Synthesis of sulfonimide-based dendrimers and dendrons possessing mixed 1 → 2 and 1 → 4 branching motifs

The synthesis of dendrimers and a chlorosulfo-dendron possessing a unique combination of 1?→?2 and 1?→?4 branching types is described. The procedure consists of a two-step preparation of 3,5-dinitrobenzene-1-sulfonyl chloride, which was used for the persulfonylation of p-toluidine and 4-(benzylthio)aniline. The obtained tetranitro compounds were reduced to the corresponding tetraamines. The latter were decorated with eight 4-toluene sulfonyl groups each to furnish the corresponding dendrimers. Oxidation of the dendrimer possessing a 4-(benzylthio)phenylene core with N-chlorosuccinimide resulted in the formation of a dendron with a sulfonyl chloride functionality at the focal point.     

A Z‐Scheme‐Inspired Photobioelectrochemical H2O/O2 Cell with a 1 V Open‐Circuit Voltage Combining Photosystem II and PbS Quantum Dots

A biohybrid photobioanode mimicking the Z‐scheme has been developed by functional integration of photosystem II (PSII) and PbS quantum dots (QDs) within an inverse opal TiO₂ architecture giving rise to a rather negative water oxidation potential of about ?0.55 V vs. Ag/AgCl, 1 m KCl at neutral pH. The electrical linkage between both light‐sensitive entities has been established through an Os‐complex‐modified redox polymer (P_Os), which allows the formation of a multi‐step electron‐transfer chain under illumination starting with the photo‐activated water oxidation at PSII followed by an electron transfer from PSII through P_Os to the photo‐excited QDs and finally to the TiO₂ electrode. The photobioanode was coupled to a novel, transparent, inverse‐opal ATO cathode modified with an O₂‐reducing bilirubin oxidase for the construction of a H₂O/O₂ photobioelectrochemical cell reaching a high open‐circuit voltage of about 1 V under illumination.     

Reactive Dimerization of an N‐Heterocyclic Plumbylene: C−H Activation with PbII

The N‐heterocyclic plumbylene [Fe{(η⁵‐C₅H₄)NSiMe₃}₂Pb:] is in equilibrium with an unprecedented dimer in solution, whose formation involves the cleavage of a strong C?H bond and concomitant formation of a Pb?C and an N?H bond. According to a mechanistic DFT assessment, dimer formation does not involve direct Pb^II insertion into a cyclopentadienyl C?H bond, but is best described as an electrophilic substitution. The bulkier plumbylene [Fe{(η⁵‐C₅H₄)NSitBuMe₂}₂Pb:] shows no dimerization, but compensates its electrophilicity by the formation of an intramolecular Fe?Pb bond.     

Isolation of the Metalated Ylides [Ph3P−C−CN]M (M=Li,Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

The isolation and structural characterization of the cyanido-substituted metalated ylides [Ph₃P−C−CN]M ( 1-M ; M=Li, Na, K) are reported with lithium, sodium, and potassium as metal cations. In the solid-state, most different aggregates could be determined depending on the metal and additional Lewis bases. The crown-ether complexes of sodium ( 1-Na ) and potassium ( 1-K ) exhibited different structures, with sodium preferring coordination to the nitrogen end, whereas potassium binds in an unusual η²-coordination mode to the two central carbon atoms. The formation of the yldiide was accompanied by structural changes leading to shorter C−C and longer C−N bonds. This could be attributed to the delocalization of the free electron pairs at the carbon atom into the antibonding orbitals of the CN moiety, which was confirmed by IR spectroscopy and computational studies. Detailed density functional theory calculations show that the changes in the structure and the bonding situation were most pronounced in the lithium compounds due to the higher covalency.     

Comparison of viscous and elastic properties of polyolefin melts in shear and elongation

Viscous and elastic properties of a linear polypropylene (PP) and a long-chain branched low-density polyethylene (LDPE) have been investigated by creep and creep–recovery experiments in shear and elongation. The data obtained verify the ratios between the linear values of the viscosities and the steady-state elastic compliances in shear and elongation predicted by the theory of linear viscoelasticity. In the nonlinear range, no simple correlation between the viscous behaviour in shear and elongation exists. The elongational viscosity of the PP decreases with increasing stress analogously to the shear thinning observed; the linear range extends to higher stresses in elongation than in shear, however. The LDPE shows thinning in shear and strain hardening in elongational flow. For the LDPE, a linear steady-state elastic tensile compliance corresponding to one third of the linear steady-state elastic compliance in shear was determined. For the PP, this theoretically predicted value is approximately reached. Analogous to the viscous behaviour, the linear range extends to higher stresses in elongation than in shear. For both materials, the steady-state elastic compliances in the nonlinear range decrease with increasing stress in shear as well as in elongation. However, the decrease in elongation is more pronounced.     

Dipolar bosons in a planar array of one-dimensional tubes

We investigate bosonic atoms or molecules interacting via dipolar interactions in a planar array of one-dimensional tubes. We consider the situation in which the dipoles are oriented perpendicular to the tubes by an external field. We find various quantum phases reaching from a "sliding Luttinger liquid" phase to a two-dimensional charge density wave ordered phase. Two different kinds of charge density wave order occur: a stripe phase in which the bosons in different tubes are aligned and a checkerboard phase. We further point out how to distinguish the occurring phases experimentally.     

