Photoinduced electron transfer from tetraethoxyethene to C60 and C70 studied by laser flash photolysis

Abstract

The electron transfer from tetraethoxyethene (TEOE), which has high electron-donor ability, to photoexcited C 60 or C 70 in polar and less polar solvents has been investigated by 532 nm laser flash photolysis with observation of the transient absorption bands in the near-IR region. The transient absorption bands of the triplet states of fullerenes ( T C 60 * and T C 70 *), which appeared immediately after nanosecond laser exposure, were effectively quenched by TEOE. With the decay of T C 60 * and T C 70 *, the absorption bands of C 60 Ϫ and C 70 Ϫ appeared at 1070 and 1380 nm, respectively, showing that the electron transfer takes place from TEOE to T C 60 * or to T C 70 *. Then, C 60 Ϫ and C 70 Ϫ disappear by back electron transfer to TEOE ϩ .The efficiencies and rates of the electron-transfer reactions vary with solvent polarity.

Selective One-Electron and Two-Electron Reduction of C60 with NADH and NAD Dimer Analogues via Photoinduced Electron Transfer

“…It is now well-known that the triplet excited state of C 60 is formed by efficient intersystem crossing. , The triplet excited state of C 60 has a reduction potential of E 0 red = 1.14 V versus SCE and can therefore be reduced by a variety of organic compounds giving the C 60 radical anion. ,, A long-lived transient of C 60 •- has been reported to be formed in photoinduced electron transfer from ZnO or TiO 2 semiconductor colloids to C 60 . In homogeneous systems, however, the lifetime of the generated C 60 •- is generally extremely short as a result of fast back electron transfer to the reactant pair, resulting in no net formation of C 60 •- . , We report herein that the photoinduced electron transfer from an NADH analogue, 1-benzyl-1,4-dihydronicotinamide (BNAH), and the dimer analogue [(BNA) 2 ] to the triplet excited state of C 60 ( 3 C 60 *) yields stable C 60 •- in benzonitrile solution with a surprisingly high quantum yield, exceeding unity in the latter case; Φ = 1.3. We also report the selective two-electron reduction of C 60 to the tert -butylated C 60 anion ( t -BuC 60 - ) and 1,2-dihydro[C 60 ]fullerene (1,2-C 60 H 2 ) via photoinduced electron transfer from 4- tert -butyl-1-benzyl-1,4-dihydronicotinamide ( t -BuBNAH) and 10-methyl-9,10-dihydroacridine (AcrH 2 ) to 3 C 60 *, respectively …”

Photoinduced Electron Transfer from Phthalocyanines to Fullerenes (C60 and C70)

“…Fullerenes such as C 60 and C 70 were known to accelerate the photoinduced electric conductivity when they are added into some molecules such as phthalocyanines and porphyrins. − In solutions and polymer films, the mechanisms of the photoinduced electron-transfer reactions of fullerenes have been investigated by photochemical techniques such as laser flash photolysis. − In the mixture system of C 60 (or C 70 ) with electron donors in polar solvents, C 60 •- and C 70 •- were usually produced via their triplet states ( T C 60 * and T C 70 *) which abstract the electron from the electron donors such as aromatic amines when the concentrations of electron donors are appropriately dilute. − For the C 60 compounds connected with chromophores by the covalent bonds, photoinduced electron transfer takes place via the singlet state of the chromophores. − …”

Laser Flash Photolysis Study of Photophysical and Photochemical Properties of a Higher Fullerene, C76

“…From the viewpoint of photochemistry, C 60 and C 70 are good electron acceptors and many photoinduced reactions have been reported by using these fullerenes as acceptors . For example, generations of adducts of C 60 have been observed in laser photolysis studies with anthracene 4a and with tetraethoxyethene 4b. It is also reported that doping of fullerenes to polymer films such as polyvinylcarbazole and poly( p -phenylene vinylene) results in the enhancement of photoconductivity …”