Gas permeation parameters and other physicochemical properties of a polymer of intrinsic microporosity: Polybenzodioxane PIM-1

A detailed study of gas permeation, thermodynamic properties and free volume was performed for a novel polymer of intrinsic microporosity (PIM-1). Gas permeability was measured using both gas chromatographic and barometric methods. Sorption of vapors was studied by means of inverse gas chromatography (IGC). In addition, positron annihilation lifetime spectroscopy (PALS) was employed for investigation of free volume in this polymer. An unusual property of PIM-1 is a very strong sensitivity of gas permeability and free volume to the film casting protocol. Contact with water in the process of film preparation resulted in relatively low gas permeability (P(O₂) = 120 Barrer), while soaking with methanol led to a strong increase in gas permeability (P(O₂) = 1600 Barrer) with virtually no evidence of fast aging (decrease in permeability) that is typical for highly permeable polymers. For various gas pairs (O₂/N₂, CO₂/CH₄, CO₂/N₂) the data points on the Robeson diagrams are located above the upper bound lines. Hence, a very attractive combination of permeability and selectivity is observed. IGC indicated that this polymer is distinguished by the largest solubility coefficients among all the polymers so far studied. Free volume of PIM-1 includes relatively large microcavities (R = 5 Å), and the results of the PALS and IGC methods are in reasonable agreement.     

Increasing efficiency of photoelectronic conversion by encapsulation of photosynthetic reaction center proteins in arrayed carbon nanotube electrode

The construction of efficient light energy converting (photovoltaic and photoelectronic) devices is a current and great challenge in science and technology and one that will have important economic consequences. Here we show that the efficiency of these devices can be improved by the utilization of a new type of nano-organized material having photosynthetic reaction center proteins encapsulated inside carbon nanotube arrayed electrodes. In this work, a generically engineered bacterial photosynthetic reaction center protein with specifically synthesized organic molecular linkers were encapsulated inside carbon nanotubes and bound to the inner tube walls in unidirectional orientation. The results show that the photosynthetic proteins encapsulated inside carbon nanotubes are photochemically active and exhibit considerable improvement in the rate of electron transfer and the photocurrent density compared to the material constructed from the same components in traditional lamella configuration.     

Insights into the Role of Graphitic Carbon Nitride as a Photobase in Proton-Coupled Electron Transfer in (sp3)C−H Oxygenation of Oxazolidinones

Graphitic carbon nitride (g-CN) is a transition metal free semiconductor that mediates a variety of photocatalytic reactions. Although photoinduced electron transfer is often postulated in the mechanism, proton-coupled electron transfer (PCET) is a more favorable pathway for substrates possessing X−H bonds. Upon excitation of an (sp²)N-rich structure of g-CN with visible light, it behaves as a photobase—it undergoes reductive quenching accompanied by abstraction of a proton from a substrate. The results of modeling allowed us to identify active sites for PCET—the ‘triangular pockets’ on the edge facets of g-CN. We employ excited state PCET from the substrate to g-CN to selectively cleavethe endo-(sp³)C−H bond in oxazolidine-2-ones followed by trapping the radical with O₂. This reaction affords 1,3-oxazolidine-2,4-diones. Measurement of the apparent pK_a value and modeling suggest that g-CN excited state can cleave X−H bonds that are characterized by bond dissociation free energy (BDFE) ≈100 kcal mol⁻¹.     

New Type of Neutral Binuclear Spin-Crossover Complex of Iron(III) with Twist of Two Disulfide Bridges as a Product of Electrochemical Oxidation of [FeIII(5Cl-thsa)2]− Anions

As a result of the electrochemical oxidation process, the [Fe^III(5Cl-thsa)₂]⁻ spin-crossover (SCO) anion with N₂S₂O₂ coordination sphere transforms into N₄O₂-coordinated Fe^III SCO neutral binuclear complex 2 with twist of two disulfide bridges. Each dimeric complex is a binuclear double-stranded helicate with similar chirality of both Fe centers. The crystal structure of the complex 2 ⋅ 3H₂O at 100 K has a monoclinic C2/c space group and contains large cavities (about 21.5 % of the unit cell volume) half-filled by 3 water molecules per one dimer. The N₄O₂ coordination of iron(III) with two oxygen atoms (−O⁻) of phenoxy groups, two imine-type (−N_im=) nitrogen atoms of azomethine groups, one amidrazone-type (=N_amidH) nitrogen atom and one ionized terminal group (−N_ionizH) of nitrogen has not been observed in CCDC so far. The oxidation state of the iron atoms in the dimeric complex was confirmed by ⁵⁷Fe Mössbauer spectroscopy on 90 % enriched ⁵⁷Fe sample. Mössbauer spectra and dc magnetic measurements demonstrated the partial HS-HS→LS-LS SCO in the 185–225 K temperature range. The details of the structure of complex 2 and the features of its magnetic properties were refined by theoretical analysis based on DFT calculations. The B3LYP* functional correctly predicting the energy of the spin-crossover process was revealed.     

