Photoinduced electron transfer between metal octaethylporphyrins and fullerenes (C60/C70) studied by laser flash photolysis: electron-mediating and hole-shifting cycles

Abstract

Electron transfer (ET) processes of fullerenes (C 60 /C 70 ) with metal octaethylporphyrins (MOEP) in a polar solvent have been investigated by a nanosecond laser photolysis technique in the visible/near-IR regions. By the selective excitation of C 60 /C 70 using OPO laser light it has been proved that electron transfer takes place from the ground states MOEP to the triplet excited states 3 C 60 */ 3 C 70 *. By selective excitation of MOEP the electron transfer processes via 3 MOEP* to C 60 /C 70 were also confirmed. In nonpolar toluene the lifetimes of 3 C 60 */ 3 C 70 * decreased in the presence of MOEP without evidence for electron and/or energy transfer processes. On adding benzonitrile to toluene the ion-radical formation was increased, suggesting that the triplet exciplexes 3 [MOEP (d+) -C 60 (dÀ) /C 70 (dÀ)]* would be dominant prior to the ion-pair formation in a less-polar solvent. On addition of a viologen dication the electron of the anion radicals of C 60 /C 70 transfers to the viologen dication yielding the viologen radical cation. In the system MOEP-C 60 /C 70 -aromatic amine (DTQH), as a second donor having lower oxidation potential than MOEP, the hole shift from the radical cation of MOEP to the aromatic amine was observed. These observations proved that the photosensitized electron-transfer/electron-mediating and photosensitized electron-transfer/hole-shift cycles have been confirmed by the transient absorption spectral method.

Recent Advances in Photoinduced Electron Transfer Processes of Fullerene-Based Molecular Assemblies and Nanocomposites

“…Usually in polar solvents, a mixture of pristine C 60 and zinc or magnesium porphyrins (ZnP or MgP) shows intermolecular electron transfer by visible light illumination, giving their radical anion (C 60 − ) and radical cation (MP + ), respectively, as revealed directly by the transient absorption spectral measurements [34,35]. This is also recognized when C 60 is functionalized with imidazole (C 60 Im) or pyridine (C 60 Py) entities; that is, they undergo intermolecular electron transfer as revealed by the slow rises of the C 60 − Im at 1,000 nm and MP + at 620 nm as shown in the transient absorption spectra and their time-profiles in polar solvents such as PhC≡N (Figure 2b) [36][37][38].…”

Photophysical properties of {[Ag(CN)2]−}2complexes trapped in a supramolecular electron-acceptor organic framework

“…38 The strong electron accepting potential of viologens make them very strong fluorescence quenchers for triplet MLCT luminescence producing interactions. [53][54][55][56][57][58] Quenching of the luminescence of several gold(I) complexes by different viologen derivatives has also been reported. 59 Powell and collaborators have published solid-state studies on the supra-molecular complexes formed between the viologen derivative (DNP)Cl 2 and dicyanoaurate and hexacyanoferrate.…”

The Process of Functional Conjugated Organic Polymers Derived from Triple‐Bond Building Blocks

“…It was well known that a number of linear dyads, triads, tetrads, etc (i.e., covalent and non‐covalent) that combine porphyrins/metalloporphyrins with a fullerene link have been elegantly designed and studied 38. Photoinduced electron‐transfer systems based on fullerenes and porphyrins have been accomplished for revealing basic electron‐transfer processes by Ito's group 38a, 39–51. For example, the photochemical and electrochemical properties of four chlorin‐C60 or porphyrin‐C60 dyads as shown in Figure 4 that have the same short spacer between the macrocycle and the fullerene were examined 45.…”