One-electron reduction of 3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-(1,8)-(2h,5h)-acridinedione: a pulse radiolysis study

Abstract

The radical anion formed on reaction of e_aq¯ with acridinedione dye (ADH) exhibits transient optical absorption bands at λ _max = 315, 460, and >780 nm. The bimolecular rate constant for the reaction of e_aq¯ with the dye was determined to be 2.7 × 10¹⁰ dm³ mol^-1 s^-1. It is converted to (ADH₂^•) on protonation and showed an absorption band at 310 nm. At pH = 1, acetone ketyl radicals are observed to react with the dye with a bimolecular rate constant of 2.3 × 10⁸ dm³ mol^-1 s^-1, and the transient optical absorption bands ( λ _max = 315, 540 nm) are assigned to (ADH₃)^•+. The radical anion (ADH^•-) is a strong reducing agent, with reduction potential = -1.37 V vs NHE, and is able to undergo electron-transfer reactions with methyl viologen (MV²⁺) and p-nitroacetophenone (p-NAP) with bimolecular rate constants of 4.9 × 10⁹ and 6.1 × 10⁹ dm³ mol^-1 s^-1, respectively.