Molecular Donor-Acceptor Dyads for Single-Material Organic Solar Cells.

A series of ambipolar covalently linked oligothiophene-fullerene dyads have been synthesized by systematical structural variations. In this respect, the length of linker between donor and acceptor unit was altered and in a second series the terminal acceptor units in the donor unit of the dyads were varied. Characterization of the optical and redox properties gave valuable structure-property relationships and were correlated to the photovoltaic performance in single-material organic solar cells, in which power conversion efficiencies of up to 4.3 % were reached.

Intracellular Photophysics of an Osmium Complex bearing an Oligothiophene Extended Ligand.

This contribution describes the excited-state properties of an Osmium-complex when taken up into human cells. The complex 1 [Os(bpy)2 (IP-4T)](PF6 )2 with bpy=2,2'-bipyridine and IP-4T=2-{5'-[3',4'-diethyl-(2,2'-bithien-5-yl)]-3,4-diethyl-2,2'-bithiophene}imidazo[4,5-f][1,10]phenanthroline) can be discussed as a candidate for photodynamic therapy in the biological red/NIR window. The complex is taken up by MCF7 cells and localizes rather homogeneously within in the cytoplasm. To detail the sub-ns photophysics of 1, comparative transient absorption measurements were carried out in different solvents to derive a model of the photoinduced processes. Key to rationalize the excited-state relaxation is a long-lived 3 ILCT state associated with the oligothiophene chain. This model was then tested with the complex internalized into MCF7 cells, since the intracellular environment has long been suspected to take big influence on the excited state properties. In our study of 1 in cells, we were able to show that, though the overall model remained the same, the excited-state dynamics are affected strongly by the intracellular environment. Our study represents the first in depth correlation towards ex-vivo and in vivo ultrafast spectroscopy for a possible photodrug.

Oligoprolines guide the self-assembly of quaterthiophenes.

Control over the molecular organization of π-conjugated oligothiophenes into different types of supramolecular assemblies is key to their use in organic electronics but difficult to achieve as these chromophores have a pronounced tendency to aggregate. Herein we show that oligoprolines, which do not self-assemble on their own, control the self-assembly of quaterthiophenes. Spectroscopic, microscopic, and diffraction studies with quaterthiophene-oligoproline conjugates revealed the formation of mono- or double-layered sheets or, alternatively, helically twisted ribbons - depending on the length of the oligoproline. The dimensions of the nanoscopic objects, which extend into the micrometer regime, correlate with the molecular dimensions of the quaterthiophene-oligoproline building blocks.

Self-organizing carbohydrate-oligothiophene-hybrids for eukaryotic membrane-labelling.

We report synthesis and photophysical characterization of d-(+) and l-(-) mannose terminated oligothiophene hybrids. In polar environment fluorescently quenched suprastructures were formed. Fluorescence was recovered by integration of the hybrids into phospholipidic bilayers of artificial vesicles as well as membrane compartments of myeloid cells, a defined hematopoetic lineage.

Chiral suprastructures of asymmetric oligothiophene-hybrids induced by a single proline.

Oligothiophene-proline hybrids were synthesized via click-reaction showing intriguing self-assembly behavior in an aqueous environment by forming chiral superstructures, whose helicity is controlled by the configuration of the amino acid moiety.

Mannose-functionalized dendritic oligothiophenes: synthesis, characterizations and studies on their interaction with Concanavalin A.

We have synthesized and characterized a series of dendritic oligothiophenes comprising peripheral mannose functionalities by copper-mediated 1,3-dipolar cycloaddition reaction. The hybrids were accessible either by attachment of acetyl-protected mannosides at the dendritic oligothiophene or by the direct synthesis of the deprotected mannose-oligothiophene conjugates by applying heterogeneous reaction conditions. The specific interaction of the functional dendritic hybrids with lectin protein Concanavalin A was investigated by absorption and fluorescence spectroscopic measurements. An enhancement of turbidity was observed due to the specific interaction of the mannosidic dendrimer with Con A. The specific interaction was further confirmed by fluorescence quenching upon addition of the mannosidic hybrid to Con A.

Self-organizing bioinspired oligothiophene-oligopeptide hybrids.

In this minireview, we survey recent advances in the synthesis, characterization, and modeling of new oligothiophene-oligopeptide hybrids capable of forming nanostructured fibrillar aggregates in solution and on solid substrates. Compounds of this class are promising for applications because their self-assembly and stimuli-responsive properties, provided by the peptide moieties combined with the semiconducting properties of the thiophene blocks, can result in novel opportunities for the design of advanced smart materials. These bio-inspired molecular hybrids are experimentally shown to form stable fibrils as visualized by AFM and TEM. While the experimental evidence alone is not sufficient to reveal the exact molecular organization of the fibrils, theoretical approaches based on quantum chemistry calculations and large-scale atomistic molecular dynamics simulations are attempted in an effort to reveal the structure of the fibrils at the nanoscale. Based on the combined theoretical and experimental analysis, the most likely models of fibril formation and aggregation are suggested.

Carbohydrate-functionalized oligothiophenes for concanavalin A recognition.

Versatile synthesis of fluorescent, carbohydrate-functionalized oligothiophene hybrids via Sonogashira-type cross coupling reactions is reported. The mannose derivatives reveal specific binding with the model lectin from Canavalia enisformis (Concanavalin A).

Self-assembling carbohydrate-functionalized oligothiophenes.

Carbohydrate-functionalized oligothiophenes have been synthesized applying mild Sonogashira cross-coupling conditions. In an aqueous environment the amphiphilic hybrids self-assemble into chiral superstructures as a result of multiple hydrogen bond interactions and the helicity of the aggregates is controllable by the configuration of the carbohydrate unit. By means of atomic force microscopy highly ordered layer arrangements on substrates were characterized.

Click-functionalization of conducting poly(3,4-ethylenedioxythiophene) (PEDOT).

Efficient post-functionalization of conductive polymer films was achieved by Cu(+)-catalyzed "click"-cycloaddition of novel poly(azidomethyl-EDOT) and various functionalized terminal alkynes under mild heterogeneous conditions with high conversion efficiencies.

Synthesis and conformational properties of 2,6-bis-anilino-3-nitropyridines.

The synthesis of 2,6-bis-anilino-3-nitropyridines that are alkylated or acylated at the anilino nitrogen atoms is described. These derivatives show characteristic differences in the 1H-NMR spectra compared with the unsubstituted parent compound. These differences are used to determine structure-conformation relationships of this type of compounds. The conclusions drawn from the 1H-NMR spectra in this respect are supported by X-ray crystallographic data and by 1H-NMR data of conformationally restricted analogues. Preliminary investigations indicate that these relationships can in principle be extended to other diarylamines.