Coordination around thorium(IV) in aqueous perchlorate,chloride and nitrate solutions

The coordination around the thorium(IV) ion in aqueous perchlorate, chloride and nitrate solutions has been determined from large angle X-ray scattering measurements. In perchlorate solutions, where inner-sphere complexes are not formed, the first coordination sphere contains 8.0±0.5 water molecules with Th-H₂O bond lengths of 2.48₅ Å. In chloride solutions inner-sphere complexes are formed, which lead to an increase in the coordination number. In nitrate solutions the nitrate ions are bonded as bidentate ligands to the thorium ion. The bond lengths are similar to those found in crystalline hydrates of thorium nitrate. The coordination numbers found for thorium(IV) in solution are compared with previously reported values for lower charged ions of similar size.On leave from Department of Inorganic Chemistry Royal Institute of Technology S-10044 Stockholm Sweden     

Spin polarisation in dual catalysts for the oxygen evolution and reduction reactions

Strongly correlated catalysts can be understood from precise quantum approximations. Incorporating properly electronic correlations thus let’s define Spin rules in catalysis, opening a new door towards optimum compositions for the most important reactions for a sustainable future.     

An Aggregating Amphiphilic Squaraine: A Light-up Probe That Discriminates Parallel G-Quadruplexes

G-quadruplexes (G4s) are peculiar DNA or RNA tertiary structures that are involved in the regulation of many biological events within mammalian cells, bacteria, and viruses. Although their role as versatile therapeutic targets has been emphasized for 35 years, G4 selectivity over ubiquitous double-stranded DNA/RNA, as well as G4 differentiation by small molecules, still remains challenging. Here, a new amphiphilic dicyanovinyl-substituted squaraine, SQgl , is reported to act as an NIR fluorescent light-up probe discriminating an extensive panel of parallel G4s while it is non-fluorescent in the aggregated state. The squaraine can form an unconventional sandwich π-complex binding two quadruplexes, which leads to a strongly fluorescent (Φ_F=0.61) supramolecular architecture. SQgl is highly selective against non-quadruplex and non-parallel G4 sequences without altering their topology, as desired for applications in selective in vivo high-resolution imaging and theranostics.     

On the Oxidation State of Cu2O upon Electrochemical CO2 Reduction: An XPS Study

The encouraging selectivity of copper oxides for the electroreduction of CO₂ into ethylene and alcohols has led to a vivid debate on the possible relation between their operando (sub-)surface oxidation state (i. e. fully reduced or partially oxidized) and this distinct reactivity. The high roughness of the Cu oxides used in previous studies on this matter adds complexity to this controversy and motivated us to prepare quasi-planar Cu₂O thin films that displayed a CO₂ reduction selectivity similar to that of oxide-derived copper catalysts reported in previous studies. Most importantly, when the post-mortem thin films were transferred for characterization in an air-free environment, X-ray photoelectron spectroscopy measurements confirmed their complete reduction in the course of the CO₂ reduction reaction. Thus, our results indicate that the selectivity of the Cu oxides featured in previous studies stems from their enhanced roughness, highlighting the importance of controlled sample transfer upon post-mortem characterization with ex situ techniques.     

Electrochemical behaviour of some polyoxo clusters

We describe the redox behaviour in non-aqueous solvents of some cyclopentadienyl(oxo)titanium derivatives. The derivative [Ti₄{η⁵-C₅H₄(SiMe₃)}₄(μ-O)₆] shows an electrochemically and chemically reversible le reduction process, followed by a multi-electron, chemically complicated reduction at a fairly cathodic potential. On the basis of the overall electrochemical features and the comparison with the redox behaviour of the quasi-planar compound [[Ti{η⁵-C₅H₄(SiMe₃)}Cl(μ-O)]₄] we propose an EECCEE mechanism for the first derivative, where the second electron-transfer induces a cascade of chemical reactions giving rise to irreversible cluster breakdown. The electrochemically induced fragmentation can be viewed as a retrosynthetic pathway. The heterometallic derivative [{Ti(η⁵-C₅H₄Me)₂(μ₂-MoO₄)₂}₂] shows two consecutive reduction processes; the first is chemically reversible, and the second quasi-reversible. The molybdate bridges apparently increase the stability of the electrogenerated anions. However none of these poly-oxo clusters can be considered as good models of electron ‘sinks’.     

Stereochemical aspects of the asymmetric synthesis of chiral α,β-dihydroxy phosphonates. Synthesis of α,β-dihydroxy phosphonic acids

Stereocontrol in the asymmetric phosphonylation of aldehydes via organophosphorous esters has been obtained starting from chiral aldehydes. The nature of the O-protecting group is crucial to obtain, in terms of diastereoselectivity and chemical yields, the best results. An ab initio molecular orbital study on 2-silyloxy propanal and MM2 studies on 2-alkoxy propanal show the existence of stable cyclic and acyclic conformers, which are presumably responsible for the high syn diastereoselectivity observed in the addition of non-metal carrying phosphites.     

Determination of degree of conversion as a function of depth of a photo-initiated dental restoration composite—III application to commercial Prodigy Condensable™

In this third work, we evaluated the degree of conversion (DC) versus depth of dental filling composite named Prodigy Condensable™ using infrared spectroscopy. Confirming previous results, there was a gradual reduction of DC with increasing depth but the composite exhibited extreme values of DC, an upper value (45.9%) on the surface and a lower one (6.1%) at a depth of 5 mm. The composite presented the worst performance among materials studied. The composite formulation was 80% of inorganic fillers and BisfenolA/dimethacrylate (BisGMA) (18%)/triethyleneglycoldimethacrylate (TEGDMA) (2.0%) as monomers. As stated before, type/ratio/viscosity of monomers and type, amount, size and size distribution of fillers all together had an important role in the cure reaction contributing to the final performance of the composite.     

A multi-technique nondestructive approach for characterizing the state of conservation of ancient bookbindings

Journal of Thermal Analysis and Calorimetry - The aim of this work is to evaluate the potentiality of a multi-technique nondestructive approach for characterizing the state of conservation of...     

[2‐(Imidazol‐4‐yl)ethylamine]{[2‐(imidazol‐4‐yl)ethyl][(1‐methylimidazol‐2‐yl)methyl]amine}copper(II) diperchlorate

In the title mononuclear complex, [Cu(C₅H₉N₃)(C₁₀H₁₅N₅)](ClO₄)₂, the Cu^II centre is surrounded by two N‐donor ligands, which impose a square‐pyramidal environment on the metal. The new tridentate ligand [2‐(imidazol‐4‐yl)­ethyl]­[(1‐methyl­imidazol‐2‐yl)­methyl]­amine (HISMIMA) lies in the basal plane, while the hist­amine ligand occupies the apical and one of the basal positions around the Cu^II ion.