Three Dimensional Network Polymeric Structure of (4,4′-bipyridinium)[CdBr<Subscript>4</Subscript>]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>: Supramolecular Motifs and Crystal Supramolecularity

Abstract A single crystal structure determination of the complex (4,4′-bipyridinium)[CdBr₄] _n , [henceforth (I)], has been carried out. It crystallizes in the monoclinic space group C2/c, with the following cell parameters: a = 16.119(3) ?, b = 13.206(3) ?, c = 7.2601(15) ?, β = 115.62°, V = 1393.5(6) ?³, with Z = 4 formula units. The polymeric anion forms an infinite zig-zag chain of edge-sharing octahedra along c, with a distorted octahedral stereochemistry around Cd. There are N–H···Br [Br2···N1 of 3.386(13) ? and Br1···N1 of 3.363(13) ?] and C–H···Br [Br2···C5 of 3.552(16) ?] hydrogen bonding interactions, tying the CdBr chains to the cations to form 2D-network. The resulting 2D-networks are further linked by aryl···aryl (π···π) interactions within the cationic chains leading to a 3D-network. Index Abstract Three dimensional network polymeric structure of (4,4′-bipyridinium)[CdBr₄] _n : Supramolecular motifs and crystal supramolecularity. Rawhi Al-Far and Basem F. Ali The polymeric anion consists of a zig–zag chain of distorted edge shared octahedra run along c axis. The protonated cation bridges the anion chains through N–H···Br and C–H···Br into a supramolecular array.      

A Polymorphic Azobenzene Cage for Energy-Efficient and Highly Selective p-Xylene Separation

Developing the competence of molecular sorbents for energy-saving applications, such as C8 separations, requires efficient, stable, scalable, and easily recyclable materials that can readily transition to commercial implementation. Herein, we report an azobenzene-based cage for the selective separation of p-xylene isomer across a range of C8 isomers in both vapor and liquid states with selectivity that is higher than the reported all-organic sorbents. The crystal structure shows non-porous cages that are separated by p-xylene molecules through selective CH–π interactions between the azo bonds and the methyl hydrogen atoms of the xylene molecules. This cage is stable in solution and can be regenerated directly under vacuum to be used in multiple cycles. We envisage that this work will promote the investigation of the azo bond as well as guest-induced crystal-to-crystal phase transition in non-porous organic solids for energy-intensive separations.     

Intermolecular interactions involved in the crystal structure of 2-amino-5-methylpyridinium hexabromostannate (IV), (C<Subscript>6</Subscript>H<Subscript>9</Subscript>N<Subscript>2</Subscript>)<Subscript>2</Subscript>[SnBr<Subscript>6</Subscript>]

The salt bis(2-amino-5-methylpyridinium) hexabromostannate(IV) (C₆H₉N₂)₂[SnBr₆] is monoclinic, P2 ₁ /c, with the following cell parameters: a=9.1636(18) ?, b=28.767(7) ?, c=16.956(17) ?, β=101.008(5)°, V=4387.5(17) ?³, Z=8, formula units. X-ray crystallography revealed that the structure can be regarded as a semi-regular three-dimensional array of anions, with pairs of cations forming layers perpendicular to b axis in the cavities between the anions. The cohesion forces that connects molecules in the organic layers are hydrophilic N⋯HCH₂ and HN⋯HN hydrogen bonding as well as hydrophobic π-π stacking and CH₃⋯π interactions. Cations and anions are connected via strong Br⋯H hydrogen bonding. Supplementary material CCDC 276493 contains the supplementary crystallographic data. These data can be obtained free of charge via www.ccdc. cam.ac.uk/data_request/cif, by e-mailing data_ request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033.     

