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A method for preparing carbon nanoparticles (CNPs) with controllable hierarchic structures is developed by combining the precursor-defined pyrolysis and the template method. Well-organized monodisperse CNPs, such as spherical particles with 3D porous structures (a), hollow carbon orbs containing small Pt particles (b), and graphitic microbeads with or without slits (c), are prepared by using structurally different precursors (see figure).

Novel polyphenylene–metal complexes with discotic, linear, and dendritic geometries are synthesized by using a facile approach consisting of reactions between Co₂(CO)₈ and ethynyl functionalities in dichloromethane. Various carbon nanoparticles (CNPs), including graphitic carbon nanotubes (CNTs), graphitic carbon rods, and carbon–metal hybrid particles are obtained from the solid-state pyrolysis of these complexes. The ultimate structures of the CNPs are found to be dependant on the structure and composition of the starting compounds. Precursors containing graphenes always result in graphitic CNTs in high yield, whereas dendritic precursors give rodlike carbon materials. Alternatively, linear oligo(arylethylene) precursors afford mostly carbon–metal hybrids with large amounts of amorphous carbon. Furthermore, the CNP structures could be controlled by adjusting the carbon/metal ratio, the type and position of the metal incorporated into the precursor, and the mode of pyrolysis. These results provide further chances toward understanding the mechanism of CNP formation.

The use of solvent-vapor annealing (SVA) to form millimeter-long crystalline fibers, having a sub-micrometer cross section, on various solid substrates is described. Thin films of a perylene-bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer-sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re-organize into long fibers that have a remarkably high aspect ratio, exceeding 10³. Time- and space-resolved mapping with optical microscopy allows the self-assembly mechanism to be unravelled; the mechanism is found to be a nucleation-governed growth, which complies with an Avrami-type of mechanism. SVA is found to lead to self-assembly featuring i) long-range order (up to the millimeter scale), ii) reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl₃ as solvents, iii) remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self-assembled architectures with pre-programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron-accepting character than the smaller needles of the drop-cast films. The giant fibers can be grown in situ in the gap between microscopic electrodes supported on SiO_x, paving the way towards the application of SVA in micro- and nanoelectronics.

The cover shows a fluorescence microscopy image of solvent-vapor annealed (SVA) films of an alkylated perylene-bis(dicarboximide), reported by Vincenzo Palermo, Klaus Müllen, Paolo Samorì, and co-workers on p. 3791. Upon exposure to tetrahydrofuran vapors, ultrathin films exhibiting needle-like structures rearrange into millimeter-long fibers, which have a sub-micrometer cross section. The SVA growth was found to be a nucleation-governed process leading to the formation of birefringent fibers on various substrates. (The result was obtained in the framework of the ESF-EUROCORES-SONS2-SUPRAMATES project.)

The use of solvent-vapor annealing (SVA) to form millimeter-long crystalline fibers, having a sub-micrometer cross section, on various solid substrates is described. Thin films of a perylene-bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer-sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re-organize into long fibers that have a remarkably high aspect ratio, exceeding 10³. Time- and space-resolved mapping with optical microscopy allows the self-assembly mechanism to be unravelled; the mechanism is found to be a nucleation-governed growth, which complies with an Avrami-type of mechanism. SVA is found to lead to self-assembly featuring i) long-range order (up to the millimeter scale), ii) reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl₃ as solvents, iii) remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self-assembled architectures with pre-programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron-accepting character than the smaller needles of the drop-cast films. The giant fibers can be grown in situ in the gap between microscopic electrodes supported on SiO_x, paving the way towards the application of SVA in micro- and nanoelectronics.

The synthesis, properties, and application in electronic devices of ladder and step-ladder phenylene-based oligomers and polymers are reviewed with an emphasis on control of properties by synthetic design. Bridged polyphenylenes can be prepared with a range of different amounts and types of bridges. Fully bridged polymers suffer the problem of incomplete formation of bridges during polymer analogous reactions. This problem is surmounted by the synthesis of regular stepladder polymers in which the monomers are well-characterized oligo(ladder-phenylene)s. By controlling the degree of bridging and thus the planarity of the polymer, its optical properties can be tuned. The optical and electronic properties can be further controlled by means of the type of bridges used.

A novel poly(p-phenylene) (6) has been synthesized by a cruciform combination of a polyphenylene backbone with 2,2′-(p-phenylene)-bis(4,5-diphenylimidazole) (5) as an additional, orthogonal chromophore. Polymer 6 showed in solution and in the solid state, a blue-green emission, which is obviously arising from the second bisimidazole-based chromophore. UV-Vis spectroscopy, and cyclic voltammetry revealed that the optical and electronic properties of 6 were fully determined by the incorporated 2,2′-(1,4-phenylene)bisimidazole structure. The bisimidazole unit led to high solubility and, despite the steric demand of the substituents, at the same time to the blue-green emission of the poly(p-phenylene) (6). In addition, the oxidation of 6 with potassium ferricyanide yielded a low bandgap polymer with a quinoid-type structure and a bandgap of 1.6 eV.

New polymer electrolyte membranes for fuel cell applications were synthesized via covalent bonding of phosphonic acid (PA) onto poly(benzimidazole) (PBI). PBI was functionalized via N-alkylation with an appropriate phosphonate, followed by hydrolysis of the grafted groups to the desired PA functions. Alternatively, polymer networks based on PBI and vinyl phosphonic acid (VPA) were successfully synthesized. In this second approach, PBI was first functionalized in a polymer analogous modification with polymerizable or radical-forming groups. Thermally induced ‘grafting-through’ or ‘grafting-from’ polymerization of VPA led to the corresponding PBI/PVPA networks. The structure-property relationships with respect to proton conducting properties of the membrane materials are discussed.

The ability of electric fields to align nonpolar semiconducting molecules was demonstrated using hexa(para-n-dodecylphenyl)hexabenzocoronene (HBC-PhC12) as a model compound. A solution of HBC-PhC12 was applied to a glass surface by drop-casting and the molecules were oriented into highly ordered structures by an electric field during solvent evaporation. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) showed a long-range alignment where the disclike molecules were organized in columns perpendicular to the direction of the imposed electric field. The high anisotropy of the uniaxially aligned films was characterized by cross-polarized light microscopy. The birefringence of the HBC-PhC12 films was related to the presence of extended domains of unidirectionally aligned columns in which the aromatic cores of the HBC-PhC12 molecules were perpendicular to the columnar axis. The packing and the arrangement of the molecules in the field-force ordered films were proven by electron diffraction and X-ray analyses.

Novel composites for supercapacitors: Carbon–Ru nanocomposites with mesoporous structures and homogeneously dispersed Ru nanoparticles in the carbon matrix (see SEM and TEM images), obtained by a simple pyrolysis procedure, display capacitive properties for supercapacitors.

A hexa-alkylether-substituted hexa-peri-hexabenzocoronene, as a discotic liquid crystal, spontaneously homeotropically self-orients when cooled from the isotropic phase. During this process, a dendritic morphology is formed in which a significant optical difference is observed between the dendritic shapes and their periphery. However, local structural analysis using microfocus synchrotron radiation experiments demonstrate that there is an identical supramolecular order in both areas. Three-dimensional confocal surface measurements reveal that these dendritic structures result from a dewetting process, which occurs during solidification. Thereby, the contact area between the organic material and the surface is reduced. These results are important for the design of organic electronics, since the reduction of the contact area in an electronic device might inhibit the charge transport between the discotic semiconductor and the electrode.