Simultaneous birefringence,small‐ and wide‐angle X‐ray scattering to detect precursors and characterize morphology development during flow‐induced crystallization of polymers

An experimental configuration that combines the powerful capabilities of a short‐term shearing apparatus with simultaneous optical and X‐ray scattering techniques is demonstrated, connecting the earliest events that occur during shear‐induced crystallization of a polymer melt with the subsequent kinetics and morphology development. Oriented precursors are at the heart of the great effects that flow can produce on polymer crystallization (strongly enhanced kinetics and formation of highly oriented crystallites), and their creation is highly dependent on material properties and the level of stress applied. The sensitivity of rheo‐optics enables the detection of these dilute shear‐induced precursors as they form during flow, before X‐ray techniques are able to reveal them. Then, as crystallization occurs from these precursors, X‐ray scattering allows detailed quantification of the characteristics and kinetics of growth of the crystallites nucleated by the flow‐induced precursors. This simultaneous combination of techniques allows unambiguous correlation between the early events that occur during shear and the evolution of crystallization after flow has stopped, eliminating uncertainties that result from the extreme sensitivity of flow‐induced crystallization to small changes in the imposed stress and the material. Experimental data on a bimodal blend of isotactic polypropylenes are presented.     

Useful applications of the electron localization function in high-pressure crystal chemistry

The main features of a new computational code aimed at the topological analysis of the electron localization function (ELF) in crystals are hereby presented. Besides the complete localization of all critical points, the code is able to determine the limiting surfaces that define the chemical regions associated with the so-found maxima (or attractors) of the ELF. Hence, integrations of density operators within these basins provide charges and volumes to cores, bonds and lone pairs. Two illustrative applications have been selected. Firstly, we examine the Z dependence of basin compressibilities in the elements of the first two rows of the periodic table, and secondly, we focus our attention on the chemical changes across the pathway of the zinc blende-rocksalt phase transition in BeO.     

Structure and Photochemical Behavior of the Cyclodextrin Inclusion Complexes of the Benzoylthiophene‐Derived Drugs Tiaprofenic Acid (=5‐Benzoyl‐α‐methylthiophene‐2‐acetic Acid) and Suprofen (=α‐Methyl‐4‐(2‐thienylcarbonyl)benzeneacetic Acid)

The effect of β‐cyclodextrin (β‐CD) on the excited‐state reactivity of the two benzoylthiophene derivatives, tiaprofenic acid (TPA; 2 ) and suprofen (SPF; 3 ) in their carboxylate forms is studied. The presence of β‐cyclodextrin does not affect the nature of the photoproduced transients and the photoproducts, but increases the photodegradation quantum yields of both drugs. The efficiency of the photodecarboxylation process is enhanced. This effect is rationalized in the light of the inclusion of 2 and 3 in the β‐CD cavity, affecting the energy of the lowest excited states of the drugs. The structure of the complexes is determined by induced circular dichroism, and molecular‐mechanics and dynamic Monte Carlo calculations. The photoreactivity of the decarboxylated photoproduct 7 of tiaprofenic acid ( 2 ) in presence of β‐CD is also examined.     

Influence of the primary and secondary coordination spheres on nitric oxide adsorption and reactivity in cobalt(ii)–triazolate frameworks

Nitric oxide (NO) is an important signaling molecule in biological systems, and as such, the ability of porous materials to reversibly adsorb NO is of interest for potential medical applications. Although certain metal–organic frameworks are known to bind NO reversibly at coordinatively unsaturated metal sites, the influence of the metal coordination environment on NO adsorption has not been studied in detail. Here, we examine NO adsorption in the frameworks Co₂Cl₂(bbta) (H₂bbta = 1H,5H-benzo(1,2-d:4,5-d′)bistriazole) and Co₂(OH)₂(bbta) using gas adsorption, infrared spectroscopy, powder X-ray diffraction, and magnetometry. At room temperature, NO adsorbs reversibly in Co₂Cl₂(bbta) without electron transfer, with low temperature data supporting spin-crossover of the NO-bound cobalt(ii) centers of the material. In contrast, adsorption of low pressures of NO in Co₂(OH)₂(bbta) is accompanied by charge transfer from the cobalt(ii) centers to form a cobalt(iii)–NO⁻ adduct, as supported by diffraction and infrared spectroscopy data. At higher pressures of NO, characterization data indicate additional uptake of the gas and disproportionation of the bound NO to form a cobalt(iii)–nitro (NO₂⁻) species and N₂O gas, a transformation that appears to be facilitated by secondary sphere hydrogen bonding interactions between the bound NO₂⁻ and framework hydroxo groups. These results provide a rare example of reductive NO binding in a cobalt-based metal–organic framework, and they demonstrate that NO uptake can be tuned by changing the primary and secondary coordination environment of the framework metal centers.

Nitric oxide (NO) shows differences in adsorption and reactivity in two related cobalt(ii)–triazolate frameworks, demonstrating how the primary and secondary coordination sphere of metal centers in adsorbents can be designed for targeted delivery.