Detection of a Single Dendrimer Macromolecule with a Fluorescent Dihydropyrrolopyrroledione (DPP) Core Embedded in a Thin Polystyrene Polymer Film

Design, synthesis, and application in OFET of a small molecule based on π-expanded fused diketopyrrolopyrrole

Diketopyrrolopyrrole (DPP) and its derivatives, as electron deficient units, are widely used as building blocks in organic field-effect transistors, obtaining high performance. However, further modification of the DPP structure is crucial for the development of organic semiconductors. In this work, an FDPP is synthesized and characterized. The results show that FDPP exhibited not only a good planar core structure with a good conjugation system, but also strong aggregation in the solid state. As a consequence, FDPP presents p-type behavior with a hole mobility of ∼9.7 × 10-3 cm2 V-1 s-1. This study suggests that FDPP is a promising electron deficient unit for high performance semiconductors.

Centrosymmetric Thiophenemethyleneoxindole-Based Donor-Acceptor Copolymers for Organic Field-Effect Transistors

Two novel, donor-acceptor-type π-conjugated polymers (P1 and P2) with 3'-(thieno[3,2-b]thiophene-2,5-diylbis(methan-1-yl-1-ylidene))bis-(indolin-2-one) (ITTI) as the acceptor and thiophene/bithiophene as the donor are designed and synthesized by palladium-catalyzed Stille coupling. The optical and electrochemical properties of these polymers are characterized and further implemented into organic field-effect transistors (OFET). Both polymers exhibit excellent thermal stability, broad UV-vis absorption, and high highest occupied molecular orbital energy levels. Thermal annealing induces a well-ordered structure, a highly planar π-system (oxygen-sulfur interaction), and a bathochromic shift in the polymers; furthermore, significant enhancement of the long wavelength intensity is also observed. Both polymers exhibit p-type charge transport behavior, with hole mobilities up to 0.51 cm² V^-1 s^-1 for P1 and 0.65 cm² V^-1 s^-1 for P2. This work demonstrates that ITTI can be a promising building block for the construction of donor-acceptor polymers with high-performance OFETs.

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

Research activities in the field of diketopyrrolopyrrole (DPP)-based polymers are reviewed. Synthetic pathways to monomers and polymers, and the characteristic properties of the polymers are described. Potential applications in the field of organic electronic materials such as light emitting diodes, organic solar cells and organic field effect transistors are discussed.

Simultaneous Measurement of Orientational and Spectral Dynamics of Single Molecules in Nanostructured Host−Guest Materials

Nanostructured host-guest materials are important for various applications in nanoscience, and therefore, a thorough understanding of the dynamics of the guest molecules within the host matrix is needed. To this aim we used single-molecule fluorescence techniques to simultaneously examine the spectral and the orientational behavior of single molecules in nanostructured porous host materials. Two types of host-guest systems have been investigated. First, oxazine-1 dye molecules were fixed rigidly in the channels of microporous AlPO4-5 crystals. Second, it was shown that terrylenediimide (TDI) dye molecules move in the mesoporous network of an uncalcined M41S thin film. In the first sample both spectral fluctuations ( approximately 5 nm) and rare spectral jumps (>10 nm) of the emission maximum were observed. However, the orientation of the emission dipole of the dye molecules remained constant. In contrast, the second system showed orientational dynamics as well as substantially more spectral dynamics. In this system the molecules were found to move between different regions in the host. The typical motion of the TDI molecules in the pores of M41S was not continuous but characterized by jumps between specific sites. Moreover, the spectral and orientational dynamics were correlated and arose directly from the different environments that were being explored by the mobile molecule.

Revealing competitive Forster-type resonance energy-transfer pathways in single bichromophoric molecules

We demonstrate measurements of the efficiency of competing Förster-type energy-transfer pathways in single bichromophoric systems by monitoring simultaneously the fluorescence intensity, fluorescence lifetime, and the number of independent emitters with time. Peryleneimide end-capped fluorene trimers, hexamers, and polymers with interchromophore distances of 3.4, 5.9, and on average 42 nm, respectively, served as bichromophoric systems. Because of different energy-transfer efficiencies, variations in the interchromophore distance enable the switching between homo-energy transfer (energy hopping), singlet-singlet annihilation, and singlet-triplet annihilation. The data suggest that similar energy-transfer pathways have to be considered in the analysis of single-molecule trajectories of donor/acceptor pairs as well as in natural and synthetic multichromophoric systems such as light-harvesting antennas, oligomeric fluorescent proteins, and dendrimers. Here we report selectively visualization of different energy-transfer pathways taking place between identical fluorophores in individual bichromophoric molecules.

Energy transfer within perylene-terrylene dendrimers evidenced by polychromatic transient absorption measurements

The time dependent spectral properties of a first and a second generation dendrimer with peryleneimide chromophores at the rim and a terrylenediimide chromophore in the core were investigated by time resolved polychromatic transient absorption measurements. The obtained results of the dendritic structures were compared with those of three model compounds. In the perylene-terrylene dendrimers a very fast energy transfer process was observed. Besides energy transfer singlet-singlet annihilation could be observed. It could be concluded that competition between the rates of energy transfer and of singlet-singlet annihilation is dependent on the dendrimer generation.

Generation dependent singlet–singlet annihilation within multichromophoric dendrimers studied by polychromatic transient absorption

Intramolecular kinetic processes in a series of shape-persistent meta- and para-substituted polyphenylene dendrimers bearing different peryleneimide chromophores at the rim have been investigated using time-resolved polychromatic transient absorption measurements. The influence of the generation number and different substitution patterns upon these processes was revealed by comparing different compounds. In particular, in multichromophoric systems a singlet-singlet annihilation process was detected. The corresponding time constant was dependent on the generation number.