Two synthetic routes for the benzannulation in the “bay”-region of rylenebis(dicarboximide)s leading to new π-system-expanded chromophores are described. The first route follows a two-step approach: Suzuki coupling of bromo-substituted perylenebis(dicarboximide) with 2-bromophenylboronic acid, followed by palladium-catalysed dehydrobromination. The second route is best described as a palladium-assisted cycloaddition of benzyne, formed in situ, to the bay-region of the bromo-substituted rylene core. Two new types of core-expanded rylene dyes were synthesised: yellow dibenzocoronenebis(dicarboximide)s, absorbing at 490 nm, and a green dinaphthoquaterrylenebis(dicarboximide), which absorbs at 700 nm. These new chromophores are characterised by significant hypsochromic shifts of absorption, compared to their parent rylenebis(dicarboximide)s, excellent photostabilities and high fluorescence quantum yields.

Like two monkeys attacking a pineapple “bay”-positions of dibromorylene dyes are attacked by dehydrobenzene molecules (formed from trimethylsilylbenzene triflate with CsF). Pd⁰-catalyzed benzannulation affords novel core-expanded rylenebis(dicarboximides) bearing pentacene units in the aromatic core. Synthesized new chromophores are characterized by a significant hypsochromic shift of absorption (40–60 nm relative to parent dyes), excellent photostabilities, and high fluorescence quantum yields. The details of the study are presented in the Full Paper by K. Müllen et al. on page 6555 ff.

Triangles and zigzags: Large triangle-shaped C₃-symmetrical polycyclic aromatic hydrocarbons with multiple zigzag peripheries were synthesized. The molecules display mesophase stability over a wide temperature range as a result of helical packing. Moreover, a 2D honeycomb pattern was observed for one of the larger structures (see picture).

Current developments: The combination of a template method with electrochemical procedures has led to the controlled preparation of 1D nanoscale carbon/platinum electrodes with large surface areas and with small platinum nanoparticles homogeneously dispersed in the interconnected porous carbon matrix (see TEM images). The electrodes display excellent catalytic activities in the oxygen electroreduction.

Mind your PQPs: 1D nanostructures were fabricated by the self-assembly of amphiphilic centrally charged discotic 9-alkyl-2-phenylbenzo[8,9]quinolizino[4,5,6,7-fed]phenanthridinylium (PQP) salts. Increasing the alkyl chain length of the PQP salts resulted in nanoscaled lamellar structures, whereas changing the counterion of the PQP salts from Cl⁻ to BF₄⁻ led to a change from nanoribbons to helices and tubes.

Variable Steuerung: 1D-Nanostrukturen wurden durch die Selbstorganisation amphiphiler zentral geladener diskotischer 9-Alkyl-2-phenylbenzo[8,9]chinolizino[4,5,6,7-fed]phenanthridinylium(PQP)-Salze erhalten. Längere Alkylketten in den PQP-Salzen führten zu nanoskaligen lamellaren Strukturen, der Wechsel des Gegenions der PQP-Salze von Cl⁻ zu BF₄⁻ dagegen verwandelte die Nanobänder in Nanohelices und -röhren.

Hex, hex: Das gezeigte heteroatomstabilisierte, ringförmig anellierte Hexapyrrolohexaazacoronen wurde als Repräsentant einer neuen Klasse stickstoffhaltiger Moleküle mit ausgedehnten π-Systemen synthetisiert und isoliert. Sein reversibles Redoxverhalten, eine Folge der inneren N-Atome, lässt an Anwendungen in der organischen Elektronik denken.

The heteroatom-stabilized annularly fused hexapyrrolohexaazacoronene shown (N blue, F green) was synthesized and isolated as a representation of a new class of nitrogen-containing molecules with extended π systems. The reversible redox behavior, a consequence of the interior N atoms, hints at potential applications in organic electronics.

Dreiecke und Zickzackketten: Große C₃-symmetrische polycyclische aromatische Kohlenwasserstoffe mit Dreieckform und mehrfachen Zickzack-Peripherien wurden synthetisiert. Die Mesophasen der Moleküle sind als Folge der helicalen Packung über einen großen Temperaturbereich stabil. Des Weiteren wurde bei einer der größeren Strukturen ein zweidimensionales Wabenmuster beobachtet (siehe Bild).

Klein, aber fein: Die Kombination einer Templatmethode mit elektrochemischen Verfahren ermöglichte die gezielte Synthese von nanoskaligen eindimensionalen Kohlenstoff-Platin-Elektroden mit großen Oberflächen und kleinen Platinnanopartikeln, die homogen in der vernetzten porösen Kohlenstoffmatrix dispergiert sind (siehe TEM-Bilder). Die Elektroden zeigen eine ausgezeichnete katalytische Aktivität bei der Sauerstoff-Elektroreduktion.

A novel alkyl-substituted polycyclic aromatic hydrocarbon (PAH) with D_2h symmetry and 78 carbon atoms in the aromatic core (C78) was synthesized, thereby completing a homologous series of soluble PAH compounds with increasing size of the aromatic π system (42, 60, and 78 carbon atoms). The optical band gaps were determined by UV/Vis and fluorescence spectroscopy in solution. Scanning tunneling microscopy (STM) and spectroscopy (STS) revealed diode-like current versus voltage (I–V) characteristics through individual aromatic cores in monolayers at the interface between the solution and the basal plane of graphite. The asymmetry of the current–voltage (I–V) characteristics increases with the increasing size of the aromatic core, and the concomitantly decreasing HOMO–LUMO gap. This is attributed to resonant tunneling through the HOMO of the adsorbed molecule, and an asymmetric position of the molecular species in the tunnel junction. Consistently, submolecularly resolved STM images at negative substrate bias are in good agreement with the calculated pattern for the electron densities of the HOMOs. The analysis provides the basis for tailoring rectification with a single molecule in an STM junction.

Abstract

Two novel discotic macrocycles, substituted cyclohexa-m-phenylene (CHP) and cyclo-3,6-trisphenanthrylene (CTP), and the linear oligomer 3,3′:6′,3′′-terphenanthrene (TP) as a model substance have been synthesized by repetitive cross-coupling reactions. To correlate the molecular design with the supramolecular architecture and the established macroscopic order, 2D wide-angle X-ray scattering experiments were performed on mechanically extruded filaments. At room temperature in their crystalline phases, all three compounds revealed columnar assemblies in which the macrocycles self-organized by π-stacking interactions. The degree of macroscopic order was found to depend upon the planarity and stiffness of the aromatic core. The flexible CHP ring showed a poor macroscopic order of the columnar structures and a low isotropization temperature, whereas the more-planar, less-flexible CTP self-assembled into well-defined superstructures. The larger π-stacking area and the more-pronounced intermolecular interactions for CTP led to the formation of a mesophase over a very large temperature range. The surprising columnar organization of the “open” TP system was explained by back-folding of the molecule into a ringlike structure.

