Magnetic and photo-physical investigations into DyIII and YbIII complexes involving tetrathiafulvalene ligand

Abstract

Three lanthanide-based complexes involving a tetrathiafulvalene derivative (L) in which the lanthanide ion has a pseudo-D_4d symmetry have been reported. One is a dinuclear compound of formula [Dy(hfac)₃(L)]₂ (1) while the two others are isostructural and described as mononuclear complexes of formulae [Ln(tta)₃(L)]·xCH₂Cl₂ (Ln^III = Dy and x = 1.41 (2); Yb and x = 2 (3)). The nuclearity of the species is driven by the nature of the ancillary ligands. Magnetic properties revealed that 1 and 3 behave as single molecule magnets, while 2 does not. The crystal field splitting of the ground multiplet state has been theoretically determined as well as the orientation of the easy axis of the ground M_J state. The results of ab initio calculations are in agreement with the experimental determinations of the anisotropy axis. Irradiation of the lowest-energy charge transfer bands of 3 led to an intense and resolved Yb-centred emission which can be correlated to the magnetic data. Thus 3 can be described as a redox-active luminescent field-induced single-molecule magnet.