Effect of solvent on the flash photolysis and laser photolysis of N,N,N′,N′-tetramethyl-paraphenylene diamine in solution

Abstract

The photolysis of TMPD has been studied in cyclohexane, ethanol and water, by microsecond flash photolysis, by nanosecond laser flash photolysis and by conventional steady-state photolysis techniques. In cyclohexane the fluorescence of TMPD singlet is observed with t_½= 3.2 ns. The triplet state of TMPD is also observed; it decays by a bimolecular triplet-triplet annihilation process accompanied by delayed fluorescence. Several solutes, e.g., N₂O, SF₆ and CO₂ react with the excited singlet state; N₂O also reacts with the triplet forming a charge transfer complex. Fluorescence with t_½= 5.1 ns is observed in the flash photolysis of TMPD in ethanol. The triplet state of TMPD is also observed, but this decays rapidly in ethanol over several 100 ns. Another long-lived species is produced independent of the excited singlet or triplet states of TMPD. No fluorescence or is produced independent of the excited singlet or triplet states of TMPD. No fluorescence or triplet state is observed in the photolysis of TMPD in water, but the cation of TMPD and the hydrated electron e^–_aq are observed. Possible mechanisms leading to the ionization of TMPD in water are discussed.