(E,E)-N1,N2-Bis(2,6-di­fluoro­benzyl­idene)ethane-1,2-di­amine.

The asymmetric unit of the title compound, C16H12F4N2, comprises half of the potentially bidentate Schiff base ligand, with an inversion centre located at the mid-point of the central C—C bond. The crystal packing is stabilized by inter­molecular C—H⋯N and π–π inter­actions [centroid–centroid distance = 3.6793 (12) Å and inter­planar spacing = 3.4999 (7) Å]

Tricarbonylchlorido(6'7'-dihydro-5’H-spiro[cyclopentane-1,6'-dipyrido-[3,2-d:2',3'-f][1,3]diazepine]-κ2N1,N11)-rhenium(I)

In the title compound, [ReCl(C15H16N4)(CO)3], the ReI ion is coordinated in a distorted octahedral geometry by one Cl atom, two N atoms of the bidentate ligand and three carbonyl groups. The cyclopentane group is orientated in a transoid fashion with respect to the chloride ligand. The dihedral angle between the pryridine rings is 10.91 (12)°. In the crystal, N-H...Cl hydrogen bonds link complex molecules, forming a two-dimensional network parallel to (001)

Tricarbonylchlorido(6’,7’-dihydro-5’H-spiro[cyclohexane-1,6’-dipyrido[3,2-d :2’,3’-f][1,3]diazepine]-κ2N1,N11)rhenium(I)

In the title compound, [ReCl(C16H18N4)(CO)3], the ReI ion is coordinated in a distorted octahedral geometry by one Cl atom, two N atoms of the bidentate ligand and three carbonyl groups. The cyclohexane group is orientated in a transoid fashion with respect to the chloride ligand. In the crystal, N-H...Cl hydrogen bonds link complex molecules, forming a two-dimensional network parallel to (100)

Particle-stabilized oscillating diver: a self-assembled responsive capsule

We report the experimental discovery of a self-assembled capsule, with density set by interfacial glass beads and an internal bubble, that automatically performs regular oscillations up and down a vial in response to a temperature gradient. Similar composites featuring interfacial particles and multiple internal compartments could be the solution to a variety of application challenges.Comment: 7 pages, 3 figure

The Gaussian Plasma Lens in Astrophysics. Refraction

We consider the geometrical optics for refraction of a distant radio source by an interstellar plasma lens, with application to a lens with a Gaussian electron column density profile. The refractive properties of the lens are specified completely by a dimensionless parameter, alpha, which is a function of the wavelength of observation, the lens' electron column density, the lens-observer distance, and the transverse diameter of the lens. Relative motion of the observer and lens produces modulations in the source's light curve. Plasma lenses are diverging so the light curve displays a minimum, when the lens is on-axis, surrounded by enhancements above the unlensed flux density. Lensing can also produce caustics, multiple imaging, and angular position wander of the background source. If caustics are formed, the separation of the outer caustics can constrain alpha, while the separation of the inner caustics can constrain the size of the lens. We apply our analysis to 0954+654, a source for which we can identify caustics in its light curve, and 1741-038, for which polarization observations were obtained during and after the scattering event. We find general agreement between modelled and observed light curves at 2.25 GHz, but poor agreement at 8.1 GHz. The discrepancies may result from a combination of lens substructure or anisotropic shape, a lens that only grazes the source, or unresolved source substructure. Our analysis places the following constraints on the lenses: Toward 0954+654 (1741-038) the lens was 0.38 AU (0.065 AU) in diameter, with a peak column density of 0.24 pc cm^{-3} (1E-4 pc cm^{-3}) and an electron density of 1E5 cm^{-3} (300 cm^{-3}). The angular wander caused by the lens was 250 mas (0.4 mas) at 2.25 GHz. For 1741-038, we place an upper limit of 100 mG on the lens' magnetic field.Comment: 26 pages, LaTeX2e using AASTeX macro aaspp4, 11 PostScript figures; to be published in Ap

The Sensitivity of Structure to Ionic Radius and Reaction Stoichiometry: A Crystallographic Study of Metal Coordination and Hydrogen Bonding in Barbiturate Complexes of All Five Alkali Metals Li–Cs

