Photoinduced Electron Transfer from Aromatic Aldehyde Hydrazones to Triplet States of C60 and C70; Electron-Mediating and Hole-Shifting Systems

Abstract

Photoinduced electron transfer of fullerenes such as C60 and C70 in the presence of aromatic aldehyde hydrazones (AAH’s) has been studied by the nanosecond laser photolysis which measures the transient absorption spectra in the visible and near-IR regions. Electron-transfer takes place from AAH’s to the triplet states of fullerenes; the rates and efficiencies of electron transfer are strongly affected by the electron-donor ability of AAH’s as evaluated by their oxidation potentials. The absorption bands of the radical cations of AAH’s appeared in the near-IR reagion, indicating that the radical-cation center (hole) delocalizes in the entire region of each AAH. On addition of a viologen dication to C60/C70–AAH, the electron of the anion radical of fullerenes moves to viologen dication yielding the viologen radical cation. In the systems of octaethyl porphyrinatozinc (ZnOEP)–C60/C70–AAH, the hole shift was observed from the radical cation of ZnOEP, which was produced by photoinduced electron transfer from the triplet state of ZnOEP to C60/C70, to AAH.

Generation of long-lived radical ions through enhanced photoinduced electron transfer processes between [60]fullerene and phenothiazine derivatives

“…• − to HV 2+ , which is referred to as the electron-mediating process. 8 The E red of HV 2+ (−0.40 V vs. SCE) also suggests that this process occurs irreversibly because this is an exothermic reaction (ca. 0.3 eV).…”

“…25 Furthermore, we investigate the role of hexylviologen dication (HV 2+ ) in addition to the photoinduced electron-transfer systems of C 60 and phenothiazines, because viologen dications are known as efficient electron mediating reagents. 8 We anticipate that the long-lived hexylviologen radical cation (HV • + ) will be generated due to the electron mediation process from C 60…”

Photoinduced Electron Transfer and Electron‐Mediating Systems of [60]Fullerene and Triphenylamine Derivatives in the Presence of Viologen Dication in Polar Solvent

“…The absorption spectra of the radical cations of TPA's were observed by the stepwise addition of FeCl 3 to the TPA's solutions. 15 Transient absorption spectra in the visible and near-IR regions were obtained by using a laser-flash photolysis apparatus. In the systems of C 60 -TPA and C 60 -TPA-HV 2+ , C 60 was excited with the SHG (532 nm) light of a Nd:YAG laser (Quanta-Ray; 6 ns fwhm).…”

“…[11][12][13] As one of the routes of photoinduced electron-transfer processes of fullerenes in the presence of aromatic amines, it has been reported that fullerenes in the excited states accept electrons from the ground states of electrondonors. [14][15][16] The relative contribution of the singlet states and the triplet states of fullerenes to the photoinduced electron-transfer process varies with concentration of electron-donors. 17 In the present study, we employed three aromatic amines such as triphenyl amine (TPA), tri-p-tolylamine (TTA), and 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC) (structures are shown in Scheme I).…”

“…Furthermore, we investigate the role of hexylviologen dication (HV 2+ ) by adding to the photoinduced electron-transfer reaction systems of C 60 and amines, because HV 2+ is known as an efficient electron mediating reagent. 15 We anticipate that long-lived hexylviologen radical cation (HV ·+ ) will be generated due to electron mediation process from C 60 ·-to HV 2+ . Furthermore, in the presence of 1-ben- …”