Photochemistry of 3,4,9,10-perylenetetracarboxylic dianhydride dyes. 4. Spectroscopic and redox properties of oxidized and reduced forms of the bis(2,5-di-tert-butylphenyl)imide derivative

Four oxidation states of N,N{prime}-bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylenebis(dicarboximide) (DBPI) are characterized electrochemically and spectroscopically. The oxidation of DBPI to its radical cation (DBPI{sup {sm bullet}+}) is irreversible and occurs at an electrode potential of about +2.2 V vs SCE. The reductions of DBPI to the radical anion (DBPI{sup {sm bullet}+}) and BDPI{sup {sm bullet}+} to the dianion (DBPI{sup 2{minus}}) are reversible with reduction potentials of -0.73 and -0.96 V vs SCE, respectively. The radical anion is stable with respect to disproportionation. All three electron-transfer products of DBPI, which were produced either by radiolysis or by chemical reduction, have intense ({epsilon} {approx} 10{sup 5} M{sup {minus}1} cm{sup {minus}1}) absorption bands in the visible or near-infrared region, with maxima near 600 nm (DBPI{sup {sm bullet}+}), 700 nm (DBPI{sup {sm bullet}+}), or 545 nm (DBPI{sup 2{minus}}). The kinetic parameters of pulse radiolytic oxidation and reduction of DBPI are determined, and the redox potentials of the first excited singlet and triplet states of DBPI are estimated.