The absorption spectra of the d(1) complexes (C5H5)(NbCl2)-Cl-IV and [(C5H5
)Nb-IV(2,2'-bipyridine)](2+) show longest-wave length absorptions at 340 an
d 350 nm, respectively, which are assigned to LMCT or, more likely, LF tran
sitions. Both complexes are luminescent at 77 K with lambda(max) approximat
e to 600 nm. The emission is a spin-allowed process and may originate from
the lowest LF state. (C) 1999 Elsevier Science B.V. All rights reserved.