C₆₀ as a Photocatalyst of Electron-Transfer Processes:  Reactions of Triplet C₆₀ with Chloranil, Perylene, and Tritolylamine Studied by Flash Photolysis and FT-EPR

Abstract

Photoprocesses in benzonitrile solutions of C60 and chloranil (CA) have been studied by complementary techniques of nanosecond laser photolysis and Fourier transform EPR. Direct oxidation of 3C60 by CA is slow (k = (2.0 ± 0.3) × 107 M-1 s-1), consistent with the high oxidation potential of 3C60. However, the formation rate and yield of CA- are much increased by addition of perylene (Pe) or tritolylamine (TTA) via the fast reactions 3C60 + Pe → C60 + 3Pe, followed by 3Pe + CA → Pe+ + CA-, or 3C60 + TTA → C60 - + TTA+, followed by C60 - + CA → C60 + CA-. These reactions utilize the broad absorption and initial high triplet yield of C60, as well as the low oxidation potential of 3Pe or high reduction potential of 3C60, to catalyze efficient formation of CA- and enhance separation of radicals. Triplet C60 also reacts with Pe by electron transfer, forming Pe+ and C60 - with rate one-third that of energy transfer. However, the CA- formed in the Pe-catalyzed reaction is strongly spin-polarized, indicating that it is formed primarily via the 3Pe pathway. The extinction coefficient of C60 - at 1080 nm is measured (ε = 18 300 ± 1100 M-1 cm-1) using the TTA reaction.

Photoinduced Electron Transfer from Nitoxide Free Radicals to the Triplet State of C60

“…20 The ratios show the saturation upon increasing the concentration of the free radicals, as shown in Figure 6. 19,20 At sufficiently high concentrations of the free radicals above ca.…”

“…Finally, the electron-transfer rate constants (k et ) are obtained from k et ) Φ et k q as listed in Table 2. 20 The k et values are considerably smaller than the diffusion-controlled limit (k diff ) 5.2 × 10 9 M -1 s -1 in PhCN), 21 although the ∆G°e t values calculated from the Rehm-Weller equation are all sufficiently negative (Table 1) to predict the diffusion-controlled secondorder rate constants for the electron-transfer processes.…”

The use of a photoinduced electron-transfer reaction for optical limiting in fullerene-containing solutions

“…The addition of TMB resulted in the appearance and a considerable increase in limitation with an increase in the concentration of the additive. Evidently, the limitation observed can be considered as evidence for the formation of the ë 60 radical anion, which strongly absorbs radiation at the excitation wavelength ( ε ≅ 18000 l mol -1 cm -1 [16]). In this case, the formation of can be due only to two-photon absorption in accordance with scheme (2), since ë 60 does not exhibit absorption from the ground state in the given spectral region.…”

“…The probable course If this solution were used for the limitation of firstharmonic radiation from a YAG : Nd 3+ laser, it would be a more efficient limiter than a solution without Per additives. The Per radical cation, whose absorption band maximum lies in the region 535-545 nm ( ε ≅ 50 000 l mol -1 cm -1 [15,16]), is also a product of reaction (3). Because of this, this solution is also promising in terms of the limitation of second-harmonics radiation from a YAG : Nd 3+ laser.…”

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

“…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). These amines are considered to be interesting electron donors; [18][19][20] especially, TAPC includes two triphenyl amine moieties in the same molecule. 9,10 It has been reported that TAPC shows high hole mobility (10 -2 cm 2 /Vs) in vapor deposited thin films, [21][22][23] photoconducting properties, 8 and charge-generating and hole-transporting properties in electroluminescence devices.…”