Br···HN, N···HC, Br···HC, and Br···Br intermolecular interactions as supramolecular synthons: Synthesis and crystal structure of bis(2-amino-5-methylpyridinium) tetrabromomercurate(II)

The bis(2-amino-5-methylpyridinium) tetrabromomercurate(II) (C₆H₉N₂)₂[HgBr₄] salt is triclinic, P1, with the following cell parameters: a=8.060(8) ?, b=9.035(9) ?, c=14.964(10) ?, α=96.032(19)°, β=90.317(15)°, γ=113.32(2)°, V=993.8(15) ?³, with Z=2 formula units. The crystal structure consists of alternating stacks of inorganic HgBr₄ ²⁻ anions and organic layers of 2-amino-5-methylpyridinium cations parallel to c-axis. The cohesion forces that connect molecules in the organic layers are N···HC hydrogen bonding and π–π stacking. The HgBr₄ ²⁻ units in the inorganic stacks are attracted via Br···Br intermolecular interactions.Supplementary material CCDC 270395 contains the supplementary crystallographic data. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by e-mailing at data_request@ccdc.cam.ac.uk, or by contacting the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: + 44(0)1223-336033.     

Manganese speciation in paired serum and CSF samples using SEC-DRC-ICP-MS and CE-ICP-DRC-MS

Occupational manganese (Mn) overexposure leads to accumulation in the brain and has been shown to cause progressive, permanent, neuro-degenerative damage with syndromes similar to idiopathic Parkinsonism. Mn is transported by an active mechanism across neural barriers (NB) finally into the brain; but to date, modes of Mn neurotoxic action are poorly understood. This paper investigates the relevant Mn-carrier species which are responsible for widely uncontrolled transport across NB. Mn speciation in paired serum/cerebrospinal fluid (CSF) samples was performed by size exclusion chromatography–inductively coupled plasma–dynamic reaction cell–mass spectrometry (SEC-ICP-DRC-MS) and capillary zone electrophoresis coupled to ICP-DRC-MS in a 2D approach for clear identification. For additional species verification, electrospray ionization–Fourier transform ion cyclotron resonance–mass spectrometry was used after SEC-ICP-DRC-MS (second 2D approach). The Mn species from the different sample types were interrelated and correlation coefficients were calculated. In serum protein-bound Mn species like Mn-transferrin/albumin (Mn-Tf/HSA) were dominant, which had the main influence on total Mn in serum if Mn_total was <1.5 μg/L. Above serum Mn_total concentration of 1.6 μg/L the serum Mn_total concentration was correlated with increasing Mn-citrate (Mn-Cit) concentration. In parallel Mn_total and Mn species in CSF were determined. It turned out that Mn_total from CSF was about half of Mn_total in serum; Mn-Tf/HSA was only about 10 % compared to serum. It turned out that above 1.6 μg/L Mn_total in serum Mn-Cit was not only the leading Mn species in serum but also was the main influencing factor of both Mn_total and Mn-Cit concentration in CSF. These results were further investigated using two statistical models (orthogonal partial least squares discriminant analysis, canonical discriminant analysis). Both models discriminated the samples in two groups where CSF samples were either correlated to Mn_total and Mn-Cit (samples with serum Mn_total?>?1,550 ng/L) or correlated to Mn-Tf/HSA (samples with serum Mn_total?<?1,550 ng/L). We conclude that elevated Mn-Cit_serum could be a valuable marker for increased total Mn in CSF (and brain), i.e., it could be a marker for elevated risk of Mn-dependent neurological disorders such as manganism in occupational health.     

Electrostatic Assembly/Disassembly of Nanoscaled Colloidosomes for Light‐Triggered Cargo Release

Colloidosome capsules possess the potential for the encapsulation and release of molecular and macromolecular cargos. However, the stabilization of the colloidosome shell usually requires an additional covalent crosslinking which irreversibly seals the capsules, and greatly limits their applications in large‐cargos release. Herein we report nanoscaled colloidosomes designed by the electrostatic assembly of organosilica nanoparticles (NPs) with oppositely charged surfaces (rather than covalent bonds), arising from different contents of a bridged nitrophenylene‐alkoxysilane [NB; 3‐nitro‐N‐(3‐(triethoxysilyl)propyl)‐4‐(((3‐(triethoxysilyl)propyl)‐amino)methyl)benzamid] derivative in the silica. The surface charge of the positively charged NPs was reversed by light irradiation because of a photoreaction in the NB moieties, which impacted the electrostatic interactions between NPs and disassembled the colloidosome nanosystems. This design was successfully applied for the encapsulation and light‐triggered release of cargos.     

