Molecular Dumbbells Research Articles

Organic Cage Dumbbells.

Molecular dumbbells with organic cage capping units were synthesised via a multi-component imine condensation between a tri-topic amine and di- and tetra-topic aldehydes. This is an example of self-sorting, which can be rationalised by computational modelling.

Controlling association kinetics in the formation of donor–acceptor pseudorotaxanes

We report a systematic investigation of size-complementary stoppering groups used to determine the kinetics of threading a cyclophane, namely cyclobis(paraquat-p-phenylene), onto a series of molecular dumbbells. We have identified a set of simple functionalized phenyl and biaryl groups that present activation energy barriers between 16.7 and 26.6kcalmol−1 to threading the dumbbells. These barriers will be employed as ‘steric speed bumps’ to modulate kinetics in artificial molecular pumps that operate based upon a delicate balance of noncovalent bonding interactions.

Fulleropyrrolidine molecular dumbbells act as multi-electron-acceptor triads. Spectroscopic, electrochemical, computational and morphological characterizations

Three novel fulleropyrrolidine dumbbells consisting three electron acceptor moieties joined by alkyl linker displaying tunable electrical and morphological properties were synthesized and characterized.

Fullerene and pi-Conjugated Oligomer Hybrids as Advanced Functional Nanomaterials

Two classes of pi-conjugated oligomer linked bis-fullerene molecules with a triad motif of C60-pi-C60 were synthesized and investigated. In the first series of C60-pi-C60 hybrids, electron-rich OPE/OPV conjugated oligomers were employed to function as the central pi-bridges and as the electron donors. Electrochemical and electronic absorption/emission spectral analyses indicate that the electronic interactions between the fullerene cage (acceptor) and the oligomer unit (donor) varied depending on the nature of the bridging unit. Complex excited state decay dynamics on the nanosecond timesccale were observed with time-resolved transient absorption spectroscopy. The second series of fullerene-oligomer hybrids use conjugated polyynes as the pi-bridges. The unique structural rigidity and solid-state reactivity of the polyyne units impart these bisfullerene molecular dumbbells interesting interfacial aggregation behavior by forming spherical nanostructures on s urfaces. This property could be useful for solid-state synthesis of fullerene based nanomaterials.

Nanorings from the Self-Assembly of Amphiphilic Molecular Dumbbells

We have prepared amphiphilic dumbbell molecules consisting of hydrophobic alkyl chains and hydrophilic oligoether dendrons at each end of the rod segment. The molecular dumbbells, in aqueous solution, self-assemble into toroids as an intermediate nanostructure between spherical and long cylindrical micelles. The formation of toroidal structure is likely to originate from side by side connections of discrete bundles through the combination of strong hydrophobic interactions and anisotropic aggregation of rod segments.

Self-Assembling Molecular Dumbbells: From Nanohelices to Nanocapsules Triggered by Guest Intercalation

Vielseitige Hanteln: Hantelförmige Moleküle auf der Basis eines Hexa-p-phenylenderivats selbstorganisieren sich in wässriger Lösung in gut definierte linksgängige helicale Fasern. Diese helicalen Nanofasern gehen bei der Einlagerung von aromatischen Gastmolekülen (rote Kugeln) reversibel in hohle Nanokapseln über.

Self‐Assembling Molecular Dumbbells: From Nanohelices to Nanocapsules Triggered by Guest Intercalation

Dumbbells that are not dumb: Dumbbell-shaped molecules based on a hexa-p-phenylene derivative self-assemble into well-defined left-handed helical fibers in aqueous solution. These helical nanofibers convert reversibly into hollow nanocapsules by intercalation of aromatic guest molecules (red spheres).

Synthesis and Electrochemistry of Molecular Dumbbells. Triblock Copolymers of Dendrons and Rigid Rods

Polyether dendrons, generations 1−4, were connected to naphthalene diimides and rigid rod naphthalene diimide-benzidine oligomers. This provided a series of well-defined triblock copolymers with flexible dendrons on both ends of rigid rods. The largest of these used generation-4 dendrons with a 4.4-nm rigid rod containing two diimides and three benzidines. The estimated length of this molecule is 10 nm. Electrochemical reduction in DMF provided anion radicals on each diimide of the rigid rod. The diffusion coefficients and rates of these reductions were measured using cyclic voltammetry. The diffusion coefficients were successfully compared with predictions for diffusing prolate ellipsoids. Comparison of the heterogeneous rate constants showed that larger dendrons slowed the electrochemical reaction, and had slightly larger effects when the rod was shorter. It is proposed that the bulky dendrons prevent access of the diimide groups to the electrode even when they are not directly connected to the diimide....

Hybrid Molecular Dumbbells: Bridging Polyoxometalate Clusters with an Organic π-Conjugated Rod

Strong electronic interactions occur between the polyoxometalate (POM) clusters and the π electrons of the conjugated organic bridge in hybrid molecular dumbbells such as 1 which were synthesized by Pd-catalyzed coupling reactions of organoimido-substituted POMs.

Hybrid Molecular Dumbbells: Bridging Polyoxometalate Clusters with an Organic π-Conjugated Rod

Hybrid Molecular Dumbbells: Bridging Polyoxometalate Clusters with an Organic π-Conjugated Rod

Self-assembly of molecular dumbbells into organized bundles with tunable size.

Dumbbell-shaped molecules consisting of three biphenyls connected through vinyl linkages as a conjugated rod segment and aliphatic polyether dendritic wedges with different cross-sections (i.e., dibranch (1), tetrabranch (2) and hexabranch (3)) were synthesized and characterized. The molecular dumbbells self-assemble into discrete bundles that organize into three-dimensional superlattices. Molecule 1, based on a dibranched dendritic wedge, organizes into primitive monoclinic-crystalline and body-centered, tetragonal liquid crystalline structures, while molecules 2 and 3, based on tetra- and hexabranched dendritic wedges, respectively, form only body-centered, tetragonal liquid crystalline structures. X-ray diffraction experiments and density measurements showed that the rod-bundle cross-sectional area decreases with increasing cross-section of the dendritic wedges. The influences of supramolecular structure on the bulk-state optical properties were investigated by measuring the UV/Vis absorption and steady state fluorescence spectroscopies. As the cross-section of the dendritic wedge of the molecule increases, the absorption and emission maxima shift to higher energy. This can be attributed to a quantum size effect of the three-dimensionally confined nanostructure.

Synthesis and Electrochemistry of Nanometer-Scaled Molecular Dumbbells

Nanoscale molecular dumbbells were prepared by joining dendrons to the ends of rigid rod oligoimides.