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

Abstract Previous studies on the crystal structure of a complex formed with 2,2′-bipyridine-1,1′-dioxide (bpyO 2 ) 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 D 4 symmetry. In this paper we describe high-resolution luminescence and circularly polarized luminescence results on Eu(bpyO 2 ) 4 3+ . The appearance of several crystal-field transitions in the emission for the Eu(III) complex are interpreted in terms of distortions from the D 4 symmetry seen for the La(III) analog. Extraordinarily large absorption and emission intensities for the hypersensitive transitions of Nd(bpyO 2 ) 4 3+ and Eu(bpyO 2 ) 4 3+ are observed and discussed. Large circularly polarized luminescence is observed from Eu(bpyO 2 ) 4 3+ 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.