Gravitational radiation in quantum gravity

The effective field theory of quantum gravity generically predicts non-locality to be present in the effective action, which results from the low-energy propagation of gravitons and massless matter. Working to second order in gravitational curvature, we reconsider the effects of quantum gravity on the gravitational radiation emitted from a binary system. In particular, we calculate for the first time the leading order quantum gravitational correction to the classical quadrupole radiation formula which appears at second order in Newton’s constant.     

Density functional theory calculations of pentabromidooxomolybdate(V) anion with 2,2′-bipyridinium cation: Comparison between the calculated geometry and the crystal structure determination at 293 and 90 K

Mo^V ion complex in the [MoOBr₅]²⁻ anion is crystallized with 2,2′-bipyridinium dication. Mo^V is in a distorted octahedral environment at both 293 and 90 K, and is displaced from the plane of the four bromido ligands, with the Mo–Br_trans to the oxo ligand being significantly longer than the other equatorial bromido ligands. Extensive hydrogen bonding of the types (C,N)–H···(Br,O) and offset face-to-face interactions leading to a supramolecular crystal lattice that engineers the entrapment of [MoOBr₅]²⁻ anion. This is further stabilized by the Br···Br intermolecular interactions that hold the anionic network. The anisotropic cell contraction results in significant changes in nonbonding contacts. DFT calculations at the B3LYP level of theory using the pseudo potentials of “LANL2DZ” and “LANL2TZ (Mo)/6-31G*(C, N, Br, H)”, Slater Type Orbital (STO) and 3-21G basis sets were carried out. DFT calculations results from different basis sets were compared, and results show that the optimized calculated geometry is relatively consistent with the X-ray data and hence the observed structure for the complex is indeed possible. HOMO and LUMO orbitals and the energy gag were also determined.     

Exploring rearrangements along the fragmentation of glutaric acid negative ion: a combined experimental and theoretical study

Glutaric acid, a common short‐chain aliphatic dicarboxylic acid, was investigated in the negative ion mode by subjecting its [M–H]^? ion to collision‐induced dissociation (CID) experiments in an infinity ion cyclotron resonance (ICR) cell coupled to a hexapole–quadrupole–hexapole ion guide. A 12 Tesla magnet was used for high‐resolution measurements. Two distinctive main pathways were observed in the MS/MS spectrum. The fragmentation pathways were also thoroughly investigated in a density functional theory (DFT) study involving a B3LYP/6‐311+G(2d,p)//B3LYP/6‐311+G(d,p) level of theory. Elimination of CO₂ from the [M–H]^? ion of the dicarboxylic acid takes place in a concerted mechanism, by which a 1,5 proton shift occurs from the intact carboxyl group to the methylene moiety located in the α position relative to the deprotonated carboxyl group. This concerted mechanism stabilizes the terminal negative charge and deprotonates the second carboxylic acid group. Water elimination from the [M–H]^? ion does not take place by means of a simple proton removal from the α methylene group – and OH^? release from the carboxylate group to abstract an additional α proton thus leading to the formation of a deprotonated ketene anion. In the case of this dicarboxylic acid, a new mechanism was found for water elimination, which differs from that known for aliphatic monocarboxylic acids. An intramolecular interaction between the deprotonated and the intact carboxyl groups plays a key role in making a new energetically favourable mechanism. The DFT study also reveals that a combined loss of CO₂ and H₂O in the form of H₂CO₃ is possible. Copyright © 2010 John Wiley & Sons, Ltd.