| Abstract
| - In a neutral aqueous solution of acridine-1,8-dione (AD)the eaq- was observed to react with abimolecularrate constant of 1.5 × 1010 dm3mol-1 s-1 and form transient opticalabsorption bands with λmax = 305, 475nm, a shoulder at 680 nm, and increasing absorption with λ > 800 nm.The entire spectrum from λ > 450nm decayed by first-order kinetics with k = 1.5 ×105 s-1, whereas the absorption at 315 nmshowed growthwith k = 1.6 × 105 s-1.It decayed by second-order kinetics with2k/εl = 1 × 104s-1. The transient opticalabsorption bands at 305, 475, 680, and >800 nm are assigned to theelectron adduct, AD•-, which onprotonation forms H adduct (ADH•) with λmax= 315 nm and a pK value of 4.7. In basic solutions(pH =13), AD•- does not show slow transformation toADH• while in acidic solutions (pH = 3), onlyADH• wasobserved (λmax = 315 nm). ADH• inhighly acidic solutions (pH < 3) protonates to form(ADH2)•+ (λmax=315, 560 nm) with a pK value of 2.6.AD/AD•- established an equilibrium withMV2+/MV•+ and the reductionpotential for AD/AD•- couple was determined to be−0.586 ± 0.03 V. α-Hydroxyalkly radicals(CH3)2C•OH,CH3C•HOH, and•CH2OH) were able to reduce AD withbimolecular rate constant values of 3.2 × 108,2.3× 108, and 1.2 × 108 dm3mol-1 s-1, respectively. The radicalanion AD•- was able to transfer electrontop-nitroacetophenone with a bimolecular rate constant of 6× 109 dm3 mol-1s-1.
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