Internal heavy-atom effect on spin–orbit and vibronic–spin–orbit coupling: nπ∗ phosphorescence of 9,10-anthraquinone haloderivatives Original Research Article

The heavy-atom effect on the components kso and kvso of the nπ∗ phosphorescence rate constant kph with kso and kvso depending on the spin–orbit (SO) and vibronic–spin–orbit (VSO) coupling, respectively, is investigated in series of halogenated compounds. This information obtained in this paper with a use of data on vibronic line intensities in the fine-structure nπ∗ phosphorescence spectra for 2,3,6,7-tetrachloro-9,10-anthraquinone (TCA) is correlated with that derived by us earlier for 9,10-anthraquinone and its β-monohaloderivatives with halogen Cl, Br, I. The vibronic spectrum of TCA is interpreted on the basis of IR and Raman spectra and calculated vibrational frequencies. The interesting regularities in the internal heavy-atom effect on kso and kvso are revealed experimentally and explained by computer simulations.