Structure‐Dependent Photoinduced Electron Transfer in Fullerodendrimers with Light‐Harvesting Oligophenylenevinylene Terminals

Abstract

Oligophenylenevinylene (OPV)-terminated phenylenevinylene dendrons G1-G4 with one, two, four, and eight "side-arms", respectively, were prepared and attached to C60 by a 1,3-dipolar cycloaddition of azomethine ylides generated in situ from dendritic aldehydes and N-methylglycine. The relative electronic absorption of the OPV moiety increases progressively along the fullerodendrimer family C60G1-C60G4, reaching a 99:1 ratio for C60G4 (antenna effect). UV/Vis and near-IR luminescence and transient absorption spectroscopy was used to elucidate photoinduced energy and electron transfer in C60G1-C60G4 as a function of OPV moiety size and solvent polarity (toluene, dichloromethane, benzonitrile), taking into account the fact that the free-energy change for electron transfer is the same along the series owing to the invariability of the donor-acceptor couple. Regardless of solvent, all the fullerodendrimers exhibit ultrafast OPV-->C60 singlet energy transfer. In CH2Cl2, the OPV-->C60 electron transfer from the lowest fullerene singlet level ((1)C60*) is slightly exergonic (deltaG(CS) approximately = 0.07 eV), but is observed, to an increasing extent, only in the largest systems C60G2-C60G4 with lower activation barriers for electron transfer. This effect has been related to a decrease of the reorganization energy upon enlargement of the molecular architecture. Structural factors are also at the origin of an unprecedented OPV-->C60 electron transfer observed for C60G3 and C60G4 in apolar toluene, whereas in benzonitrile, electron transfer occurs in all cases. Monitoring of the lowest fullerene triplet state by sensitized singlet oxygen luminescence and transient absorption spectroscopy shows that this level is populated through intersystem crossing and is not involved in photoinduced electron transfer.

Fullerene C60–Perylene‐3,4:9,10‐bis(dicarboximide) Light‐Harvesting Dyads: Spacer‐Length and Bay‐Substituent Effects on Intramolecular Singlet and Triplet Energy Transfer

“…[11] Consequently, competition between energyand electron-transfer in a functionalized electron-donorfullerene dyad has to be carefully considered in designing new systems for photovoltaic applications. In many examples it was shown that efficient photoinduced electron transfer from a donor such as oligophenylenevinylene, [12] oligothiophene [13] or perylene [14] to fullerene C 60 was the main pathway, whereas energy transfer could appear as a competitive process. [15] Following the observation of the very fast photoinduced electron transfer occurring on the subpicosecond timescale from conducting polymers to C 60 , [16] a major breakthrough towards efficient organic photovoltaic devices was realized with the development of the bulk-heterojunction concept.…”

Photochemical Conversion of Solar Energy

“…[109] OPV units are also increasingly used to obtain photoactive dendrimers. [110] Energy transfer in single OPV vesicles, [111] chiral co-assemblies of hydrogen-bonded OPV and porphyrin, [112] and self-assembled OPV functionalized with perylene-bisimide units [113] have been recently investigated.…”

Convenient Access to Acyl‐Substituted Bis(styrylbenzenes) Based on Building Blocks Using Julia Olefination and Weinreb Amide Chemistry

“…This route involved acetal protection [11] of one of the aldehyde groups in terephthalaldehyde 12 to give monoprotected aldehyde 13, which then underwent a reduction to give alcohol 14a [12] in 80 % yield. This route involved acetal protection [11] of one of the aldehyde groups in terephthalaldehyde 12 to give monoprotected aldehyde 13, which then underwent a reduction to give alcohol 14a [12] in 80 % yield.…”

“…The compounds 13, [11] 14a, [12] 30, [19] 31, [20] 32, [21] and 36 [22] are known in the literature.…”