Unsymmetrical Tripodal Ligand for Lanthanide Complexation: Structural, Thermodynamic, and Photophysical Studies

Two tridentate and one bidentate binding strands have been anchored on a carbon atom to provide a new ursymmetrical tripodal ligand L for Ln(III) coordination. The ligand itself adopts a single conformation in solution stabilized by intramolocular hydrogen bonds evidenced in the solid state. The reaction of L with trivalent lanthanides provides different coordination complexes depending oil the metal/ligand ratio. The speciation studies With selected lanthanides were performed in solution by means of NMK ESMS, and spectrophotometric titrations. ifferences in coordinabon properties along die lanthanide series were evidenced and may be associated with die changes in the ionic size. However, thermodynamic stability constant: for the species of the same stoichiometry do not significantly vary. In addition, the structure of die dinuclear complex [Eu2L2](6+) has been elucidated in the solid state, where the complex crystallizes predominantly as an M-isomer. The crystal structure shows the coordination of two different ligands to each europium cation through tridentate strands, and die europium nine-coordinate sphere is convicted With three solvent molecules. Finally, die results of photophysical investigations or [Eu2L2](6+) are in close agreement With the structural parameters determined by crystallography.