Coordination Properties of Tripodal Phosphine Oxide Ligand with Phthalimide Pendants

Coordination properties of tripodal phosphine oxide ligand L with phthalimide pendants toward lanthanides (La, Eu, Tb, and Lu) have been studied by IR and NMR spectroscopy and X-ray diffraction. Powdered complexes with La(III), Eu(III), Tb(III) nitrates and Lu(III) chloride are monoligand, while complex with Lu(III) nitrate is bis-ligand. Unit cells of crystalline complexes with Eu(III), Tb(III) and Lu(III) nitrates contain two ligand molecules, one of which is coordinated, while the second molecule binds to cation through water molecule. The ligand shows monodentate coordination via PO group, CO groups form H bonds with coordinated water molecules, except for lutetium chloride complex, where they are free. In solutions, all complexes have 1 : 1 composition even on excess of the ligand, except of  complex with lutetium nitrate which includes two ligand molecules. Study of luminescence in solution and solid state showed that Eu(III) and Tb(III) complexes exhibit solid-phase luminescence with high quantum yields.