Nanoscale phase-segregated functional architectures can be formed both in monolayers at the solid/liquid interface and in the bulk by self-assembling electron-acceptor–electron-donor dyads and triads based on hexa-peri-hexabenzocoronene (HBC) and perylene monoimide (PMI). The figure shows charge transfer through the vertically segregated HBC and PMI channels in the bulk phase.

Controlling self-organization: The chemical variation of alkyl substituents on the discotic hexa-peri-hexabenzocoronene allows the molecular orientation to be controlled with respect to a substrate, which is a key prerequisite to implement such semiconductors into electronic devices (see figure). Charge-carrier mobility determined by a time-of-flight technique reveals a high anisotropy along and perpendicular to the established columnar superstructure.

Summary: A novel non-aqueous emulsion system, consisting of cyclohexane as the continuous and acetonitrile as the dispersed phase, is described. Stabilization of the system can be achieved by using polyisoprene-block-poly(methyl methacrylate) copolymers as emulsifiers. The suitability of this system for performing water-sensitive, catalytic, and oxidative polymerizations and polycondensations is demonstrated by the synthesis of poly(3,4-ethylenedioxythiophene), poly(thiophene-3-yl-acetic acid), and polyacetylene. In all cases spherical nanoparticles with diameters as small as 23 nm can be obtained.

First- and second-generation polyphenylene dendrimers were synthesized starting from benzophenone as core. Variation of the size and the density of the dendrimer shell resulted in different isolation of the cores. To investigate the effect of shielding upon the reactivity of the core, chemical functionalizations as well as the alkali-metal reduction of the encapsulated benzophenone core were performed. The herein presented synthetic concept opens the way to spatially well-defined spherical nanoparticles bearing a single isolated function in the center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The cover picture shows shape-persistent first- and second-generation polyphenylene dendrimers grown from a single benzophenone unit as core. To investigate the influence of the size and the density of the dendritic shell upon the reactivity of the core, “postsynthetic” chemical functionalizations with reagents of different size as well as alkali-metal reduction of the encapsulated benzophenone were performed. Details are discussed in the article by K. Müllen et al. on p. 2523 ff.

Summary: Light-emitting conjugated polyphenylenes and poly(phenyleneethynylene)s have been synthesized, which comprise of 9,10-linked anthracene repeat units with branched alkyl side-chains (2-octyldecyl) at the 2,6-positions with p-terphenyl (P1), p-diethynylbenzene (P2), and diphenylacetylene (P3) units. Both Sonogashira-Hagihara and Suzuki-Miyaura-type cross-coupling reactions under palladium catalysis were used as polycondensation methods. The branched alkyl side chains not only improve the solubility of the resulting copolymers but also prevent stacking in the solid state as evident from the almost identical PL spectra in solution and film. The copolymers P1 and P3 display pure blue emission while P2 exhibits green emission due to the extended π-system along the polymer backbone. All polymers possess high thermal stability and P1 shows the best solubility and film-forming ability among the three copolymers investigated. Furthermore, the enhanced color stability of this material is demonstrated by the almost identical PL spectra obtained on annealing at 200 °C.

Starting from the fourfold ethynyl-substituted chromophore 1,3,6,8-tetraethynylpyrene as core, a series of polyphenylene dendrimers was prepared in high yield by combining divergent and convergent growth methods. The fluorescence quantum yields (Q_f>0.92) of the encapsulated pyrene chromophore were independent of the size of the polyphenylene shell. Fluorescence quenching studies and temperature-dependent fluorescence spectroscopy were performed to investigate the site isolation of the core. They indicate that a second-generation dendrimer layer is needed to efficiently shield the encapsulated pyrene and prevent aggregate formation. Alkali-metal reduction of the encapsulated pyrene core was carried out to afford the corresponding pyrene radical anions, for which hampered electron transfer to the core was observed with increasing dendrimer generation, which is further proof of the site isolation due to the polyphenylene shell. To improve film formation and solubility of the material, solubilizing alkyl chains were introduced on the periphery of the spherical particles. Furthermore, highly transparent films obtained by a simple drop-casting method showed blue emission mainly from the unaggregated species. The materials presented herein combine high quantum efficiency, good solubility, and improved film-forming properties, which make them possible candidates for several applications in electronic devices.

Single-nucleotide polymorphisms (SNPs) are the most common form of DNA sequence variation. There is a strong interest from both academy and industry to develop rapid, sensitive and cost effective methods for SNP detection. Here we report a novel structural concept for DNA detection based on fluorescence dequenching upon hybridization. The so-called “twin probe” consists of a central fluorene derivative as fluorophore to which two identical oligonucleotides are covalently attached. This probe architecture is applied in homogeneous hybridization assays with subsequent fluorescence spectroscopic analysis. The bioorganic hybrid structure is well suited for sequence specific DNA detection and even SNPs are identified with high efficiency. Additionally, the photophysical properties of the twin probe were investigated. The covalent attachment of two single stranded oligonucleotides leads to strong quenching of the central fluorescence dye induced by the nucleobases. The twin probe is characterized by supramolecular aggregate formation accompanied by red-shifted emission and broad fluorescence spectra.

Round up: A fully conjugated cyclododeca-2,7-carbazole is prepared around a porphyrin template and the corresponding empty macrocycle then released. Single molecules could be visualized by STM (see image) and their arrangement by atomic force microscopy. The macrocycles self-assemble into a hexagonal array of columns. Efficient energy transfer occurs from the peripheral carbazole π system to the central porphyrin core.

Im Roten: Die Synthese und die optischen Eigenschaften homologer, im Nah-IR absorbierender Chromophore vom Leitertyp werden vorgestellt: von zwei Pentarylenbis(dicarboximiden) (grüne Spektren; siehe Bild) und einem Hexarylenbis(dicarboximid) (gelbes Spektrum). Wie die übrigen Spektren belegen, führt eine zunehmende Anellierung zu einer starken bathochromen Verschiebung des Absorptionsmaximums.

We describe a Kelvin Probe Force Microscopy (KPFM) study on the morphological and electronic properties of complex mono and bi-molecular ultrathin films self-assembled on mica. These architectures are made up from an electron-donor (D), a synthetic all-benzenoid polycyclic aromatic hydrocarbon, and an electron-acceptor (A), perylene-bis-dicarboximide. The former molecule self-assembles into fibers in single component films, while the latter molecule forms discontinuous layers. Taking advantage of the different solubility and self-organizing properties of the A and D molecules, multicomponent ultrathin films characterized by nanoscale phase segregated fibers of D embedded in a discontinuous layer of A are formed. The direct estimation of the surface potential, and consequently the local workfunction from KPFM images allow a comparison of the local electronic properties of the blend with those of the monocomponent films. A change in the average workfunction values of the A and D nanostructures in the blend occurs which is primarily caused by the intimate contact between the two components and the molecular order within the nanostructure self-assembled at the surface. Additional roles can be ascribed to the molecular packing density, to the presence of defects in the film, to the different conformation of the aliphatic peripheral chains that might cover the conjugated core and to the long-range nature of the electrostatic interactions employed to map the surface by KPFM limiting the spatial and potential resolution. The local workfunction studies of heterojunctions can be of help to tune the electronic properties of active multicomponent films, which is crucial for the fabrication of efficient organic electronic devices as solar cells.

