(2E)-N-(3,5-Dibromo-4-methoxy­phen­yl)-2-(hydroxy­imino)acetamide

The title compound, C9H8Br2N2O3, is planar (r.m.s. deviation = 0.030 Å) with the exception of the terminal methyl group which lies out of the plane [1.219 (3) Å]. The conformation about the C=N double bond [1.268 (3) Å] is E. An intra­molecular N—H⋯N hydrogen bond occurs. Linear supra­molecular chains along the b axis mediated by O—H⋯O hydrogen-bonding inter­actions feature in the crystal structure. These chains are also stabilized by weak C—H⋯N contacts

Methyl 1-{4-[(S)-2-(meth­oxy­carbon­yl)pyrrolidin-1-yl]-3,6-dioxocyclo­hexa-1,4-dien-1-yl}pyrrolidine-2-carboxyl­ate

The complete mol­ecule of the title diproline ester quinone, C18H22N2O6, is generated by a crystallographic twofold axis, which passes through the centre of the benzene ring. Both –CO2Me groups are orientated to the same side of the benzene ring, with the carbonyl groups pointing roughly towards each other. The conformation of the proline residue is an envelope. In the crystal, a three-dimensional network is sustained by C—H⋯O inter­actions involving both the quinone and carbonyl O atoms

The 1:1 co-crystal of 2-bromonaphthalene-1,4-dione and 1,8-dihydroxyanthracene-9,10-dione: crystal structure and Hirshfeld surface analysis

The asymmetric unit of the title co-crystal, C10H5BrO2·C14H8O4 [systematic name: 2-bromo-1,4-dihydronaphthalene-1,4-dione–1,8-dihydroxy-9,10-dihydroanthracene-9,10-dione (1/1)], features one molecule of each coformer. The 2-bromonaphthoquinone molecule is almost planar [r.m.s deviation of the 13 non-H atoms = 0.060 Å, with the maximum deviations of 0.093 (1) and 0.099 (1) Å being for the Br atom and a carbonyl-O atom, respectively]. The 1,8-dihydroxyanthraquinone molecule is planar (r.m.s. deviation for the 18 non-H atoms is 0.022 Å) and features two intramolecular hydroxy-O—H...O(carbonyl) hydrogen bonds. Dimeric aggregates of 1,8-dihydroxyanthraquinone molecules assemble through weak intermolecular hydroxy-O—H...O(carbonyl) hydrogen bonds. The molecular packing comprises stacks of molecules of 2-bromonaphthoquinone and dimeric assembles of 1,8-dihydroxyanthraquinone with the shortest π–π contact within a stack of 3.5760 (9) Å occurring between the different rings of 2-bromonaphthoquinone molecules. The analysis of the Hirshfeld surface reveals the importance of the interactions just indicated but, also the contribution of additional C—H...O contacts as well as C=O...π interactions to the molecular packing

1,3-Bis(4-bromo­phen­yl)imidazolium chloride dihydrate

In the title hydrated salt, C15H11Br2N2 +·Cl−·2H2O, the complete imidazolium cation is generated by a crystallographic twofold axis, with one C atom lying on the axis. The chloride ion and both water mol­ecules of crystallization also lie on a crystallographic twofold axis of symmetry. The cation is non-planar, the dihedral angle formed between the central imidazolium and benzene rings being 12.9 (3)°; the dihedral angle between the symmetry-related benzene rings is 25.60 (13)°. In the crystal, O—H⋯Cl hydrogen bonds result in supra­molecular chains along c mediated by eight-membered {⋯HOH⋯Cl}2 synthons. These are consolidated by C—H⋯O and π–π [centroid–centroid distance = 3.687 (3) Å] inter­actions

