2022, Lazarević, N., Baum, A., Milosavljević, A., Peis, L., Stumberger, R., Bekaert, J., Šolajić, A., Pešić, J., Wang, Aifeng, Šćepanović, M., Abeykoon, A. M. Milinda, Milošević, M.V., Petrovic, C., Popović, Z.V., Hackl, R.

A Raman scattering study covering the entire substitution range of the FeSe1-xSx solid solution is presented. Data were taken as a function of sulfur concentration x for 0≤x≤1, of temperature and of scattering symmetry. All types of excitations including phonons, spins, and charges are analyzed in detail. It is observed that the energy and width of the iron-related B1g phonon mode vary continuously across the entire range of sulfur substitution. The A1g chalcogenide mode disappears above x=0.23 and reappears at a much higher energy for x=0.69. In a similar way the spectral features appearing at finite doping in A1g symmetry vary discontinuously. The magnetic excitation centered at approximately 500 cm-1 disappears above x=0.23 where the A1g lattice excitations exhibit a discontinuous change in energy. The low-energy mode associated with fluctuations displays maximal intensity at the nematostructural transition and thus tracks the phase boundary.

2021, Chen, Lisa, Arnold, Mona, Blinder, Rémi, Jelezko, Fedor, Kuehne, Alexander J. C.

Derivatives of the stable, luminescent tris-2,4,6-trichlorophenylmethyl (TTM) radical exhibit unique doublet spin properties that are of interest for applications in optoelectronics, spintronics, and energy storage. However, poor reactivity of the chloride-moieties limits the yield of functionalization and thus the accessible variety of high performance luminescent radicals. Here, we present a pathway to obtain mixed-bromide and chloride derivatives of TTM by simple Friedel–Crafts alkylation. The resulting radical compounds show higher stability and site-specific reactivity in cross-coupling reactions, due to the better leaving group character of the para-bromide. The mixed halide radicals give access to complex, and so far inaccessible luminescent open-shell small molecules, as well as polymers carrying the radical centers in their backbone. The new mixed-halide triphenyl methyl radicals represent a powerful building block for customized design and synthesis of stable luminescent radicals.