Excited Doublet States of Electrochemically Generated Aromatic Imide and Diimide Radical Anions

Abstract

The radical anions of aromatic diimides have been implicated recently in a wide variety of photochemical electron transfer reactions. Photoexcitation of these radical anions produces powerfully reducing species. Yet, the properties of the π* excited doublet states of these organic radical anions remain obscure. The radical anions of three aromatic imides with increasingly larger π systems, N-(2,5-di-tert-butylphenyl)phthalimide, 1, N-(2,5-di-tert-butylphenyl)-1,8-naphthalimide, 2, and N-(2,5-di-tert-butylphenyl)perylene-3,4-dicarboximide, 3, as well as the three corresponding aromatic diimides, N,N ‘-bis(2,5-di-tert-butylphenyl)pyromellitimide, 4a, N,N ‘-bis(2,5-di-tert-butylphenyl)-naphthalene-1,8:4,5-tetracarboxydiimide, 5a, and N,N ‘ -bis(2,5-di-tert-butylphenyl)perylene-3,4:9,10-tetracarboxydiimide, 6, were produced by electrochemical reduction of the neutral molecules in an optically transparent thin layer electrochemical cell. The radical anions of these imides and diimides all exhibit intense visible and weaker near-IR absorption bands corresponding to their D0 → D n transitions. Excited states of the radical anions were generated by subpicosecond excitation into these absorption bands. Excitation of 1 •- and 2 •- resulted in decomposition of these radical anions, whereas excitation of 3 •-−6 •- yielded transient spectra of their D1 → D n transitions and the lifetimes of D1. The lifetimes of the D1 excited states of the radical anions of 3 •-−6 •- are all less than 600 ps and increase as the D0−D1 energy gap increases. These results impose design constraints on the use of these excited radical anions as electron donors in electron-transfer systems targeted toward molecular electronics and solar energy conversion.

Wire-like charge transport at near constant bridge energy through fluorene oligomers

“…Microelectrode techniques with a 10-m platinum working microelectrode were used to obtain oxidation potentials for the fluorene oligomers in toluene at 40°C containing 0.1 M tetra-n-hexylammonium perchlorate (27). Redox potentials for N-phenylphenothiazine (28) and perylene-3,4:9,10-bis(dicarboximide) (PDI) (29) have been reported. All electrochemical measurements are summarized in Table 1.…”

Anthraquinones as Photoredox Catalysts for the Reductive Activation of Aryl Halides

“…[28] Although the radical anions of quinone derivatives are common intermediates in natural and synthetic photochemical energy storage, [16,30] they have not yet been applied in photoredox catalytic reductive transformations. As the excited states of radical anions act as powerful reductants, [12,13,28,29,31] we en- [40] In the inset, the luminescence spectrum (λ Ex = 427 nm) of Aq-OH-H -is shown. For the formation of the radical anion and the semiquinone anion of Aq-OH upon photoirradiation in the presence of Et 3 N, see Figure 3. visioned that anthraquinone derivatives could be employed for the photoredox catalytic reduction of aryl halide substrates, including aryl chlorides, to obtain aryl radicals either for metalfree dehalogenation reactions [12,[32][33][34][35] or for synthetically important carbon-carbon [12,32,[36][37][38] bond-formation reactions.…”

A new donor–acceptor double‐cable carbazole polymer with perylene bisimide pendant group: Synthesis, electrochemical, and photovoltaic properties

“…6). 19 The peaks at 482 and 521 nm were observed in the neutral polymer film. Upon applying potential between À0.56 and À0.72 V, new absorption peaks were observed at 564, 718, and 804 nm attributed to monoanion radicals of the poly-Cbz-PDI.…”

“…18 These molecules have been widely used in electron transfer studies because they undergo reversible one-electron reduction at modest potentials to form stable radical anions. 19 The main configuration of the OSCs is the bulk heterojunction structure, where the photoactive layer of the cell consists of an interpenetrating network of a p-conjugated p-type polymer and soluble n-type molecule, usually fullerene derivative. 8 But this system has some problems that have to be taken into consideration.…”