Rigid Dendritic Donor−Acceptor Ensembles:  Control over Energy and Electron Transduction

Abstract

Several generations of phenylenevinylene dendrons, covalently attached to a C(60) core, have been developed as synthetic model systems with hierarchical, fine-tuned architectures. End-capping of these dendritic spacers with dibutylaniline or dodecyloxynaphthalene, as antennas/electron donors, yielded new donor-bridge-acceptor ensembles in which one, two, or four donors are allocated at the peripheral positions of the well-defined dendrons, while the electron accepting fullerene is placed at the focal point of the dendron. On the basis of our cyclic voltammetry experiments, which disclose a single anodic oxidation and several cathodic reduction processes, we rule out significant, long-range couplings between the fullerene core and the end-standing donors in their ground-state configuration. Photophysical investigations, on the other hand, show that upon photoexcitation an efficient and rapid transfer of singlet excited-state energy (6 x 10(10) to 2.5 x 10(12) s(-1)) controls the reactivity of the initially excited antenna portion. Spectroscopic and kinetic evidence suggests that yet a second contribution, that is, an intramolecular electron-transfer, exists, affording C(60)(.-) -dendron(.+) with quantum yields (Phi) as high as 0.76 and lifetimes (tau) that are on the order of hundreds of nanoseconds (220-725 ns). Variation of the energy gap modulates the interplay of these two pathways (i.e., competition or sequence between energy and electron transfer).

[60]Fullerene-based liquid crystals acting as acid-sensitive fluorescent probes

“…This result is consistent with an electron transfer process from the bis-(N,N-dibutylaminostyryl)benzene moiety to C 60 as previously observed in related systems. 12,13 No emission at 710 nm (ascribed to the fullerene cage) is observed under these conditions.…”

Tuning the reorganization energy of electron transfer in supramolecular ensembles – metalloporphyrin, oligophenylenevinylenes, and fullerene – and the impact on electron transfer kinetics

“…[19][20][21][22][23][24] As a further elaboration, electron donors, such as ferrocene etc. have been attached covalently to C 60 -oPPVs and the resulting conjugates have been probed by means of photophysical and electrochemical techniques.…”

Fullerene Derivatives Substituted with Differently Branched Phenyleneethynylene Dendrons: Synthesis, Electronic and Excited State Properties

“…Subsequent treatment with K 2 CO 3 in THF/MeOH gave terminal alkyne 9 in 91 % yield. The second generation dendron 10 was then obtained in 96 % yield by Pd-catalyzed cross-coupling between 9 and 3,5-dibromobenzaldehyde (2). Finally, reaction of 10 with C 60 and N-methylglycine in refluxing toluene gave C 60 -G2 in 52 % yield.…”

“…This compound was prepared from 2 (0.40 g, 1.52 mmol), 1 (2.14 g, 4.55 mmol), Pd(PPh 3 ) 2 General Procedure for the Preparation of G1, G2, Y1, and Y2: A 1  DIBAL-H solution in hexane was slowly added to a solution of the appropriate benzaldehyde in THF at 0°C under argon. After 3 h, methanol then water were added.…”

“…[1] Interestingly, their electronic properties can be easily tailored by either introducing various substituents, [2] changing the conjugation lengths of the different fragments within the dendritic shell, [3] or modulating the substitution pattern of the branching aromatic units. [4,5] The characteristic features of these compounds, such as large molar extinction coefficients and sometimes high fluorescence efficiencies, make them attractive photoactive components for the hybrid systems.…”