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

Previous studies on the crystal structure of a complex formed with 2,2'-bip yridine-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 lum inescence 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 s ymmetry seen for the La(III) analog. Extraordinarily large absorption and e mission intensities for the hypersensitive transitions of Nd(bpyO(2))(4)(3) and Eu(bpyO(2))(4)(3+) are observed and discussed. Large circularly polar ized luminescence is observed from Eu(bpyO(2))(4)(3+) dissolved in acetonit rile following circularly polarized laser excitation. This result suggests that the complex occurs in solution as a racemic complex that does not race mize on the emission time scale. (C) 2000 Elsevier Science B.V. All rights reserved.