1-Nitro-7-Donor Functionalized Perylenediimides: Synthesis, Photophysical Properties, Redox Behavior, and Nanosecond Transient Studies

Abstract

A set of push�pull donor substituted nitro-perylenediimide (NO2-PDI)-based derivatives NPDI 1�4 were designed and synthesized via nitration reaction of the mono-brominated-PDI (Br-PDI) followed by Pd(II)-catalyzed Sonogashira cross�coupling reaction in good yields. The nitro group was substituted at the bay position of the PDI-NO2, and a variety of donors (phenothiazine (PTZ), carbazole(CBZ), and N,N-dimethylaniline(NND) were functionalized on the other bay side. The photophysical, electrochemical, spectroelectrochemical, computational calculations, and nanosecond transient absorption (ns-TA) studies were performed on the synthesized derivatives NPDI 1�4. The photophysical properties of NPDI 2�4 exhibit absorption in the NIR region due to strong push�pull interaction, resulting in stabilized LUMO energy levels to a greater extent. The electrochemical study reveals that the redox potentials of NPDI 1�4 derivatives shifted toward the anodic side due to the strong electron-withdrawing nature of the NO2-PDI moiety. The spectroelectrochemical analysis revealed the absorption spectra shifted toward the bathochromic region during the reduction cycles, while a hypochromic shift occurred during the oxidation cycles. Nanosecond transient absorption spectral studies show that for the compounds containing strong electron donors (such as PTZ), either a short triplet state lifetime (?T�=�0.47��s for NPDI2) or no ISC was observed (NPDI4). For the compounds with moderate or no electron donor attached in the molecular structure, long triplet state lifetimes were observed (?T�=�86.9��s for NPDI1 and ?T�=�47.8��s for NPDI3). For the compounds lacking ISC ability, an intermolecular triplet photosensitizing method, and long triplet state lifetimes were observed (?T�=�46��s for NPDI4). � 2026 Wiley-VCH GmbH.