The cooling of atomic and molecular gas in DR21

We present an overview of a high-mass star formation region through the major (sub-)mm, and far-infrared cooling lines to gain insight into the physical conditions and the energy budget of the molecular cloud. We used the KOSMA 3m telescope to map the core ($10'\times 14'$) of the Galactic star forming region DR 21/DR 21 (OH) in the Cygnus X region in the two fine structure lines of atomic carbon CI and four mid-$J$ transitions of CO and $^{13}$CO, and CS J=7\TO6. These observations have been combined with FCRAO J=1\TO0 observations of $^{13}$CO and C$^{18}$O. Five positions, including DR21, DR21 (OH), and DR21 FIR1, were observed with the ISO/LWS grating spectrometer in the \OI 63 and 145 $\mu$m lines, the \CII 158 $\mu$m line, and four high-$J$ CO lines. We discuss the intensities and line ratios at these positions and apply Local Thermal Equilibrium (LTE) and non-LTE analysis methods in order to derive physical parameters such as masses, densities and temperatures. The CO line emission has been modeled up to J=20. From non-LTE modeling of the low- to high-$J$ CO lines we identify two gas components, a cold one at temperatures of T_\RM{kin}\sim 30-40 K, and one with T_\RM{kin}\sim 80-150 K at a local clump density of about n(H$_2$)$\sim 10^4-10^6$ cm$^{-3}$. While the cold quiescent component is massive containing typically more than 94 % of the mass, the warm, dense, and turbulent gas is dominated by mid- and high-$J$ CO line emission and its large line widths. The medium must be clumpy with a volume-filling of a few percent. The CO lines are found to be important for the cooling of the cold molecular gas, e.g. at DR21 (OH). Near the outflow of the UV-heated source DR21, the gas cooling is dominated by line emission of atomic oxygen and of CO

On the influence of small chemical changes upon the supramolecular association in substituted 2-(phenoxy)-1,4-naphthoquinones

X-ray crystallography reveals the common feature of the title compounds is a 1,4-naphthoquinone ring system with a substituted phenoxy residue adjacent to an oxo-group to give 1 (H), 2 (3-Br), 3 (3-CF3), 4 (4-CN) and 5 (4-NO2). To a first approximation the fused ring system along with the two oxo substituents is planar with the major difference between the molecules relating to the relative orientations of the pendant phenoxy residues: dihedral angles range from 56.56(4)° (3) to 87.52(10)° (2). The presence of intermolecular C‒H…O interactions is the common feature of the supramolecular association in the crystals of 1-5. In each of 1 and 5, these extend in three-dimensions but, only to supramolecular dimers in 4, chains in 2 and layers in 3. Each crystal also features C=O…π interactions, pointing to the importance of these points of contact in this series di-oxocompounds. In 2, these, along with C‒Br…π interactions lead to a threedimensional architecture. For 3, the C=O…π and π…π interactions occur within the layers which stack without directional interactions between them. In 4, C‒H…O and C=O…π interactions combine to give a supramolecular layer, which also stack without directional interactions in the interlayer region. Further analysis of the molecular packing was conducted by a Hirshfeld surface analysis (HSA). This points to the significant role of H…H, C…H/H…C and O…H/H…O contacts in the packing of 1. Notably different roles for these contacts are found in the other crystals correlating with the participation of the respective substituents in the molecular packing. The HSA suggests the association between layers in 3 (weak F…F and H…F interactions) and 4 (weak H…N interactions) is contributed by the phenoxy-substituents

Strong CH+ J=1-0 emission and absorption in DR21

We report the first detection of the ground-state rotational transition of the methylidyne cation CH+ towards the massive star-forming region DR21 with the HIFI instrument onboard the Herschel satellite. The line profile exhibits a broad emission line, in addition to two deep and broad absorption features associated with the DR21 molecular ridge and foreground gas. These observations allow us to determine a CH+ J=1-0 line frequency of 835137 +/- 3 MHz, in good agreement with a recent experimental determination. We estimate the CH+ column density to be a few 1e13 cm^-2 in the gas seen in emission, and > 1e14 cm^-2 in the components responsible for the absorption, which is indicative of a high line of sight average abundance [CH+]/[H] > 1.2x10^-8. We show that the CH+ column densities agree well with the predictions of state-of-the-art C-shock models in dense UV-illuminated gas for the emission line, and with those of turbulent dissipation models in diffuse gas for the absorption lines.Comment: Accepted for publication in A&