Substituted propanes: V. The vibrational spectra,dipole moments and conformations of 1,2-dichloro-, 1-chloro-2-bromo- and 1,2-dibromopropane

The infrared and Raman spectra of 1,2-dichloro-, 1-chloro-2-bromo- and 1,2-dibromopropane were recorded as liquids, in polar and non-polar solvents and in the crystalline state at low temperatures. The infrared spectrum of a high pressure crystal of 1,2-dibromopropane was recorded at ambient temperature. Dipole measurements were carried out in CCl₄ and C₆H₆solutions.Each of the 1,2-dihalopropanes existed as a mixture of three conformers in the liquid state, the one with the halogens in the anti position was in large abundance. Spectral and dipole measurements revealed a comparatively larger concentration of the two polar gauche conformers in polar solvents. All the compounds crystallized in the anti form. The C-halogen stretching vibrations have been interpreted in detail. Vibrational analyses of the anti conformers have been carried out and a tentative assignment of the majority of the gauche bands has been proposed.     

Synthesis and characterization of poly(ethylene glycol) based β-cyclodextrin polymers

A series of novel water soluble β-cyclodextrin (βCD) polymers has been synthesized from functionalized poly(ethylene glycol) (PEG). The chemical composition of the polymers has been characterized by ¹H NMR and the βCD content is found to be between 48 and 33% (w/w). The molecular weight has been determined by Size Exclusion Chromatography (SEC) and depends on the ratio between βCD and PEG, varying from 2.1 × 10⁴ to 8.6 × 10⁴ g mol^?1. The physico chemical properties have been characterized by differential scanning calorimetry (DSC), viscometry and isothermal titration calorimetry (ITC). ITC shows that the polymers have association constants comparable to βCD with different guest molecules, indicating a good accessibility of the CDs.     

Adsorbate-induced alloy phase separation: a direct view by high-pressure scanning tunneling microscopy

The influence of high pressures of carbon monoxide (CO) on the stability of a Au/Ni(111) surface alloy has been studied by high-pressure scanning tunneling microscopy. We show that CO induces a phase separation of the surface alloy at high pressures, and by means of time-lapsed STM movies we find that Ni atoms are removed from the surface layer during the process. Density functional theory calculations reveal the thermodynamic driving force for the phase separation to be the Au-induced compression of the CO overlayer with a resulting CO-CO repulsion. Furthermore, the atomistic mechanism of the process is shown to be kink-site carbonyl formation and evaporation which is found to be enhanced by the presence of Au.     

Unimodality of the Freely Selfdecomposable Probability Laws

We show that any freely selfdecomposable probability law is unimodal. This is the free probabilistic analog of Yamazato’s result in (Ann. Probab. 6:523–531, 1978).     

Adsorption of Unstructured Protein β-Casein to Hydrophobic and Charged Surfaces

In this Monte Carlo simulation study we use mesoscopic modeling to show that β-casein, an unstructured milk protein, adsorbs to surfaces not only due to direct electrostatic and hydrophobic interactions but also due to structural rearrangement and charge regulation due to proton uptake and release. β-casein acts as an amphiphilic chameleon, changing properties according to the chemical environment, and binding is observed to both positively and negatively charged surfaces. The binding mechanisms, however, are fundamentally different. A detailed, per-residue-level analysis shows that the adsorption process is controlled by a few very specific regions of the protein and that these change dramatically with pH. Caseins, being the most abundant proteins in milk, are crucial for the properties of fermented dairy products, such as nutrition, texture, and viscosity, but may also influence adhesion to packaging materials. The latter leads to product losses of about 10%, leading to economical and environmental problems.     

A molecular‐level computational study of the diffusion and solubility of water and oxygen in carbonaceous polyethylene nanocomposites

Monte Carlo and molecular dynamics simulations were performed to investigate the effect on the solubility, diffusion, and permeability of water and oxygen when adding graphene or single‐walled carbon nanotubes (SWCNTs) to polyethylene (PE). When compared with pure PE, addition of graphene lowered the solubility of water, whereas at lower temperatures, the oxygen solubility increased because of the oxygen–graphene interaction. Addition of SWCNTs lowered the solubility of both water and oxygen when compared with pure PE. A detailed analysis showed that an ordered structure of PE is induced near the additive surface, which leads to a decrease in the diffusion coefficient of both penetrants in this region. The addition of graphene does not change the permeation coefficient of oxygen (in the direction parallel to the filler) and, in fact, may even increase this coefficient when compared with pure PE. In contrast, the water permeability is decreased when graphene is added to PE. The addition of SWCNTs decreases the permeability of both penetrants. Graphene can consequently be added to selectively increase the solubility and permeation of oxygen over water, at least at lower temperatures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 589–602     

