The Intra-annular Internal Heavy-atom Effect on the Fluorescence and Phosphorescence Properties of Oxygen, Sulphur or Selenium Containing Heterocyclic Systems Related to Dibenzo [b,n] perylene

Fluorescence and phosphorescence properties of dibenzo [2,3:10,11] perylo [1,12-bcd] furan (1), dibenzo [2,3:10,11] perylo [1,12-bcd] thiophene (2), and dibenzo [2,3:10,11 ] perylo [1,12-bcd] selenophene (3) have been studied. Fluorescence quantum yields as well as phosphorescence lifetimes correlate linearly with where c k are the Hückel AO coefficients in the HOMO of the parent carbocyclic system dibenzo [b, n] perylene (4) on carbon centres k to which the hetero-atom is bound, and ζ is the spin-orbit coupling constant of the heavy-atom present. The half-value concentration of fluorescence quenching (quencher: methyl iodide) of 1 - 3 increases with increasing strength of the internal heavy-atom effect present