Characterization of polyoxometalate/polymer photo-composites: A toolbox for the photodegradation of organic pollutants

Different inorganic/organic photocomposites based on polyoxometalate (POM) nanoparticles have been developed for photocatalytic applications. Currently, polyoxometalate nanoparticles have been successfully in-situ embedded into an acrylate polymer network by photopolymerization upon mild visible light irradiation at 405 nm. The proposed POM/polymer photocomposites have been characterized using complementary techniques for a better understanding of their photocatalytic activity. Interestingly, the obtained photocomposites exhibit high rigidity, excellent thermal stability, a non-negligible porosity and new functionalities such as light reactivity and redox properties. Moreover, developed composites showed efficient catalytic activity for the color removal of aqueous solutions of erythrosine and rose Bengal under Light Emitting Diodes LED@375 nm irradiation reaching 80 and 90% as a final color removal, respectively.     

Untersuchung und Beurtheilung der Teigwaaren

Ohne Zusammenfassung     

Improving the picture of atomic structure in nonoriented polymer domains using the pair distribution function: A study of polyamide 6

Investigations of the atomic structures within polyamides started over 80 years ago and continue today. These weakly ordered materials diffract X-rays poorly and typically require postprocessing to obtain idealized samples for structural studies. An important goal remains to develop techniques to study the local structure in its natural state, with atomic resolution, and with sensitivity to subtle changes due to synthesis conditions or other technologically relevant processing procedures. Here, we compare the structures of as-produced, nonoriented polyamide 6 ([C₆H₁₁NO] _n) from both hydrolytic and anionic processes. A total scattering pair distribution function approach is used to elucidate information about the atomic bonding, molecular conformation, chain packing, crystallite size, and ratio of ordered to disordered domain content. The results are compared with those from standard analytical methods.     

Frontispiece: From Phosphidic to Phosphonium? Umpolung of the P4-Bonding Situation in [CpFe(CO)(L)(η1-P4)]+ Cations (L=CO or PPh3)

Upon coordinating P₄ to electron poor cyclopentadienyl-iron cations, the average P−P bond distances shrink and the respective P₄ breathing mode in the Raman spectra (600 cm⁻¹, P_{4, free}) is blueshifted by >40 cm⁻¹ in [CpFe(CO)(L)(η¹-P₄)]⁺ cations (L=CO or PPh₃). Analysis suggests that this corresponds to an umpolung of the bonding from more phosphidic in the known, electron-rich systems to more phosphonium-like in the reported electron-poor versions. This may open new functionalization pathways for white phosphorus P₄.     

The Taming of Redox-Labile Phosphidotitanocene Cations

Tame d⁰ phosphidotitanocene cations stabilized with a pendant tertiary phosphane arm are reported. These compounds were obtained by one-electron oxidation of d¹ precursors with [Cp₂Fe][BPh₄]. The electronic structure of these compounds was studied experimentally (EPR, UV/Vis, and NMR spectroscopy, X-ray diffraction analysis) and through DFT calculations. The theoretical analysis of the bonding situation by using the electron localization function (ELF) shows the presence of π-interactions between the phosphido ligand and Ti in the d⁰ complexes, whereas dπ–pπ repulsion prevents such interactions in the d¹ complexes. In addition, CH–π interactions were observed in several complexes, both in solution and in the solid state, between the phosphido ligand and the phosphane arm. The d⁰ complexes were found to be light sensitive, and decompose through Ti−P bond homolysis to give Ti^III species. A naked d⁰ phosphidotitanocene cation has been trapped by reaction with diphenylacetylene, yielding a Ti/P frustrated Lewis pair (FLP), which was found to be less reactive than a previously reported Zr analog.     

Insights into the Two-Electron Reductive Process of [FeFe]H2ase Biomimetics: Cyclic Voltammetry and DFT Investigation on Chelate Control of Redox Properties of [Fe2(CO)4(κ2-Chelate)(μ-Dithiolate)]

The electrochemical reduction of complexes [Fe₂(CO)₄(κ²-phen)(μ-xdt)] (phen=1,10-phenanthroline; xdt=pdt ( 1 ), adt^iPr ( 2 )) in MeCN-[Bu₄N][PF₆] 0.2 m is described as a two-reduction process. DFT calculations show that 1 and its monoreduced form 1⁻ display metal- and phenanthroline-centered frontier orbitals (LUMO and SOMO) indicating the non-innocence of the phenanthroline ligand. Two energetically close geometries were found for the doubly reduced species suggesting an intriguing influence of the phenanthroline ligand leading to the cleavage of a Fe−S bond as proposed generally for this type of complex or retaining the electron density and avoiding Fe−S cleavage. Extension of calculations to other complexes with edt, adt^iPr bridge and even virtual species [Fe₂(CO)₄(κ²-phen)(μ-adt^R)] (R=CH(CF₃)₂, H) or [Fe₂(CO)₄(κ²-phen)(μ-pdt^R)] (R=CH(CF₃)₂, iPr) showed that the relative stability between both two-electron-reduced isomers depends on the nature of the bridge and the possibility to establish a remote anagostic interaction between the iron center {Fe(CO)₃} and the group carried by the bridged-head atom of the dithiolate group.