Photophysical Properties of Lanthanide Complexes with Asymmetric Dodecahedron Structures
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Distorted coordination structures and luminescence properties of novel lanthanide complexes with oxo-linked bidentate phosphane oxide ligands, 4,5-bis(diphenylphosphoryl)-9,9-dimethylxanthene (xantpo), 4,5-bis(di-tert-butylphosphoryl)-9,9-dimethylxanthene (tBu-xantpo) and bis[(2-diphenylphosphoryl)phenyl]ether (dpepo) and low-vibrational frequency hexafluoroacetylacetonato (hfa) ligands are reported. The lanthanide complexes exhibit characteristic square antiprism and trigonal dodecahedron structures with octa-coordinated oxygen atoms. The luminescence properties of these complexes are characterized by their emission quantum yields, emission lifetimes, and their radiative and non-radiative rate constants. Lanthanide complexes with dodecahedron structures offer markedly high emission quantum yields (Eu: 55–72 %, Sm: 2.4–5.0 % in acetone-d 6) due to enhancement of the electric dipole transition and suppression of vibrational relaxation. These remarkable luminescence properties are elucidated in terms of their distorted coordination structures.
KeywordsSamarium Coordination structure Dodecahedron Asymmetry Shape measure
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