Synthesis, Spectra, and Electron-Transfer Reaction of Aspartic Acid-Functionalized Water-Soluble Perylene Bisimide in Aqueous Solution

Abstract

An aspartic acid-functionalized water-soluble perylene bisimide, N,N′-di(2-succinic acid)-perylene-3,4,9,10-tetracarboxylic bisimide (PASP) was synthesized and characterized. It has absorbance maximum A^0–0 and A^0–1 at 527 and 498 nm (ε ≈ 1.7 × 10⁴ L cm^–1 mol^–1) respectively in pH 7.20 HEPES buffer. Two quasi-reversible redox processes with E_1/2 at −0.17 and −0.71 V (vs Ag/AgCl) respectively in pH 7–12.5 aqueous solutions. PASP can react with Na₂S in pure aqueous solution to form monoanion radical and dianion species consecutively. PASP^–• has EPR signal with g = 1.998 in aqueous solution, whereas PASP^2- is EPR silent. The monoanion radical formation is a first-order reaction with k = 8.9 × 10^–2 s^–1. Dianion species formation is a zero-order reaction and the rate constant is 4.3 × 10^–8 mol L^–1 s^–1. The presence of H₂O₂ greatly increases the radical formation rate constant. PASP as a two-electron transfer reagent is expected to be used in the water photolysis.