Seven-Coordinate Lanthanide Sandwich-Type Complexes with a Tetrathiafulvalene-Fused Schiff Base Ligand

Three seven-coordinate lanthanide­(III) sandwich-type mononuclear complexes with π-conjugated TTF-Schiff base ligand H2L (L2– = 2,2′-((2-(4,5-bis­(methylthio)-1,3-dithiol-2-ylidene)-1,3-benzodithiole-5,6-diyl)­bis­(nitrilomethylidyne)­bis­(4-chlorophenolate)) and the tripodal ligand LOEt– (LOEt– = [(η5-C5H5)­Co­(P­(O)­(OEt)2)3]−), [(LOEt)­Ln­(L)]·0.25H2O (Ln3+ = Dy3+, 1; Tb3+, 2; Ho3+, 3), have been synthesized and structurally characterized. All of the complexes are also characterized by absorption spectra and electrochemical, spectroelectrochemical, and magnetic studies. The Dy complex exhibits the field-induced slow relaxation of magnetization with an energy barrier of 41.6 K, indicating it shows single lanthanide-based SMM behavior. Introduction of the redox-active TTF unit into the sandwich-type lanthanide­(III) complexes with interesting magnetic properties renders them promising for elaboration of new hybrid inorganic–organic materials.