Solvent effect on the physical quenching of singlet molecular oxygen by p-quinones

Abstract

Rate constants for the interaction between singlet molecular oxygen [O₂(¹Δ_g)] and the p-quinones 1,4-benzoquinone (BQ), duroquinone (DQ), 9,10-anthraquinone (AQ) and 1,8-dihydroxy-9,10-anthraquinone (OHAQ) are reported for several solvents at room temperature. The solvent effect on the total quenching rate constant (k_t) was analysed employing the semiempirical solvatochromic equation proposed by Kamlet and Taft. The higher values of k_t (2–7 × 10⁷ M⁻¹ s⁻¹) were obtained when the hydrogen-bond donor solvent ability is increased (higher α parameter values). The results indicate the importance of specific solvent interactions in governing the rates of the quenching.