Synchrotron X-Ray Absorption Spectroscopy (XAS) Studies on Structural and Magnetic Properties of T’-Pr2-xCexCuO4 Nanocrystals

We have succeeded in synthesizing electron-doped cuprates T’-Pr2-xCexCuO4 (PCCO) with x = 0 and 0.10 nanocrystals prepared by the chemically dissolved method. Reduction annealing of the PCCO samples at 700°C under a flowing argon gas atmosphere has been performed for the removal of excess oxygen in the apical sites. The XRD data showed that the reduction annealing process decreases c-axis length indicating successful removal of the excess oxygen. The bond distortion of PCCO including coordination number and bond distance between the absorber atoms with the nearest neighboring atoms (Cu-O) was investigated by extended x-ray absorption fine structure (EXAFS) using Cu K-edge. The implication of our results is discussed on the basis of tremendous influence of oxygen vacancies on the magnetism of the nanosized T’-cuprates at the normal state.

Nickel-Catalyzed Negishi Cross-Coupling of N-Acylsuccinimides: Stable, Amide-Based, Twist-Controlled Acyl-Transfer Reagents via N–C Activation

This paper reports a room temperature, nickel-catalyzed Negishi cross-coupling of N-acylsuccinimides with arylzinc reagents via selective N–C bond cleavage enabled by amide bond twist. The reaction proceeds using a commercially available, air-stable Ni(II) precatalyst in the absence of additives under exceedingly mild conditions. Of broad interest, this report introduces N-acylsuccinimides as stable, crystalline, electrophilic, cost-effective, benign, amide-based acyl transfer reagents via acyl metal intermediates. The reaction selectivity is governed by half-twist of the amide bond in N-acylsuccinimides, thus opening the door for applications in metal-catalyzed manifolds via redox­-neutral reaction pathways tuneable by amide bond distortion.

Extended bond-valence model as a tool for designing topology of inorganic crystal structures

The simple rules, based on the bond-valence matching and coordination numbers balance, are extended to minimum-size polyhedral cluster in order to describe all probable bonding topologies for a given inorganic substance. This approach, referred to as the Extended Bond-Valence Model (EBVM), allows one to construct the corresponding connectivity matrices and then to calculate predicted bond valences and bond lengths. The subsequent estimates of individual and average bond distortion indices make it possible to select most probable bonding geometry and compare it with experimental data, whenever feasible. The EBVM approach is applied to predict the bonding topologies of Al