluated in vitro, by examining their inhibitory effect against three strains of Candida viz. C. albicans, C. glabrata and C. tropicalis with MIC values in the range 2.5 to 10 µg.mL−1. The screening of the susceptibility of M. canis and T. rubrum clinical strains on the three porphyrinic derivatives is also reported.

Exploring the use of the pentaphenylcyclopentadienyl ligand in uranium chemistry: the crystal structure of (C

The reaction of UI3 with NaC5Ph5 in THF generated (η5-C5Ph5)UI2(THF)2 which was characterized by X-ray crystallography. The complex has a four-legged piano stool structure with a 2.539 Å U– (C5Ph5 ring centroid) distance that is slightly longer than the 2.504 Å distance in (η5-C5Me5)UI2(THF)3 which has a larger formal coordination number. Although the synthesis of the mono-cyclopentadienyl complex was facile, no bis-cyclopentadienyl complexes were isolated from reactions using two equivalents of the pentaphenylcyclopentadienyl ligand per uranium. In one UI3/2NaC5Ph5 synthesis, the X-ray crystal structure of (THF)3Na(η5-C5Ph5) was obtained. Attempts to reduce (η5-C5Ph5)UI2(THF)2 did not give evidence for a UII product. KC8 reductions of the in situ reaction of NdI3 and NaC5Ph5, analogous to the synthesis of (η5-C5Ph5)UI2(THF)2, yielded an X-ray crystal structure of a solvent-separated ion pair (SSIP), [K(18-crown-6)(THF)2][C5Ph5].

Insight into structural description of novel 1,4-Diacetyl-3,6-bis(phenylmethyl)-2,5-piperazinedione: synthesis, NMR, IR, Raman, X-ray, Hirshfeld surface, DFT and docking on breast cancer resistance protein

In this work, novel 1,4-diacetyl-3,6-bis(phenylmethyl)-2,5-piperazinedione (2) is prepared exclusively as the (R,S)-stereoisomer evidenced and confirmed by X-ray diffraction analysis. In addition, spectroscopic (NMR, IR, Raman) analyses were used to characterize the new compound. 2 crystallizes in the Pbca orthorhombic space group, with a symmetry center located at the centroid of the diketopiperazine ring. The structure of 2 is compact with the two phenyl rings folded over and under the diketopiperazine ring, conferring thereby a unique S shape to the molecule. The crystal structure is stabilized by intramolecular interactions, whereas the crystal packing is stabilized by intermolecular H-bond and C−H···π interactions. The different intermolecular interactions were confirmed using Hirshfeld surface analysis and molecular fingerprint. Molecular 2D fingerprint that quantify the different interactions highlights that H···H (58.2%), H···O/O···H (24.8%) and C···H/H···C (14.2%) account for 97.2% of all contacts. The topology of the interaction energy in the crystal structure is obtained and described. The Cremer and Pople puckering parameters indicate that the diketopiperazine ring adopts a flattened chair conformation with Θ = 0.00 ° and Q = 0.2233 (11) Å. Moreover, a computational investigation revealed that the optimized structure of 2 using DFT calculation shows excellent agreement with the experimental data. As potential pharmacological active molecule, the molecular docking on breast cancer resistance protein (BCRP) reveals that 2 could interacts with the binding domain residues Phe728, Tyr949, Ser975 and Val978 and could be consider as promising BCRP inhibitor.

Observing the Inner Shadow of a Black Hole: A Direct View of the Event Horizon

Abstract Simulated images of a black hole surrounded by optically thin emission typically display two main features: a central brightness depression and a narrow “photon ring” consisting of strongly lensed images superimposed over the direct emission. The photon ring closely tracks a theoretical curve on the image plane corresponding to light rays that asymptote to bound photon orbits. The size and shape of this critical curve are purely governed by the Kerr geometry; in contrast, the size, shape, and depth of the observed brightness depression depend on the details of the emission region. For instance, images of spherical accretion models display a distinctive dark region—the “black hole shadow”—that completely fills the photon ring. By contrast, in models of equatorial disks extending to the event horizon, the darkest region in the image is restricted to a much smaller area—an inner shadow—whose edge lies near the direct lensed image of the equatorial horizon. Using both general relativistic MHD simulations and semi-analytic models, we demonstrate that the photon ring and inner shadow may be simultaneously visible in submillimeter images of M87*, where magnetically arrested disk simulations predict that the emission arises in a thin region near the equatorial plane. We show that the relative size, shape, and centroid of the photon ring and inner shadow can be used to estimate the black hole mass and spin, breaking degeneracies in measurements of these quantities from the photon ring alone. Both features may be accessible to direct observation via high-dynamic-range images with a next-generation Event Horizon Telescope.

Synthesis, photophysical, cyclic voltammetry properties, and molecular structure study of novel (5,10,15,20-tetratolylphenyl porphyrinato)zinc(II) with pyrazine

The precursor (5,10,15,20)-tetratolylporphyrin (H2TTP) (1) and Zn(II) complex (5,10,15,20)-tetratolylporphyrinato)zinc(II) [Zn(TTP)] (2) have been synthesized and utilized to afford a novel complex (3) bearing pyrazine as fifth coordination site on axial position, i.e. (pyrazine)(5,10,15,20-tetratolylporphyrinato)zinc(II) hemi-pyrazine hemidichloromethane solvate [Zn(TTP) (pyz)]0.0.5(pyz.CH2Cl2). Photophysical, electrochemical and X-ray diffraction were investigated. The single-crystal X-ray analysis indicated that in complex (3) (i) Zn(II) ion is penta coordinated, (ii) slight displacement of Zn atom by −0.28 Å towards the axial ligand (pyrazine) and (iii) the crystal lattice is made up of two dimensional layers stabilised by C−H…Cg intra- and intermolecular interactions (Cg is the centroid of pyrrole ring). Optical absorption studies revealed a redshifted of the Soret (B) and Q bands of the Zn-porphyrins complexes. Contrarily, a hypsochromic shift of Q bands in emission spectra of the complexes is noted as compared to the H2TPP. Lifetime of the electrons in (1–3) were determined and compared. Overall, this study would assist in understanding the impact of incorporation of pyrazine at the axial position on optical and electronic properties. Cyclic voltammetry (CV) was applied for the study of the electrochemical behavior of both (2) and (3) complexes in 0.2 M Tetra-n-butyl ammonium perchlorate (TBAP) solution in CH2Cl2. The results of electrochemical confirmed the potentials redox peaks shift more negative ca 60 mV to that is caused by the coordination of pyrazine ligand.

Di-μ2-chlorido-bis-{chlorido-[2,4,6-tris-(pyridin-2-yl)-1,3,5-triazine-κ3 N 2,N 1,N 6]nickel(II)}.

In the title compound, [Ni2Cl4(C18H12N6)2], the NiII ions are hexa-coordinated in a distorted octa-hedral coordination environment defined by three N atoms of the tridentate 2,4,6-tri-2-pyridyl-1,3,5-triazine ligand and three Cl- anions in a meridional geometry. The two NiII ions are bridged by two Cl anionic ligands, thereby forming a dinuclear complex. A crystallographic centre of inversion is located at the centroid of the Ni2Cl2 ring.