About Supramolecular Assemblies of π-Conjugated Systems

Synthesis and Characterization of Soluble Oligo (9,10-Bisalkynylanthrylene)s

[structure: see text] Soluble oligo(9,10-bialkynylanthrylene)s up to pentamers were synthesized by means of the Suzuki coupling reaction. A solution processed thin film field-effect transistor from pentamer OA-5b shows a charge carrier mobility of 2.95 x 10(-)(3) cm(2)/V x s.

Chain morphologies in semicrystalline polyfluorene: evidence from Raman scattering

The beta phase in di-octyl substituted polyfluorene (PF8) exhibits a surprising level of conformational order at nanometer length scales compared to other phases. We present Raman scattering studies of PF8 as a function of thermal cycling, which establishes a connection between the conformational isomers and the side and main chain morphology. Density-functional calculations of the vibrational spectra of single chain oligomers in conjunction with the experimental results demonstrate the incompatibility of the beta phase with the overall alpha crystalline phase in PF8.

An Enantiomeric Nanoscale Architecture Obtained from a Pseudoenantiomeric Aggregate: Covalent Fixation of Helical Chirality Formed in Self-Assembled Discotic Triazine Triamides by Chiral Amplification

Covalent fixation of a chiral helical structure which is created in a self-assembling system by a chiral-amplification method based on the sergeants/soldiers principle is reported. Disk-shaped triazine triamides self-assembled to form columnar-type helical aggregates through pi-stacking interactions among the central triphenyltriazine moieties, hydrogen-bonding interactions among the amide groups, and van der Waals interactions among the alkyl groups in nonpolar solvents such as hexane, octane, toluene, and p-xylene. When the achiral triazine triamide soldier component is mixed with a tiny amount of the chiral triazine triamide sergeant component, control of the intrinsic supramolecular helicity of the self-assembled soldier component by the sergeant component leads to chiral amplification and formation of a pseudoenantiomeric aggregate with only one handedness of the helix. The helicity can be preserved by ring-closing olefin metathesis polymerization mediated by Grubbs catalyst when an achiral component with terminal olefinic groups forms the pseudoenantiomeric aggregate in the presence of a tiny amount of the chiral component without olefinic groups. After polymerization and removal of the chiral component, the polymeric architecture obtained from the achiral soldier component is optically active and thus can be regarded as an enantiomeric object in which the chiral information transferred from the chiral sergeant component is preserved. The nanoscale chiral structure is fixed perfectly, as indicated by CD spectroscopic evidence obtained in a polar THF medium at high temperature and low concentration. AFM and TEM observations show a nanoscale fibrous structure with a diameter of 2-4 nm, which corresponds to the molecular size of the triazine triamide monomer.

Spiropyran-based liquid crystals: the formation of columnar phases via acid-induced spiro–merocyanine isomerisation

Hexagonal columnar liquid-crystalline phases are induced for a new fan-shaped spiropyran compound as the result of an acidichromism effect of spiro-merocyanine isomerisation through protonation upon incorporation of 4-methylbenzenesulfonic acid.

Columnar liquid crystalline π-conjugated oligothiophenes

Polycatenar oligothiophenes possessing three alkoxy chains at each terminal self-organise into columnar liquid crystalline phases, and one-dimensional columnar stacks can be oriented uniaxially by mechanical shearing in the mesophases.

Synthetic method for multifunctionalized oligoarenes using pinacol esters of hydroxyphenylboronic acids

A synthetic method for multifunctionalized oligoarenes using rapid Suzuki-Miyaura coupling of pinacol esters of hydroxyphenylboronic acids and subsequent triflation of the hydroxy group was developed.

A columnar liquid crystal based on triphenylphosphine oxide—its structural changes upon interaction with alkaline metal cations

A triphenylphosphine oxide (TPPO) compound bearing 3,4,5-tridodecyloxybenzyloxy moieties exhibits a columnar liquid crystalline phase, and by changing its self-assembled structure, is responsive to alkaline metal cations due to cation-phosphine oxide interactions.

Functional organogels from highly efficient organogelator based on perylene bisimide semiconductor

A new n-type semiconducting perylene bisimide dye has been synthesized that gelates a broad variety of organic solvents to afford well-defined nano- and mesoscopic helical fibers and bundles.

A water-soluble hexa-peri-hexabenzocoronene: synthesis, self-assembly and role as template for porous silica with aligned nanochannels

A water-soluble hexa-peri-hexabenzocoronene was prepared and shown to undergo ordered columnar self-assembly either in water solution or bulk and therefore served as template for the fabrication of porous silica with aligned nanochannels.

