One-electron reduction of acridine-1,8-dione in aqueous solution: a pulse radiolysis study

Mohan, H. ; Srividya, N. ; Ramamurthy, P. ; Mittal, J. P. (1997) One-electron reduction of acridine-1,8-dione in aqueous solution: a pulse radiolysis study Journal of Physical Chemistry A, 101 (16). pp. 2931-2935. ISSN 1089-5639

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp9628141

Related URL: http://dx.doi.org/10.1021/jp9628141

Abstract

In a neutral aqueous solution of acridine-1,8-dione (AD) the eaq¯ was observed to react with a bimolecular rate constant of 1.5 × 1010 dm3 mol-1 s-1 and form transient optical absorption bands with λ max = 305, 475 nm, a shoulder at 680 nm, and increasing absorption with λ > 800 nm. The entire spectrum from λ > 450 nm decayed by first-order kinetics with k = 1.5 × 105 s-1, whereas the absorption at 315 nm showed growth with k = 1.6 × 105 s-1. It decayed by second-order kinetics with 2k/el = 1 × 104 s-1. The transient optical absorption bands at 305, 475, 680, and >800 nm are assigned to the electron adduct, AD•-, which on protonation forms H adduct (ADH) with λ max = 315 nm and a pK value of 4.7. In basic solutions (pH = 13), AD¯ does not show slow transformation to ADH while in acidic solutions (pH = 3), only ADH was observed (λ max = 315 nm). ADH in highly acidic solutions (pH < 3) protonates to form (ADH2)•+max = 315, 560 nm) with a pK value of 2.6. AD/AD¯ established an equilibrium with MV2+/MV•+ and the reduction potential for AD/AD•- couple was determined to be -0.586 ± 0.03 V. α-Hydroxyalkly radicals (CH3)2COH, CH3CHOH, and ·CH2OH) were able to reduce AD with bimolecular rate constant values of 3.2 × 108, 2.3 × 108, and 1.2 × 108 dm3 mol-1 s-1, respectively. The radical anion AD•- was able to transfer electron to p-nitroacetophenone with a bimolecular rate constant of 6 × 109 dm3 mol-1 s-1.

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