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

Six new 3d4f heterobimetallic dinuclear complexes, [(L-1)-MLn(hfac)(3)] [M = Cu-II, Ni-II; Ln = Y-III, Er-III, Yb-III; L-1 = 4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenylenebis(salicylideneimine) and hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate], and one tetranuclear complex, [(L-2)Cu(OH)Er(hfac)(3)](2) (where L-2 = 4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenylenearninosalicylideneimine), 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 Gd-III (1.29 cm(-1)) and Tb-III (0.40 cm(-1)) and the antiferromagnetic interaction for Dy-III (-0.46 cm(-1)) and Yb-III (-2.25 cm(-1)), while in the case of Er-III, 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 [(L-1)NiY(hfac)(3)] induces a ligand-centered fluorescence at 14450 cm(-1).