Durch Mischen eines Hexa-peri-hexabenzocoronen(HBC)-Derivats mit einem Perylen- oder Terrylendiimid entstehen komplexe helicale Anordnungen in den kolumnaren Überstrukturen. Wegen der schwachen Donor-Acceptor-Wechselwirkungen zwischen dem elektronenreichen HBC und den elektronenarmen Rylen-Farbstoffen bilden sich streng alternierende, weitreichend geordnete Kolumnen. Die Mischungen zeigen eine homöotrope Orientierung auf Oberflächen (Beispiel siehe Bild).

Ring frei! Ein voll konjugiertes Cyclododeca-2,7-carbazol wurde um ein Porphyrin-Templat synthetisiert und im Anschluss der leere Makrocyclus (vorn im Bild) freigesetzt. Einzelmoleküle wurden mittels Rastertunnel- (STM) und Rasterkraftmikroskopie charakterisiert (siehe STM-Aufnahme). Die Makrocyclen organisieren sich in Form hexagonal gepackter Kolumnen. Zwischen den Carbazol-Einheiten und dem Porphyrin-Kern gibt es einen effizienten Energietransfer.

Hyperbranched polyphenylene nanotubes are fabricated by Diels– Alder reactions of tetraphenylcyclopentadienones in the nanochannels of porous alumina membranes. Nanotubes with different structures and morphologies, and even highly porous carbon nanotubes (see Figure), can be obtained by adjusting the starting materials and the conditions of in-situ polymerization.

Uniform carbon/Co nanorods with unique cross-sections (see Figure), Co/carbon core/shell nanospheres, and multiwalled carbon nanotubes are selectively prepared in high yield by solid-state thermolysis of polyphenylene dendrimer/cobalt complexes under controlled heating procedures. The obtained materials have potential catalytic and magnetic applications.

Field-effect transistors with highly ordered active layers are fabricated by zone-casting discotic dodecyl-substituted hexa-peri-hexabenzocoronene molecules onto hydrophobic substrates to form semiconducting columnar structures (see Figure). The discs form columns that possess long-range order on the scale of square centimeters, and the devices show order-of-magnitude improvements in charge-carrier mobilities over previously reported devices.

Three different hexa-peri-hexabenzocoronene (HBC) derivatives with carboxylic acid functions have been synthesized to study the effect of hydrogen bonding on the already pronounced columnar π-stacking. This functionalization improves the degree of order in the bulk and influences the surface patterning at solid-liquid interfaces as well as the thermal properties of these materials. The length of the tether between the aromatic core and the hydrogen-bond-forming carboxy group appears as a key factor influencing the supramolecular self-assembly, since only the HBCs with shorter spacers showed a strong synergetic effect of the columnar π-stacking with the hydrogen-bonding motifs. Clear signatures for this are unusually high mesophase transition temperatures and non-tilted columnar stacking in the pseudocrystalline phase.

As model systems, HBC dyads have been synthesized with the two HBC disks linked through a covalent spacer fitting the intercolumnar distance of the short-tethered, hydrogen-bridged dimer. This comparison emphasized the impact of the hydrogen bonds on the supramolecular properties of the materials. A broad range of analytical methods have been used, including differential scanning calorimetry, wide-angle X-ray diffractometry, solid-state NMR spectroscopy, and scanning tunneling microscopy.

The thermal properties and self-organization of hexa-peri-hexabenzocoronene (HBC) derivatives with dove-tailed alkyl chains of various lengths have been investigated using polarized optical microscopy and wide-angle X-ray scattering. It is shown that the size-related increase of steric interactions among the peripheral side chains substituted to the aromatic core leads to a dramatically lowered isotropization temperature, allowing thermal processing at practical temperatures. Additionally, the introduction of ether linkages within the side chains enhances the affinity of the discotic molecules towards polar surfaces, resulting in homeotropic self-assembly when the compounds are processed from the isotropic state between two surfaces and, for the first time, as a thin film on a single surface. It is established that the degree of homeotropic order is influenced by the phase behavior, the supramolecular order in the bulk, and the surface affinity of the corresponding derivatives. These results are important for the design of photovoltaic cells based on HBC derivatives.

Summary: We present a new method for preparing a nanocomposite containing highly dispersed ZnO nanoparticles. The essence of this approach is the formation of surface modified inorganic particles and their homogeneous incorporation into a polymeric matrix. Therefore, an inverse emulsion of an inorganic salt, for example, zinc acetate stabilized by amphiphilic statistical copolymers, is prepared. By hydrolysis under basic conditions ZnO particles of a size below 100 nm are formed within the micelles. As the surfactant remains adsorbed on the surface of the particles, a surface functionalization with hydrophobic chains is performed. These chains can be considered as compatibilizers for blending of the ZnO nanoparticles in PMMA affording transparent nanocomposite films avoiding particle aggregated. The present approach is in principle applicable to all nanoparticles prepared in a sol-gel process.

Strukturelle Perfektion von Polyphenylendendrimeren bis zur fünften Generation ließ sich durch das Einfügen von para-Terphenyl-Spacern in die Arme einer jeden Verzweigungseinheit erreichen (siehe Bild). Die steifen, monodispersen Makromoleküle mit Durchmessern bis 22 nm wurden stufenweise aufgebaut, wobei die Topologie der Verzweigungseinheiten kontrolliert wurde. Die so synthetisierten hoch porösen Dendrimere enthielten bis zu 1368 Phenylringe.

Sehr stark gebogenes permethoxyliertes Hexa-peri-hexabenzocoronen wurde durch einfache Cyclodehydrierung mithilfe von FeCl₃ zugänglich. Die Kombination eines starren „doppelt konkaven“ aromatischen Kerns mit 18 flexiblen Methoxygruppen an der Peripherie macht die Verbindung zu einem bemerkenswerten Wirtmolekül, wie die Strukturanalyse ihrer kristallinen Einschlusskomplexe mit Hexafluorbenzol- und Fulleren-Gastmolekülen (siehe Bild) belegt.

Graphitic carbon nanotubes that comprise graphene layers aligned perpendicular to the tube axis (see image; arrow indicates tube axis) were obtained by stepwise carbonization of preorganized disclike molecules in a porous alumina template. The alignment, size, wall thickness, and shape of the tubes were all controlled by this method.

Two new synthetic approaches to terrylenediimides, highly photostable fluorescent dyes, are described. For the first time terrylenediimide has been synthesised in a straightforward procedure that makes large quantities available. The second route includes an efficient cross-coupling reaction followed by a cyclodehydrogenation. Monofunctionalisation of the imide structure allows terrylenediimides now to be coupled with a variety of compounds, for example, by Suzuki cross-coupling, which can lead to an array of terrylenediimides with new functional groups such as hydroxy, amino, or carboxy groups needed to link up with other molecules. The functionalisation in the bay region is used to tune the properties of terrylenediimides and extend the range of applications, for example, by introducing water solubility. These tetrasubstituted terrylenediimides offer, depending on the substituents used, exciting features such as good solubility in common organic solvents, water solubility, or NIR absorption.

