Redox-Modulations of Photophysical and Single-molecule Magnet Properties in Ytterbium Complexes Involving Extended-TTF Triads.

The reaction between the 2,2'-benzene-1,4-diylbis(6-hydroxy-4,7-di--butyl-1,3-benzodithiol-2-ylium-5-olate triad () and the metallo-precursor [Yb(hfac)]2HO led to the formation of a dinuclear coordination complex of formula [Yb(hfac)()]0.5CHCl (). After chemical oxidation of in 2,2'-cyclohexa-2,5-diene-1,4-diylidenebis(4,7-di--butyl-1,3-benzodithiole-5,6-dione (), the latter triad reacted with the [Yb(hfac)]2HO precursor to give the dinuclear complex of formula [Yb(hfac)()] (). Both dinuclear compounds have been characterized by X-ray diffraction, DFT optimized structure and electronic absorption spectra. They behaved as field-induced Single-Molecule Magnets (SMMs) nevertheless the chemical oxidation of the semiquinone to quinone moieties accelerated by a factor of five the relaxation time of the magnetization of compared to the one for . The triad efficiently sensitized the Yb luminescence while the chemical oxidation of into induced strong modification of the absorption properties and thus a quenching of the Yb luminescence for . In other words, both magnetic modulation and luminescence quenching are reached by the oxidation of the protonated semiquinone into quinone.