A systematic study has been conducted on barbiturate complexes of all five alkali metals, Li–Cs, prepared from metal carbonates or hydroxides in an aqueous solution without other potential ligands present, varying the stoichiometric ratio of metal ion to barbituric acid (BAH). Eight polymeric coordination compounds (two each for Na, K, and Rb and one each for Li and Cs) have been characterised by single-crystal X-ray diffraction. All contain some combination of barbiturate anion BA− (necessarily in a 1:1 ratio with the metal cation M+ ), barbituric acid, and water. All organic species and water molecules are coordinated to the metal centres via oxygen atoms as either terminal or bridging ligands. Coordination numbers range from 4 (for the Li complex) to 8 (for the Cs complex). Extensive hydrogen bonding plays a significant role in all the crystal structures, almost all of which include pairs of N–H\ub7\ub7\ub7O hydrogen bonds linking BA− and/or BAH components into ribbons extending in one dimension. Factors influencing the structure adopted by each compound include cation size and reaction stoichiometry as well as hydrogen bonding

Synthesis and crystal structure of a silver(I) 6-methylmercaptopurine riboside complex

Silver nitrate reacts with 6-methylmercaptopurine riboside (6-MMPR) in aqueous solution containing methanol and DMSO at room temperature to give a colourless crystalline complex. The crystal structure, determined from synchrotron diffraction data, shows a central Ag(I) ion on a crystallographic twofold rotation axis, coordinated in an almost linear fashion by two 6-MMPR ligands via N7, with the nitrate counterion loosely coordinated as a bidentate ligand, forming a discrete molecular complex as an approximate dihydrate. The complex and the water molecules are connected in a three-dimensional network by hydrogen bonding

Extended Hydrogen-Bonded Molybdenum Arrays Derived from Carboxylic Acids and Dianilines: ROP Capability of the Complexes and Parent Acids and Dianilines

From reactions involving sodium molybdate and dianilines [2,2′ -(NH2 )C6H4 ]2 (CH2 )n (n = 0, 1, 2) and amino-functionalized carboxylic acids 1,2-(NH2 )(CO2H)C6H4 or 2-H2NC6H3 -1,4-(CO2H)2 , in the presence of Et3N and Me3SiCl, products adopting H-bonded networks have been characterized. In particular, the reaction of 2,2′ -diaminobiphenyl, [2,2′ -NH2 (C6H4 )]2 , and 2-aminoterephthalic acid, H2NC6H3 -1,4-(CO2H)2 , led to the isolation of [(MoCl3 [2,2′ -N(C6H4 )]2 }{HNC6H3 -1-(CO2 ),4- (CO2H)]\ub72[2,2′ -NH2 (C6H4 )]2 \ub73.5MeCN (1\ub73.5MeCN), which contains intra-molecular N–H\ub7\ub7\ub7Cl Hbonds and slipped π\ub7\ub7\ub7π interactions. Similar use of 2,2′ -methylenedianiline, [2,2′ -(NH2 )C6H4 ]2CH2 , in combination with 2-aminoterephthalic acid led to the isolation of [MoCl2 (O2CC6H3NHCO2SiMe3 ) (NC6H4CH2C6H4NH2 )]\ub73MeCN(2\ub73MeCN). Complex 2 contains extensive H-bonds between pairs of centrosymmetrically-related molecules. In the case of 2,2′ ethylenedianiline, [2,2′ -(NH2 )C6H4 ]2CH2CH2 , and anthranilic acid, 1,2-(NH2 )(CO2H)C6H4 , reaction with Na2MoO4 in the presence of Et3N and Me3SiCl in refluxing 1,2-dimethoxyethane afforded the complex [MoCl3 {1,2-(NH)(CO2 )C6H4 }{NC6H4 CH2CH2C6H4NH3 }]\ub7MeCN (3\ub7MeCN). In 3, there are intra-molecular bifurcated H-bonds between NH3 H atoms and chlorides, whilst pairs of molecules H-bond further via the NH3 groups to the non-coordinated carboxylate oxygen, resulting in H-bonded chains. Complexes 1 to 3 have been screened for the ring opening polymerization (ROP) of both ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) using solvent-free conditions under N2 and air. The products were of moderate to high molecular weight, with wide 0 values, and comprised several types of polymer families, including OH-terminated, OBn-terminated (for PCL only), and cyclic polymers. The results of metal-free ROP using the dianilines [2,2′ -(NH2 )C6H4 ]2 (CH2 )n (n = 0, 1, 2) and the amino-functionalized carboxylic acids 1,2-(NH2 )(CO2H)C6H4 or 2-H2NC6H3 -1,4-(CO2H)2 under similar conditions (no BnOH) are also reported. The dianilines were found to be capable of the ROP of δ-VL (but not ε-CL), whilst anthranilic acid outperformed 2-aminoterephthalic acid for both ε-Cl and δ-VL