Photophysical properties of some pyrichromine derivatives

Authors:

• Bronisław Marciniak,
• H. Kozubek,
• S. Paszỳc

Abstract

The absorption-emission characteristics, photophysical properties and acid-base equilibria of trimethylated pyrichrominium ions in the ground and lowest excited singlet and triplet states were studied. Analysis of the lifetime quantum yield data indicated that at 77 K fluorescence and phosphorescence are the main processes of deactivation of the excited states for the A⁺ and HA²⁺ forms. The strong temperature dependence of the fluorescence of the protonated form HA²⁺ is discussed on the basis of a phototautomerization reaction. The acidities in the excited singlet and triplet states are several pK_a units higher than those in the ground state. The trimethylpyrichrominium ions in water undergo a slow photochemical reaction in the presence of oxygen. © 1985.