Alexey Mavrinskiy

Fluorenyl Hexa‐peri‐hexabenzocoronene‐Dendritic Oligothiophene Hybrid Materials: Synthesis, Photophysical Properties, Self‐Association Behaviour and Device Performance

Apart from molecular properties, intermolecular forces play a vital role in defining the performance of organic electronic devices. This is particularly relevant in bulk heterojunction (BHJ) solar cells in which the arrangement of electron-donor and -acceptor materials into distinct crystalline phases of ideal size and distribution can lead to better power conversion efficiencies. In this study, a series of fluorenyl hexa-peri-hexabenzocoronenes (FHBC) decorated with thiophene dendrons (DOT) of variable size was obtained by using a convergent synthetic approach. With such variety of molecular sizes and shapes in hand, the objective of this study is to highlight the relationships between molecular properties, bulk properties and device performance. Correlations between π-π stacking ability and dendrimer generation were established from self-organisation studies in solution and solid state. The synergistic combination of molecular organisation at the nanoscale and photophysical characteristics derived from the FHBC and DOT moieties leads to a notable improvement of the photovoltaic performance.

Molecular Triangles: Synthesis, Self-Assembly, and Blue Emission of Cyclo-7,10-tris-triphenylenyl Macrocycles

A set of cyclo-7,10-tris-triphenylenyl macrocycles have been prepared by a Yamamoto cyclotrimerization protocol. In these novel macrocycles, three triphenylene units are covalently linked to each other, resulting in the formation of triangular-shaped molecules. The fully planar derivative revealed pronounced self-assembly behavior. NMR spectroscopy was used to determine the association constant in solution. 2D wide-angle X-ray scattering was applied to the study of the liquid crystallinity of this new discotic mesogen in the bulk state. Furthermore, nonplanar, laterally substituted derivatives were successfully tested as blue emitters in organic light-emitting diodes owing to their unique optoelectronic properties and their high stability. In this case, substitution with sterically demanding phenyl groups was efficiently used to suppress intermolecular packing, thus preventing undesired quenching effects.

Columnar Self‐Assembly in Electron‐Deficient Heterotriangulenes

A series of soluble carbonyl-bridged heterotriangulenes, in which flexible n-dodecyl chains are attached through different spacers to the planar nitrogen-centered polycyclic core, have been synthesized. The introduction of triisopropylsilylethynyl moieties enabled, for the first time, the characterization of single-crystal columnar packing of a substituted heterotriangulene by X-ray crystallography. Electrochemical studies disclosed the carbonyl-bridged heterotriangulene core as a reasonably strong acceptor for a reversible two-electron transfer. The tendency of substituted heterotriangulenes to self-assemble in solution, on surfaces, and in the bulk appeared to sensitively depend on the nature of the lateral substituents, their steric demand, and the applied solution processing conditions. It can be concluded that 1) additional phenylene moieties between the heterotriangulene core and the n-dodecyl chains facilitate self-assembly by extending the π-conjugated polycyclic disc, 2) the rod-like ethynylene spacers introduce some additional flexibility and hence lower the overall aggregation tendency, and 3) the combination of both features in the phenylene-ethynylene moieties induces thermotropic liquid crystallinity.

