Modulated perturbation theory for molecular interactions

Modulated Murrell-Shaw-Musher-Amos perturbation theory is used in second order to calculate the interaction energy between two ground-state hydrogen atoms in the region of intermediate internuclear separations from 0 to 6 bohr. Using a small set of variationally optimized two-electron functions accounting for the majority of induction and for spherical and dipole contributions to dispersion, fairly accurate results are obtained for the interaction over the whole range of distances including the united atom. A marked reduction in the induction energy is observed in short range when second-order exchange is introduced.     

Chelation of Theranostic Copper Radioisotopes with S-Rich Macrocycles: From Radiolabelling of Copper-64 to In Vivo Investigation

Copper radioisotopes are generally employed for cancer imaging and therapy when firmly coordinated via a chelating agent coupled to a tumor-seeking vector. However, the biologically triggered Cu²⁺-Cu⁺ redox switching may constrain the in vivo integrity of the resulting complex, leading to demetallation processes. This unsought pathway is expected to be hindered by chelators bearing N, O, and S donors which appropriately complements the borderline-hard and soft nature of Cu²⁺ and Cu⁺. In this work, the labelling performances of a series of S-rich polyazamacrocyclic chelators with [⁶⁴Cu]Cu²⁺ and the stability of the [⁶⁴Cu]Cu-complexes thereof were evaluated. Among the chelators considered, the best results were obtained with 1,7-bis [2-(methylsulfanyl)ethyl]-4,10,diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S). DO2A2S was labelled at high molar activities in mild reaction conditions, and its [⁶⁴Cu]Cu²⁺ complex showed excellent integrity in human serum over 24 h. Biodistribution studies in BALB/c nude mice performed with [⁶⁴Cu][Cu(DO2A2S)] revealed a behavior similar to other [⁶⁴Cu]Cu-labelled cyclen derivatives characterized by high liver and kidney uptake, which could either be ascribed to transchelation phenomena or metabolic processing of the intact complex.     

Remarkably efficient activation of glycosyl trichloro- and (N-phenyl)trifluoroacetimidates with bismuth(III) triflate

Easily handled and nontoxic Bi(OTf)₃ is a powerful activator for trichloro- and (N-phenyl)trifluoroacetimidate glycosyl donors. This catalyst allows glycosidations to be performed at low temperatures in very short times. Rewarding yields were obtained from a wide range of donors of varying reactivity.     

Surface and electrocatalytic properties of well-defined and vicinal RuO2 single crystal faces

The kinetics of Cl₂ evolution from concentrated NaCl solutions on the (110) and (230) faces of RuO₂ single crystals has been investigated by determining the Tafel slope, the stoichiometric number and the reaction orders with respect to Cl^– and H⁺. The experimental parameters suggest that the mechanism is presumably similar to that put forward earlier by Krishtalik [51] for RuO₂ layers, but a step common to oxygen evolution, like the case of polycrystalline samples, is present only with the (230) face. Reasons for this difference and for the apparent lower activity of the (110) face with respect to the (230) are discussed. A detailed analysis of the surface behavior of the two faces in Cl^– free acid and alkaline solutions has also been carried out by cyclic voltammetry.Dedicated to Professor G. Horanyi on the occasion of his 70th birthday     

X-band EPR imaging of polymers irradiated with UV light

The determination of nitroxide radical distributions within polypropylene plaquettes containing amine stabilisers as weli as other additives, which had been irradiated under air on one surface for several months, have been determined by an X-band EPR-Imaging apparatus. It is shown that the EPR Imaging technique represents a powerful tool for investigating the way in which the concentration inside polymers of nitroxide radicals changes both in time and in the space, thus providing information not easily obtainable by means of other techniques.     

Many-body perturbation theory using the density-functional concept: beyond the GW approximation

We propose an alternative formulation of many-body perturbation theory that uses the density-functional concept. Instead of the usual four-point integral equation for the polarizability, we obtain a two-point one, which leads to excellent optical absorption and energy-loss spectra. The corresponding three-point vertex function and self-energy are then simply calculated via an integration, for any level of approximation. Moreover, we show the direct impact of this formulation on the time-dependent density-functional theory. Numerical results for the band gap of bulk silicon and solid argon illustrate corrections beyond the GW approximation for the self-energy.     

Picosecond-laser-induced structural modifications in the bulk of single-crystal diamond

Arrays of through laser-graphitized microstructures have been fabricated in type IIa single-crystal 1.2-mm-thick diamond plates by multipulse laser irradiation with 10-ps pulses at λ=532 nm wavelength. Raman and photoluminescence (PL) spectroscopy studies of the bulk microstructures have evidenced the diamond transformation to amorphous carbon and graphitic phases and the formation of radiation defects pronounced in the PL spectra as the self-interstitial related center, the 3H center, at 504 nm. It is found that the ultrafast-laser-induced structural modifications in the bulk of single-crystal diamond plates occur along {111} planes, known as the planes of the lowest cleavage energy and strength in diamond.     

Engineering of CH3NH3PbI3 Perovskite Crystals by Alloying Large Organic Cations for Enhanced Thermal Stability and Transport Properties

The number of studies on organic–inorganic hybrid perovskites has soared in recent years. However, the majority of hybrid perovskites under investigation are based on a limited number of organic cations of suitable sizes, such as methylammonium and formamidinium. These small cations easily fit into the perovskite's three‐dimensional (3D) lead halide framework to produce semiconductors with excellent charge transport properties. Until now, larger cations, such as ethylammonium, have been found to form 2D crystals with lead halide. Here we show for the first time that ethylammonium can in fact be incorporated coordinately with methylammonium in the lattice of a 3D perovskite thanks to a balance of opposite lattice distortion strains. This inclusion results in higher crystal symmetry, improved material stability, and markedly enhanced charge carrier lifetime. This crystal engineering strategy of balancing opposite lattice distortion effects vastly increases the number of potential choices of organic cations for 3D perovskites, opening up new degrees of freedom to tailor their optoelectronic and environmental properties.