Excited states quenching of phenosafranine dye by electron donors

The quenching of the excited singlet and triplet states of phenosafranine by aromatic amines, methoxybenzenes and triethanolamine was investigated in acetonitrile and methanol. The rate constants for the aromatic quenchers present a typical dependence of an electron transfer process with the one-electron redox potential of the donor. A Rehm-Weller correlation is obtained with the driving force. The fitting parameters are very similar in both solvents. The electron transfer nature of the quenching reaction is further confirmed by the detection of the radical cations of the quenchers and the semireduced form of the dye in laser flash photolysis experiments. The absorption coefficients of the transient species were estimated, and the quantum yield of the charge separation process was determined.