Kinetic, spectral and redox properties of the transients formed on one-electron reduction of 3,3,6,6-tetramethyl-3,4,6,7,9-pentarydro-10-phenyl (1,8)(2H,5H) acridine-dione in aqueous-organic mixed solvent system: A pulse radiolysis study

The phenyl substituted acridine-1,8-dione (AD) dye reacts with (CH3)(2)(COH )-C-. radicals with a bimolecular rate constant of 0.6 x 10(8) dm(3) mol(-1 ) s(-1) in acidic aqueous-organic mixed solvent system. The transient optic al absorption band (lambda (max) = 465 nm, epsilon = 6.8 x 10(2) dm(3) mol( -1) cm(-1)) is assigned to ADH(.) formed on protonation of the radical anio n. In basic solutions, (CH3)(2)(COH)-C-. radicals react with a bimolecular rate constant of 4.6 x 10(8) dm(3) mol(-1) s(-1) and the transient optical absorption band (lambda (max) = 490 nm, epsilon = 10.4 x 10(3) dm(3) mol(-1 ) cm(-1)) is assigned to radical anion, AD(.-), which has a pK(a) value of 8.0. The reduction potential value of the AD/AD(.-) couple is estimated to be between -0.99 and -1.15 V vs NHE by pulse radiolysis. studies. The cycli c voltammetric studies showed the peak potential close to -1.2 V vs Ag/AgCl .