Synthesis, Characterization and Photophysical Properties of NIR-NIR Lanthanide(III)-Based Metallacrowns with Non-Covalently-Bound Chromophores.

International audienc

Covalent and Non-covalent Approaches for the Tuning of the Functional Properties of Lanthanide(III)-based Metallacrowns Emitting in the NIR-II Range.

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Functionalized cationic [4]helicenes with unique tuning of absorption, fluorescence and chiroptical properties up to the far-red range

Unprecedented regioselective post-functionalization of racemic and enantiopure cationic diaza [4]helicenes is afforded. The peripheral auxochrome substituents allow a general tuning of the electrochemical, photophysical and chiroptical properties of the helical dyes (26 examples). For instance, electronic absorption and circular dichroism are modulated from the orange to near-infrared spectral range (575–750 nm), fluorescence quantum efficiency is enhanced up to 0.55 (631 nm) and circularly polarized luminescence is recorded in the red (|glum| ∼ 10−3)

Investigation of the phase occurrence, H sorption properties, and electrochemical behavior in the composition ranges La0.75-0.80Mg0.30-0.38Ni3.67

cited By 4International audienceTo explore the possible occurrence of new stacking sequences within the La-Mg-Ni system, two alloys in the composition range La15.6-16.8Mg6.3-7.8Ni76.5-76.9 (at. %) have been synthesized by Spark Plasma Sintering (SPS). The X-ray diffraction analyses show that the obtained alloys contain a mixture of A2Ni7 and A5Ni19 phases (A = La, Mg) with coexistence of hexagonal and rhombohedral polymorphs. Such structures can be described as a stacking along the c crystallographic axis of mAB5 units (labeled C) and nA2B4 units (labeled L). Up to now, compounds with 1 ≠ m ≠ 4, but only n = 1 were confirmed in the La-Mg-Ni system. One composition has been particularly studied here by High-Angle Annular Dark-Field (HAADF) Scanning Transmission Electron Microscopy (STEM). A continuous change of the stacking sequences (from C + L to 4C + L) is observed within a 50 nm region. In addition, two types of stacking faults (twinning and dislocation) have been revealed. The expected stacking sequence with n > 1 has not been observed in the present work. The hydrogen storage capacity and the electrochemical capacity are not significantly affected by the phase compositions, while the cyclic stability appears particularly sensitive to the Mg content