Absorption spectra and CT transitions of compounds containing Re I(CO) 3Cl, S 2+ and Se 2+ as donors and o-benzoquinone diimine as acceptor

Abstract

The electronic spectra of the cations [(BQDI)Se II] 2+ and [(BQDI)S II] 2+ are compared to that of [(BQDI)Re I(CO) 3Cl] with BQDI = o-benzoquinone diimine. While these species show a BQDI-localized ππ ∗ absorption between 300 and 360 nm, a longer-wavelength band extends to the visible region. This absorption is attributed to a CT transition from Re I ( λ max = 538), Se II ( λ max = 432) and S II ( λ max = 360 nm) to the π ∗ orbitals of BQDI. The analogy of MLCT and related CT transitions involving non-metals as CT donors is emphasized.