Solution and solid state spectroscopy of tetrakis complexes of 2,2′-bipyridine-1,1′-dioxide with europium(III)

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Previous studies on the crystal structure of a complex formed with 2,2′-bipyridine-1,1′-dioxide (bpyO2) and La(III) ions have shown the existence of an tetrakis eight coordinate complex in which the metal ion sits in a site of approximate D4 symmetry. In this paper we describe high-resolution luminescence and circularly polarized luminescence results on Eu(bpyO2)43+. The appearance of several crystal-field transitions in the emission for the Eu(III) complex are interpreted in terms of distortions from the D4 symmetry seen for the La(III) analog. Extraordinarily large absorption and emission intensities for the hypersensitive transitions of Nd(bpyO2)43+ and Eu(bpyO2)43+ are observed and discussed. Large circularly polarized luminescence is observed from Eu(bpyO2)43+ dissolved in acetonitrile following circularly polarized laser excitation. This result suggests that the complex occurs in solution as a racemic complex that does not racemize on the emission time scale.

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Journal of Luminescence