Photoluminescence of dicyclopentadienylniobium(IV) complexes

The absorption spectra of the d1 complexes (C5H5)NbIVCl2 and [(C5H5)NbIV(2,2′-bipyridine)]2+ show longest-wavelength absorptions at 340 and 350 nm, respectively, which are assigned to LMCT or, more likely, LF transitions. Both complexes are luminescent at 77 K with λmax≈600 nm. The emission is a spin-allowed process and may originate from the lowest LF state.