Extremely nonplanar permethoxylated hexa-peri-hexabenzocoronene can be prepared by using a facile ferric chloride cyclodehydrogenation procedure. The combination of a rigid “double-concave” aromatic core with 18 flexible methoxy groups at the periphery makes it a remarkable host molecule, as revealed by single-crystal analysis of its crystalline inclusion complexes with hexafluorobenzene and fullerene guest molecules (see crystal structure).

Unusual conductivity effects: Suitably functionalized dendrimers (see picture) are capable of forming truly covalent three-dimensional networks with remarkably high conductivity on electrochemical doping. Depending on the charging level of the electroactive components used as building blocks for the dendrimer core and the perimeter, two separated regimes of electrical conductivity can be observed.

The development of nanotechnology using organic materials is one of the most intellectually and commercially exciting stories of our times. Advances in synthetic chemistry and in methods for the investigation and manipulation of individual molecules and small ensembles of molecules have produced major advances in the field of organic nanomaterials. The new insights into the optical and electronic properties of molecules obtained by means of single-molecule spectroscopy and scanning probe microscopy have spurred chemists to conceive and make novel molecular and supramolecular designs. Methods have also been sought to exploit the properties of these materials in optoelectronic devices, and prototypes and models for new nanoscale devices have been demonstrated. This Review aims to show how the interaction between synthetic chemistry and spectroscopy has driven the field of organic nanomaterials forward towards the ultimate goal of new technology.

Graphitische Kohlenstoffnanoröhren aus Graphenschichten, die senkrecht zur Röhrenachse orientiert sind (siehe Bild; der Pfeil zeigt die Achse an), wurden durch schrittweise Verkokung vororganisierter scheibenförmiger Moleküle in einem porösen Aluminiumoxidtemplat erhalten. Die Ausrichtung der Schichten sowie Größe, Wandstärke und Form der Röhren konnten auf diesem Weg eingestellt werden.

Auffallend hoch ist die Leitfähigkeit in kovalent gebundenen dreidimensionalen Netzwerken aus geeignet funktionalisierten Dendrimeren (siehe Bild) nach elektrochemischer Dotierung. Bei Variation des Potentials für die Beladung der elektroaktiven Komponenten, die als Bausteine für den Dendrimerkern bzw. -perimeter eingesetzt wurden, treten zwei getrennte Leitfähigkeitsbereiche auf.

Die Entwicklung der Nanotechnologie mit organischen Materialien schreibt eine der größten intellektuellen, aber auch kommerziellen Erfolgsgeschichten unserer Zeit. Fortschritte in der Synthesechemie und bei Methoden zur Untersuchung und Manipulation einzelner Moleküle und kleiner Molekül-Ensembles brachten entscheidende Fortschritte im Bereich organischer Nanomaterialien hervor. Neue Erkenntnisse über die optischen und elektronischen Eigenschaften von Molekülen, die mit den Methoden der Einzelmolekül-Spektroskopie und Rastersondenmikroskopie gewonnen wurden, bildeten die Grundlage für den Entwurf und die Synthese neuartiger molekularer und supramolekularer Systeme. Auch für die Anwendung solcher Materialien in optoelektronischen Bauelementen wurde nach Methoden gesucht, wobei Prototypen und Modelle nanoskaliger Funktionseinheiten vielfach beschrieben sind. Ziel dieses Aufsatzes ist es aufzuzeigen, wie das gegenseitige Wechselspiel von Synthesechemie und Spektroskopie das Gebiet der organischen Nanomaterialien hin zum letztendlichen Ziel einer neuen Technologie führt.

Fluorescence spectroscopy is employed to follow the ion exchange of an emissive dye—a carboxylated perylene imide—on a layered double hydroxide. The exchange of the carboxylate ions starts at the edges of the layered double hydroxide crystals and is followed by diffusion to the basal plane. Such space-resolved observations provide a solid basis for modelling and studying the mechanisms of exchange.

We report a Kelvin-probe force microscopy (KPFM) investigation on the structural and electronic properties of different submicron-scale supramolecular architectures of a synthetic nanographene, including extended layers, percolated networks and broken patterns grown from solutions at surfaces. This study made it possible to determine the local work function (WF) of the different π-conjugated nanostructures adsorbed on mica with a resolution below 10 nm and 0.05 eV. It revealed that the WF strongly depends on the local molecular order at the surface, in particular on the delocalization of electrons in the π-states, on the molecular orientation at surfaces, on the molecular packing density, on the presence of defects in the film and on the different conformations of the aliphatic peripheral chains that might cover the conjugated core. These results were confirmed by comparing the KPFM-estimated local WF of layers supported on mica, where the molecules are preferentially packed edge-on on the substrate, with the ultraviolet photoelectron spectroscopy microscopically measured WF of layers adsorbed on graphite, where the molecules should tend to assemble face-on at the surface. It appears that local WF studies are of paramount importance for understanding the electronic properties of active organic nanostructures, being therefore fundamental for the building of high-performance organic electronic devices, including field-effect transistors, light-emitting diodes and solar cells.

Coarsening of 2D polycrystals of rod-like oligomers self-assembled at the solid–liquid interface can be visualized using scanning tunneling microscopy with sub-molecular resolution, providing insight into the thermodynamics and kinetics governing this 2D Ostwald- ripening phenomenon.

Summary: New carbazole-based ladder-polymers have been prepared utilising a 3,6-diacyl-2,7-dibromocarbazole building block 4. Suzuki polycondensation of 4 with carbazole-2,7-diboronic acid followed by addition of methyl lithium and ring closure with boron trifluoride gave ladder-polymers 9 with all methine bridges, analogous to ladder-type poly(para-phenylene). In very dilute solution, these polymers show blue-green fluorescence similar to that from the corresponding LPPP. At higher concentrations, a broader red-shifted emission is seen which suggests that the chains are aggregating in solution. Homopolymerisation of 4 followed by condensation of the carbonyls with boron sulfide produced a novel ladder-type structure 13 with alternating five- and six-membered rings. This ladder-polymer displays bright yellow-green fluorescence. Cyclic voltammetry indicated that these materials have HOMO energy levels comparable to the work function of ITO, making them good candidates for use as hole accepting emissive materials for LEDs.

Ein Doppelkabel: Ein neues Synthesekonzept machte Hexa-peri-hexabenzocoronene (HBCs) hoch atomökonomisch zugänglich. Die coaxiale Anordnung der HBCs und Arylamine ermöglichte einen „Doppelkabel“-Lochtransport (siehe Bild), d. h. einen Transport durch den zentralen Kern (weiß) und die äußere Schale (grün).

Flüssigkristalle aus großen Graphitsegmenten: Diskotische Verbindungen, basierend auf substituierten Superphenalenen, wurden auf einfachem Weg hergestellt und in ungewöhnlicher Weise zu weichen und sehr gut löslichen columnaren flüssigkristallinen Phasen weiterverarbeitet. Die regiospezifische Synthese führt zu einer „Windrad“-ähnlichen C₃-Symmetrie.

DNA–dye polymer: Two complementary perylenediimide–bis(oligonucleotide) conjugates (see picture) were synthesized that are soluble in water and can be transferred into nonpolar solvents, such as n-decane, by means of detergents. Self-assembled DNA–dye polymers formed when solutions of these conjugates are mixed.

