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-tert-butyl-1,3-benzodithiol-2-ylium-5-olate triad (H(2)SQ) and the metallo-precursor [Yb(hfac)(3)]⋅2H(2)O led to the formation of a dinuclear coordination complex of formula [Yb(2)(hfac)(6)(H(2)SQ)]⋅0.5CH(2)Cl(2) (H(2)SQ-Yb). After chemical oxidation of H(2)SQ in 2,2’-cyclohexa-2,5-diene-1,4-diylidenebis(4,7-di-tert-butyl-1,3-benzodithiole-5,6-dione (Q), the latter triad reacted with the [Yb(hfac)(3)]⋅2H(2)O precursor to give the dinuclear complex of formula [Yb(2)(hfac)(6)(Q)] (Q-Yb). 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 Q-Yb compared to the one for H(2)SQ-Yb. The H(2)SQ triad efficiently sensitized the Yb(III) luminescence while the chemical oxidation of H(2)SQ into Q induced strong modification of the absorption properties and thus a quenching of the Yb(III) luminescence for Q-Yb. In other words, both magnetic modulation and luminescence quenching are reached by the oxidation of the protonated semiquinone into quinone.