Synthesis and Self-Assembly of Macrocyclic Mesogens Based on 1,10-Phenanthroline

Over the past few years, great efforts have been directed to the design and synthesis of discotic liquid crystals based on macrocyclic compounds owing to their applications in organic electronics. Such structures consist of a relatively rigid and planar, or nearly planar, p-electron-rich core decorated by flexible aliphatic substituents that additionally enhance solubility. These molecules have the propensity to form supramolecular assemblies via p p interactions which give rise to three-dimensional nanostructures, guest–host complexes, and porous supramolecular architectures. 3] Among many nitrogen-containing macrocycles that have been used as building blocks for liquid crystals are a variety of derivatives of porphyrins and phthalocyanines, both free bases and metalated species. The incorporation of metals into liquid crystals (to form metallomesogens) results in new electrical and magnetic properties as well as modifies the mesomorphic behavior of the free ligand by stabilization or suppression of existing mesophases. The design and synthesis of new macrocycles with controllable supramolecular organization of discotic liquid crystals constitutes a major challenge in the search for functional materials with novel properties. The main difficulties in the tuning of the thermotropic behavior of these systems lie in balancing 1) the weak intermolecular interactions, such as p p stacking and hydrogen bonding, with 2) nano-segregation between rigid aromatic cores and peripheral soft alkyl chains. As part of our ongoing research on the design of advanced materials based on phenylene, carbazole, and fluorene macrocycles for discotic liquid crystals, which provide a degree of control over the intermolecular interactions, we became interested in the synthesis and investigation of the mesogenic properties of novel macrocycles based on the 1,10-phenanthroline framework. Phenanthroline derivatives are among the most widely studied chemical systems owing to their applications in the synthesis of herbicides, pharmaceuticals, and analytical probes as well as their relevance in optoelectronic devices. Structural features of this unit, such as planarity, rigidity, as well as intense fluorescence, render the phenanthroline core an ideal candidate as building block for applications in materials science. Furthermore, phenanthroline can form stable complexes with various dand f-block transition metals that leads to interesting magnetic, redox, and photophysical properties. 11,12] As such, the incorporation of 1,10-phenanthroline into liquid crystals provides the opportunity to combine the unique properties of this building block with those of liquid crystals. However, examples of mesomorphic metaland metal-free 1,10-phenanthroline systems are rare. This paucity can be attributed to the difficulties in the synthesis and purification as well as low solubility of the final products. Herein, we report the first successful synthesis of mesomorphic macrocycles, based on the 1,10-phenanthroline unit, that have alkoxy substituents on their peripheries. Their photophysical and thermotropic properties are studied by UV/Vis absorption and emission spectroscopy, differential scanning calorimetry (DSC), and two-dimensional wideangle X-ray scattering (2D WAXS) measurements. Our synthetic strategy is one-pot, concise and straightforward, and, [a] Dr. H. Norouzi-Arasi, Dr. W. Pisula, Dr. A. Mavrinskiy, Dr. X. Feng, Prof. Dr. K. M llen Max Planck Institute for Polymer Research Ackermannweg 10, 55128 Mainz (Germany) Fax: (+49) 6131-379-350 E-mail : norouzi@mpip-mainz.mpg.de muellen@mpip-mainz.mpg.de [] Present address: Evonik Degussa GmbH, Process Technology & Engineering, Process Technology New Processes Rodenbacher Chaussee 4, 63457 Hanau-Wolfgang (Germany) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201000642.

Electronic Properties and Supramolecular Organization of Terminal Bis(alkylethynyl)-Substituted Benzodithiophenes

Benzodithiophene (BDT) was symmetrically bisubstituted in the terminal positions with five different alkynes C≡C-(C(n)H(2n+1)) with n = 4, 6, 8, 10, 12. The materials were characterized as potential materials for field-effect transistor applications. Electrochemical measurements in solution and photophysical measurements in solution and in the solid state, together with UV photoelectron spectroscopy in air and quantum-chemical calculations, elucidate the nature of the frontier orbitals and of the excited states as well as their deactivation pathways. Structural information on the molecular assembly in the solid state, both at room temperature and at elevated temperatures, is obtained by a combination of DSC, polarized optical microscopy, and 2D-WAXS, which point to the crystallinity of the compounds in all phases and reveal π-stacking arrangements independently of the length of the alkyl side chains.

Electrochromic and liquid crystalline polycarbonates based on telechelic oligothiophenes

The triphosgene carbonate synthesis is adapted as a convenient route towards an alternating main-chain rod/coil polycarbonate based on a telechelic sexithiophene oligomer, yielding an electroactive polymer that is a vibrantly electrochromic material despite the conjugation break. This polymer displays morphological behaviour typical of a liquid-crystalline polymer, with stacking distances between chromophores suitable for potential charge transport applications.

Curvature as design concept for semiconducting benzodithiophene-containing polymers in organic field-effect transistors

Organic semiconductors are expected to play an important role in low-cost and energy-efficient electronic products, especially transistors. Our concept to improve the active materials is to introduce curvature into the polymer backbone. The beneficial contribution of the curvature is shown by a series of five isomeric polymers which demonstrate that an intermediate degree of curvature is the optimum compromise between good solubility and high order in the film. In this way, a polythiophene is developed that is easily synthesized, well soluble, exhibits high charge-carrier mobility using mild annealing conditions, and is stable under operation. When processed on a flexible substrate, it shows average mobilities as high as 0.5 cm2V-1s-1 .