The hole story: using a new synthetic concept the title hexa-peri-hexabenzocoronenes (HBCs) were synthesized with high atom economy. The coaxial arrangement of the HBCs and arylamines allowed a “double-cable” hole transport (see picture), that is, transport through the central core (white) and the outer shell (green).

Novel perylene-3,4,9,10-tetracarboxdiimides (PDI) dyes functionalized with polyphenylene dendrimers attached at the bay region are reported. Derivatives of PDI bearing polyphenylene dendrimers up to the second generation, substituted with an increasing number of triphenylamine (TPA) moieties at the periphery, as well as a related nondendronized model compound were prepared. Intramolecular energy transfer was demonstrated by the observation of PDI emission on excitation of the triphenylamines, and electron transfer was detected by comparing photoluminescence quenching in solvents of different polarity.

Eine hoch geordnete helicale columnare Packung in Einkristallen (siehe Bild) entsteht durch rationales Design aus einem einfachen, nichtchiralen aromatischen Pyrenderivat. Die Packungspräferenz wird einer Kombination aus maximierten Dipol-Dipol-Wechselwirkungen und der Anordnung voluminöser tert-Butylgruppen zugeschrieben.

DNA-Farbstoff-Polymer: Zwei komplementäre wasserlösliche Perylendiimid-Bis(oligonucleotid)-Konjugate (siehe Bild), die mithilfe von Detergentien in nichtpolare Lösungsmittel wie n-Decan überführbar sind, wurden synthetisiert. Durch Mischen der Konjugate entstehen selbstorganisierte DNA-Farbstoff-Polymere.

Liquid crystals from large graphitic segments: Discotic compounds based on substituted superphenalenes were prepared by a surprisingly simple synthesis and processed to give soft and highly soluble columnar liquid-crystalline materials. The regiospecific synthesis leads to compounds with pinwheel-type C₃ symmetry.

Dying to be seen: A series of water-soluble and highly fluorescent perylenetetracarboxdiimides (PDIs) have been synthesized in high yields by introducing charged groups into the bay region of PDI (see picture; C gray, H white, S yellow, O red). They can be used for staining living cells as they are nontoxic.

A highly ordered helical columnar packing in single crystals (see picture) can be generated from a simple and nonchiral aromatic system based on pyrene by rational design. The packing preference can be attributed to the combined effect of maximized dipole–dipole interaction and the compatible accommodation of bulky tert-butyl groups.

A systematic approach towards highly fluorescent, water-soluble perylene-3,4:9,10-tetracarboxylic acid diimide chromophores is presented. Water solubility was introduced first through the attachment of four hydrophilic substituents onto the bay region of the perylene dye. Positively and negatively charged groups were then applied to the chromophore, and their number and their distance from the aromatic scaffold were systematically varied. To suppress aggregation, the chromophore was further isolated within a dendritic shell. Such variation of structural features and a thorough investigation of the resulting optical properties facilitated the first synthesis of perylene-3,4:9,10-tetracarboxylic acid diimides combining the properties of water solubility and fluorescence quantum yields (FQYs) close to unity, which makes them attractive as high-performance fluorescence probes in aqueous media.

The synthesis of dendritic multichromophores based on a rigid polyphenylene scaffold is presented. Different rylene chromophores are incorporated into the core, the branches, and the surface of the dendrimer. In this way, two generations of dendritic dyads consisting of a terrylenediimide core, a stiff polyphenylene scaffold, and a perylenemonoimide periphery were obtained. Furthermore, the first synthetic approach to a dendritic triad is introduced. The outer sphere of this macromolecule is formed by naphthalenemonoimide chromophores, whereas perylenemonoimide groups are located in the dendritic scaffold, and the terrylenediimide chromophore serves as a core molecule. This multichromophore absorbs over the whole range of the visible spectrum and shows well-separated absorption envelopes. In the course of dendrimer synthesis new attempts towards a straightforward functionalization strategy for rylene dyes are also presented.

Es kommt Farbe ins Spiel: Wasserlösliche und hoch fluoreszente Perylentetracarboxdiimide (PDIs) wurden in hohen Ausbeuten durch Einführung geladener Gruppen in die Einbuchtung der PDI-Struktur erhalten (siehe Bild; C grau, H weiß, S gelb, O rot). Die Farbstoffe sind nichttoxisch und können daher zur Färbung lebender Zellen genutzt werden.

Two novel tetra- and hexahydroxy functionalized perylene chromophores have been used as initiators for the Sn(oct)₂ catalyzed ring-opening polymerization of different lactones. The arms of the resulting star polymers were comprised of either crystallizable poly(L-lactide) or poly(ε-caprolactone) arms or of amorphous poly[γ-(tert-amyl)-ε-caprolactone] chains. The star polymers were investigated by differential scanning calorimetry, X-ray scattering and dynamic mechanical and optical spectroscopy. Whereas the thermal properties of the poly(ε-caprolactone) stars were barely affected by the star topology, crystallization of the poly(L-lactide) stars was strongly hindered by the star-shaped architecture. Interestingly, for the amorphous poly[γ-(tert-amyl)-ε-caprolactone] stars a decrease in T_g with increasing chain length was found, reflecting the declining influence of the rigid perylene core on segmental mobility with increasing arm length. While the solid state and solution optical properties of high molar mass polyester stars were identical, the excitation and fluorescence emission spectra of spin-coated films of the low molecular weight polymers revealed a red shift, pointing towards perylene – perylene interactions in these samples. The optical spectroscopy experiments suggested that arm length, rather than the number of arms, is the most important parameter determining encapsulation and preventing aggregation of the perylene core moieties in the solid state.

Ein unlöslicher scheibenförmiger Baustein, Hexa(4-iodphenyl)-peri-hexabenzocoronen (siehe Formel), wurde durch eine effiziente Methode synthetisiert und in einer Serie von löslichen sternförmigen Hexabenzocoronenen (HBCs) mit bemerkenswertem Selbstorganisationsverhalten umgewandelt. Das Produktspektrum umfasst hoch geordnete flüssigkristalline Materialien, dendronisierte HBCs und Triarylamin-substituierte HBCs.

An insoluble disclike building block hexa(4-iodophenyl)-peri-hexabenzocoronene (see picture) was synthesized in an efficient way, and subsequent functionalization led to a series of soluble, star-type hexabenzocoronenes (HBCs), all showing remarkable self-assembly behavior: 1) highly ordered liquid-crystalline materials, 2) dendronized HBCs, and 3) triarylamine-substituted HBCs.

Taken to the limit: The synthesis of a new amino-functionalized polymer containing one amino group on each carbon of the backbone, is presented. This compound, poly(methylene amine), can be considered as the polymer with the highest content of amino functions known.

Mehr geht nicht: Vorgestellt wird die Synthese eines Polymers, das eine Aminogruppe an jedem Kohlenstoffatom der Polymerhauptkette trägt (siehe Schema). Das Produkt, Poly(methylenamin), weist die bislang höchste Zahl an Aminofunktionen in einer Polymerhauptkette auf.