On the Rigidity of Polynorbornenes with Dipolar Pendant Groups

A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C-5,6 positions was synthesized by ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod-like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod-like structure.

Synthetic functional π-stack architecture in lipid bilayers

Neglected until recently, pi-stack architecture is rapidly emerging as a powerful strategy to create function in lipid bilayer membranes. Recent reports describe supramolecular rosettes acting as hosts of intercalating guests, to assemble in bilayer membranes and, in the case of stacked guanosine and folate quartets, to form ion channels. The introduction of rigid-rod pi-stack architecture allowed us to address one of the great challenges in the field, i.e. ligand gating. Inspiring pi-stack chemistry from related fields, covering rainbow coloration, conductivity, as well as the critical dependence of charge mobilities on the precision of supramolecular organization is summarized to zoom in on arguably the most promising application of functional pi-stack architecture in lipid bilayers, that is the creation of multifunctional photosystems.

Energy transfer in chiral co-assemblies of triple hydrogen-bonded oligo(p-phenylene vinylene)s and porphyrin

Pi-pi stacking of hydrogen-bonded porphyrin and oligo(p-phenylene vinylene)s (OPVs) yields helical co-assemblies which exhibit energy transfer from OPV to porphyrin.

Supramolecular metallomesogens. Self-organization of an H-bonded tetrameric assembly into columnar phase from single component

The first example of supramolecular metallomesogens derived from palladium complexes exhibiting columnar phase is reported, and the formation of the mesophase is induced by H-bonding in a tetrameric assembly.

Design of self-assembling peptide nanotubes with delocalized electronic states

Redox-promoted self-assembly of an eight-residue cyclic D,L-α-peptide bearing four 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) side chains results in the formation of electronically delocalized peptide nanotubes hundreds of nm in length. The supramolecular approach described provides a rational basis for the design and fabrication of 1-D materials with potential utility in optical and electronic devices.

Functional polymers: scanning force microscopy insights

Scanning force microscopy (SFM) and related techniques make it possible to visualize polymer systems with a molecular resolution. Beyond imaging, they also enable the unveiling of a variety of (dynamic) physico-chemical properties of both isolated polymer chains and their supramolecular architectures, including structural, mechanical and electronic properties. This article reviews recent progress in the use of SFM on polymers, with a particular emphasis on the mechanical properties of copolymers and single polymer chains, as well as on the bottom-up fabrication of supramolecular polymeric (helical) nanostructures in particular based upon pi-conjugated macromolecules as building blocks for nanoelectronics. Through a detailed understanding of the polymer behavior, we propose solutions for the generation of organic functional (nano)systems.

Surface-assisted one-dimensional self-assembly of a perylene based semiconductor molecule

Chloroform-vapor annealing of thin films of propoxyethyl perylene tetracarboxylic diimide (PE-PTCDI, an n-type semiconductor) deposited on glass or mica leads to formation of well-defined one-dimensional self-assemblies (e.g. nanobelts), which show optically uniaxial properties as demonstrated by the linearly polarized emission.

Tunable interchromophore electronic interaction of a merocyanine dye in hydrogen-bonded supramolecular assemblies scaffolded by bismelamine receptors

The absorption and fluorescence properties of a barbiturate-type donor-pi-acceptor (D-pi-A) merocyanine dye are controlled by complexation with dimeric melamine receptors featuring different tether lengths.

Chiral, cross-conjugated isopolydiacetylenes

A series of chiral, monodisperse enyne oligomers (isopolydiacetylenes) based on a 1,1-binaphthyl core has been synthesized and characterized spectroscopically.

Fractal-like Self-Assembly of Oligo(p-phenylene vinylene) Capped Gold Nanoparticles

Reversible interparticle self-organization is reported for gold nanoparticles functionalized with an oligo(p-phenylene vinylene) moiety in butanol. The aggregates show a clear melting temperature at 80 degrees C, and atomic force microscopy and transmission electron microscopy indicate a fractal-like organization of the particles.

Energy Transfer in Self-Assembled [n]-Acene Fibers Involving ≥100 Donors Per Acceptor

Anthracene derivatives self-assemble into fibers with a high molecular order, as is evidenced by probing the structure with energy-trapping tetracene analogues. Efficient energy transfer processes involving tens to hundreds of donors per acceptor and high emission quantum yields are outstanding characteristics displayed in these self-assembled fibers.

