Magnetic and Photo-Physical Properties of Lanthanide Dinuclear Complexes Involving the 4,5-Bis(2-Pyridyl-N-Oxidemethylthio)-4 ',5 '-Dicarboxylic Acid-Tetrathiafulvalene-, Dimethyl Ester Ligand

The reaction between the 4,5-bis(2-pyridyl-N-oxidemethylthio)-4', 5'-dicarboxylic acid-tetrathiafulvalene-, dimethyl ester ligand (L) and the metallo-precursors Ln(hfac)(3).2H(2)O leads to the formation of two dinuclear complexes of formula [Ln(2)(hfac)(6)(L)].(CH2Cl2).(C6H14)(0.5) (Ln(III) = Dy-III (1) and Yb-III (2)). The X-ray structure reveals a quite regular square anti-prism symmetry for the coordination sphere of the lanthanide ion. UV-visible absorption properties have been experimentally measured and rationalized by TD-DFT calculations. The functionalization of the tetrathiafulvalene (TTF) core by two methyl ester moieties induces the appearance of an additional absorption band in the lowest-energy region of the spectrum. The latter has been identified as a HOMO (Highest Occupied Molecular Orbital). LUMO (Lowest Unoccupied Molecular Orbital) Intra-Ligand Charge Transfer (ILCT) transition in which the HOMO and LUMO are centred on the TTF and methyl ester groups, respectively. Irradiation at 22,222 cm(-1) of this ILCT band induces an efficient sensitization of the YbIII-centred emission that can be correlated to the magnetic properties.