The emission properties of polyindenofluorenes with various proportions of straight- and branched-chain alkyl substituents have been compared. The polymer with straight octyl substituents shows green emission due to formation of aggregates, while the polymer with branched 2-ethylhexyl substituents shows blue emission. Studies of the film morphology show the presence of ordered structures due to π-stacking of the polymer chains for the octyl-substituted polymer, whereas the polymer with branched side-chains shows no such order. Copolymers show intermediate behavior. A clear correlation is established between the degree of straight-chain alkyl substitution, the formation of ordered structures in the films, and the amount of long wavelength emission in the solid-state spectra.

This paper describes the synthesis of two novel tetra 2-bromoisobutyric acid-substituted perylene fluorophores and their use as initiators for the atom transfer radical polymerization of styrene. Different star-shaped polystyrenes covering a wide range of molecular weights were prepared by variations in the initial molar ratio between styrene and the perylene chromophores. Bulk properties of the star polymers were investigated by X-ray scattering, differential scanning calorimetry, and dynamic mechanical measurements. These studies revealed that the polystyrene arms effectively suppress the aggregation of the perylene chromophores and indicated that, especially at low degrees of polymerization, the rigid-core moiety significantly affects the segmental dynamics of the arms. Spin-casting of the polystyrene stars afforded optically transparent films, which displayed high fluorescent quantum yields. Due to the covalent linkage between the polystyrene chains and the perylene chromophore, the dye-contents of such films can be much higher than those achievable by dissolution of the corresponding low-molar-mass perylene dye in a polystyrene matrix. In addition, the polystyrene arms are likely to reduce the mobility of the chromophore within a polystyrene matrix. These features make these fluorescent star-shaped polymers of interest to improve the migration fastness of colored polystyrene samples.

In this paper we present the synthesis and characterization of the so far largest polycyclic aromatic hydrocarbon (PAH), containing 222 carbon atoms or 37 separate benzene units. First a suitable three-dimensional oligophenylene precursor molecule is built up by a sequence of Diels–Alder and cyclotrimerization reactions and then planarized in the final step by oxidative cyclodehydrogenation to the corresponding hexagonal PAH. Structural proof is based on isotopically resolved MALDI-TOF mass spectra and electronic characteristics are studied by UV/Vis spectroscopy.

Das Titelbild zeigt die berechnete energieminimierte 3D-Struktur eines in einer mehrstufigen Synthese hergestellten Polyphenylendendrimers. Das Nanoteilchen enthält drei unterschiedliche Chromophortypen, die sich im Zentrum (Terrylen), innerhalb des Gerüstes (Perylen) und an der Peripherie (Naphthalin) befinden. Diese Multichromophortriade absorbiert über den gesamten sichtbaren Bereich und ermöglicht einen schrittweisen vektoriellen Energietransfer über eine Entfernung von 30 Å von der Oberfläche zum Kern. Mehr über Polyphenylenchromophore erfahren Sie in der Zuschrift von Müllen et al. auf S. 1980 ff.

Dendritic multichromophores based on a rigid polyphenylene scaffold contain up to three different types of rylene chromophores incorporated at the focal point, the scaffold, and the periphery of the dendrimer. An energy gradient between the periphery and the core is thus generated and allows an efficient transfer of excitation energy (see picture).

The cover picture shows the calculated energy-minimized 3D-structure of a polyphenylene dendrimer, which was prepared in a multistep synthesis. The nanoparticle carries three different types of chromophores, located in the center (terrylene), within the scaffold (perylene), and at the periphery (naphthalene). This multichromophoric triad absorbs over the whole range of the visible spectrum and shows, as shown in the picture, a stepwise vectorial energy transfer over a distance of 30 Å from the surface to the core. There is more about polyphenylene chromophores in the communication from Müllen et al. on p. 1900 ff.

A series of first-generation polyphenylene dendrimers based on three different cores were prepared by Diels–Alder cycloaddition and their single-crystal structures were determined. Consisting exclusively of interlocked, twisted phenyl rings, these polyphenylene nanostructures have exciting structural and dynamic properties. Single crystals of dendrimers, suitable for X-ray structure analysis, were grown from different solvent mixtures by slow evaporation at room temperature. It should be pointed out that one of the described polyphenylene dendrimers represents up to now the biggest oligophenylene nanostructure from which crystallographic data is available.

A hierarchic build-up of functional nano- and microparticles allows the generation of smart organic supports for metallocene catalysts. Latices, well defined in size and surface structure, are made by emulsion polymerization using poly(ethylene oxide)-containing surfactants. Micron-sized catalyst beads are formed by reversible loading/crosslinking with a metallocene/methylaluminoxane complex. As a result of the network fragmentation during ethylene polymerization, the catalysts achieve very high productivities, hard polyethylene particles and homogeneous distributions of nanometer-sized fragments in the product.

A novel synthesis is presented of a fourfold ethynyl-substituted perylene diimide dye 4, which acts as a core molecule for the buildup of polyphenylene dendrimers. Around the luminescent core 4, a first-generation (5), a second-generation (6), and a third-generation (7) polyphenylene dendritic environment consisting of pentaphenylbenzene building blocks are constructed. The dendrimers 5 and 6 are synthesized by an exclusively divergent route, whereas for 7, a combination of a divergent and convergent approaches is applied. Absorption and emission spectra of 5–7 in different solvents and in a film have been measured and compared to a nondendronized model compound 13. In solution, the internal chromophore is scarcely influenced by the dendritic scaffold; however, in the solid state, aggregation of the perylene diimide is prevented very effectively by the four rigid dendrons. Additionally, fluorescence quantum yields in solution have been determined for 5–7 and 13; they decrease as the number of generation increases.

New perylene chromophores, phenyl-substituted diindeno[1,2,3-cd:1′,2′,3′-lm]perylenes 5 a,b and 4,4′,7,7′-tetraphenyldiacenaphtho[1,2-k:1′,2′,k′]diindeno[1,2,3-cd:1′,2′,3′-me]perylenes 22 a,b, have been synthesized from substituted fluoranthene derivatives 3 a,b and 4 a,b by means of a surprisingly simple oxidative cyclodehydrogenation reaction. The resulting chromophores, when substituted with alkyl chains at the periphery, show good solubility in organic solvents, and a full characterization of the novel red, green, and blue dyes by field-desorption mass spectrometry, UV/Vis and ¹H and ¹³C NMR spectroscopy becomes possible.

Rigid, dendritic poly(paraphenylene)s (see picture) are excellently suited as sensitive and selective coatings for gravimetric sensors (quartz microbalances), since they incorporate guest molecules reversibly into their interior voids. The variety of their potential designs allows an optimal match of these multitalented hosts to the guests (analytes) to be monitored.