Energy-Transfer Efficiency in Stacked Oligo(p-phenylene vinylene)s: Pronounced Effects of Order

The supramolecular structure of two types of oligo(p-phenylene vinylene) (OPV) building blocks in dodecane solution is studied. Monofunctional chromophores (MOPV) form well-defined helical assemblies, whereas bifunctional molecules (BOPV) aggregate into so-called frustrated stacks, lacking any higher helical order. This difference in organization has a major influence on the transfer of excitation energy through the assemblies. Energy transfer to supramolecularly incorporated guests (MOPV with lower bandgap) is used to probe the intrinsic differences in exciton mobility in these two types of mixed aggregates. From the observed donor fluorescence quenching, it can be concluded that the helically ordered nature of the MOPV stacks facilitates the transfer of excitation energy, yielding evidence for higher exciton mobility in the well-ordered assemblies than in the frustrated stacks. Finally, the concept of energy transfer in supramolecular assemblies is extended to the solid state by the successful implementation in a light-emitting diode (LED).

Synthesis of Functionalized Asymmetric Star Polymers Containing Conductive Polyacetylene Segments by Living Anionic Polymerization

Novel 3-arm ABC, 4-arm ABCD, and 5-arm ABCDE asymmetric star polymers comprising the conductive polyacetylene precursor, poly(4-methylphenyl vinyl sulfoxide) (PMePVSO), and other segments, such as polystyrene, poly(alpha-methylstyrene), poly(4-methoxystyrene), poly(4-trimethylsilylstyrene), and poly(4-methylstyrene), were synthesized by the methodology based on living anionic polymerization using DPE-functionalized polymers. This methodology involves the addition reaction of a DPE-functionalized polymer to a living anionic polymer followed by the living anionic polymerization of MePVSO initiated from the in situ formed polymer anion with two, three, or four polymer segments. The resultant asymmetric star polymers possessed predetermined molecular weights, narrow molecular weight distributions (Mw/Mn < 1.03), and desired compositions as confirmed by SEC, 1H NMR, SLS, and elemental analysis. After thermal treatment, the PMePVSO segment in the star polymer could be completely converted into a conductive polyacetylene segment, evident from TGA and elemental analysis. These asymmetric star polymers are expected to exhibit interesting solution properties and unique microphase-separated morphological suprastructures with potential applications in nanoscopic conductive materials. Moreover, this methodology can afford the target asymmetric star polymers with arm segments varying in a wide range and enables the synthesis of more complex macromolecular architectures.

Polarized Emission of Individual Self-Assembled Oligo(p-phenylenevinylene)-Based Nanofibers on a Solid Support

We have prepared 5 nm diameter, micrometer long tetra(p-phenylenevinylene) (OPV)-based nanofibers on a graphite surface. The fluorescence emission of an individual fiber shows a profound polarization over its entire length that directly corresponds to its orientation on the substrate. Quantitative analysis of the fluorescence polarization, including the depolarizing effect of the underlying graphite, evidences the high degree of organization within chiral fibers with the OPV molecules perpendicular to the fiber axis. The control of the internal order within self-assembled fibers, and the ability to measure it, is a crucial step to obtain uniform organic fibers that can be applied in nanosized electronics at room temperature.

Click-chemistry as an efficient synthetic tool for the preparation of novel conjugated polymers

The Cu(I)-catalysed 1,3-dipolar "click" cycloaddition is utilised as an efficient reaction for the preparation of novel fluorene-based conjugated polymers.

Synthesis, processing and properties of conjugated polymer networks

Despite the diverse research activities focused on the chemistry, materials science and physics of conjugated polymers, the feature of conjugated cross-links, which can provide electronic communication between chains, has received little attention. This situation may be a direct consequence of the challenge to introduce such links while retaining adequate processability. Focusing on recent studies of materials for which charge transport or electrical conductivity data are available, this feature article attempts to present an overview of the synthesis, processing and electronic properties of conjugated polymer networks. For the purpose of this discussion, two distinctly separate architectures-featuring covalent cross-links on the one hand and non-covalent organometallic bridges on the other-are treated in separate sections. The available data indicate that cross-linking can have significant benefits for intermolecular charge transfer if the polymers are carefully designed.

On the influence of porphyrin π–π stacking on supramolecular chirality created in the porphyrin-based twisted tape structure

Achiral porphyrin derivatives 1-M form twisted supramolecular assemblies and the pitch of the twisted tape structure can be altered by changing the central metal.

Anion-directed self-organization of thermotropic liquid crystalline materials containing a guanidinium moiety

New wedge-shaped thermotropic liquid crystalline materials containing a guanidinium moiety at the apex organize into various supramolecular structures such as hexagonal columnar, rectangular columnar and Pm3n cubic mesophases depending on anions illustrating guest-directed self-organization in mesophases.