3d4f Heterobimetallic Dinuclear and Tetranuclear Complexes Involving Tetrathiafulvalene as Ligands: X-ray Structures and Magnetic and Photophysical Investigations

Six new 3d4f heterobimetallic dinuclear complexes, [(L1)­MLn­(hfac)3] [M = CuII, NiII; Ln = YIII, ErIII, YbIII; L1 = 4,5-bis­(propylthio)­tetrathiafulvalene-N,N′-phenylenebis­(salicylideneimine) and hfac– = 1,1,1,5,5,5-hexafluoroacetylacetonate], and one tetranuclear complex, [(L2)­Cu­(OH)­Er­(hfac)3]2 (where L2 = 4,5-bis­(propylthio)­tetrathiafulvalene-N,N′-phenyleneaminosalicylideneimine), have been synthesized. All of the X-ray structures of the coordination complexes have been resolved from single-crystal diffraction. A quantitative magnetic approach has allowed one to determine the Cu–Ln ferromagnetic interaction for GdIII (1.29 cm–1) and TbIII (0.40 cm–1) and the antiferromagnetic interaction for DyIII (−0.46 cm–1) and YbIII (−2.25 cm–1), while in the case of ErIII, the magnetic interactions are negligible. The UV–visible absorption properties have been studied in a chloroform solution and rationalized by DFT and TD-DFT calculations. Upon oxidation, intramolecular SOMO → LUMO (20800 cm–1) and SOMO–n → SOMO (11350 cm–1) charge transfers appear, while the HOMO → LUMO charge transfers (20750 cm–1) disappear. The reversibility of the oxidation has been confirmed by electrochemistry and absorption properties upon the addition of a reducing agent. Irradiation at the HOMO → LUMO charge-transfer energy of the dinuclear complex [(L1)­NiY­(hfac)3] induces a ligand-centered fluorescence at 14450 cm–1.