Structure and activity of oxidized Pt(110) and alpha-PtO2

We present a density functional theory study of the structure and reactivity of Pt(110) under high loads of atomic oxygen. Surface structures in which the oxygen adsorbs on PtO2-like stripes along the Pt ridges of the Pt(110) are found to be highly stable. The structures become further stabilized when Pt atoms are ejected from the Pt ridges since this allows for stress relief along the PtO2 stripes. Our results thus corroborate the Pt(110)-(12x2)-22O surface oxide structure proposed by Li et al. [Phys. Rev. Lett., 2004, 93, 146104]. We further considered the structure and stability of bulk alpha-PtO2 oxide surfaces. The (0001) and (1010) facets are found to be the lowest energy facets. Finally, the reactivity of the surface oxide and the oxide surfaces in terms of CO oxidation was investigated. We find small energy barriers for the reaction at the Pt(110)-(12x2)-22O surface oxide and at the (1010) facet of alpha-PtO2, but only large barriers over the alpha-PtO2(0001) surface.     

1,3,4‐Thiadiazolidine‐2,5‐dione: Crystal Structure,Calculation of Aromaticity and Photodecomposition Quantum Yield

Single crystals of 1,3,4‐thiadiazolidine‐2,5‐dione ( 1 ) have been grown and the X‐ray crystal structure showed the molecule to be planar with sp²‐hybridized nitrogen atoms. Density functional theory calculations of nucleus‐independent chemical shifts profiles show that 1 is non‐aromatic. From actinometry, it was found that continuous photolysis of 1 in methanol at λ = 254 nm resulted in a decomposition with the quantum yield Φ = 0.076(7) mol/Einstein at room temperature.     

Multistate Switches: Ruthenium Alkynyl–Dihydroazulene/Vinylheptafulvene Conjugates

Multimode molecular switches incorporating distinct and independently addressable functional components have potential applications as advanced switches and logic gates for molecular electronics and memory storage devices. Herein, we describe the synthesis and characterization of four switches based on the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermoswitch pair functionalized with the ruthenium‐based Cp*(dppe)Ru ([Ru*]) metal complex (dppe=1,2‐bis(diphenylphosphino)ethane; Cp*=pentamethylcyclopentadienyl). The [Ru*]–DHA conjugates can potentially exist in six different states accessible by alternation between DHA/VHF, Ru^II/Ru^III, and alkynyl/vinylidene, which can be individually stimulated by using light/heat, oxidation/reduction, and acid/base. Access to the full range of states was found to be strongly dependent on the electronic communication between the metal center and the organic photoswitch in these [Ru*]–DHA conjugates. Detailed electrochemical, spectroscopic (UV/Vis, IR, NMR), and X‐ray crystallographic studies indeed reveal significant electronic interactions between the two moieties. When in direct conjugation, the ruthenium metal center was found to quench the photochemical ring‐opening of DHA, which in one case could be restored by protonation or oxidation, allowing conversion to the VHF state.     

Drug loading in cyclodextrin polymers: dexamethasone model drug

In pharmaceutical formulations cyclodextrins (CDs) are used to improve the aqueous solubility, stability, dissolution rate, bioavailability and/or local tolerance of drugs. Moreover, water-soluble polymers can be used to stabilize drug/CD complexes through formation ternary complexes. Alternative approach is to use CD-polymers, which can both enhance the aqueous solubility of a drug and result in sustained drug release. The aim of this work was to compare the solubilizing effects of ternary drug/CD/polymer complexes with two novel high molecular weight CD-polymers, i.e. poly(ethylene glycol) based ??-cyclodextrin (??CD) polymer (PEG/??CD) and epichlorohydrin-??-cyclodextrin polymer (EPI/??CD) using dexamethasone (Dex) as a model drug, as well as the drug loading capacity of those selected CD-polymers. Hydroxypropyl methylcellulose and carboxymethylcellulose sodium salt were shown to have negligible effect on the solubilizing efficacy of ??CD while hexadimethrine bromide increases the solubilization efficacy. The stability of the polymers was tested and it was adequate for the experimental conditions used. The solubilization efficacy of both CD-polymers was higher than that of the parent ??CD and these ??CD based polymers are able to load greater amount of Dex than the parent ??CD.