Ligand-field asymmetry-controlled luminescent europium (III) and samarium(III) tris(β-diketonate) complexes of diphenyl-(2-pyridyl-N-oxide)- phosphine oxide

Eight new complexes of the type Ln(OO)3.2 L1, Ln(OO)3.L2 (where Ln=Eu, Sm; OO=thenoyl trifluroacetonate(TTA) and dibenzoylmethanate(DBM); L1=diphenyl, (2-pyridyl) phosphine oxide (PON) and diphenyl-(2-pyridyl-N-oxide)phosphine oxide (PONO)) were synthesized for the first time. Complexes were characterized by FTIR, CHN analyses and Single crystal X-ray diffraction techniques. Structures of samarium complexes show that the L1 behaves as a monodentate ligand and bonds through P=O group to metal centre, whereas L2 behaves as a bidentate ligand and bonds through P=O as well as N−O groups to metal centre. Photophysical properties of all the complexes were measured in solid as well as solution states. Due to increase in ligand field asymmetry around the metal centre (by changing ligand from L1 to L2), the asymmetry ratio REu in Europium(III) tris( diketonate)-L2 complexes were increased. This leads to increase in intrinsic quantum yield complexes with ligand L2 as compared to that of complexes of ligand L1