Internal heavy-atom effect on spin-orbit and vibronic-spin-orbit coupling:: nπ * phosphorescence of 9,10-anthraquinone haloderivatives

The heavy-atom effect on the components k(so) and k(vso) of the pi* phosphorescence rate constant k(ph) with k(so) and k(vso) 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 pi* 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 beta-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 k(so) and k(vso) are revealed experimentally and explained by computer simulations. (C) 1999 Elsevier Science B.V. All rights reserved.