Excited states of aminoanthracenes. An experimental approach to electron density distribution

Abstract

Several excited state properties are evaluated for three isomeric mono-aminoanthracenes (AA) and anthrylammonium cations (AAH⁺). Absorption and fluorescence spectra, their polarizations and solvent-shifts, phosphorescence spectra and triplet-triplet absorptions are described and interpreted in terms of energies, protolytic pK, dipole moments µ, and net charges q_N on the nitrogen atom in the ground state G, in the lowest triplet state T₁, and in the lowest excited singlet state S₁. The value ΔpK^*_S=–8.8 is equal for all isomers; Δµ^*_S are differentiated : 6.7, 5.4 and 3.5 D, for 1-, 2-, and 9-AA, respectively. The q_N values evaluated for the S₁ state from both series of independent experiments are mutually consistent. All pK_T values are close to pK_G values. All experimental data are compared with available results of π-electron approximations.