REACTION OF H-CENTER-DOT, (OH)-O-CENTER-DOT, O-CENTER-DOT- AND SPECIFIC ONE-ELECTRON OXIDANTS WITH 3,3,6,6-TETRAMETHYL-3,4,6,7,9,10-HEXAHYDRO-(1,8) (2H,5H)-ACRIDINEDIONE - GROUND-STATE AND EXCITED-STATE AND TRANSIENT ACID-BASE PROPERTIES

Acridinedione dye is able to exist in neutral, protonated and deproton ated forms in acid-base conditions. The neutral form shows an absorpti on at 400 nm and emits at 463 nm. The absorption under acidic conditio ns is blue shifted and the emission intensity at 463 nm decreases with the formation of a new emission peak. In basic solution, the dye is d eprotonated and absorbs at 470 nm and emits at 525 nm. The ground-and excited-state pK(a) have been calculated. The pulse radiolysis experim ents were carried out with specific one-electron oxidants, such as Br- 2(.-), N-3(.), Cl-2(.-), I-2(.-). They show transient absorption bands at 305 and 630 nm. Pulse radiolysis of acidic solutions of the dye sh ow transient bands with absorption maxima at 315 and 545 nm and are as signed to a solute radical cation, which deprotonates in neutral solut ions. The reaction of H-., (OH)-O-. and O.- with the dye has been stud ied and the transient absorption bands in the neutral solution are ass igned to a neutral carbon centred radical, which deprotonates in basic solution. The pK(a) values of the transient species are determined. T he redox potential for the one-electron oxidation of the dye is determ ined as 1.01 +/- 0.02 V vs. NHE which compares well with the value obt ained by an electrochemical method.