Article

Electron transfer at the single-molecule level in a triphenylamine-perylene imide molecule.

Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium.
ChemPhysChem (Impact Factor: 3.36). 06/2005; 6(5):942-8. DOI: 10.1002/cphc.200400567
Source: PubMed

ABSTRACT Photoinduced electron transfer (ET) processes in a donor-acceptor system based on triphenylamine and perylene imide have been studied at the single-molecule (SM) and ensemble levels. The system exists as two isomers, one of which undergoes forward and reverse ET in toluene with decay constants of 3.0 and 2.2x10(9) s(-1), respectively, resulting in the dual emission of quenched and delayed fluorescence while the other isomer remains ET-inactive. The fluorescence of both isomers is heavily quenched in the more polar solvent, diethyl ether, by ET. A broad range of ET dynamics is seen at the SM level in polystryene with the two isomers nonresolvable indicating that the local nanoenvironment of the SMs varies considerably throughout the polymer matrix. Both the electronic coupling and the driving force for ET are shown to influence the ET dynamics. Many fluorescence trajectories of SMs show long periods (tens of milliseconds to seconds) where the count rate is attenuated either partly (a "dim" state) or to the background level (an "off-time"). During these periods, the reduction or interruption of emission is attributed to cycles of rapid charge separation followed by charge recombination to the ground state reducing the fluorescence quantum yield of the SM.

0 Bookmarks
 · 
113 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report the synthesis, self-assembly characteristics, and ultrafast electron transfer dynamics of a perylene-3,4-dicarboximide (PMI) covalently linked to an N,N′-bis(3,4,5-tridodecyloxyphenyl)melamine electron donor (D) via a biphenyl spacer (PMI-Ph2-D). Synchrotron-based small- and wide-angle X-ray scattering (SAXS/WAXS) measurements in methylcyclohexane solution show that PMI-Ph2-D self-assembles into π–π stacked, hydrogen-bonded foldamers consisting of two or three hexameric rings or helices. Ultrafast transient absorption spectroscopy reveals that photoinduced charge separation within these nanostructures occurs by a unique pathway that is emergent in the assembly, whereas electron transfer does not occur in the PMI-Ph2-D monomers in tetrahydrofuran.
    Journal of Physical Chemistry Letters 12/2012; 3. · 6.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Extremely pure polymer matrices were used for elucidating the fluorescence properties of singly isolated charge-transfer (CT) complexes formed between the donor N-ethylcarbazole and the acceptor 1,2,4,5-tetracyanobenzene. Simultaneous measurements (time traces of CT fluorescence intensities and lifetimes) using single-molecule fluorescence spectroscopy showed three patterns: (1) fluctuations in the fluorescence intensities and lifetimes seldom occurred, (2) the fluorescence intensities frequently fluctuated together with the lifetimes, or (3) in addition to the above fluctuations with time, blinking and/or off-states longer than 1 s were observed. For methacrylate polymers, both the degree of fluctuations in the CT fluorescence lifetimes and the percentage of the CT complexes showing off-states increased with the free volume of the host polymers. These results suggest that the degree of fluctuations in the relative geometrical arrangements of the donor and acceptor molecules is related to the availability of space in the host polymer, and that the free volume provides the necessary space for formation of non-fluorescent donor–acceptor geometries of the CT complexes and/or temporal dissociation of the CT complexes. Survival times of the CT fluorescence were also closely related with the free volume of the host polymers.
    Journal of Photochemistry and Photobiology A Chemistry 01/2012; 227(1):65–70. · 2.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the present study we report on the linear and nonlinear optical properties of C60–triphenylamine (TPhA) hybrids. The synthesized materials were prepared following the 1,3-dipolar cycloaddition of azomethine ylides onto the skeleton of C60 forming the TPhA-based monoadduct, equatorial bis-adduct and dumbell C60. Complementary spectroscopic techniques, such as NMR, MALDI-TOF-MS, and ATR-IR are applied for the structural characterization of the hybrid materials, while intermolecular electronic interactions are investigated by UV-Vis measurements. In all considered cases, C60 serves as an acceptor while the triphenylamine unit is chosen as a donor. In order to investigate the dependence of the second-order hyperpolarizability on the architecture of the systems (D–A, A–D–A) we use a Z-scan technique employing 532 nm, 35 ps laser pulses. We have found that the total second-order hyperpolarizability of the C60–TphA–C60 system is several times larger than that of TPhA–C60. The results of experimental measurements are supported by quantum-chemical calculations.
    Physical Chemistry Chemical Physics 01/2010; 12(2). · 4.20 Impact Factor

Full-text (2 Sources)

Download
69 Downloads
Available from
Jun 5, 2014