Polyphenylenes, ranging from one-dimensional wire-like conjugated polymers to two-dimensional disc-shaped polyaromatic hydrocarbons and three-dimensional sphere-like dendrimers, have been prepared using methods that allow synthetic control of their molecular and supramolecular order in order to optimise their physical, especially optical and electrical, properties. 1D-conjugated polymers can be used as emitting materials in LEDs, with their colours tuned so as to give emission across the whole visible spectrum. Their supramolecular order can be manipulated by attachment of bulky sidechains to suppress aggregation, and by formation of rod-coil block copolymers. 2D polycyclic aromatic hydrocarbons form stable columnar mesophases with high charge carrier mobilities. Their size, shape, and substitution patterns can be altered so as to maximise their intra- and intercolumnar order. 3D polyphenylene dendrimers can be prepared in ways that enable control of their shape, and their surfaces can be selectively functionalised in ways that permit them to act as functionalised nanoparticles. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:243–257, 2001

Starre, dendritische Poly(paraphenylene) (siehe Bild) eignen sich hervorragend als empfindliche, selektive Schichten für gravimetrische Sensoren (z. B. Schwingquarz-Mikrowaagen), da sie reversibel Gastmoleküle in ihre Cavitäten einlagern können. Vielfältige Gestaltungsmöglichkeiten gestatten eine optimale Anpassung dieser Wirte an ihre Gäste (=Analyte).

The hexa-tert-butyl substituted hexa-peri-hexabenzocoronene was synthesized in an overall yield of 83 % from 4-tert-butylphenylacetylene. The key step was the oxidative cyclodehydrogenation of hexa(4-tert-butylphenyl)benzene with anhydrous FeCl₃ in CH₂Cl_2. The high solubility of hexa-tert-butyl-hexa-peri-hexabenzocoronene in common organic solvents allowed a comprehensive spectroscopic characterization of this compound in solution. Electrochemical oxidation at −30 °C in the presence of tetrabutylammonium hexafluoroarsenate led to the formation of a stable radical cation salt. Reaction of hexa-tert-butyl-hexa-peri-hexabenzocoronene with an excess of tricarbonyl(naphthalene)chromium in THF/dioxane afforded a mixture of mono- and bis-tricarbonylchromium complexes which could be separated by chromatography. The molecular structures of the parent compound, its radical cation salt and its mono- tricarbonylchromium complex were determined by X-ray analysis and discussed in detail. Remarkably, the crystal structures of these compounds are mainly dominated by the formation of dimers of the aromatic cores.

In this paper we report on a zirconocene dichloride/methylaluminoxane catalyst system supported on a crosslinked polystyrene in order to provide ethylene polymerization catalysts for gas phase or slurry processes. Our novel approach uses the Diels-Alder reaction of cyclopentadiene functions as the final, cross-linking synthetic step. This provides polymer supported zirconocene catalysts with a homogeneous distribution of active sites. The catalysts were shown to be highly active and to form spherical beads as proven by scanning electron microscopy.

Candidates for molecular nanowires for the interconnection of gold nanoelectrodes in a molecular-scale electronic device are to be found in end-functionalised poly(para-phenyleneethynylene)s. The self-assembly of these polymers was studied on atomically flat solid substrates. On graphite, sub-molecularly resolved imaging with scanning tunneling microscopy revealed nanorods in a 2 D nematic-like texture, while on mica, scanning force microscopy (see picture) shows that the nanorods can self-assemble into highly oriented micrometer-long nanoribbons with a molecular cross-section.

A functionalized dialkylperylene and a modified terrylenetetracarboxdiimide (TTCDI) were joined by a hexanediyl spacer. The resulting bichromophoric molecule 1 (R = 4-tert-butylphenoxy) is a suitable model system for donor–acceptor energy transfer studies at the single-molecule level.

The differences in the fluorescence behavior of a polyphenylene dendrimer with eight peryleneimides chromophores (1) and a single hexaphenylperyleneimide chromophore have been investigated at a single-molecule level through the combination of ultrasensitive fluorescence detection and microscopy.

Unterschiede im Fluoreszenzverhalten eines Polyphenylendendrimers mit acht Perylenimidchromophoren (1) und eines einzelnen Hexaphenylperylendicarbonsäureimidchromophors werden durch Einzelmoleküluntersuchungen mit Hilfe der Kombination aus ultraempfindlicher Fluoreszenzdetektion und Mikroskopie nachgewiesen.

The synthesis of the poly(para-phenyleneethynylene)-block-poly(ethylene oxide) block copolymer (PPE-b-PEO) (1) via condensation of endfunctionalized poly(para-phenyleneethynylene) (PPE) (5) and poly(ethylene oxide) monomethyl ether (PEO) is reported. This is achieved by the initial synthesis of a PPE homopolymer with quantitative terminal functionalization, as proven by ¹H NMR and field desorption mass spectrometry (FD-MS). Reaction of the latter with PEO affords the block copolymer 1, which was characterized by ¹H NMR spectroscopy, FD-MS and gel permeation chromatography (GPC). Furthermore it is shown that matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) is a suitable method to investigate PPE-b-PEO with respect to molecular weights and copolymer composition.

This paper describes a new way to synthesize rod-coil block copolymers consisting of poly(p-phenylene) (PPP) as rigid rod and either polystyrene (PS) or poly(ethylene oxide) (PEO) as flexible coil. The Suzuki-coupling of the AB-type monomer 4-bromo-2,5-diheptylbenzeneboronic acid (1) under strictly proton-free conditions leads to the control of PPP endgroups and hence allows the synthesis of a variety of differently end-functionalized poly(p-phenylene)s. The poly(2,5-diheptyl-p-phenylene)-block-polystyrene (7) is then prepared via condensation via condensation of anionically polymerized living polystyrene (6) with α-(4-formylphenyl)-ω-phenyl-poly(2,5diheptyl-p-phenylene) (4). Toluenesulfonic acid catalyzed condensation of α-methyl-ω-amino-poly(oxyethylene) (8) with PPP 4 yields poly(2,5-diheptyl-p-phenylene)-block-poly(ethylene oxide) (9).

A new approach for the synthesis of extremely large PAHs in high yield is the oxidative cyclodehydrogenation of suitable oligophenylenes under Kovacic conditions. The synthesis of oligophenylene precursors and their cyclodehydrogenation (figure) are presented, and the supramolecular structures observed for large PAHs are discussed.

Tempernvon Polystyrolfilmen, die die neuartigen flüssigkristallinen Coronendiimide 2 enthalten, führt in wenigen Sekunden zu einer Verschiebung der Emission, was zur pixelweisen Einfärbung und mithin für optische Anzeigen genutzt werden könnte. Die Photolumineszenzeigenschaften von 2 in fester Matrix hängen von der Art der gebildeten Addukte ab. Hergestellt werden diese Coronenderivate auf einfache Weise aus Perylentetracarbonsäuredianhydrid 1.

Tempering of polystyrene films containing the novel liquid crystalline coronenebis(dicarboximide)s 2, which are formed by an easy route from perylene-3,4;9,10-tetracarboxylic dianhydride (1), leads to a shift of the emission within a few seconds. This could be used for dot-by-dot coloring and thus optical displays. The photoluminescence properties of 2 in the solid matrix are dependent on the nature of the aggregates formed.

An die Grenzen der Analytik stößt man bei dem nanodimensionalen C₆₀-Graphitsegment 1, das dank langkettiger Alkylsubstitution löslich ist und dessen Monolagen auf Graphit durch Rastertunnelmikroskopie charakterisiert werden können.

At the limits of analytical investigation one finds the nanodimensional C₆₀ graphite segment 1, which, thanks to its long-chain alkyl substituents, is soluble. Monolayers of 1 on graphite can be characterized by scanning tunneling microscopy.