Total Reflection X-Ray Fluorescence Determination of Rare Earth Elements in Mineral Water Using a Combined Preconcentration Technique

A combined approach for the simultaneous determination of lanthanum, cerium, praseodymium, neodymium, and samarium in mineral water in the range from?·?10^?2 to 10¹?µg/L by total reflection X-ray fluorescence analysis is reported. The combined technique of preconcentration of the rare earth elements ions includes the codeposition of their hydroxides on a collector and dispersive liquid–liquid microextraction by chloroform to form complexes with 1-(2-pyridylazo)-2-naphthol. The results for the determination of lanthanum and light lanthanides in natural water samples with the combined approach are in good agreement with measurements obtained by inductively coupled plasma–mass spectrometry.     

Coordination Properties of Perfluoroethyl‐ and Perfluorophenyl‐Substituted Phosphonous acids,RfP(OH)2

Phosphinic acids, R^fP(O)(OH)H (R^f=CF₃, C₂F₅, C₆F₅), turned out to be excellent preligands for the coordination of phosphonous acids, R^fP(OH)₂. Addition of C₂F₅P(O)(OH)H to solid PtCl₂ under different reaction conditions allows the isolation and full characterization of the mononuclear complexes [ClPt{P(C₂F₅)(OH)O}{P(C₂F₅)(OH)₂}₂] and [Pt{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}] containing hydrogen‐bridged [R^fP(OH)O]^? and R^fP(OH)₂ units. Further deprotonation of [Pt{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}₂] leads to the formation of the dianionic platinate, [Pt{P(C₂F₅)(OH)O}₄]^2?, revealing four intramolecular hydrogen bridges. With PdCl₂ the dinuclear complex [Pd₂(μ‐Cl)₂{[P(C₂F₅)(OH)O]₂H}₂] was isolated and characterized. The Cl^? free complex [Pd{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}₂] was also prepared and deprotonated to the dianionic palladate, [Pd{P(C₂F₅)(OH)O}₄]^2?. Both compounds were characterized by NMR spectroscopy, IR spectroscopy, and X‐ray analyses. In addition, the C₆F₅ derivatives [ClPt{P(C₆F₅)(OH)O}{P(C₆F₅)(OH)₂}₂] and [Pd₂(μ‐Cl)₂{[P(C₆F₅)(OH)O]₂H}₂] as well as the CF₃ derivative [Pd₂(μ‐Cl)₂{[P(CF₃)(OH)O]₂H}₂] were synthesized and fully characterized. Phosphonous acid complexes are inert towards air and moisture and can be stored for several months without decomposition. The catalytic activity of the palladium complexes in the Suzuki cross‐coupling reaction between 1‐bromo‐3‐fluorobenzene and phenyl boronic acid was demonstrated.     

Hydrogenation of Secondary Amides using Phosphane Oxide and Frustrated Lewis Pair Catalysis

The metal-free catalytic hydrogenation of secondary carboxylic acid amides is developed. The reduction is realized by two new catalytic reactions. First, the amide is converted into the imidoyl chloride by triphosgene (CO(OCCl₃)₂) using novel phosphorus(V) catalysts. Second, the in situ generated imidoyl chlorides are hydrogenated in high yields by an FLP-catalyst. Mechanistic and quantum mechanical calculations support an autoinduced catalytic cycle for the hydrogenation with chloride acting as unusual Lewis base for FLP-mediated H₂-activation.     

Intracellular Breakable and Ultrasound‐Responsive Hybrid Microsized Containers for Selective Drug Release into Cancerous Cells

This work reports an efficient and straightforward strategy to fabricate hybrid microsized containers with reduction‐sensitive and ultrasound‐responsive properties. The ultrasound and reductive sensitivity are visualized using scanning electron microscopy, with the results showing structural decomposition upon ultrasound irradiation and in the presence of reducing agent. The ultrasound‐responsive functionalities of hybrid carriers can be used as external trigger for rapid controlled release, while prolonged drug release can be achieved in the presence of reducing agent. To evaluate the potential for targeted drug delivery, hybrid microsized containers are loaded with the anticancer drug doxorubicin (Dox). Such hybrid capsules can undergo structural intracellular degradation after cellular uptake by human cervical cancer cell line (HeLa), resulting in Dox release into cancer cells. In contrast, there is no Dox release when hybrid capsules are incubated with human mesenchymal stem cells (MSCs) as an example of normal human cells. The cell viability results indicate that Dox‐loaded capsules effectively killed HeLa cells, while they have lower cytotoxicity against MSCs as an example of healthy cells. Thus, the newly developed intracellular‐ and ultrasound‐responsive microcarriers obtained via sol‐gel method and layer‐by‐layer technique provide a high therapeutic efficacy for cancer, while minimizing adverse side effect.