Energy transfer and photodecomposition of antharacene laser dyes

Abstract

Energy transfer from anthracene and seven anthracene derivatives to Rhodamine 6G has been studied in propan-2-ol by steady-state emission measurements. It was found that the Stern–Volmer relation is obeyed, giving rate constants of energy transfer (k_ET) from 1.7 ± 0.13 × 10¹² to 0.1 ± 0.03 × 10¹² dm³ mol^–1 s^–1. The experimental critical transfer distances, R₀, have been calculated for each dye. The values of k_ET and R₀ indicate a Förster-type energy-transfer mechanism. The photochemical quantum yields (ϕ_c; λ_ex= 254 nm) of five anthracene laser dyes together with parent anthracene have been studied in different halomethane solvents and ethanol. The ϕ_c values in CCl₄ were several orders of magnitude higher than those in ethanol, and the ϕ_c values decrease in the order: CCl₄ < CHCl₃ < CH₂Cl₂ C₂H₅OH. The excited-state lifetime (τ) and the role of molecular oxygen in deactivation of the excited-singlet state of these anthracene derivatives have been studied and the second-order quenching rate constants have been determined.