Characteristic Structures and Photophysical Properties of Nona-Coordinated Eu(III) Complexes with Tridentate Phosphine Oxides

Abstract

Structures and photophysical properties of f-block metal complexes with tandem-connected tridentate phosphane oxide ligands (bis(o-diphenylphosphoryl phenyl)phenylphosphane oxide)tris(hexafluoroacetylacetonato)europium(III) (Eu(hfa)3(dpppo)) (bis(o-diphenylphosphorylpyridyl)phenylphosphane oxide)tris(hexafluoroacetylacetonato)europium(III) (Eu(hfa)3(dppypo)) and (bis(o-diphenylphosphorylbenzothienyl)phenylphosphane oxide)tris(hexafluoroacetyl acetonato)europium(III) (Eu(hfa)3(dpbtpo)), are reported. The coordination geometries of Eu(hfa)3(dpppo) and Eu(hfa)3(dpbtpo) provide characteristic distorted, capped square antiprism structures with nona-coordinated oxygen atoms. The emission properties related to the electric transition are characterized by the emission spectra, the emission quantum yields, the emission lifetimes, and the radiative and non-radiative rate constants. Eu(III) complexes with tridentate phosphane oxide ligands offer relatively high emission quantum yields (>60 % in acetone-d 6) due to their low-symmetric and low-frequency vibrational structures. The electric dipole transition intensities in the emission spectra depend on the chemical structures of tridentate phosphane oxides. The characteristic photophysical properties of polyhedral f-block metal complexes, nona-coordinated Eu(III) complexes with tridentate phosphane oxide, are demonstrated for the first time.